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Emile van Zyl
Department MicrobiologyUniversity of Stellenbosch
jou kennisvernoot • your knowledge partner
Conversion of small grains biomass to bioethanol
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Content
3. Ethanol production from starch grains
1. Why considering biofuels?
2. Bioethanol as renewable fuel
6. Conclusions
4. Next generation technologies for starch
5. Future technologies for lignocellulose
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1Why considering
bioethanol?
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Fossil fuel
Petrol
Excess CO2 inatmosphere
FuelFossil fuel
CO2
Air pollution
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Greenhouse effect
In past 150 years CO2 levels raised from 280 ppm to >360 ppm, 30 ppm in the last 17 years!
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Alternative fuel
Ethanol
Closed carbon cycle !
Fuel
CO2Renewable resource
Lignocellulose& Starch
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Bioethanol as renewable fuel
1. Bioethanol recently gained much attention with the soaring crude oil prices.
3. This is bound to change in the future with limiting oil resources, the treat of greenhouse gas production as well as global security risks associated with limiting oil resources.
2. Biofuels has to date hardly made a dent in the use of petroleum fuels.
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4. In 2005 the USA bioethanol production (primarily from maize starch) surpassed 15 billion liter per annum.
6. The maximum bioethanol production capacity from maize in the USA is estimated at 50 billion liter/annum, that brings it just above 6%!
5. However their liquid transportation fuel consumption is more than 800 billion liter per annum. Current bioethanol production thus providing <2% of USA needs!
Bioethanol as renewable fuel
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7. The only way the USA could accomplish 30% displacement of fossil fuel (their target for 2030!) would be through the conversion of lignocellulosics biomass, of which the USA can potentially produce 1 billion tons per annum!
8. I will first talk on the technologies for converting starch to bioethanol and later refers to South Africa’s potential for the conversion of ligno-cellulosics.
Bioethanol as renewable fuel
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2Ethanol productionfrom starch grains
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Wheat Triticale Rye
Wheatgerm
Endosperm
Bran
Starch composition
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α-1,4-linkages
α-1,6-linkages
Starch composition
Structure of amylopectin in raw starch
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Starch degradation
Liquefaction step[pH 6.0; 95-105ºC; 90 min]
α
α
αα
α α α
α
α
α
α
α = α-amylase
Small starcholigo-
saccharides
Amylo-pectin
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Starch degradation
PP
P
PG G
GGG
GGG
G
G
GG
G
G G
G
Glucose
[pH 4.5; 60-62ºC; 12-96 h] Saccharification step
G = glucoamylaseP = Pullulanase
Small starcholigo-
saccharides
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Sugar fermentation
Glucose
Ethanol
Yeast
C6H12O6Glucose [180]
2x C2H6OEthanol [2x 46]
+ 2x CO2[2x 44]
Ethanol Yield = 92/180 x 1.1 = 0.56
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Ethanol production from starch
DDGS
Liquefaction
SecondaryLiquefaction
95ºC, ~90 min
Grinding
MaizeWheat
TriticaleRye
Water
Slurrytank
Jet Cooker>100ºC
>5 - 8 min
Thermostableα-amylase Glucoamylase Yeast Alcohol
recovery
Fuelblending
Saccharification Fermentation Distillation & dehydration
Adjust pH to 6.0Adjust pH to 4.5
Storagetank
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Ethanol production from starch
Northeast Missouri Grain plant that produces 75 million liter ethanol per year
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Challenges using small grains?1. Positive attributes are:
(i) High starch content (up to 60% or even higher!).
(ii) More hardy for cultivation in Western Cape Area.
(iii) Some genetic variants have high auto-amylolytic activity, assisting in mobilizing the starch to maltose and glucose.
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2. Uncertainties:
Challenges using small grains?
(i) How adaptable is starch conversion technology in maize to triticale? How efficient will commercial enzymes work. Any inhibitory factors in triticale starch?
(ii) How well can auto-amylolytic activity be controlled not to end up in contamination risk?
(iii) Published data suggests triticale is comparable to wheat for ethanol production, however, we need to establish that in South African scenario and gain necessary experience to do Q&A for routine bioethanol production from triticale crops.
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3Next generation
technologies for starch
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Genencor introduce StargenTM
1. Genencor introduced StargenTM. What is special about it?
3. What is in the StargenTM mixture? They also use α-amylase and glucoamylase, but selected enzymes with high ability to attach raw amylopectin.
2. StargenTM contain raw-starch degrading enzymes, (called granular starch degrading enzymes (GSHE) by Genencor). That simply means these enzymes can hydrolyse uncooked starch.
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Genencor introduce StargenTM
1. Why make them special? They eliminate the heating step after α-amylase activity. Starch can be hydrolyses in one step at lower temperature.
2. Second advantage is that enzymes can operate in same temperature, which is lower than before – you don’t have to adjust pH between hydrolysis steps.
