small grain to bioethanol - stellenbosch universityacademic.sun.ac.za/genetics/biobrandstof...

Emile van Zyl

Department MicrobiologyUniversity of Stellenbosch

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Conversion of small grains biomass to bioethanol

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

1Why considering

bioethanol?

Fossil fuel

Petrol

Excess CO2 inatmosphere

FuelFossil fuel

CO2

Air pollution

Greenhouse effect

In past 150 years CO2 levels raised from 280 ppm to >360 ppm, 30 ppm in the last 17 years!

Alternative fuel

Ethanol

Closed carbon cycle !

Fuel

CO2Renewable resource

Lignocellulose& Starch

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.

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

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

2Ethanol productionfrom starch grains

Wheat Triticale Rye

Wheatgerm

Endosperm

Bran

Starch composition

α-1,4-linkages

α-1,6-linkages

Starch composition

Structure of amylopectin in raw starch

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

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

Sugar fermentation

Glucose

Ethanol

Yeast

C6H12O6Glucose [180]

2x C2H6OEthanol [2x 46]

+ 2x CO2[2x 44]

Ethanol Yield = 92/180 x 1.1 = 0.56

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

Ethanol production from starch

Northeast Missouri Grain plant that produces 75 million liter ethanol per year

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.

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.

3Next generation

technologies for starch

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.

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.

[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

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

4Third generation

technologies for starch??

Raw-starch degrading yeast?

Glucose

Ethanol

Yeast

α-amylase &glucoamylase

Raw-starch degrading yeast?

Yeast

α-amylase&glucoamylase

amylopectin

Raw-starch degrading yeast?

Glucose

Ethanol

Yeast

Is this possible?

Maize starch with recombinantamylolytic yeast growing. Stainedafterwards with iodine to showstarch degradation.

AmylolyticYeast!

Ethanol production from starch

DDGS

Storagetank

Water

Distillation & dehydration

Grinding

MaizeWheat

TriticaleRye

Slurrytank

Alcoholrecovery

Fuelblending

Adjust pH to 5.0

Water

Slurrytank

Fermentation

5Future technologies

for lignocellulose

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

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)

Lignocellulose composition

Sugarcane bagasse Lignin28%

Arabinan2%

Xylan25%

Cellulose46%

Hexoses(fermentable) Pentoses

(fermentable)

Non-fermentablesugars

high energy aromatics

Cellulose hydrolyses and fermentation

Enzyme hydrolysis

Fermentation

cellulose

yeast

glucose

ethanol

[REF][EG1]

[SFI][CEL5]

Yeast grow on amorphous cellulosewith production of cellulases

Acid swollenamorphous

cellulose

recombinantyeasts

Cellulose hydrolyses and fermentation

Glucose

yeastsFermentation

ethanol

Cellulose hydrolyses and fermentation

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

Yeast that grow on xylose in fermenter

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)

maize stover

Lignocellulose sources

bagasse

woodchips Miscanthus as energy crop

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!

Thank you!