Capitulo Lignina 2014.1-37

Complimentary Contributor Copy

BIOCHEMISTRY RESEARCH TRENDS

LIGNIN

STRUCTURAL ANALYSIS, APPLICATIONS IN BIOMATERIALS AND ECOLOGICAL SIGNIFICANCE

No part of this digital document may be reproduced, stored in a retrieval system or transmitted in any form orby any means. The publisher has taken reasonable care in the preparation of this digital document, but makes noexpressed or implied warranty of any kind and assumes no responsibility for any errors or omissions. Noliability is assumed for incidental or consequential damages in connection with or arising out of informationcontained herein. This digital document is sold with the clear understanding that the publisher is not engaged inrendering legal, medical or any other professional services.



Additional books in this series can be found on Novas website under the Series tab.

Additional e-books in this series can be found on Novas website under the e-book tab.



LIGNIN

STRUCTURAL ANALYSIS, APPLICATIONS IN BIOMATERIALS AND ECOLOGICAL SIGNIFICANCE

FACHUANG LU EDITOR

New York


Copyright 2014 by Nova Science Publishers, Inc. All rights reserved. No part of this book may be reproduced, stored in a retrieval system or transmitted in any form or by any means: electronic, electrostatic, magnetic, tape, mechanical photocopying, recording or otherwise without the written permission of the Publisher. For permission to use material from this book please contact us: Telephone 631-231-7269; Fax 631-231-8175 Web Site: http://www.novapublishers.com

NOTICE TO THE READER The Publisher has taken reasonable care in the preparation of this book, but makes no expressed or implied warranty of any kind and assumes no responsibility for any errors or omissions. No liability is assumed for incidental or consequential damages in connection with or arising out of information contained in this book. The Publisher shall not be liable for any special, consequential, or exemplary damages resulting, in whole or in part, from the readers use of, or reliance upon, this material. Any parts of this book based on government reports are so indicated and copyright is claimed for those parts to the extent applicable to compilations of such works. Independent verification should be sought for any data, advice or recommendations contained in this book. In addition, no responsibility is assumed by the publisher for any injury and/or damage to persons or property arising from any methods, products, instructions, ideas or otherwise contained in this publication. This publication is designed to provide accurate and authoritative information with regard to the subject matter covered herein. It is sold with the clear understanding that the Publisher is not engaged in rendering legal or any other professional services. If legal or any other expert assistance is required, the services of a competent person should be sought. FROM A DECLARATION OF PARTICIPANTS JOINTLY ADOPTED BY A COMMITTEE OF THE AMERICAN BAR ASSOCIATION AND A COMMITTEE OF PUBLISHERS. Additional color graphics may be available in the e-book version of this book. Library of Congress Cataloging-in-Publication Data

LCCN: 2014934032

Published by Nova Science Publishers, Inc. New York

ISBN: (eBook)


CONTENTS

Preface vii

Chapter 1 Polyvalent Lignin: Recent Approaches in Determination and Applications 1 Wanderley Dantas dos Santos, Rogrio Marchiosi, Flvia Carolina Moreira Vilar, Rogrio Barbosa Lima, Anderson Ricardo Soares, ngela Valderrama Parizotto, Dyoni Matias de Oliveira and Osvaldo Ferrarese-Filho

Chapter 2 The DFRC (Derivatization Followed by Reductive Cleavage) Method and Its Applications for Lignin Characterization 27 Fachuang Lu and John Ralph

Chapter 3 Structural Characterization of Lignin by Syringyl to Guaiacyl Ratio and Molecular Mass Determination 67 Frantiek Kak, Jaroslav urkovi and Danica Kakov

Chapter 4 Structural Characterization and Thermal Properties of Enzymatic Hydrolysis Lignins 91 Jia-Long Wen, Sheng Yang, Shao-Long Sun, Tong-Qi Yuan and Run-Cang Sun

Chapter 5 Fully Biodegradable Composites of Poly(butylene Succinate)/ Enzymatic Hydrolysis Lignin: Structure, Thermal and Mechanical Properties 111 Linli Xu, Lingdie Meng, Min Wu, Jiangxin Geng and Yong Huang

Chapter 6 Physicochemical Properties and Potential Applications of Lignins from Various Sources 127 Araceli Garca, Xabier Erdocia, Mara Gonzlez Alriols and Jalel Labidi


Contents vi

Chapter 7 Kraft Lignins from Spent Cooking Liquors: Structural and Biotechnological Application 161 Carmen Fernndez-Costas, Susana Gouveia, Mara ngeles Sanromn and Diego Moldes

Chapter 8 Novel Developments on the Valorization of Lignin-Containing Paper Mill By-Products for the Preparation of Porous Biopolymers 193 Herv Deleuze and Marc Birot

Chapter 9 Kraft Lignin As an Adsorbent to Remove Heavy Metal Ions from Water 231 Marina iban and Mirjana Brdar

Chapter 10 Lignin-Based Thermoplastic Composites and Compatibilization Methods 253 Lei Hu, Tatjana Stevanovic and Denis Rodrigue

Chapter 11 Esterified Kraft Lignin: A Potential Coupling Agent for Wood Plastic Composites (WPC) 283 Nicolas Mariotti, Tatjana Stevanovic, Denis Rodrigue and Xiang-Ming Wang

Chapter 12 Comparison of Physicochemical and Thermal Properties of Esterified and Non-Esterified Kraft Lignins for Biocomposite Application 309 Diane Schorr, Papa Niokhor Diouf and Tatjana Stevanovic

Chapter 13 The Pyrolysis Behavior of Lignins: Contemporary Kinetics Overview 329 Bojan . Jankovi

Chapter 14 Lignin Controls on Soil Ecosystem Services: Implications for Biotechnological Advances in Biofuel Crops 375 Shamim Gul, Sandra F. Yanni and Joann K. Whalen

Index 417


PREFACE As one of the major and crucial components of plant cell walls, the lignin polymer

constitutes about 15 to 25% of woody plants and is the second most abundant renewable bioresource on the earth. Lignins produced on a large scale from the pulping industry are mostly burned to recover chemicals and energy. With the increased interest in converting lignocellulosic biomass to fuels or chemicals, even more lignins could be available, offering considerable opportunity to use this abundant aromatic natural resource for production of chemicals and materials. This book aims to provide updated knowledge and research results on selected topics including analytical methods, structural characterization of lignin preparations, and applications of lignins (such as in bio-absorbents, biocomposites, and soil conditioners).

Advancements in science and technology relating to lignin applications relies on vital and adequate information about lignins themselves, which requires versatile and sophisticated analytical methods specifically for lignins. Many methods have been developed for lignin characterization. The 1992 book, Methods in Lignin Chemistry, edited by S. Y. Lin and C. W. Dence, summarized most of the available analytical methods relating to lignins at that time. Significant advances in lignin analytical methods have been made since then. In particular, advanced NMR techniques in multi-dimensional NMR experiments, as well as improvements in heteronuclear NMR, and the availability of high magnetic field instrumentation with sensitive cryoprobes, can all be applied to tremendously improve our knowledge of lignin structure, as illustrated in the recent book, Lignin and Lignans: Advances in Chemistry, edited by C. Heitner, D. R. Dimmel, and J. A. Schmidt. Meanwhile, traditional degradative methods for lignin analysis still play an important role in lignin-related research and new alternative methods continue to emerge providing new insights into lignin structure and the associated biosynthetic pathways. The Derivatization Followed by Reductive Cleavage (DFRC) method, developed in 1997, is one example of a recent analytical methods for lignin characterization with many unique features. It has been use widely in lignin-related fields and has been briefly reviewed in the past; Chapter 2 in this book now presents the most comprehensive account of the DFRC method and its applications.


Fachuang Lu viii

Lignins composition, functionality, purity, molecular weight and degree of cross-linking, which are highly dependent upon the origins of lignin and the methods used to prepare it, largely determine its physicochemical properties and impinge on the subsequent potential applications. The ratio of syringyl/guaiacyl (S/G) units is commonly used to describe a lignins composition and to predict its reactivity under various processing conditions, whereas the molecular weight and molecular weight distribution of lignin are important characteristics that affect lignins chemical and physical properties. Chapter 3 proposes accurate and reliable methods for analysis of nitrobenzene oxidation products from lignin (for S/G ratio determination) by high performance liquid chromatography and for measurement of lignin molecular mass (and its distribution) by size-exclusion chromatography. Structural characterization and thermal properties of lignins from enzymatic hydrolysis of lignocellulosics, lignins potentially available at large scale from bioethanol production, are given in Chapter 4. Utilization of enzymatic hydrolytic lignins for making biodegradable composites is described in Chapter 5. In Chapter 6, a detailed evaluation is provided on physicochemical properties of lignins from various sources and processing methods. Currently the most available industrial lignin is the kraft lignin produced as a byproduct of the kraft pulping process to produce chemical pulp from wood. Therefore conversion of kraft lignin into various chemicals, materials and liquid fuels has been and still is the focus of research related to utilization of natural polymers. In the past, significant effort has been devoted to research and development in this area with limited success. However, increasing social concerns on the depletion of fossil oil reserves, and the greenhouse effect caused by burning fossil fuels, revives research and innovation activities relating to the use of renewable and carbon-neutral resources including lignocellulosic biomass. Compared to carbohydrates, lignin is structurally more complicated and difficult to utilize effectively. Although there are some lignin-derived products made commercially, mostly from lignosulfonates and used as dispersants, the great potential of lignins (especially kraft lignin and hydrolytic lignin) as renewable feedstocks has not been realized.