3. Third significant advantage is that starch hydrolysis and yeast fermentation can take place simultaneously.
4. You thus avoid feedback inhibition of high sugar concentrations on enzyme activity, and limit contamination risk after hydrolysis before fermentation.
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[Buleon, A., P. Colonna, V. Planchot, and S. Ball. 1998. Starch granules: structure and biosynthesis. Int. J. Biol. Macromol. 23:85-112.]
Enzymatic hydrolysis of raw starch
Treated withAspergillusα-amylase
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StargenTMEnzyme &
Yeast
Ethanol production from starch
DDGS
Storagetank
Water
Distillation & dehydration
Grinding
MaizeWheat
TriticaleRye
Slurrytank
Alcoholrecovery
Fuelblending
Adjust pH to 4.5
Water
Slurrytank
Hydrolysis andFermentationFermentation
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4Third generation
technologies for starch??
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Raw-starch degrading yeast?
Glucose
Ethanol
Yeast
α-amylase &glucoamylase
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Raw-starch degrading yeast?
Yeast
α-amylase&glucoamylase
amylopectin
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Raw-starch degrading yeast?
Glucose
Ethanol
Yeast
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Is this possible?
Maize starch with recombinantamylolytic yeast growing. Stainedafterwards with iodine to showstarch degradation.
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AmylolyticYeast!
Ethanol production from starch
DDGS
Storagetank
Water
Distillation & dehydration
Grinding
MaizeWheat
TriticaleRye
Slurrytank
Alcoholrecovery
Fuelblending
Adjust pH to 5.0
Water
Slurrytank
Fermentation
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5Future technologies
for lignocellulose
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the most abundant renewable carbon sources on earth; 10-50 x 109 tons annually produced with about 4 x 109 tons annually available for conversion to energy and feedstuffs!
Wood is 70 – 80% cellulose and hemicellulose -
Renewable biomassLignin
Cellulose
Hemicellulose
Esters
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Renewable biomass (2)
Ligninases(laccases, lignin peroxidases,Mn-peroxidases)
Cellulases(endoglucanases, cellobiohydrolases,β-glucosidases)
Hemicellulases(xylanases,β-xylosidasesα-arabinofuranosidases
α-glucuronidases)
Esterases(feruloyl esterases,coumaroyl esterases)
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Lignocellulose composition
Sugarcane bagasse Lignin28%
Arabinan2%
Xylan25%
Cellulose46%
Hexoses(fermentable) Pentoses
(fermentable)
Non-fermentablesugars
high energy aromatics
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Cellulose hydrolyses and fermentation
Enzyme hydrolysis
Fermentation
cellulose
yeast
glucose
ethanol
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[REF][EG1]
[SFI][CEL5]
Yeast grow on amorphous cellulosewith production of cellulases
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Acid swollenamorphous
cellulose
recombinantyeasts
Cellulose hydrolyses and fermentation
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Glucose
yeastsFermentation
ethanol
Cellulose hydrolyses and fermentation
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Dry
Bio
mas
s (g/
L)
0.000.050.100.150.200.250.30
020406080
100
0.00.20.40.60.81.0
% V
isco
sity
Etha
nol (
g/L)
REF SFI EG1 CEL5 CEL5PASC
Growth on amorphous cellulose
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Yeast that grow on xylose in fermenter
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Renewable biomass available1. Residues
AgricultureMaize residues 6.7 Mt/a (118 PJ/a)Sugarcane bagasse 3.3 Mt/a (58 PJ/a)Wheat straw 1.6 Mt/a (28 PJ/a)Sunflower residues 0.6 Mt/a (11 PJ/a)Agricultural subtotal 12.3 Mt/a (214 PJ/a)Forrestry industryPlantatation residues 4.0 Mt/a (69 PJ/a)Sawmill residues 0.9 Mt/a (16 PJ/a)Paper & board mill slurry 0.1 Mt/a (2 PJ/a)Forrestry industrie subtotal 5.0 Mt/a (87 PJ/a)
2. Energy crops From 10% of available land 67 Mt/a (1 170 PJ/a)
3. Intruder plants 8.7 Mt (151 PJ)Total, annual basis 84 Mt/a (1 470 PJ/a)
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maize stover
Lignocellulose sources
bagasse
woodchips Miscanthus as energy crop
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Conclusions
1. Fossil fuel won’t last! Biofuels are here to stay – get use to it!
3. However, if we come to grip with 1 & 2 above, South Africa can be a force in the biofuels field, locally and abroad. We had and we still have know-how and excellence – we have to nurture it wisely!
2. South Africa has potential to play in the biofuels arena, we should not be too hasty and we should learn from other’s mistakes.
4. If we make a concerted effort and invest in lignocellulosics in time, be willing to change to a sustainable future and investing in energy crops too, South Africa can provide for himself in the future!
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Thank you!