BIOACCUMALATION AND BIOSORPTIONTECHNIQUES IN BIOREMEDIATION

5/7/2015THURSDAY

SUBMITTED TO: SIR IMRAN

SUBJECT: ENVIRONMENTAL BIOTECHNOLOGY

CONTENTS

PAGE 1: CONTENTS

PAGE 2: BIOREMEDIATION (INTRODUCTION)

PAGE 3: IMPORTANCE AND LIMITATIONS

PAGE 4: BIOSORPTION

PAGE 5: MECHANISMS AND FACTORS AFFECTING BIOSORPTION

PAGE 6: APPLICATIONS OF BIOSORPTION

PAGE 7: APPLICATIONS OF BIOSORPTION

PAGE 8: BIOACCUMALATION

PAGE 9: FACTORS AFFECTING BIOACCUMALATION

PAGE 10: APPLICATIONS OF BIOACCUMALATION

PAGE 11: REFERENCES

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BIOREMIDIATIONBioremediation is the use of living organisms, primarily microorganisms, to degrade environmental contaminants into less toxic forms. Research has demonstrated that there are very few environments where microbes have not been able to survive, adapt, and indeed, thrive. Microbes are able to utilize a near infinite combination of electron donors and electron acceptors to drive their metabolism. In addition to these redox (oxidation / reduction) reactions, they have also developed a myriad of other strategies enabling them to detoxify their environment. Bioremediation applies these principles to select a suitable combination of microbial community activity, electron donor / acceptor / contaminant concentrations and other physical and practical parameters to remediate / recover a targeted pollutant.

More recently, the advances in the field of genetic engineering have allowed scientists to attempt to create artificial strains of organisms, specifically designed to break down and remove highly toxin, harmful or radioactive waste. Though still in its infancy, such a breakthrough has proven ground-breaking in bioremediation strategies.

VARIOUS METHODS OF BIOREMEDIATION

Bioremediation techniques can generally be divided into two categories: in situ and ex situ. The former involves treating the contaminated area on site while the latter involves removing it to an alternative location for treatment. The varying methods and branches of bioremediation are manifold and distinct, but some of them include:

Bio augmentation: The introduction of strains which are known to have

decompositional properties into a contaminated area.

Bio stimulation: The addition of organic or inorganic compounds to cause

indigenous organisms to effect remediation of the environment, e.g. fertilizer, surfactants.

Bioleaching: This is aimed at extracting precious or polluting metals from their

ore through the introduction of living organisms.

Bio sorption: Passive concentration and binding of contaminants onto cellular

structures of biomass.

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Bioaccumulation: Accumulation of substances, such as pesticides, or other

chemicals by active concentration into an organism.

IMPORTANCE OF BIOREMEDIATION TECHNIQUES:

• It is a natural process. Microbes able to degrade the contaminant increase in numbers when the contaminant is present, however when the contaminant is degraded, the biodegradative population declines. The residues for the treatment are usually harmless products.

• Bioremediation also requires a very less effort and can often be carried out on site, often without causing a major disruption of normal activities. This also eliminates the need to transport quantities of waste off site and the potential threats to human health and the environment that can arise during transportation.

• Bioremediation is also a cost effective process as it lost less than the other conventional methods that are used for clean-up of hazardous waste.

• It also helps in complete destruction of the pollutants, many of the hazardous compounds can be transformed to harmless products, and this feature also eliminates the chance of future liability associated with treatment and disposal of contaminated material.

• It does not use any dangerous chemicals. The nutrients added to make microbes grow are fertilizers commonly used on lawns and gardens. Because bioremediation changes the harmful chemicals into water and harmless gases, the harmful chemicals are completely destroyed..

Limitations of Bioremediation:-

• Bioremediation is limited to those compounds that are biodegradable. Not all compounds are susceptible to rapid and complete degradation.

• There are some concerns that the products of biodegradation may be more persistent or toxic than the parent compound. Biological processes are often highly specific. Important site factors required for success include the presence of metabolically capable microbial populations, suitable environmental growth conditions, and appropriate levels of nutrients and contaminants.

• It is difficult to extrapolate from bench and pilot-scale studies to full-scale field operations.

• Research is needed to develop and engineer bioremediation technologies that are appropriate for sites with complex mixtures of contaminants that are not

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evenly dispersed in the environment. Contaminants may be present as solids, liquids, and gases.

• Bioremediation often takes longer than other treatment options, such as excavation and removal of soil or incineration.

BIOSORPTIONBiosorption is a physio-chemical process that occurs naturally in certain biomass which allows it to passively concentrate and bind contaminants onto its cellular structure. Biosorption can be defined as the selective sequestering of metal soluble species that result in the immobilization of the metals by microbial cells.

The major advantages of biosorption using microbial, algal and fungal species over conventional treatment methods include:

Low cost

High efficiency

Minimization of chemical and biological sludge

No additional nutrient requirement

Regeneration of bio sorbent

Possibility of metal recovery.

PROCESS

The biosorption process involves a solid phase (sorbent or biosorbent; biological material) and a liquid phase (solvent, normally water) containing a dissolved species to be sorbed (sorbate, metal ions). Due to higher affinity of the sorbent for the sorbate species, the latter is attracted and bound there by different mechanisms.

