Corn Grading, Cleaning, Milling and Cooking - USP · Comparison between Roller Mill and Hammer Mill...
Transcript of Corn Grading, Cleaning, Milling and Cooking - USP · Comparison between Roller Mill and Hammer Mill...
Singh – Grading, Cleaning, Milling and CookingIst US-Brazil Fulbright Course on Biofuels, Sao Paulo, Brazil
University of Illinois at Urbana-Champaign
Corn Grading, Cleaning, Milling and CookingCooking
Vijay Singh
Associate ProfessorDepartment of Agricultural & Biological Engineering
University of Illinois at Urbana-Champaign, Urbana, IL
1st Brazil-U.S. Biofuels Short Course
São Paulo, Brazil
July 27 - August 7, 2009
Topics of Discussion
• Feedstock Grading and Storage
• Cleaning and Milling• Cleaning and Milling
• Cooking
Singh – Grading, Cleaning, Milling and CookingIst US-Brazil Fulbright Course on Biofuels, Sao Paulo, Brazil
University of Illinois at Urbana-Champaign
Feedstock Storage:Farm or Elevator
• Corn is harvested in the US once a year (July-Sept)
• Storage of corn is required• Storage of corn is required– For year round operation
– Minimize the carbohydrate losses due to spoilage or sprouting
• Storage time is dependent on
– Moisture content and grain temperature
– Drying is generally required at the time of harvest
Recommended Moistures for Safe Storage
Grain Type & Storage Time Maximum M i t %Moisture, %
Shelled Corn & Sorghum
Sold by Spring 15.5 Stored 6 - 12 mos. 14 Stored more than a year 13
Singh – Grading, Cleaning, Milling and CookingIst US-Brazil Fulbright Course on Biofuels, Sao Paulo, Brazil
University of Illinois at Urbana-Champaign
Feedstock Quality and Grading
• Corn delivered at plant is measured for– Moisture content– Moisture content
– Mycotoxins
– BCFM (broken corn and foreign material)
– Test Weight
– Grade
Grade Requirements
Singh – Grading, Cleaning, Milling and CookingIst US-Brazil Fulbright Course on Biofuels, Sao Paulo, Brazil
University of Illinois at Urbana-Champaign
Mycotoxin Detection
• Use of black light to detect mold growth in corn g
• It is the mold that fluoresces not mycotoxins
• Definitive detection of mycotoxins is done by HPLC
• In dry grind ethanol plant mycotoxins end up in DDGS (animal foodstuff)(animal foodstuff)
• Mycotoxins potentially stress yeast and lower ethanol yields
Effect of Mycotoxins on Dry Grind Ethanol
Murthy, G.S., Townsend, D.E., Meerdink, G.L., Bargren, G.L., Tumbleson, M.E. and Singh, V. 2005. Effect of aflatoxin B1 on dry grind ethanol process. Cereal Chem. 82:302-304.
Singh – Grading, Cleaning, Milling and CookingIst US-Brazil Fulbright Course on Biofuels, Sao Paulo, Brazil
University of Illinois at Urbana-Champaign
Effect of Mycotoxins on Dry Grind Ethanol
Wet Grains Thin Stillageg
%
Control - -
100 ppb 55.2 44.8
204 ppb 47.2 52.8
342 ppb 58.1 41.9pp
772 ppb 74.4 25.6
Murthy, G.S., Townsend, D.E., Meerdink, G.L., Bargren, G.L., Tumbleson, M.E. and Singh, V. 2005. Effect of aflatoxin B1 on dry grind ethanol process. Cereal Chem. 82:302-304.