This book by no means covers all aspects related to lignin applications; it provides brief reviews on selected applications of lignin (Chapter 1, general; Chapter 13, bio-oils; Chapter 14, soil ecosystems) and recent research results on lignin applications in the areas of environmental science (Chapters 8 and 9), agricultural biotechnology (Chapter 7), and materials science (Chapters 10-12). Specifically, Chapter 1 briefly reviews commonly used methods for detection, characterization, and quantification of lignin as well as various applications of lignins; Chapter 7, deals with kraft lignin structure and its enzymatic modification for applications as biocides, biocomposites, and biosorbents; Chapters 8 and 9 present unpublished results from recent studies on using kraft lignin or porous lignin products to remove pollutants from water; Chapters 10-12 discuss physicochemical and thermal properties of modified kraft lignin, and potential applications of esterified kraft lignin in making biocomposites; Chapter 13 is related to pyrolysis of lignins to produce fuels and chemicals; Chapter 14 reviews the role of lignin in soil ecosystem services. Overall, this book is expected to serve as a textbook for students and a reference for scientists in the field of lignin chemistry and applications.


Preface ix

I sincerely thank the contributing authors for their effort in presenting the updated knowledge and advances in their respective fields. Kindest thanks are also extended to my colleagues John Grabber and Jane Marita from the USDA Dairy Forage Research Center, Maggie Phillips, Steven Karlen, and Alden Voelker from DOE Great Lakes Bioenergy Research Center, University of Wisconsin-Madison, for their reviewing and proof-reading. My special thanks are given to John Ralph for his constructive discussion and suggestions.

Fachuang Lu

Department of Biochemistry and Great Lakes Bioenergy Research Center, The Wisconsin Energy Institute, University of Wisconsin-Madison

1552 University Avenue, Madison, WI 53726, USA Tel: (608) 890-2552

[email protected]


In: Lignin ISBN: 978-1-63117-452-0 Editor: Fachuang Lu 2014 Nova Science Publishers, Inc.

Chapter 1

POLYVALENT LIGNIN: RECENT APPROACHES IN DETERMINATION

AND APPLICATIONS

Wanderley Dantas dos Santos, Rogrio Marchiosi, Flvia Carolina Moreira Vilar, Rogrio Barbosa Lima,

Anderson Ricardo Soares, ngela Valderrama Parizotto, Dyoni Matias de Oliveira and Osvaldo Ferrarese-Filho*

Laboratory of Plant Biochemistry, Department of Biochemistry, University of Maring, Av. Colombo, Maring, PR, Brazil

ABSTRACT

Due to its limited presence in the plant kingdom, lignin has been classified as a secondary metabolite even though it is effectively the second-most abundant biopolymer after cellulose. While absent in bryophytes (mosses, hornworts and liverworts), lignin is an essential component in the cell walls of tracheophytes. Its mechanical resistance and hydrophobicity marked a tipping point in the success of the plants in land environments and, as a result, the success of the whole continental ecosystem (including humans). The mechanical strength of lignin is also the responsible for the rigidity required for larger-sized trees from which our ancestors built weapons, tools, boats and shelters. Even today, lignocellulose is a universal raw material for construction, furniture and metallurgic industries, as well as energy production. Furthermore, lignin is a component of plant defense systems against biological attacks, and an important target of study for areas such as livestock, forage digestibility and production of cellulosic ethanol. Lignin also hinders the production of paper and cellulose, which has been traditionally addressed by using chemical approaches. However, this model is not applicable to bioethanol production and is important because the emergent bioenergy industry must be economically and energetically sustainable. Lignin is a central question in any application involving plant biomass. This chapter reviews the more common methods for detection, characterization

* Corresponding Author address: Email: [email protected].


W. Dantas dos Santos, R. Marchiosi, F. Carolina Moreira Vilar et al. 2

and quantification of lignin as well as biological and industrial applications of this important polymer.

Keywords: Lignification, lignin detection, lignin characterization, lignin quantification, lignin application

INTRODUCTION About 430 million years ago, plants started their challenging journey for conquest of the

continents. This conquest of land remained limited to wet regions until the emergence of tracheas and fibers capable of transporting water to the upper parts of more robust plants. Such anatomical adaptations became possible only after the appearance of lignin, a polymer of phenolic compounds that confers strength to vascular tissues used for water transport [1]. These communities of herbs and trees in forest ecosystems provided a rich and stable environment for heterotrophic evolution, which included primates and hominids. Our ancestors and cousins have been using wood for tools and firewood since the middle of the Pleistocene, about one million years ago [2, 3]. Fire was one of the first human experiences using non-human energy, a mark of the civilization. Fire offered protection and increased the diversity and nutritional power of foods, which seems to have been fundamental to the spread of man out of Africa [4].

Based on the importance of plant biomass for building, clothing, tools, fire, livestock and agriculture in human history it would be absurd not to consider lignocellulosic biomass as the most important source of energy and crude matter for early civilizations. However, since the industrial revolution, fossil fuels, steel and concrete have replaced biomass as a primary source of energy and raw material.

Oil and coal have become the primary sources of energy because of their ready abundance and versatility [5] though the Era of Oil is likely coming to an end. In 1956, M. King Hubbert, chief geology consultant for Shell Co. accurately foresaw a peak in the production rate of conventional crude oil in USA which would occur in less than 20 years [6]. The precision of Hubberts calculation might arguably be an exception when compared with the oil curves from other regions and may not be accurate in predicting all possible technological improvements in surveying and exploring new sources of unconventional oil such as shale, bituminous sand and deep water [7, 8]. However, even considering technological advances, there is an inescapable truth in Hubberts logic: oil is a finite resource and there is increasing evidence that we are living during a plateau in oil production with a low probability of recovery [9]. Moreover, the release of CO2 from the burning of fossil fuels threatens to unbalance the environment in ways which may be more dangerous to the world economy than the decrease in oil production itself [10].

Petroleum will not be able to sustain our level of growth forever. At this time, nuclear energy is also incapable of substituting for oil in meeting our current energy requirements, in addition to being a non-renewable energy source [11]. Thus, a massive investment in new pathways to convert solar energy into useful fuels and crude materials is the last chance to sustain civilization. Plant-derived fuels such as ethanol and biodiesel are renewable resources having a high potential for replacing fossil fuels [11, 12]. Currently, the main sources of biofuels are: 1) ethanol produced by fermentation of soluble sugars such as sucrose and


Polyvalent Lignin 3

hydrolyzed starch, and 2) biodiesel produced from the transesterification of plant oil. Scientific and technological developments have been devoted to creating a second generation of liquid biofuels from lignocellulose. The main focus is upon the hydrolysis of cellulose, a major component of plant residues, which is the simplest to ferment as it is composed exclusively of glucose residues. Other polysaccharides such as hemicelluloses and pectins, are rich in sugars that cannot be fermented by Saccharomyces cerevisiae (common fermenter), although they can be fermented by other yeast strains or genetically modified organisms [11].

Lignin comprises the third part of lignocellulose. Recalcitrant to conventional conversion, lignin is a rich source of energy and its conversion to liquid fuels can be accomplished by thermochemical methods [13]. However, lignin confers resistance to enzymatic digestion of polysaccharides and must be chemically removed to improve the saccharification. Alternatively, highly lignified tissues can be separated for lignin extraction, while less-lignified tissues can be used to saccharification. Apart from a source of energy, lignin has been explored as a versatile crude material for a wide range of applications, which can serve to reduce the costs of cellulosic ethanol. This chapter describes the most frequently applied methods for detection, characterization and quantification of lignin as well as biological and industrial applications.

LIGNIN COMPOSITION In tracheophytes, up to 40% of photosynthetic energy is devoted to lignin synthesis

indicating the importance of lignin to plants and the carbon cycle. Overall, plant fibers contain ~45% carbon, 6% hydrogen and 49% oxygen while lignin is composed of ~65% carbon, 6% hydrogen and 29% oxygen. This distribution reveals the reduced state of lignin carbons, which reflects on its high calorific content.

Lignin is formed by free radical polymerization of mainly three hydroxycinnamic alcohols, which vary in their degree of methoxylation [14], in addition to a diverse set of other minor components. These three precursors or monolignols are p-coumaryl, coniferyl and sinapyl alcohols. After polymerization, these monolignols are converted to structural units called p-hydroxyphenyl (H), guaiacyl (G) and syringyl (S) units respectively (Figure 1). The proportion of each lignin monomer (or unit) can vary throughout the cell wall layers as well as cell wall types, growth stages and plant species. For example, lignins from ferns and straws have less than 10% methoxyl groups, and those from grass culms such as bamboo, sugarcane and coniferous wood, have 14 to 16% methoxyl groups, while lignins from hardwoods contain up to 23% methoxyl groups.

The content of lignin in wood also varies widely, softwoods containing 25 to 50% lignin and hardwoods containing 20 to 25%. Due to its complexity and heterogeneity in plants and tissues, it is very difficult to accurately measure the lignin content in different materials [15]. Moreover, the numerous linkages between the monomers and other cell wall components makes extraction of lignin a clear challenge which, in turn, is crucial for accurate quantification.