Biosorbent material: Strong biosorbent behavior of certain micro-organisms towards metallic ions is a function of the chemical make-up of the microbial cells. One type of biosorbent consists of dead and metabolically inactive cells, another type may contain living and metabolically active microbial cells.

Biosorption mechanisms:

Physical adsorption: Physical adsorption takes place with the help of vander Waals' forces. It is hypothesized that uranium, cadmium, zinc, copper and cobalt biosorption by dead bio-masses of algae, fungi and yeasts takes place through

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electrostatic interactions between the metal ions in solutions and cell walls of microbial cells.

Ion Exchange: Cell walls of microorganisms contain polysaccharides and bivalent metal ions exchange with the counter ions of the polysaccharides. For example, the alginates of marine algae occur as salts of K+, Na+, Ca2+, and Mg2+. These ions can exchange with counter ions such as CO2+, Cu2+, Cd2+ and Zn2+ resulting in the biosorptive uptake of heavy metals.

Complexation: The metal removal from solution may also take place by complex formation on the cell surface after the interaction between the metal and the active groups. Complexation was found to be the only mechanism responsible for calcium, magnesium, cadmium, zinc, copper and mercury accumulation by Pseudomonas syringae. Microorganisms may also produce organic acids (e.g., citric, oxalic, gluonic, fumaric, lactic and malic acids), which may chelate toxic metals resulting in the formation of metal-lo-organic molecules. Metals may be bio-sorbed or complexed by carboxyl groups found in microbial polysaccharides and other polymers.

Precipitation: Microbes may react in the presence of toxic metal producing compounds, which favor the precipitation process. Or it may be a consequence of the chemical interaction between the metal and the cell surface.

FACTORS AFFECTING BIOSORPTION PROCESS:

pH seems to be the most important parameter in the biosorptive process: it

affects the solution chemistry of the metals, the activity of the functional

groups in the biomass and the competition of metallic ions

Biomass concentration in solution seems to influence the specific

uptake, some hypothesis suggest that an increase in biomass concentration

leads to interference between the binding sites, whereas others suggest a

direct relation between biomass and bio sorption.

Types and concentrations of sorbent: the removal of one metal

ion may be influenced by the presence of other metal ions. For example:

cobalt uptake by different microorganisms seemed to be completely

inhibited by the presence of uranium, lead, mercury and copper

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APPLICATIONS OF BIOSORPTION

METAL BEARING WASTE WATER TREATMENT

The microbial cells are immobilized in a chemical matrix then exposed to sorbent particles, finally, the desorption of metals is done to make the process economically sound by regenerating biomass adsorptive capability. Usually the metals are recovered by leaching with a desorbing agent, such as dilute acid or chelating compounds.

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COMMERCIAL NAME FOR BIOSORBENT

Bonds formation between metals, amino and carboxyl groups of cell wall polysaccharides:

Copper biosorption by the bacterium Zoogloea ramigera and alga

Chlorella vulgaris.

Chromium biosorption by fungus Ganoderma lucidum and Aspergillus

niger.

The brown alga Sargassum fluitans has been found particularly effective in binding heavy metal ions of gold, cadmium, copper and zinc. More specifically, it is the properties of cell wall constituents, such as alginate and fucoidan, which are chiefly responsible for heavy metal chelation. 

Ion exchange method supporting bioadsorption:

Copper bioadsorption by fungus Ganoderma lucidium and Aspergillus niger

BIOSORPTION OF RADIOACTIVE ISOTOPES

Uranium is one of the most seriously threatening heavy metals because of its high toxicity and some radioactivity. Excessive amounts of uranium have found their ways into the environment through the activities associated with the nuclear industry posing a threat in some surface and ground waters, and have attracted creation of new techniques for its removal. Various non-living biomass has been used for the removal of uranium by biosorption. Organisms such as:

The fresh water green algae, Chlorella regularis and Chlorella vulgaris. The marine algae are capable of biologically concentrating various radionuclides such as radium, thorium and uranium.

Other common examples include the yeast Saccharomyces cerevisiae and bacteria Pseudomonas aeruginosa.

Recombinant bacteria for metal removal:

A highly specific lead-binding peptide was displayed on Escherichia coli, and lead adsorption characteristics of the recombinant bacteria were enhanced significantly. Cell surface-displayed peptide was expressed under the control of an arabinose promoter expressing recombinant genes and using outer membrane protein C as an anchoring motif.

A novel cell surface display system was developed by employing Escherichia coli outer membrane protein C (OmpC) as an anchoring motif. Polyhistidine peptides could be successfully displayed on the seventh

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exposed loop of OmpC. Recombinant cells displaying polyhistidine could adsorb up to 32.0 micromol of Cadmium Cd(2+) per g (dry weight) of cells.

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BIOACCUMALATION

DEFINITION:

“Bioaccumulation means an increase in the concentration of a chemical in biological organism over time as compared to chemical’s concentration in the environment.” Compounds accumulate in living things any time they are taken up and stored faster then they are broken down (metabolized) or excreted.