Cleaning and Milling
• CleaningPrior to processing corn is cleaned for BCFM– Prior to processing corn is cleaned for BCFM
• Stones, metals, other debris
• Can cause problems with screens and other equipment
• Dust problems
– Cleaning can be done by sieving or blowing air
Singh – Grading, Cleaning, Milling and CookingIst US-Brazil Fulbright Course on Biofuels, Sao Paulo, Brazil
University of Illinois at Urbana-Champaign
Cleaning and Milling
• Milling– Starch is present in corn in small cells. Milling exposes cells for p g p
hydration, liquefaction and conversion to glucose
– The objectives of Milling are• Split and remove the pericarp which is cutinized from outside and impervious
to penetration of water
• Disintegrate the inner portion of corn kernel into small pieces to make all the constituents readily accessible to enzymatic action
• Minimize the quantity of very fine flour
– prevent balling during slurring
– prevent increase in amount of soluble solids in thin stillage
Milling Equipment
Singh – Grading, Cleaning, Milling and CookingIst US-Brazil Fulbright Course on Biofuels, Sao Paulo, Brazil
University of Illinois at Urbana-Champaign
Comparison between Roller Mill and Hammer Mill for Size Reduction
Ground Corn Ground Wheat
Roller Mill Hammer Mill
Efficiency Comparison between Roller Mills and Hammer Mills
Singh – Grading, Cleaning, Milling and CookingIst US-Brazil Fulbright Course on Biofuels, Sao Paulo, Brazil
University of Illinois at Urbana-Champaign
• Mill outlet is controlled by retention screen
Control of Particle Size
by retention screen• The screens are
normally in size range of 0.125 (6/64”) - 0.172 inches (11/64”)
• Sieve analysis is done to determine the particle psize of the ground flour
Hammer Mill Operation
Singh – Grading, Cleaning, Milling and CookingIst US-Brazil Fulbright Course on Biofuels, Sao Paulo, Brazil
University of Illinois at Urbana-Champaign
Sieve Analysis of Corn Meal
802.0 mm 0.84 mm 0.6 mm 0.43 mm 0.35 mm 0.25 mm <0.25 mm
30
40
50
60
70
% R
etaine
d on
Scr
een
0
10
20
1 2 3 4 5 6 7 8 9
%
Plant #
Rausch et al. 2005. Trans of ASABE.
Effect of Grind Size on Ethanol Yield
8 X2 ft
1 ft1 ft
1 ft
2 ft
2 ft
V = 8 ft3; SA=24 ft2 V = 8 ft3; SA=48 ft2
Singh – Grading, Cleaning, Milling and CookingIst US-Brazil Fulbright Course on Biofuels, Sao Paulo, Brazil
University of Illinois at Urbana-Champaign
Effect of Grind Size on Ethanol Yield
Effect of Grind Size on Ethanol Yield
Singh – Grading, Cleaning, Milling and CookingIst US-Brazil Fulbright Course on Biofuels, Sao Paulo, Brazil
University of Illinois at Urbana-Champaign
Effect of Grind Size on Thin Stillage
Effect of Grind Size
Screen size
mm
#8 3.18
Particle size (micron)
#8 3.18
#6 2.38
#4 1.59
#1.2 0.51
Smaller screen sizes gave higher distribution of finer particle sizes
Soong et al. 2009. Novozymes NA. Grind size study in conventional process – Effects of α-amylase and glucoamylase doses on the processing parameters. Proceedings for International Starch Conference, Urbana, IL
Singh – Grading, Cleaning, Milling and CookingIst US-Brazil Fulbright Course on Biofuels, Sao Paulo, Brazil
University of Illinois at Urbana-Champaign
Post Liquefaction – Insoluble Starch
Smaller screen sizes produced lower insoluble starch values after liquefaction Factors that contribute insoluble starch : a) Incomplete gelatinization; b) Inefficient
liquefaction process
Soong et al. 2009. Novozymes NA. Grind size study in conventional process – Effects of α-amylase and glucoamylase doses on the processing parameters. Proceedings for International Starch Conference, Urbana, IL
Effect of Grind Size on SSF –Fermentation Kinetics
Smaller screen sizes gave faster fermentation kinetics and higher ethanol titers
Note: Liquozyme dose, 0.024% w/w corn as isSpirizyme Fuel, 0.055% w/w corn as is (typical industry dose)
Soong et al. 2009. Novozymes NA. Grind size study in conventional process – Effects of α-amylase and glucoamylase doses on the processing parameters. Proceedings for International Starch Conference, Urbana, IL
Singh – Grading, Cleaning, Milling and CookingIst US-Brazil Fulbright Course on Biofuels, Sao Paulo, Brazil
University of Illinois at Urbana-Champaign
% Solids Content of Corn Slurry
3534
36 3637
3435
40sh 34
29
32
30
3332
2930
27
32
3433
30
33
25
30
35
% S
olids
Cont
ent
in C
orn
Mas
20
No No No No No No No No Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes
SD MN SD SD MO SD SD MN IA IA IA IL SD SD IN IL IA NE
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18
Plants # (Yes - Jet Cooker Used; No - Jet Cooker Not Used)
Johal and Deinhammer, Proceeding of Corn Utilization Tech Conf, 2006, p57-61
Liquefaction
• Jet cooked with split dosage
• Non jet cooked with single dosage• Non jet cooked with single dosage
Singh – Grading, Cleaning, Milling and CookingIst US-Brazil Fulbright Course on Biofuels, Sao Paulo, Brazil
University of Illinois at Urbana-Champaign
Jet cooking
Slurry
Steam
Liquefied Slurry
Courtesy: Hydrothermal Corp.