Figure 1. A simplified scheme for the synthesis of lignin. PAL, phenylalanine ammonia-lyase; C4H, cinnamate 4-hydroxylase; 4CL, 4-coumarate:CoA ligase; HCT, p-hydroxycinnamoyl-CoA:shikimate/quinate p-hydroxycinnamoyl transferase; C3H, p-coumarate 3-hydroxylase; CCoAOMT, caffeoyl-CoA 3omethyltransferase; CCR, cinnamoyl-CoA reductase; CAD, cinnamyl alcohol dehydrogenase; F5H, ferulate 5-hydroxylase; COMT, caffeic acid 3omethyltransferase; POD, peroxidase. H, p-hydroxyphenyl; G, guaiacyl; S, syringyl.

LIGNIN ANALYSES

Lignin analyses can be divided into three main and distinct groups: detection,

characterization and quantification. Figure 2 summarizes the three groups as well as the most current methods used for these purposes.

Detection Methods Lignin detection aims to determine the presence or absence of this heteropolymer and

also the abundance of structural units in a given sample. Two widely used methods are the Wiesner and Male reactions.


Polyvalent Lignin 5

Figure 2. Current methods for detection, characterization and quantification of lignin.

Wiesner Reaction Phloroglucinol has been widely used by botanists to detect lignin in plant tissues and a

solution of phloroglucinol in strong hydrochloric acid is known as Wiesner reagent. In this reaction, p-hydroxycinnamaldehyde end groups condense with phloroglucinol-HCl to give a characteristic visible color which can vary from red to yellow (Figure 3). Reactions with syringaldehyde, coniferaldehyde and coniferyl and sinapyl alcohols yield red chromophores while vanillin, p-hydroxybenzaldehyde and anisaldehyde produce yellow chromophores [16]. Although the Wiesner reagent is only sensitive for one specific kind of lignin component, this procedure is still often used to detect lignin in plant cell walls [17].

Figure 3. The Wiesner reaction.

Male Reaction In the Male reaction, a sequential treatment with potassium permanganate, HCl and

ammonium hydroxide gives colors that vary from black to beige [18]. Potassium permanganate-HCl converts the guaiacyl (G) and syringyl (S) units into catechol and



methoxycatechol, respectively while the concentrated ammonium hydroxide reacts with the catechols, generating the respective o-quinones (Figure 4). The brown color generated from gymnosperms is due to the presence of the G monomer in the lignin, while in angiosperms, the S unit gives a red color [16].

Histochemical stains have been widely used for lignin detection, however the results require careful analysis due to potential interference from non-lignin compounds or staining reaction errors [19].

Figure 4. The Male reaction.

Ultraviolet Spectroscopy In addition to the Wiesner and Male reactions, another method used for lignin detection

involves ultraviolet (UV) spectroscopy, which is a simple and easy method to detect it. The ability of lignin to absorb light in the UV region comes from the high conjugation degree of the aromatic nucleus, while hydroxyl and ether groups contribute significantly to maximum absorption around 280 nm (Figure 5). However, it is necessary to note that spectral absorption is sample dependent as lignin structure and composition differ between plants and tissues [20].

Figure 5. The ultraviolet (UV) spectrum of 500 L mL-1 lignin obtained from sugarcane bagasse.


Polyvalent Lignin 7

Characterization Methods Lignin characterization is difficult because it is not possible to isolate intact lignin

polymer. Lignin is highly hydrophobic and is not extracted from plant tissues by either aqueous or organic solvents [21]. The characterization of lignin identifies the monolignol, the types of linkages between monomers and the cell wall components.

Analyses for lignin characterization are grouped into degradative or non-degradative procedures (Figure 2). Cupric oxide (CuO) oxidation, nitrobenzene oxidation, thioacidolysis, derivatization followed by reductive cleavage (DFRC method), and Pyrolysis-Gas Chromatography/Mass Spectrometry (Pyrolysis-GC/MS) are degradative techniques. Fourier Transform Infrared Spectrometry (FT-IR), Fourier Transform Raman Spectroscopy (FT-Raman), and Nuclear Magnetic Resonance (NMR) are non-degradative procedures.

Degradative Techniques

CuO Oxidation In this procedure, lignin is oxidized in an alkaline cupric oxide (CuO) solution [22].

Degradation of lignin releases p-hydroxybenzaldehyde from p-hydroxyphenyl (H), vanillin from guaiacyl (G) and syringaldehyde from syringyl (S). The products of CuO oxidation are easy separated and quantified by high-performance liquid chromatography (HPLC) at 290 nm using the corresponding standards (Figure 6). Yields vary from 25 to 35% total lignin, depending upon the plant material.

Figure 6. HPLC chromatogram of phydroxybenzaldehyde (H), vanillin (G) and syringaldehyde (S) standards.

Nitrobenzene Oxidation Under similar alkaline reaction conditions, lignin is oxidized with a nitrobenzene solution

which releases the same kinds of phenolic aldehydes (p-hydroxybenzaldehyde, vanillin and



syringaldehyde) in similar proportions and yields as for CuO oxidation. HPLC is used to separate and quantify these products (Figure 6).

The reaction with nitrobenzene is more aggressive than CuO oxidation and by-products can be produced, though both methods have limitations. Cleavage of the alkyl side chains does not allow for analysis of the interunit linkages of lignin. In addition, the release of phenolic aldehydes from materials other than lignin moieties (p-coumaric and ferulic acids, for example) can affect the accurate determination of lignin monomer composition [16].

Thioacidolysis

The thioacidolysis degradation procedure is widely used because it cleaves various linkages in lignin. This method also provides information about lignin constituents, though monomeric and dimeric products can be observed. The condensed dimers are released by cleavage of alkylaryl ether bonds in lignin. In this procedure, the sample is treated with boron trifluoride etherate in combination with dioxanethanethiol at high temperature. The monomers can be analyzed by gas chromatography after silylation while dimeric products can be analyzed after removal of sulfur substituents by Raney-nickel reduction [23]. The yield of thioacidolysis degradation can reach 50% total lignin, depending upon the plant material.

DFRC Method

In general, the three techniques described earlier are used to estimate the p-hydroxyphenyl (H), guaiacyl (G) and syringyl (S) ratios, which are important to evaluate the lignin monomer composition in different plant materials.

The most frequent interunit linkages in lignin are arylglycerol--aryl ethers (Figure 7) and arylglycerol--aryl ethers [24]. Derivatization followed by reductive cleavage (DFRC method) is based on two highly selective reactions able cleave the ,-ether bonds to produce acetylated lignin monomers [25, 26]. In general, the method provides data similar to those from thioacidolysis degradative technique. The yield of DFRC degradation can reach 97% for models and about 30% for lignins. It is a simple, selective and powerful method to provide detailed information about lignin structure and its monomeric composition [25-27]. A comprehensive review about this method and its applications is included in chapter 2 of this book.

Figure 7. Arylglycerol--aryl ether: the main interunit linkage in lignin.


Polyvalent Lignin 9

Pyrolysis-GC/MS For pyrolysis gas chromatography/mass spectrometry (Pyrolysis-GC/MS), lignin is

rapidly heated in the absence of oxygen and volatile products separated by GC and subsequently identified by MS [16]. This procedure requires a small amount of sample, is highly sensitive in addition to being simple and rapid since the lignin does not need to be isolated [28]. However, it releases only 20% of the total lignin, which makes this procedure disadvantageous for lignin quantitation.

Non-Degradative Techniques

Fourier Transform Infrared Spectrometry (FT-IR)

This technique is used to obtain an infrared absorption spectrum of a material (solid, liquid or gas), relies on the absorption of energy from an illuminating laser and collects spectral data in a wide spectral range. FT-IR identifies different linkages in a complex sample due to the atomic interactions with electromagnetic radiation in a process of molecular vibration and is appropriate for a rapid characterization of lignin in situ. Among other advantages of the FT-IR method are high sensitivity and need for small amounts (nanograms) of dried sample [29].

Fourier Transform Raman Spectroscopy (FT-Raman)

Raman spectroscopy also relies on molecular vibration spectra and is complementary to FT-IR for lignin analysis. In this procedure, it is possible to detect weak bonds and linkages by FT-IR in addition to information about bond types in a complex sample [30]. Similar to the FT-IR technique, FT-Raman identifies sample amounts in the range of nanograms and is capable of analyzing lignin from individual plant cell walls. More recently, other Raman-based analyses have been developed such as Micro Raman, Raman Imaging, Resonance and Preresonance Raman and Surface Enhanced Raman, which provide more information about sample structure with potential applications to lignocellulosic investigations [16].

Nuclear Magnetic Resonance (NMR)

Nuclear Magnetic Resonance (NMR) spectroscopy is a powerful tool used for lignin analysis, especially for providing detailed information on polymer structure. In NMR, the sample is placed in a strong static magnetic field and excited by radiofrequency pulses. Active nuclei such as 1H, 13C or 31P, resonate at a specific frequency providing a spectrum which describes the neighborhood of the nucleus in addition to atom arrangements, allowing the chemical structure and molecular conformation to be resolved.

Through the years, NMR analyses have evolved from simple hydrogen NMR to 3D NMR and, more recently, solid-state NMR which does not require lignin isolation from other cell wall components.