THE BIOACCUMULATION PROCESS:

Bioaccumulation is a normal and essential process for the growth and nurturing of organisms. All animals, including humans, and microorganisms daily bio accumulate many vital nutrients, Such as vitamins A, D and K, Trace minerals, Essential fats and amino acids.

Because bioaccumulation is the net result of the interaction of uptake, storage and elimination of a chemical, these parts of the process will be examined further.

UPTAKE:

Bioaccumulation begins when a chemical passes from the environment into a microorganism's cells. Uptake is a complex process which is still not fully understood. Scientists have learned that chemicals tend to move, or diffuse, passively from a place of high concentration to one of low concentration. The force or pressure for diffusion is called the chemical potential, and it works to move a chemical from outside to inside an organism.

STORAGE:

The same factors affecting the uptake of a chemical continue to operate inside a micro-organism, hindering a chemical's return to the outer environment. Some chemicals are attracted to certain sites, and by binding to proteins or dissolving in fats, they are temporarily stored.

ELIMINATION

Another factor affecting bioaccumulation is whether a microorganism can break down and/or excrete a chemical. The biological breakdown of chemicals is termed metabolism. This ability varies among individual microorganisms and species and also depends on characteristics of the chemical itself.

FACTORS AFFECTING BIOACCUMULATION:9

BINDING:

Some chemicals bind to specific sites in the body of microorganism, prolonging their stay, whereas others move freely in and out.

TIME:

The time between uptake and eventual elimination of a chemical directly affects bioaccumulation. Chemicals that are immediately eliminated, for example, do not bio accumulate.

DURATION OF EXPOSURE:

Similarly, the duration of exposure is also a factor in bioaccumulation. Most exposures to chemicals in the environment vary continually in concentration and duration, sometimes including periods of no exposure. In these cases, equilibrium is never achieved and the accumulation is less than expected.

VARIATION BETWEEN INDIVIDUAL MICROORGANISM/SPECIE:

Bioaccumulation varies between individual microorganisms as well as between species. Large, fat, long-lived individuals or species with low rates of metabolism or excretion of a chemical will bio accumulate more than small, thin, short-lived organisms. Thus, an old lake trout may bio accumulate much more than a young bluegill in the same lake.

LIPOPHILIC:

Some chemicals do not mix well with water. They are called lipophilic, meaning "fat loving," or hydrophobic, meaning "water hating." In either case, they tend to move out of water and enter the cells of an organism, where there are lipophilic microenvironments.

WATERSOLUBILITY:

One factor important in uptake and storage is water solubility; the ability of a chemical to dissolve in water. Usually, compounds that are highly water soluble have a low potential to bio accumulate and do not leave water readily to enter the cells of a microorganism. Once inside, they are easily removed unless the cells have a specific mechanism for retaining them.

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APPLICATIONS OF BIOACCUMALATION

REMOVAL OF HEAVY METALS FROM WATER, SOIL OR SEDIMENT

Bacterial strains were isolated from soil, sediment and water samples of metal contaminated industrial area and investigated the heavy metal resistance and bioaccumulation potential of the isolates. Cadmium resistance studies of the bacterial isolates showed that out of 164 isolates collected most of them showed low resistance (<500µg/ml) and many isolates showed high resistance of  >1500µg/ml. Ten bacterial genera were represented in soil and 11 from water, while only 5 bacterial genera were recorded from sediment samples.  Bacillus, pseudomonas and Enterobacter were found in soil, sediment and water samples. Results of cadmium removal study revealed that with increase in time, the biomass of the selected Pseudomonas sp. increased. Correspondingly, with increase in biomass, the cadmium bioaccumulation was also increased. Relatively an Increased removal of cadmium was observed in the first day of the experiment. About 40% of the cadmium in the experimental flask was reduced while only 5% reduction occurs in the control flasks till the end of the experiment (74hours). Comparatively cadmium showed higher reduction at pH 7. From the results, it could be concluded that the selected bacterial isolates possessed potential in respect of bioaccumulation activity and thus, appeared to be an appropriate nominee in bioremediation processes.

HEAVY METAL REMOVAL FROM INDUSTRIAL WASTES AND CONVERSION INTO NON-TOXIC FORMS

The mercury produced during many industrial processes has started accumulated in the surrounding area. The bacterial strains isolated from those areas were able to active accumulate mercury in their cells and then convert the mercury into methyl mercury and then to volatile mercury thus reducing the mercury pollution from the environment by using method of bioaccumulation.

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SUBMITTED BY:

Risham Hussain

Maimoona Ashfaq

Ayesha Ilyas

Neelam Faraz

Waseem Abbas

REFERENCES:

BIOREMEDIATION, SMALL SOLUTIONS TO BIG PROBLEMS by Prof. Esta van Heerden and Dr. Peter Williams

Bioremediation: Features, Strategies and applications by Shilpi Sharma, (Asian Journal of Pharmacy and Life Science).

Environmental Biotechnology by Lawrence K. Wang and Yung Tse Hung.

Environmental biotechnology, Theory and Applications by Gareth M. Evans and Judith C. Furlong.

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