Jet Cooking with Split Dose
• Jet cooking with split dose Primary 107°C for 3 6 minutes Secondary Primary 107°C for 3-6 minutes
Secondary 85°C for 90-120 minutes
Slurry Solids 32-35%ds
pH ideally 5.6-5.8
30-35% thin stillage
Thermostable alpha amylase
12-14 DE and <1500 cP viscosity
Primary
Secondary
Jet @ 104°C, 3-6 min residence
Slurry @75-85°C 10-20 min
Hold TimeSecondary 90 min
@85°C
Thermostable alpha amylase
Steam
Singh – Grading, Cleaning, Milling and CookingIst US-Brazil Fulbright Course on Biofuels, Sao Paulo, Brazil
University of Illinois at Urbana-Champaign
Flow Diagram for Liquefaction:Non Jet Cooked with Single Dosage
Secondary
Primary
Secondary
Slurry @75-85°C 10-20 min
Hold TimeSecondary 90 min
@85°C
Thermostable alpha amylase
Non Jet Cooking with Single Dose
• Hold at 85°C for 60-120 minutes Slurry Solids 32-35%ds
H id ll 5 6 5 8 pH ideally 5.6-5.8
30-35% thin stillage
Thermostable alpha amylase
12-14 DE and <1500 cP viscosity
Singh – Grading, Cleaning, Milling and CookingIst US-Brazil Fulbright Course on Biofuels, Sao Paulo, Brazil
University of Illinois at Urbana-Champaign
Liquefaction Process
• ParametersDE
Measure reducing ends of sugar
Viscosity
Flowability, thinning
Typical DE and Viscosity Progression
Viscosity profile
4000Just after jet
DE profile
14
1000
1500
2000
2500
3000
3500
Visc
osit
y (c
P)
pH 5.8
pH 5.5
Secondary Liquefaction4
6
8
10
12
DE
pH 5.8
pH 5 5
0
500
0 50 100 150Incubation Time, min at 85 C
After slurry time
0
2
0 20 40 60 80 100Incubation Time, min at 85 C
pH 5.5
Reference: Vivek Sharma, Genencor International, Dry Grind Ethanol Course, UIUC, 2008
Singh – Grading, Cleaning, Milling and CookingIst US-Brazil Fulbright Course on Biofuels, Sao Paulo, Brazil
University of Illinois at Urbana-Champaign
Effect of Thin Stillage on Alpha Amylase
Alpha Amylase: Effect of thin stillage of the whole ground corn batch liquefaction (no jet) 90C
16
Alpha Amylase: Effect of thin stillage of the whole ground corn batch liquefaction (no jet) 90C
16000% 10% 30% 50%
4
6
8
10
12
14
DE
0% 10% 30% 50%
400
600
800
1000
1200
1400
Vis
cosi
ty (
cP)
0% 10% 30% 50%
0
2
4
0 20 40 60 80 100
Incubation Time, min at 90C
0
200
400
30 60 90
Incubation Time, min at 90C
Reference: Vivek Sharma, Genencor International, Dry Grind Ethanol Course, UIUC, 2008
Evaluation of Liquefaction Process
• Iodine test
• DE measurement• DE measurement
• Sugar Profiles
Singh – Grading, Cleaning, Milling and CookingIst US-Brazil Fulbright Course on Biofuels, Sao Paulo, Brazil
University of Illinois at Urbana-Champaign
pH of Corn Mash
6.1
6.4 6.4 6.46.2
6.3
5 9
6.5
7
5
4.4
5.1
4.6
5.2
5.9
4.8
5.7
4.44.5
4.6
5.1
4
4.5
5
5.5
6
3
3.5
No No No No No No No No Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes
SD MN SD SD MO SD SD MN IA IA IA IL SD SD IN IL IA NE
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18
Johal and Deinhammer, Novozymes, NA, Proceeding of Corn Utilization Tech Conf, 2006, p57-61
% DE of Corn Mash
16 6 16 9
19.1
17.3
20
13.6 13.7
16.116.6
11.2
14.5 14.213.3
10.4
16.9
12.712 11.7
10.6
12.6
14.8
10
15
Johal and Deinhammer, Novozymes, NA, Proceeding of Corn Utilization Tech Conf, 2006, p57-61
5
No No No No No No No No Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes
SD MN SD SD MO SD SD MN IA IA IA IL SD SD IN IL IA NE
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18
Singh – Grading, Cleaning, Milling and CookingIst US-Brazil Fulbright Course on Biofuels, Sao Paulo, Brazil
University of Illinois at Urbana-Champaign
• Complete Saccharification (Continuous and Batch)
• P S h ifi i f ll d b Si l
Saccharification/Fermentation Systems
• Pre-Saccharification followed by Simultaneous Saccharification/Fermentation