Although the technique yields valuable information about monomer composition and bond types in the lignin molecule, NMR spectroscopy is not suitable for lignin quantification due to overlapping signals that appear on the final NMR spectrum [31].



Quantification Methods Lignin quantification is a basic procedure applied in almost all areas of research and by

business companies where the main raw material is lignocellulosic. However, the quantification of this polymer is difficult, not only because of lignins varying monomeric composition, but also its covalently linkage to cell wall carbohydrates, proteins, phenolics and other compounds [21]. Over time, several methods have been developed and improved to quantify lignin in various plant tissues [32], and although widely used, no consensus exists on which method best represents the real amount of lignin in a sample [16, 32, 33].

Methods of lignin quantification can be divided into two groups: gravimetric and spectrophotometric. Gravimetric methods are based on the separation of lignin followed by weighing while spectrophotometric methods involve the exclusion of possible interfering compounds, solubilization and determination of lignin by light absorbance. The main gravimetric methods are 1) Klason, 2) acid detergent and 3) potassium permanganate oxidation. The main spectrophotometric methods are 1) thioglycolic acid and 2) acetyl bromide.

Gravimetric Methods

Klason Klason is the oldest and most common method used for lignin quantification. It is based

on partial digestion of the sample in 72% sulfuric acid, where the cell wall polysaccharides are dissolved leaving lignin (also called Klason lignin) as the unique insoluble residue [34]. The acid hydrolysis is separated in two phases. The first consists in the treatment of the biomass with 72% H2SO4 at room temperature. In the second stage, distilled water is added to dilute the solution to approximately 3% H2SO4 followed by heating at 120C until complete hydrolysis. Initially developed for gymnosperms species, the Klason method is the global standard method in the pulp and paper industries.

The advantages of this method are reproducibility (if standard conditions are strictly followed), simple and easy to handle equipment, and low cost. However, the technique has serious limitations arising from the presence of interfering compounds not belonging to lignin such as ash, phenol aldehyde polymers, tannins, Maillard polymers, cutin, waxes and protein can result in the overestimation of Klason lignin [35]. When applied to herbaceous samples, the Klason method seems to be most negatively affected by the high protein content and concentrations of cutin and waxes which are usually present in the leaves of forage plant [32]. It is also important to note that a fraction of lignin, especially from hardwood samples, is soluble in sulfuric acid and must be estimated by UV spectrophotometry [22].

Acid Detergent Lignin

The acid detergent lignin method developed by Van Soest [36] is widely used in animal and agricultural studies for analysis of protein-rich forage samples in an attempt to minimize errors found with the Klason method. In this procedure, crude sample is initially treated with an acid detergent solution such as acetyl trimethylammonium bromide, to form acid detergent fibers which are then treated with 72% acid sulfuric, forming an insoluble residue called acid


Polyvalent Lignin 11

detergent lignin [35]. Although the acid detergent lignin method removes part of the protein content and other interfering substances, lignin is partially solubilized by the acid detergent solution leading to an underestimation of the total lignin content [37]. In tropical grasses, the loss rate of soluble lignin can reach 50% and also values from 2 to 4 times lower were found when compared the acid detergent lignin to the Klason method [38, 39]. These results suggest that Klason is better than the acid detergent lignin method for grasses, although the lower loss of lignin with this method depends of the type of material and cell wall preparation [40, 41].

Potassium Permanganate

The potassium permanganate method is used to obtain the Kappa number, which indicates the residual lignin content or bleachability of wood pulp [42]. In this procedure, the lignin concentration is expressed as the amount of oxidant per unit weight of pulp, and the results can be converted to Klason lignin using conversion factors [22]. Since there is a direct correlation between Kappa number and Klason lignin content, this method is traditionally used by the pulp and paper industry. The potassium permanganate method was originally developed by Van Soest and Wine [43] to quantify lignin in forage and herbaceous samples, and applied in animal nutritional science to correlate lignin content with digestibility [33]. It deals with acid detergent sample preparations to obtain the acid detergent fiber which is oxidized by the potassium permanganate solution. After oxidation, the insoluble residue is washed, dried, weighed and the lignin content calculated as the loss in weigh from the initial acid detergent fiber. The potassium permanganate method is an alternative to the sulfuric acid method. It has some advantages such as the possibility to determine cellulose content at the same sample, and it is a fast method which employs less corrosive chemical compared to the sulphuric method [43]. Nevertheless, the permanganate solution can oxidize phenolic and unsaturated compounds (e.g., tannins, pigments, proteins) which are not removed by the acid detergent preparation step, and may lead to an overestimation of the final lignin content [33].

Spectrophotometric Methods

Thioglycolic Acid Once solubilized, lignin can be spectrophotometrically measured [34]. Thioglycolic acid

is able to acid-displace covalent bonds between lignin and cell wall components leading to formation of thioether benzyl alcohol groups, also known as lignothioglycolic acid (LTGA) (Figure 8). After the reaction with thioglycolic acid, the LTGA is extracted from the cell wall with a NaOH solution, precipitated by the addition of concentrated HCl and subsequently dried at 60oC. The LTGA complex is soluble in alkali solution and absorbs at 280 nm. This procedure was initially developed for wood samples, but has been employed to isolate and quantify lignin in plant species such as Glycine max, Nicotina tabacum and Oriza sativa [44-48]. The authors report that this method excludes phenolic compounds that do not belong to the lignin polymer and also eliminates interference from polysaccharides. However, thioglycolic acid reacts specifically with the ether bonds of lignin, which links monomers through their propanoid moieties. Because of this, the thioglycolic acid method can underestimate the real content of lignin. Furthermore, the formation of soluble lignin that remains in the acid solution is a source of discrepancy [32].



Figure 8. The thioglycolic acid reaction (adapted from Hatfield and Fukushima, 2005).

Acetyl Bromide The acetyl bromide method also relies on lignin solubilization and spectrophotometric

determination, but unlike the thioglycolic acid procedure, reaction with 25% acetyl bromide/acetic acid solution for 30 min both extracts and solubilizes lignins, which makes this a rapid technique and with less probability of experimental errors. By this method, acetyl derivatives of unsubstituted OH groups within the lignin polymer and the bromide replacement of -carbon OH groups produce acetylate/brominated lignin that is soluble in acetic acid (Figure 9). The acetyl bromide method is more appropriate for small samples; the formation of non-lignin products is low and this technique has been assumed to yield precise absorbance values, which reflect the real lignin content [49]. Notwithstanding, questions about its accuracy have been raised with respect to the complete solubilization of lignin in the acetyl bromide/acetic acid solution, as well as polysaccharide degradation to furfurals, which can potentially interfere with the lignin value [50, 51]. Lignin solubilization in the acetyl bromide solution seems to be suitable to lignin quantification and does not require addition of any further chemical, as speculated for the perchloric acid, in an attempt to improve cell wall degradation [51]. However, spontaneous carbohydrate degradation can occur during the procedure and, in an effort to minimize interference, proposed adjustments include lowering the temperature to 50C and increasing the reaction time to 2 h [51].

The formation of furfurals can differ between samples and changes in temperature, and reaction time may not be necessary depending on lignin content of the sample. In order to address this problem, our research group evaluated the accuracy of the most commonly used methods for lignin determination comparing/contrasting the amount and quality of lignin (S:G ratio) as well as the amount and quality of polysaccharides [15]. After finding widely variable amounts in lignin content measured by the different methods, the potential causes of the discrepancies among methods were investigated. The data indicated that the Klason method underestimated the lignin content in lignin-poor tissues, the thioglycolic method underestimated lignin content due to an incomplete extraction and loss of solubilized lignin throughout the process of extraction while the acetyl bromide method provided a reproducible



determination of lignin in all tissues. The acetyl bromide method used in the experiments followed the same conditions of temperature (70C) and reaction time (30 min) reported in the 1972 paper that introduced this technique for the scientific community. The production of furfurals was proportional to the amount of polysaccharides (inversely proportional to lignin content), but their interference was significant only in tissues with less than 15% lignin. When compared to other methods, the practicality and reliability of the acetyl bromide method indicates it is the preferred method for lignin quantification [15].

Figure 9. The acetyl bromide reaction (adapted from Hatfield and Fukushima, 2005).

LIGNIN APPLICATIONS

Approximately one million tons of lignin are generated from pulping and papermaking

processes every year, but only 1-2% is used in specialty products [52]. This is because lignin is considered a waste product and is mainly used as a fuel for pulping boilers or in the conversion of biomass to ethanol, where the lignin is used as a fuel source for driving the fermentation process [53]. The pulping process itself may change the properties of the lignin obtained. The pulping processes utilized most frequently to obtain lignin from biomass are the sulfite and Kraft methods [54]. Kraft lignin accounts for about 89% of the production of chemical pulps, is obtained by pulping in an alkaline medium and is insoluble in water [55]. The sulfite process produces sulfonated lignins which are soluble in water containing suitable counter ion (Na+, Ca2+, Mg2+ etc) due the presence of a sulfonic acid linked to the backbone of lignin. Currently, a new class of sulfur-free lignins can be obtained by solvent pulping/organosolv processes and soda pulping of agricultural crop residues [52]. Sulfur-free lignins are water insoluble at neutral or acidic pH, but soluble in alkaline solutions or organic solvents. Figure 10 shows the most common biological and industrial applications of lignin.