• Simultaneous Saccharification/Fermentation
• Liquefact is hydrolyzed completely prior to starting the fermentation process (Glucose concentration > 93% w/w)
• Typical Operating Conditions and Parameters:
Complete Saccharification
yp p g
– Temperature 140 - 144°F (60 - 62°C)
– pH 4.0 - 4.5
– Dry Substance 27 - 37%
– Time 1 - 6 hr
– Dose 0.08 - 0.4 GAU/g dry solids
Singh – Grading, Cleaning, Milling and CookingIst US-Brazil Fulbright Course on Biofuels, Sao Paulo, Brazil
University of Illinois at Urbana-Champaign
• Liquefact is saccharified to a glucose level 5-25%w/w before being cooled and sent to fermentation
Pre-Sacc Followed by SSF
and sent to fermentation.
• Pre-Sacc Typical Operating Conditions and Parameters:
– Temperature: 140 - 150°F (60 - 66°C)
– pH: 4.0 - 4.5
– Dry Substance: 27 - 37%
– Time (in pre-sacc): 1-24 hours
– Dose: 0.13- 0.45 GAU/g dry solids
• Saccharification to glucose and fermentation occur simultaneously
• Typical Operating Conditions and Parameters
Simultaneous Saccharification/Fermentation (SSF)
• Typical Operating Conditions and Parameters
– Temperature: 86 - 92°F (30 - 33°C)
– pH: 4.0 – 5.5
– Dry Substance: 27 - 37%
– Time: 30 - 70 hr
– GA Dose: 0.3 - 0.6 GAU/g dry solids
Singh – Grading, Cleaning, Milling and CookingIst US-Brazil Fulbright Course on Biofuels, Sao Paulo, Brazil
University of Illinois at Urbana-Champaign
Saccharomyces Cerevisiae
• View of typical fermentation i h iyeast with microscope
• Yeast are identified partially by appearance
• Also identified by list of compounds used (sugars, vitamins, etc.)
5 to 10 μm 5 to 7 μm
• Yeast cell is 75% water and 25% dry matterCarbohydrate 18 44%
Chemical Composition of Yeast
– Carbohydrate 18-44%
– Protein 36-60%
– Nucleic Acids 4-8%
– Lipids 4-7%
– Total inorganics 6-10%• Phosphorus 1-3%
P i 1 3%• Potassium 1-3%
• Sulfur 0.4%
– Vitamins Trace amounts
Singh – Grading, Cleaning, Milling and CookingIst US-Brazil Fulbright Course on Biofuels, Sao Paulo, Brazil
University of Illinois at Urbana-Champaign
Glucose Uptake by Yeast
Glucose Glucose-6-phosphate Glucose Glucose-6-phosphate
Aerobic (respiration)(with oxygen)
Anaerobic (fermentation)(without oxygen)
PyruvateNADH
Krebs (TCA)Cycle & Oxidative
Triose phosphate
Pyruvate CO2
Oxygen
CO2
Cycle & OxidativePhosporylation
Yeast Biomass
Ethanol
CO2
Yeast Fermentation Products
Ethanol+CO2
Oxaloacetate
Succinate
Succinate
Source: AlcoholTextbook, Ingledew, 1999
Glucose Uptake by Yeast
• Yeast can grow in presence or absence of oxygen
• When O is present and not too much sugar is present• When O2 is present and not too much sugar is present– Yeast use all sugar for growth
• When O2 is not present and amount of sugar present is high– Yeast produces ethanol
• Yeast cell mass produced under anaerobic conditions is less than 5% of the weight of initial sugar
Singh – Grading, Cleaning, Milling and CookingIst US-Brazil Fulbright Course on Biofuels, Sao Paulo, Brazil
University of Illinois at Urbana-Champaign
Preferential Sugar Utilization by Yeast
2.5
3.0w
/v)
Glucose
F
0.5
1.0
1.5
2.0
gar
Con
cen
trat
ion
s (%
Fructose
Maltose
Maltotriose
DP4+
0.0
0 20 40 60 80
Sug
Fermenation Time (hr)
Fermentation
• Fermentation is the process of yeast converting glucose to ethanol and carbon dioxide in presence of oxygen
P i d d b l d– Process is moderated by several enzymes and coenzymes
– Simplified equation
MW = 162 MW = 180 MW = 2 x 46 MW = 2 x 44
Singh – Grading, Cleaning, Milling and CookingIst US-Brazil Fulbright Course on Biofuels, Sao Paulo, Brazil
University of Illinois at Urbana-Champaign
Calculate Amount of Ethanol Produced
• How many kg of starch is used to produce 150 kg of ethanol?– 150/0 511 = 293 54 kg glucose– 150/0.511 = 293.54 kg glucose
– 293.54/1.111 = 264.21 kg starch
How Yeast Makes Ethanol
• Glycolysis, the degradation of sugar to alcohol with
Substrates
production of energy (ATP) for cell growth
• 12 Enzymes convert ~90% of all produced glucose to ethanol and CO2 under conditions of controlled oxidation/reduction balance
End
Source: Alcohol Textbook, Ingledew, 2009
products
Singh – Grading, Cleaning, Milling and CookingIst US-Brazil Fulbright Course on Biofuels, Sao Paulo, Brazil
University of Illinois at Urbana-Champaign
Ethanol Production: Gycolysis Pathway
• Ethanol production is proportional to growth• As sugar is used, energy (ATP) and pyruvic acid is made. The energy is
d f d h d h d d kused for cell production (growth), and the pyruvic acid is used as a sink for the reduced enzyme cofactor made in glycolysis which otherwise would accumulate
• Growing cells make ethanol 33 times faster than non-growing • Pyruvic acid is converted through acetaldehyde to ethanol using
reduced NADH + H+ and regenerating NAD• Glycerol is made due to the accumulation of excess reducing power
How Yeast Makes Ethanol
Substrates
• When a few molecules of these are taken by the cell for
End
growth, this leads to increases in NADH and lower ethanol (not noticed)
glycerolNADH
Xproducts
Source: Alcohol Textbook, Ingledew, 2009
Singh – Grading, Cleaning, Milling and CookingIst US-Brazil Fulbright Course on Biofuels, Sao Paulo, Brazil
University of Illinois at Urbana-Champaign
Differences in Yeast
• Yeast vary in maximum temperature for growth from about 25 to 39°Cto 39 C
• Yeast vary in morphology, size of 5 to 10 microns, roundness, chain formation
• Yeast vary in production of cogeners, especially esters and higher alcohols
• Yeast vary in growth response
• Yeast characteristics are checked by lab fermentations
Yeast Stress
Source: AlcoholTextbook, Ingledew, 1999
Singh – Grading, Cleaning, Milling and CookingIst US-Brazil Fulbright Course on Biofuels, Sao Paulo, Brazil
University of Illinois at Urbana-Champaign
Osmotic Stress
• Due to high sugar concentration
• Increase in glycogen synthesis• Increase in glycogen synthesis
• Increase in glycerol synthesis (instead of ethanol)
• If starch is left in form of dextrins and slowly converted to glucose by enzymes, osmotic pressure will be lowered
Loss of Viability in Stressed Yeast
• Always seems to occur in same three stages no matter what the causecause– Loss of ability to form new cells
– Loss of membrane integrity
– Loss of intracellular enzymes able to chemically reduce many chemicals
Singh – Grading, Cleaning, Milling and CookingIst US-Brazil Fulbright Course on Biofuels, Sao Paulo, Brazil
University of Illinois at Urbana-Champaign
Signs of Yeast Aging
• Increase in bud scar number
• Cell size• Cell size
• Surface wrinkles
• Granularity
• Daughter cell being retained
Tests for Viability
• Viable yeast count
• Methylene blue viability test• Methylene blue viability test– Dead cells lose ability to keep methylene blue outside
– Dead cells lose ability to reduce the dye to a colorless form very quickly
• Ability to form new cells on a thin layer of agar medium on a microscope slide is considered the reference method
Fl i di d i ll l d• Flourescein diacetate dyes measure intracellular enzymes and give a good viability measure
Singh – Grading, Cleaning, Milling and CookingIst US-Brazil Fulbright Course on Biofuels, Sao Paulo, Brazil
University of Illinois at Urbana-Champaign
Antinutritive Factors: Weak Acids
• Weak acids can have inhibitory effects on yeast if the free, unionized acid can enter the yeast cellfree, unionized acid can enter the yeast cell