Figure 10. The most common biological and industrial applications of lignin.

Biological Applications of Lignin

The increased global demand for food requires greater efficiency in agriculture, which

has resulted in the extensive use of agrochemicals to control pests such as insects, fungi and weeds. However, 90% of herbicides applied to control an infestation will not reach the target, but they will contaminate air, water and foods [52] affecting the human health and environment [53]. Furthermore, the efficiency of pesticides is associated with the applied concentrations and contact times with the pest. If the pesticide is rapidly degraded when exposed to environmental conditions, its effectiveness is also drastically reduced.

The utilization of controlled release formulations (CRFs) of pesticides emerged as an attempt to resolve the problems of environmental pollution and loss of activity. The CRFs allow the release of pesticides at a given rate and maintain the concentration within optimal limits for a given period of time. When developing CRFs, the material utilized for pesticide encapsulation should be degradable by microbial decomposers or by environmental factors such as light, water, heat, oxidation, wind and rain. The materials most widely utilized for the encapsulation of pesticides are natural polymers (starch, ethyl cellulose, lignin and alginate) which are preferred to synthetic polymers due to their low cost and biodegradability. They are classified according to the degree of biodegradation: 1) starch and systems based on amylose; 2) other polysaccharides; 3) proteins; 4) rubber and waxes; 5) synthetic polymers; 6) miscellaneous lignins, resins and biopolymers modified by substitution [56].

Among these matrices, cellulose and lignin, which are the most abundant. Lignin degrades more slowly than polysaccharides. Because of this, Kraft lignin has been used for encapsulation of a large number of pesticides (2,4-D [57], bromacil [58], diuron [59], and fluometuron [60]), particularly those with high mobility in soil and those which are considered groundwater pollutants (chloridazon and metribuzin) [61].



Of the available methods for producing lignin-based CRFs, the formation of a solid matrix is the simplest and most advantageous [55]. Certain pesticides have the ability to dissolve Kraft lignin when heated to the melting point, though if dissolution is not possible, a melting agent (glycerol) is added. After cooling, a matrix is formed from which the pesticide is slowly released by diffusion. In the other methods, the active ingredient is bonded to lignin or retained in materials modified by cross-linking. Therefore, there are two possible mechanisms for releasing pesticides in formulations based on lignin: 1) diffusion of the active ingredients through the matrix, and 2) hydrolysis of ester bonds formed between the phenolic groups in the lignin and carboxyl groups of the active ingredient during the formulation process [58]. The first mechanism applies to the diuron (from commercially available pine Kraft lignin) [59] and both mechanisms can be found in lignin based CRF for 2,4-D[57].

In a recent study, chlordazon and metribuzin (herbicides) were incorporated into granules of different sizes composed of pine Kraft lignin and the release kinetics in water and soil mobility were evaluated [61]. The CRF granules were produced by mixing each herbicide with pine Kraft lignin at a 1:1 ratio (w:w) under melting conditions and the resulting matrix are triturated and sieved to obtain granules of different sizes (0.5 to 3.0 mm). The CRF granules reduced the release rate of both herbicides in water compared to conventional formulations and a reduction in the quantity of herbicides in soil leachates was also observed, demonstrating that the utilization of CRFs might reduce environmental pollution caused by these herbicides. Release rate was found to be dependent on granule size, with the larger granules releasing at lower rates. Very similar results were obtained for the encapsulation of Isoproturon, Imidacloprid and Cyromazine (all systemic pesticides) with pine Kraft lignin [62]. Additives are often added to CRFs because they improve the physical properties of the formulations and affect the kinetics of release. For example, the addition of urea to CRFs allows the use of a minimum amount of pesticide due to the solvation of lignin. Furthermore, urea is an inexpensive and environmentally safe soil fertilizer. The addition of urea increased the release of Diuron from pine Kraft lignin matrix [59] due to the formation of pores resulting from the rapid dissolution of urea.

Lignin, besides being an anti-oxidant compound and good sorbent for pesticides, also absorbs UV light. This feature is the basis for the enhancement of biological pest control used as an alternative to chemical control. The use of natural pathogens for insect control dates to 1839, when V. Audouin reported the case of a sericulturist that noted the death of defoliant larvae days after discarding silkworms infected with fungus in the vicinity of infested trees [63]. Granuloviruses and nucleopolyhedrovirus constitute a large group of viruses that included the major pathogens for a variety of insects and have been used in developing of microbial pesticides. Although they are less harmful to the environment than chemical pesticides and suitable for integrated pest management, their very sensitivity to UV light (280-320 nm) limits the development of commercially viable microbial pesticides. In one study, it was found that granuloviruses encapsulated with sodium lignin were more stable in sunlight during field tests conducted on infested apple trees [64]. Therefore, a lignin-based matrix can provide protection from UV light for some types of virus used to control agricultural pests. Although lignin-based formulations have been effective only with high virus dosages, virus encapsulation appears to be an alternative to frequent virus reapplications due to short residual activity.



Industrial Applications of Lignin

Utilization of Lignin in the Production of Carbon Fiber Carbon fibers have been used as reinforcing materials since the 1950s. The carbon fibers

are synthesized by a carbonization process, where a precursor fiber is thermally treated. The high stiffness, high tensile strength, high modulus, and low weight of carbon fibers makes them ideal for use in sports equipment, construction, aircraft and the automotive industry [65]. Indeed, the use of carbon fibers in the automotive industry has reduced the weight of vehicles with a consequent reduction in fuel consumption and CO2 emission [66]. On the other hand, carbon fibers are produced from polyacrylonitrile (PAN), petroleum and coal based materials and rayon. The high cost of raw materials associated with the high cost of production, makes carbon fibers a very expensive material (20 times more expensive than steel) which limits wide use in automotive industry. Furthermore, some of these are nonrenewable materials. Nevertheless, approximately 50,000 tons of carbon fibers are used annually world-wide [67] and new cheaper and renewable precursors that can replace petroleum are desirable.

A high-volume of lignin is obtained from paper production that, besides being underutilized, is a low-cost renewable material. In order to reduce the production cost for carbon fibers, researchers have incorporated lignin into these fibers. Kayacarbon (Nippon Kayaku Co in Japan) was the first lignin-based carbon fiber manufactured and the only one commercially available. Kayacarbon fibers were produced from lignosulfonate with polyvinyl alcohol added as a plasticizer, however, the low quality of these fibers led to discontinuation of its manufacture. More recently, some specifications required for the use of lignin as a precursor for carbon fiber manufacture were recognized in a study at the Oak Ridge National Laboratory [68]. Considering the abundance of lignin in nature and the increase in lignin production as a residue of the emergent cellulosic ethanol industry, lignin might be the key to overcome the cost-limiting factors of carbon fibers.

Utilization of Lignin in Plastics

Plastics (from Greek plastikos meaning able to be molded in different forms) are primarily thermoplastic or thermosetting synthetic organic polymers derived from petroleum that can be used to produce a wide variety of objects [69]. Although plastics, especially polyolefins, have desirable properties such as low cost and durability, they are not easily degraded by biotic and abiotic factors. This is due to their barrier properties (that prevent the attack by enzymes secreted from microorganisms) and high molecular weights (which limits entry into the cells of microorganisms for degradation by intracellular enzymes) [70]. Furthermore, as plastics were recently created by man, evolution has not had sufficient time to select for enzymes capable of degrading them [71].

In this context, the incorporation of lignin into plastics in order to increase their biodegradability has shown good results. The Jack pine Kraft lignin obtained from black liquor by precipitation with acid was used for the first time to produce 85% Kraft lignin-based plastic containing 12.6% 90,000 molecular weight polyvinyl acetate, 1.6% diethyleneglycol dibenzoate and 0.8% indene [72]. The results show that Kraft lignin-based thermoplastics have high tensile strength that varies linearly with the molecular weight. The results also



suggest that Kraft lignin-based plastics can be extrusion-molded, as determined by melt-flow index measurements.

An interesting study was conducted in order to produce a plastic/moldable lignin without the need for synthetic resins [73]. For this, softwood Kraft lignin (Indulin AT, Mead Westvaco) was modified by reaction with benzyl chloride and the benzylated lignin was injection-molded into bars and discs at 180C. The results showed that the benzylated lignin had similar properties to common plastics and wood-plastic composites.

Utilization of Lignin in Phenolic Resins

Phenolic resins are derived from the reaction of formaldehyde and phenol, wherein water is produced as a by-product [74]. Phenol is conventionally synthesized from benzene and propylene [75], in a three-step procedure named the cumene-based co-product acetone process [53]. Phenolic resins are widely used in the construction of oriented strand-board, furniture coatings (Formica), manufacture of pulleys, cable pans, and friction products such as automotive brake pads. However, phenolic resin components are derived from petrochemicals, nonrenewable materials that could be replaced by lignin (which contains large amounts of phenolic groups) for the production of alternative environmentally-friendly materials.

In a study, methanol-soluble lignin extracted from soda-lignin (Harima Chemicals) was incorporated into phenolic resins used in the manufacture of brake friction materials [76]. Phenolic resins containing 25-75% lignin (w:w) were produced by polymer blend methods (solvent blend and in situ polymerization). Results showed that the incorporation of lignin improved the fade resistance, as the products of lignin degradation did not become liquid on the friction surface since they were cross-linked by the heat of friction.