• Acids which enter the cell in the unionized form may ionize at the higher pH inside the cell
• Acetic acid is a potent anti yeast factor
Source: Narendranath et al. 2001. Journal of the Am. Soc. of Brewing Chemists 59:187-194Narendranath et al. 2001. Journal of Ind. Microbiology and Biotechnology 26:171-177
Nitrogen Requirements
• Amount of urea usedNH2
C=O
NH2
– 8 mM (480 mg urea/L) to 16 mM urea (960 mg urea/L)
• Amount used depends upon “gravity” of mash (solids content)
• Virtually none remains after fermentation
Singh – Grading, Cleaning, Milling and CookingIst US-Brazil Fulbright Course on Biofuels, Sao Paulo, Brazil
University of Illinois at Urbana-Champaign
300
36.530.3
24.719.0
14 0)
21
36.5
No Urea Nitrogen Added
100
200
14.0
Ferm
enta
tion
time
(h)
9
12
15
1830.3
24.7
19.0
14.0
Eth
anol
(% v
/v)
17 20 24 27 30 330
Temperature (°C)3530252015
6
Temperature (°C)
Source: Alcohol Textbook, Ingledew, 2009
300 36.530.324 7
21 36.5
30 3
Urea Nitrogen Added
100
200
24.719.014.0
erm
enta
tion
time
(h)
9
12
15
18 30.3
24.7
19.0
14.0
Eth
anol
(% v
/v)
17 20 24 27 30 33
0
Temperature (°C)
Fe
35302520156
Temperature (°C)
Source: Alcohol Textbook, Ingledew, 2009
Singh – Grading, Cleaning, Milling and CookingIst US-Brazil Fulbright Course on Biofuels, Sao Paulo, Brazil
University of Illinois at Urbana-Champaign
Fermentation
• Continuous
• Batch
Continuous Fermentation
• Fresh substrate added and product removed at the same rate
• Reduce time required for filling emptying and cleaning• Reduce time required for filling, emptying and cleaning
• Simplify Control
• Operate continuously for several months without constant shutdown, cleaning and decontamination
• In reality many problems with contamination have been observed– Source of problem difficult to locate
Singh – Grading, Cleaning, Milling and CookingIst US-Brazil Fulbright Course on Biofuels, Sao Paulo, Brazil
University of Illinois at Urbana-Champaign
Batch Fermentation
• Each fermentor is individually controlled
• Each fermentor is processed cleaned and restarted with new• Each fermentor is processed, cleaned and restarted with new batch of yeast
• Additional tanks are needed to maintain productivity
• Most of dry grind ethanol continuous fermentation plants have converted to batch fermentation
Yeast Propagation Tank
ADY SugarNutrients
Antibiotics
Singh – Grading, Cleaning, Milling and CookingIst US-Brazil Fulbright Course on Biofuels, Sao Paulo, Brazil
University of Illinois at Urbana-Champaign
Typical Fermentor Fill
GA 2 dose
Mash (70%)
Mash (90%)
Mash (5%)
GA 1 doseYeast
• Losses in Mashing
• Cell growth
Fermentation: Factors Affecting Ethanol Yield
• Cell growth
• Minor end products
• Infections
• Struck Fermentation
• Nutritional Deficiencies
Singh – Grading, Cleaning, Milling and CookingIst US-Brazil Fulbright Course on Biofuels, Sao Paulo, Brazil
University of Illinois at Urbana-Champaign
• Losses in Mashing– Unconverted starch (due to poor milling)
Factors Affecting Ethanol Yield
– Retrogradation of starch
– Starch blinding by protein
– Less than complete enzymatic hydrolysis
– Starch found in DDGS (indicator of losses in mashing)
– Use of heat damaged grains
Factors Affecting Ethanol Yield
• Higher Alcohols (Fusel Oils)
– N-propanolN propanol
– Amyl Alcohol
– Iosamyl Alcohol
– Iosbutanol
– Phenethyl Alcohol
• These can be formed from amino acids
• Yeast strain, high temperature, increased aeration increased agitation and composition of medium leads to production of higher alcohols
Singh – Grading, Cleaning, Milling and CookingIst US-Brazil Fulbright Course on Biofuels, Sao Paulo, Brazil