In another report, residues rich in activated lignin obtained from lignocellulosic ethanol production (ER) were utilized at 10 to 70% to replace phenol in the production of lignin-phenol-formaldehyde (LPF) adhesive [77]. The LPF adhesives were prepared by mixing and heating lignin, phenol and formaldehyde for 1 h at 80C and (among other parameters) the amount of free phenol, free formaldehyde and bonding strength were evaluated. The results showed that increased substitution reduced the free phenol, increased the free formaldehyde and reduced bonding strength in LPF adhesives, especially at 70% lignocellulosic ethanol residues. The incorporation of lignin into phenolic resins can be economically feasible, considering that approximately 30.6% of the global phenol production, an estimated $107 billion, is used in the synthesis of such materials [53].

Utilization of Lignin in Epoxy Resins

The most widely used epoxy resins are diglycidyl ethers of bisphenol-A obtained through the reaction of bisphenol A with epichlorohydrin [78]. Currently, these resins are used in fiberglass and carbon fiber materials, buildings (industrial floor coatings and concrete crack repair), the inner lining of beer and soft drink containers, and in the making of costume jewelry and prototypes (models and molds). The presence of hydroxyl groups in the lignin structure allow for its use in replacing the bisphenol-A in the synthesis of epoxy resins, in addition to providing greater stiffness and better thermal properties to the resin [79]. Indeed, significant amounts of lignin (


innovation. The incorporation of lignin (obtained from Kraft pulping mills in the United States and Europe or organosolv pilot-scale pulping mill in Canada) into PWB reduced the total energy required for production by 40%, without modifying physical and electrical properties. The incorporation of lignin into PWB may also have an important environmental role. Epoxy resins are synthesized from petroleum derivatives which, besides being unrecyclable, when incinerated contribute to the increase in the atmospheric CO2, and consequently to global warming. As raw material, the use of lignin reduces the demand for petroleum derivatives and the environmental impact associated to incineration. The total energy requirement for production of PWB includes its process, transport and material resource. The main energy sources used are natural gas, petroleum, coal, and non-fossil fuels (electricity and wood energy used in the pulp and paper industry). During the production of organosolv lignin/epoxy and kraft lignin/epoxy resins the requirement for non-fossil energy increased from 0.7 to 1.24 and 2.33 GJ per 100 Kg of solids resins, respectively. On the other hand, the total fossil energy requirement decreased from 17.1 to 10.6 and 9.76 GJ during the production of the Kraft lignin/epoxy and organosolv lignin/epoxy resins, respectively [77].

Utilization of Lignin in Polyurethane Foams

Polyurethanes are produced by the reaction of an isocyanate (di or polyfunctional) with a polyol (such as polyethylene adipate) in the presence of other reagents such as catalysts, chain extenders, blowing agents, and surfactants. Polyurethane foams are utilized in the manufacture of mattresses, upholstery, car seats, dashboards, bumpers, shoes, and insulation for refrigerators, freezers, and refrigerated trucks. Due to the phenolic structure of lignin, it can be used to replace the polyols used in the manufacture of polyurethanes. Hardwood organosolv ethanol lignin (HEL) (Lignol Innovation, Vancouver, Canada) and hardwood Kraft lignin (HKL), prepared from the black liquor (Westvaco, Covington, VA), were used to replace petroleum-based polyols in the production of rigid polyurethane foams (RPFs) [80]. The foams had satisfactory structure and strength when HKL or HEL was added. However, the greater miscibility of HEL with the polyol (compared to HKL) allowed their use in higher proportions (25-30%) compared with HKL (19-23%), without affecting the properties of the foam. Polyurethane foams lose weight during exposure to elevated temperatures due to the generation of toxic volatile compounds, an undesirable feature. A reduction in weight loss was improved by producing foams containing soda-lignin from yellow poplar (Liriodendron tulipifera), which emitted 34 times less volatile compounds than conventional foams [52].

Utilization of Lignin in Concrete

Concrete is a mixture of Portland cement, water, fine aggregate (sand) and coarse aggregate (gravel) which may also contain chemical additives. When mixed, a quantity of water greater than that required to hydrate its components is used and during hardening of the concrete, the excess water remains, leading to the formation of cavities which reduce the strength of the concrete. Concrete properties, such as strength, permeability and drying, may be improved by addition of water-reducing agents whose main function is to increase the fluidity of concrete by dispersing cement particles in paste [81].

Several compounds, such as sulfonated melamine formaldehyde condensates and naphthalene formaldehyde condensates, has been used for this purpose [82]. However, the wide utilization of these compounds is impaired by high cost and the toxicity of naphthalene.



Moreover, there is a growing demand for replacing water-reducers (such as naphthalene) derived from petroleum, due to the shortage of oil and global warming [83].

Although lignosulfonates (main component in the liquid waste from chemical pulp mills) have been used in concrete for decades, their water-reducing capacity is small, at best reducing the water used only by 8 to 10% [84]. Considering that only 10% of the 50 million tons of lignosulfonates produced annually are used [85], researchers are introducing modifications in order to improve their water-reducing properties. In this context, calcium lignosulfonate from sulfite pulping (from Guangzhou Papermaking Co. Ltd, China) was modified by oxidation and sulfonation to improve its water-reducing property [85]. The results showed a stronger wetting capacity for modified lignin compared to non-modified lignin. Furthermore, the lignin-based concrete exhibits flexibility and compressive strength comparable to that produced with formaldehyde condensates, which indicates calcium lignosulfonate could be used as a water-reducer. Currently, there are several companies that produce lignin derivatives for use as lignin-based concrete admixtures (Borregaard LignoTech, Pure Lignin Environmental Technology, LignoTech South Africa, LignoTech Brazil, Domtar and LoroyMan among others).

Utilization of Lignin in Asphalt Admixtures

The aging of asphalt pavement is directly related to its hardening due to oxidation. Retarding the oxidative aging of pavement would maintain the elastic properties, preventing cracking due to loads and temperature. Asphalt cement is composed of asphaltenes, saturates, naphthalene and polar aromatics, with each fraction interacting with the others to provide different properties to the asphalt. Exposure to atmospheric oxygen leads to the generation of oxygen-containing functional groups which can cause aggregation among asphalt molecules due to the formation of hydrogen bonds and van der Waals interactions [86]. Although many chemical agents (such as styrene-butadiene-styrene and styrene-b-butadiene) have been used to prevent the oxidative aging of asphalt, the majority do not yield satisfactory results. On the other hand, promising results have been obtained by the addition of lignin to asphalt mixtures as the hydroxyl groups attached to the benzene rings can act as antioxidants. In a study, two types of coniferyl-alcohol lignin were mixed with asphalt at 130C and subjected to different temperatures (130 and 150oC) in order to evaluated the anti-oxidant effect [86]. The results show that coniferyl-alcohol lignin had significant antioxidant activity at 130C that was lost when the temperature reached 150C due to its oxidation to vanillin and glycolaldehyde. The authors concluded that coniferyl-alcohol lignin can be used as an antioxidant for asphalt mixtures under conditions where the lignin does not undergo oxidation.

Other Applications

Lignin has been used to immobilize proteins, increasing the lifetime of enzymes [87]. Researchers at the University of Kansas (USA) used calcium lignosulfonate (CaL) obtained from Borregaard Lignotech (USA) to improve the cohesion of soil particles in unpaved roads. According to the researchers, more than 70% of the 98,000 miles of roads in Kansas are unpaved roads, and erosion caused by wind and traffic are frequent problems. According to the authors, lignin represents an environmentally-friendly solution compared to the use of other soil stabilizers such as ash or ground Portland cement type I, which are soil contaminants [88]. Beyond dust control for roads, lignin has been similarly used in coal mines and coal transportation.



Lignin depolymerization is also important for the production of chemicals such as guaiacol, vanillin, catechol, pyrocatechol, and syringol [89]. Furthermore, lignin improves the performance of energy storage devices (batteries) [90] and Wood pellets with better fuel value can be produced by addition of lignin [91]. Additionally, sulfonated lignins are used as thickeners, producing greases with higher lubricating properties which increase corrosion protection and provide greater resistance to tool wear [92].

CONCLUSION Human history could be divided into Ages, named according to the main raw material

that enriched life and resulted in technological advances - the Stone Ages (Paleolithic, Mesolithic and Mesolithic) and Metal Ages (Copper, Bronze and Iron Ages). Of course, the fast and concomitant advances in agriculture, politics, writing and engineering make this simplification more difficult and imprecise. However, at the end of the 19th century, a remarkable change occurred. Our ancestors had made use of simple machines [93] and energy from animals/fire for some time, but steam engines joined them together. Even more important, throughout the Industrial Revolution, coal-powered steam machines were used to remove water from mines in order to produce more coal. In other words: a machine was used to produce energy. Since then, the technological advances have been marked not only by the production of consumer goods, but also by the production of more and more energy. Remarkably: fossil energy as oil, coal and gas. Since all our technological symbols (steel, plastic, electronics or cars) are essentially dependent on fossil fuels, it would be reasonable to name our time as the Age of Fossil Fuels.

However, due either to global warming or the increasing cost of oil, this Age is giving signs that it is coming to an end [94]. It quite clear that biomass is the only source of energy that can replace oil [11]. This review shows that biomass is able to serve as much more than fuel. Lignin cannot be directly converted into liquid fuel and does impose an additional barrier to the production of ethanol from cellulose. On the other hand, lignin can (partially) substitute (with advantages) for other raw materials in the production of items iconic of modern civilization, from plastics and steel to the production of carbon fibers and epoxy resins.

REFERENCES

[1] Boundet AM. Lignins and lignification: selected issues. Plant Physiology and Biochemistry. 2000;38:81-96.

[2] Berna F, Goldberg P, Horwitz LK, Brink J, Holt S, Bamford M, et al. PNAS Plus: Microstratigraphic evidence of in situ fire in the Acheulean strata of Wonderwerk Cave, Northern Cape province, South Africa. Proceedings of the National Academy of Sciences. 2012;109(20):E1215-E20.

[3] Breuer T, Ndoundou-Hockemba M, Fishlock V. First observation of tool use in wild gorillas. PLOS Biology. 2005;3(11):2041-3.



[4] Alperson-Afil N, Goren-Inbar N. The Acheulian Site of Gesher Benot Ya'aqov Volume II: Ancient and Controlled Use of Fire. PaleoAnthropology. 2010:83-4.

[5] Buckeridge MS, Goldman GH, editors. Routes to cellulosic ethanol. New York: Springer; 2011.

[6] Hubbert MK. Nuclear energy and the fossil fuels. Shell Development Company, Exploration and Production Research Division. 1956.

[7] Brandt AR. Testing Hubbert. Energy Policy. 2007;35:3074-88. [8] Maugeri L. Oil: The next revolution. Belfer Center for Science and International

Affairs, Harvard Kennedy School. 2012. [9] Aleklett K, Qvennerstedt O, editors. Peeking at the peack oil. New York: Springer;

2012. [10] IPCC. Climate Change 2007: Synthesis Report - Contributions to the Fourth Assesment

Report. Valencia, Spain2007. p. 52. [11] Silva C. Escalando o Monte Terawatt. In: Cortez L, editor. Bioetanol de cana-de-

acar. P&D para a Produtividade e Sustentabilidade. So Paulo: Blucher; 2010. [12] Buaban B, Inoue H, Yano S, Tanapongpipat S, Ruanglek V, Champreda V, et al.

Bioethanol production from ball milled bagasse using an on-site produced fungal enzyme cocktail and xylose-fermenting Pichia stipitis. Journal of Bioscience and Bioengineering. 2010;110(1):18-25.

[13] dos Santos WD, Gomes EO, Buckeridge MS. Bioenergy and The Sustainable Revolution. In: Buckeridge M, Goldmann G, editors. Routes to Cellulosic Ethanol. New York: Springer; 2011. p. 15-26.

[14] Vanholme R, Morreel K, Ralph J, Boerjan W. Lignin engineering. Current Opinion in Plant Biology. 2008;11(3):278-85.

[15] Moreira-Vilar F. Comparao entre mtodos de determinao de lignina em tecidos vegetais. Maring: University of Maring; 2012.

[16] Dean J. Lignin analysis. In: Dashek W, editor. Methods in plant biochemistry and molecular biology. Boca Raton: CRC Press; 1997. p. 199-215.

[17] Tomnkov K, Luhov L, Petivalsk M, Pe P, Lebeda A. Biochemical aspects of reactive oxygen species formation in the interaction between Lycopersicon spp. and Oidium neolycopersici. Physiological and Molecular Plant Pathology. 2006;68(1-3):22-32.

[18] Nakagawa K, Yoshinaga A, Takabe K. Anatomy and lignin distribution in reaction phloem fibres of several Japanese hardwoods. Annals of Botany. 2012;110(4):897-904.

[19] Lewis NG, Yamamoto E. Lignin: Occurence, biogenesis and biodegradation. Annual Review of Plant Physiology and Plant Molecular Biology. 1990;41:455-96.

[20] Todorciuc T, Capraru A-M, Kratochvlov I, Popa VI. Characterization of non-wood lignin and its hydroxymethylated derivatives by spectroscopy and self-assembling investigations. Cellulose chemistry and technology. 2009;43:399-408.

[21] Zobiole LHS, dos Santos WD, Bonini E, Ferrarese-Filho O, Kremer RJ, Oliveira-Jr RS, et al. Lignin: From nature to industry. 2012. In: Lignin: Properties and applications in biotechnology and bioenergy [Internet]. New York: Nova Science Publishers.

[22] Brunow G. Methods to reveal the structure of lignin. In: Hofrichter M, Steinbchel A, editors. Lignin, humic substances and coal. 1. Weinheim: Wiley-VHC; 2001. p. 89-116.



[23] Lapierre C, Pollet B, Monties B, Rolando C. Thioacidolysis of spruce lignin: GC-MS analysis of the main dimmers recovered after Raney nickel desulphuration. 1991;45(1):61-8.

[24] Adler E. Lignin chemistry - past, present and future. Wood Scince Technology. 1977;11:169-218.

[25] Lu F, Ralph J. Derivatization followed by reductive cleavage (DFRC method), a new method for lignin analysis: Protocol for analysis of DFRC monomers. Journal of Agricultural and Food Chemistry. 1997a;45:2590-2.

[26] Lu F, Ralph J. DFRC method for lignin analysis. 1. New method for -Aryl ether cleavage: Lignin model studies. Journal of Agricultural and Food Chemistry. 1997b;45:4655-60.

[27] Peng J, Lu F, Ralph J. DFRC method for lignin analysis. 4. Lignin dimers isolated from DFRC-degraded loblolly pine wood. Journal of Agricultural and Food Chemistry. 1998;46:553-60.

[28] Galletti G, Bocchini P. Pyrolysis/gas chromatography/mass spectrometry of lignocellulose. Rapid Comunications in Mass Spectrometry. 1995;9:815-26.

[29] Derkacheva O, Sukhov D. Investigation of Lignins by FTIR Spectroscopy. Macromolecular Symposia. 2008;265(1):61-8.

[30] Agarwal U, Atalla R. Vibrational spectroscopy In: Heitner C, Dimmel D, Schmidt J, editors. Lignin and Lignans: Advances in Chemistry. New York: CCR Press; 2010.

[31] Ralph J, Landucci L. NMR of lignin In: Heitner C, Dimmel D, Schmidt J, editors. Lignin and Lignans: Advances in Chemistry. New York: CCR Press; 2010.

[32] Hatfield R, Fukushima RS. Can Lignin Be Accurately Measured? Crop Science. 2005;45(3):832.

[33] Fukushima RS, Hatfield RD. Coparison of the acetyl bromide spectrophotometric method with other analytical lignin methods for determining lignin concentration in forage samples. Journal of Agricultural and Food Chemistry. 2004;52:3713-20.

[34] Browning BL, editor. Methods of wood chemistry. New York: Wiley-Interscience; 1967.

[35] Goering GK, Soest PJV, editors. Forage Fiber: Analisys, apparatus, reagents, procedures and some applications. Washington: Agricultural Handbook; 1970.

[36] Soest PJV. Use of detergents in the analysis of fibrous foods. II A rapid method for the determination of fiber and lignin. Journal of the association of official analytical chemists. 1963;46:829-35.

[37] Kondo T, Mizuni K, Kato T. Some characteristics of forage plant lignin. Japanese Agricultural REsearch Quarterly. 1987;21:47-52.

[38] Lowry JB, Conlan AC, Schlink AC, Mcsweeney CS. Acid detergent dispersible lignin in tropical grasses. Journal of the Science of Food and Agriculture. 1994;65:41-9.

[39] Jung H, Buxton D, Hatfield R, Mertens D, Ralph J, Weimer P. Improving forage fibre digestibility. 1996;4:30-4.

[40] Sewalt V, Glasser W, Fontenot J, Allen V. Lignin impact on fibre degradation. 1 Quinone methide intermediates formed from lignin during in vitro fermentation of corn stover. Journal of the Science of Food and Agriculture. 1996;71:195-203.

[41] Hatfield R, Jung H, Ralph J, Buston D, Weimer P. A comparison of the insoluble residues produced by the Klason lignin and acid detergent lignin procedures. Journal of the Science of Food and Agriculture. 1994;65:51-8.



[42] Tasman J, Berzins V. The permanganate consumption of pulp materials. I Development of a basic procedure. Tappi. 1957;40:691-4.

[43] Soest PV, Wine R. The determination of lignin and cellulose in acid detergent fibre with permanganate. Journal of the Association of Official Analytical Chemists. 1968;52:780.

[44] Brinkmann K, Blaschke L, Polle A. Comparison of different methods for lignin determination as a basis for calibration of Near-infrared reflectance spectroscopy and implications of lignoproteins. Journal of Chemical Ecology. 2002;28(12):2483-501.

[45] Capeleti I, Ferrarese M, Krzyzanowski F, Ferrarese-Filho O. A new procedure for quantification of lignin in soybean (Glycine max (L.) Merrill) seed coat and their relationship with resistance to mechanical damage. Seed Science and Technology. 2005;33(2):511-5.

[46] dos Santos WD, Ferrarese MLL, Nakamura CV, Mouro KSM, Mangolin CA, Ferrarese-Filho O. Soybean (Glycine max) Root Lignification Induced by Ferulic Acid. The Possible Mode of Action. Journal of Chemical Ecology. 2008;34(9):1230-41.