University of Illinois at Urbana-Champaign
• Infections– Recycle streams provide nitrogen and nutrient source but also
ca se infections
Factors Affecting Ethanol Yield
cause infections
– Wet milling process• Light steep water is used in fermentation
– Dry grind process• Backset/Thinstillage is used in fermentation
– Major reasons of use of recycle steams is for water recycling/pollution controlrecycling/pollution control
• However, inhibitory levels of sodium ions, sulfite ions, lactic acid and acetic acid lead to yeast stress
Struck (Sluggish) Fermentations
• Rate of sugar utilization becomes extremely slow (especially towards the end of fermentation)towards the end of fermentation)
• Caused due to nutritional deficiency especially nitrogen and oxygen
Singh – Grading, Cleaning, Milling and CookingIst US-Brazil Fulbright Course on Biofuels, Sao Paulo, Brazil
University of Illinois at Urbana-Champaign
Very High Gravity Fermentation
• Higher concentration of solids (glucose) in fermentation broth
• Yeast nutrition and oxygen play an important role• Yeast nutrition and oxygen play an important role
• In lab final ethanol concentration as high as 23% have been achieved in fermentation broth
• More ethanol produced per batch
• Less evaporation and dehydration required– Less energy usage
Specific Gravity Measurement
• °Brix
• °Ballingg
• °Plato
Singh – Grading, Cleaning, Milling and CookingIst US-Brazil Fulbright Course on Biofuels, Sao Paulo, Brazil
University of Illinois at Urbana-Champaign
Instruments Used for Measuring Specific Gravity
Refractometers Hydrometers
Percent Alcohol Determination
• Proof of Alcohol is calculated by multiplying “alcohol volume %” by 2% by 2
– Example: 40% alcohol by volume = 80 degree proof
Singh – Grading, Cleaning, Milling and CookingIst US-Brazil Fulbright Course on Biofuels, Sao Paulo, Brazil
University of Illinois at Urbana-Champaign
Ethanol Yield
• Ethanol producers like to look at gallons of ethanol produced from a bushel of corn
Generic weight of bushel of corn = 56 lb– Generic weight of bushel of corn = 56 lb
– Moisture content in corn = 14%
– Starch content is 70%
– Assuming 100% of starch is converted into ethanol• Ethanol yield will be 2.9 gallons/bushel
– Typically yield is around 2.65 gallons/bushel (in dry grind yp y y g ( y gethanol plant)
• In terms of efficiency of starch conversion, this would be 100 x 2.65/2.9 = 90% efficiency
Monitoring Rate of Fermentation
• Alcohol level at a given time using HPCL
• Time to a repeat Brix using refractometerp g
• Rate of pH change and final levels using pH meter
• Volumetric Productivity
Singh – Grading, Cleaning, Milling and CookingIst US-Brazil Fulbright Course on Biofuels, Sao Paulo, Brazil
University of Illinois at Urbana-Champaign
Monitoring Rate of Fermentation
Monitoring Rate of FermentationHPLC Chromatogram
Singh – Grading, Cleaning, Milling and CookingIst US-Brazil Fulbright Course on Biofuels, Sao Paulo, Brazil
University of Illinois at Urbana-Champaign
Monitoring Brix During Fermentation
25.00
5.00
10.00
15.00
20.00
Brix
0.00
0 10 20 30 40 50 60 70
Fermentation Time (hr)
Monitoring pH During Fermentation
5 50
6.00
4.00
4.50
5.00
5.50
pH
Plant 1
Plant 2
Plant 3
3.00
3.50
0 10 20 30 40 50 60 70
Fermentation Time (hr)
Singh – Grading, Cleaning, Milling and CookingIst US-Brazil Fulbright Course on Biofuels, Sao Paulo, Brazil
University of Illinois at Urbana-Champaign
Monitoring Yeast Performance
• Cell Count
• Viability• Viability
• Budding Cells
Cell Count
350.00
400.00
100.00
150.00
200.00
250.00
300.00
Yeast Count (10^6)
Total
Budding
Dead
0.00
50.00
0 10 20 30 40 50 60 70
Fermentation Time (hr)