[47] Suzuki S, Suzuki Y, Yamamoto N, Hattori T, Sakamoto M, Umezawa T. High-throughput determination of thioglycolic acid lignin from rice. Plant Biotechnology. 2009;26:337-40.

[48] Freudenberg K, Neish A, editors. Constitution and Biosynthesis of Lignin. Berlin: Springer-Verlag; 1968.

[49] Dence C. The determination of lignin. In: Lin S, Dence C, editors. Methods in Lignin Chemistry. Heidelberg: Springer-Verlag; 1992. p. 33-61.

[50] Iiyama K, Wallis A. An improved acetyl bromide procedure for determining lignin in woods and wood pulps. Wood Scince Technology. 1988;22:271-80.

[51] Hatfield R, Grabber J, Raph J, Brei K. Using the acetylbromide assay to determine lignin concentrations in herbaceous plants: some cautionary notes. Journal of Agricultural and Food Chemistry. 1999;47:628-32.

[52] Lora JH, Glasser WG. Recent industrial application of lignin - A sustainable alternative to nonrenewable materials. Journal of Polymers and the Enviroment. 2002;10:39-48.

[53] Stewart D. Lignin as a base material for materials applications: Chemistry, application and economics. Industrial Crops and Products. 2008;27(2):202-7.

[54] Schild G, Sixta H, Testova L. Multifuncional alkaline pulping, delignification and hemicellulose extration. Cellulose chemistry and technology. 2010;44:35-45.

[55] Oliveira SC, Pereira FM, Ferraz A, Silva FT, Gonalves AR. Mathematical modeling of controlled-release systems of herbicides using lignis as matrices. Applied Biochemistry and Biotechnology. 2000;84:595-615.

[56] Sopea F, Maqueda C, Morillo E. Controled release formulations of herbicides based on micro-encapsulation. Ciencia e Investigacin Agraria. 2009;35(1):27-42.

[57] Ferraz A, Souza JA, Silva FT, Gonalves AR, Bruns RE, Cotrim AR. Controled release of 2,4-D from granule matrix formulation based on six lignins. Journal of Agricultural and Food Chemistry. 1997;45:1001-5.

[58] Zhao J, Wilkins RM. Controlled release of a herbicide from matrix granules based on solvent-fractionated organosolv lignins. Journal of Agricultural and Food Chemistry. 2000;48:3651-61.



[59] Cotterill JV, Wilkins RM. Controlled release of phenylurea herbicides from a lignin matrix: Release kinetics and modification with urea. Journal of Agricultural and Food Chemistry. 1996;44:2908-12.

[60] Zhao J, Wilkins RM. Controlled release of the herbicide, fluometuron, from matrix granules based on fractionated organosolv lignins. Journal of Agricultural and Food Chemistry. 2003;51:4023-8.

[61] Fernndez-Prez M, Villafranca-Snchez M, Flores-Cspedes F, Prez-Garca S, Daza-Fernndez I. Prevention of chloridazon and metribuzin pollution using lignin-based formulations. Environmental Pollution. 2010;158(5):1412-9.

[62] Garrido-Herrera FJ, Daza-Fernndez I, Gonzlez-Pradas E, Fernndez-Prez M. Lignin-based formulations to prevent pesticides pollution. Journal of Hazardous Materials. 2009;168(1):220-5.

[63] Rohrmann GF. Baculoviruses as inseticides: Three examples. 2011. In: Baculovirus Molecular Biology [Internet]. National Library of Medicine, National Center for Biotechnology Information.

[64] Arthurs SP, Lacey LA, Behle RW. Evaluation of spray-dried lignin-based formulations and adjuvants as solar protectants for the granulovirus of the codling moth, Cydia pomonella (L). Journal of Invertebrate Pathology. 2006;93(2):88-95.

[65] Kadla JF, Kubo S, Venditti RA, Gilbert RD, Compere AL, Griffith W. Lignin-based carbon fibers for composite fiber applications. Carbon. 2002;40:2913-20.

[66] Qin W, Kadla JF. Effect of Organoclay Reinforcement on Lignin-Based Carbon Fibers. Industrial & Engineering Chemistry Research. 2011;50(22):12548-55.

[67] Gellerstedt G, Sjholm E, Brodin I. The wood-based biorefinery: A source of carbon fiber? The open agriculture journal. 2010;3:119-24.

[68] Baker FS, Griffith W, Compere AL. Low-cost carbon fibers from renewable resource. Automotive light weight materials. Process Report. 2005:187-96.

[69] Mooney Brian P. The second green revolution? Production of plant-based biodegradable plastics. Biochemical Journal. 2009;418(2):219.

[70] Ammala A, Bateman S, Dean K, Petinakis E, Sangwan P, Wong S, et al. An overview of degradable and biodegradable polyolefins. Progress in Polymer Science. 2011;36(8):1015-49.

[71] Shah AA, Hasan F, Hameed A, Ahmed S. Biological degradation of plastics: A comprehensive review. Biotechnology Advances. 2008;26(3):246-65.

[72] Li Y, Mlynr J, Anen SS. The first 85% lignin-based thermoplastic. Journal of Polymer Science. 1997;35:1899-910.

[73] McDonald AG, Ma L. Plastic moldable lignin. In: Paterson RJ, editor. Lignin: Properties and applications in biotechnology and bioenergy. New York: Nova Science Publishers; 2012. p. 489-98.

[74] Cardona F, Kin-Tak AL, Fedrigo J. Novel phenolic resins with improved mechanical and toughness properties. Journal of Applied Polymer Science. 2012;123(4):2131-9.

[75] Lee B, Naito H, Nagao M, Hibino T. Alternating-Current Electrolysis for the Production of Phenol from Benzene. Angewandte Chemie International Edition. 2012;51(28):6961-5.

[76] Kuroe M, Tsunoda T, Kawano Y, Takahashi A. Application of lignin-modified phenolic resins to brake friction material. Journal of Applied Polymer Science. 2012:310-5.



[77] Zhang W, Ma Y, Xu Y, Wang C, Chu F. Lignocellulosic ethanol residue-based ligninphenolformaldehyde resin adhesive. International Journal of Adhesion and Adhesives. 2013;40:11-8.

[78] Swarup S. A Comparative Study of Bisphenol-A, Hydantoin and Cyanuric Acid Based Epoxy Resins Using XRD. Materials Sciences and Applications. 2011;02(10):1516-9.

[79] Delmas G-H, Benjelloun-Mlayah B, Bigot YL, Delmas M. Biolignin Based Epoxy resins. Journal of Applied Polymer Science. 2013:1863-72.

[80] Pan X, Saddler JN. Effect of replacing polyol by organsolv and kraft lignin on the property and structure of rigid polyurethane foam. Biotechnology for Biofuels. 2013;6(12):10.

[81] Melo KAd, Martins VdC, Repette WL. Estudo de compatibilidade entre cimento e aditivo redutor de gua. Ambiente Construdo. 2008;9(1):45-56.

[82] Mullik AK. Use of lignin-based products in concrete. 1997. In: Waste materials used in concrete manufacturing [Internet]. Noyes Publications.

[83] Yu G, Li B, Wang H, Liu C, Mu X. Preparation of concrete superplasticizer by oxidation-sulfomethylation of sodium lignosulfonate. Bioresources. 2013;8(1):1055-63.

[84] Aitcin P-C. Cements of yesterday and today concrete tomorrow. Cement and concrete research. 2000;30:1349-59.

[85] Ouyang X, Qiu X, Chen P. Physicochemical characterization of calcium lignosulfonateA potentially useful water reducer. Colloids and Surfaces A: Physicochemical and Engineering Aspects. 2006;282-283:489-97.

[86] Pan T. Coniferyl-alcohol lignin as a bio-antioxidant for petroleum asphalt: A quantum chemistry based atomistic study. Fuel. 2013;113:454-66.

[87] Uraki Y, Ishikawa N, Nishida M, Sano Y. Preparation of amphiphilic lignin derivative as a cellulase stabilizer. Journal of Wood Science. 2001;27:301-7.

[88] JR WAS. The effects of air drying on the strength of sand-lignosulfonate-water mixes. Kansas: Kansas State University; 2012.

[89] Wang H, Tucker M, Ji Y. Recent Development in Chemical Depolymerization of Lignin: A Review. Journal of Applied Chemistry. 2013;2013:1-9.

[90] Sawai K, Funato T, Watanabe M, Wada H, Nakamura K, Shiomi M, et al. Development of additives in negative active-material to suppress sulfation during high-rate partial-state-of-charge operation of leadacid batteries. Journal of Power Sources. 2006;158(2):1084-90.

[91] Khitrin KS, Fuks SL, Khitrin SV, Kazienkov SA, Meteleva DS. Lignin utilization options and methods. Russian Journal of General Chemistry. 2012;82(5):977-84.

[92] Litters T, Liebenau A, inventors; Fuchs Petrolub Ag,, assignee. Lubricating greases containing lignosulfonate, the production thereof, and the uses thereof. United States patent US20120302472A1. 2012 29, 2012.

[93] Chiu Y, editor. An Introduction to the History of Project Management From Erliest Times to A. D. 1900. Delft: Eburon Academic Publishers; 2010.

[94] Aleklett K, editor. Peaking at peak oil. New York: Springer; 2012.


Capitulo Lignina 2014.1-37

Documents

Transcript of Capitulo Lignina 2014.1-37