Sorghum Starch for BiofuelsSorghum Starch for Biofuels

Donghai WangBiological and Agricultural Engineering

Kansas State University

International Conference on Sorghum for BiofuelHouston, Texas

August 19-22, 2008

01000200030004000500060007000

Mill

ions

of G

allo

ns

'00 '01 '02 '03 '04 '05 '06 '07

Production Import

OtherBarley, wheat, cheese whey,potato waste, brewery waste

Sorghum~3.5% total

2.3 Billion bu

~85 Million bu

Raw materials for ethanol productionRaw materials for ethanol production

Current capacity is ~9 B gallons and will be ~14 B gal by 2009Driven by corn grain production, with sorghum contributions

Current capacity is ~9 B gallons and will be ~14 B gal by 2009Driven by corn grain production, with sorghum contributions

Data source: DOE-EIA

Domestic productionDomestic production

MM galMM gal Import

Composition Sorghum CornStarch (%) 71.8 73.4Protein (%) 12.3 9.1Fat (%) 3.6 4.4Ash (%) 1.6 1.4

Compositions of corn & sorghum

Corn ~96%

Relative low digestibility compared with cornNo enough scientific information about fermentation quality of sorghum to support bio-industry and breeding research. Less investment for grain research.

Relative low digestibility compared with cornNo enough scientific information about fermentation quality of sorghum to support bio-industry and breeding research.Less investment for grain research.

The main focus is to understand the key factors (genetic, composition, chemical structure, and physical properties) affecting bioconversion efficiency of grain sorghum for biofuel production.

The main focus is to understand the key factors (genetic, composition, chemical structure, and physical properties) affecting bioconversion efficiency of grain sorghum for biofuel production.

Sorghum Samples:Seventy sorghum samples with broad range of genetic backgrounds, chemical and physical features were selected from over 1200 sorghum lines and hybrids.

Variation = 9.1%Low 86.0% High 93.8%

Conversion Efficiencies (%)

Variation = 22.1%Low 12.2% High 14.8%

Ethanol Yields (%, V/V)

Starch content and type of starch

Protein content and protein quality

Protein starch interaction

Mash viscosity

Formation of amylose-lipid complex

Phenol compounds

Combined interactions

Major factors affecting sorghum bioconversion

68.5 - 72.0%

13.5%

14.5%

7.4%

Starch content vs. Ethanol yield

65.0

70.0

75.0

80.0

85.0

90.0

95.0

36 42 48 54 60 66 72

Fermentation Hours

Effic

ienc

y(%

)

Waxy Normal

Tannin

82.2%

93.8%

86%

93.1%

87.5%

Fermentation efficiency of grain sorghums

93.8%93.8%

60-85 C

68 - 132 C

Amylose content

<5%

25%

50%

70% Ferm

enta

tion

effic

ienc

y

@ 95 ºC

Inso

lubl

e pa

rtic

les

93%

70%

Low

High

Effect of amylose content on starch gelatinization, insoluble, and efficiency

Starch gelatinization during cooking – Normal starchStarch gelatinization during cooking – Normal starch

Starch gelatinization during cooking – Waxy starchStarch gelatinization during cooking – Waxy starch

40.040 60 80 100 120 140 160

Temperature (°C)

Hea

t Flo

w

Solid residues after enzymatic hydrolysis

Before enzymatic hydrolysis

After enzymatic hydrolysis

Before enzymatic hydrolysis

Amylose-lipids complex

Formation of amylose-lipids complex

8%

Effect of protein content on ethanol yield and fermentation efficiency

Ethanol fermentation efficiency vs. protein digestibility

Area/mg proteins extracted by sonication and separated by SE-HPLC

Ethanol fermentation efficiency vs. extractable proteins from mashed samples

After enzymatic hydrolysis

Starch and protein interactionStarch and protein interaction

Protein body Starch granules

The range of sorghum starch granules is from 2 to 30 m

Before steeping

After steeping with SO2

2.5%

Starch and protein interactions

Ethano

l ferm

entatio

n effic

iency

(%)

Viscosity at 95 ºC and with amylase

Viscosity is one of the key factors affecting sorghum bioconversion efficiency

-1000

3000

7000

11000

15000

0.00 2.00 4.00 6.00 8.00 10.00

Time (min)

Vis

cosi

ty (c

P)

0

20

40

60

80

100

120

Tem

pera

ture

(°C

)

Normal amylase10 times of amylase20 times of amylaseDecorticated

Effect of phonolic compounds on mash viscosityand fermentation efficiency

Sorghum Efficiency (%)

Chemical Composition (%) Protein Digestibility

(%)Starch Protein Fiber Fat Ash

High (5) 93.3 72.1 9.33 1.63 2.69 1.59 65.7

Low (5) 86.8 68.8 12.10 2.10 3.50 1.90 50.8

Difference -7.0 -3.63 13.1 15.0 2.94 11.8 -22.8(%)

Comparison of high vs. how fermentation efficiency sorghums

ELCAM: Average “base case”…ELCAM: Average “base case”…

0

10

20

30

40

50

60

70

80

90

100

Component

K Btu/gal EtOHK Btu/gal EtOH

plant

cultivate

fertilizerchemicals

Irrigateharvest

transport

Grind/cook

Other

Net energy gain= 25,500 Btu/galNet energy gain

= 25,500 Btu/galDDGS

EtOH

Sorghum, regional average, yield = 70 bu/ac

Used as the comparativebase case for analyses

Used as the comparativebase case for analyses

Ferment

DistillDehydrate

Delivery

Dr. Jim McLaren

0

3

6

9

12

15

50 70 90 110 130 150

NEV (Ref base)NEV (Ref base)

Yield bu/ac

NEV 104 Btu/gal EtOHNEV 104 Btu/gal EtOH

NEV 106 Btu/acreNEV 106 Btu/acre

Net energy value (NEV) for different levels of grain yield per acre

Sorghum can make a great contribution…Sorghum can make a great contribution…

Data Source: USDA

Main Corn Belt

The research to-date shows thatsorghum is a viable renewable

resource for biofuel production.

The research to-date shows thatsorghum is a viable renewable

resource for biofuel production.

Future research on sorghum bioconversion:

Develop new or modified sorghum hybrids for biofuel production with high fermentation efficiency and low energy input.

Increase starch content and grain yield per acre.

Develop advanced bioprocessing technology to increase sorghum fermentation efficiency.

Acknowledgement

Research Associates and Graduate students in Wang’s research group,

Drs. Bean, McLaren, Seib, Tuinstra, Shi, Hays, Madl, Mr. Lenz,

Company: Monsanto Company, Novozymes, Inc.,

KansasSorghum

Commission

KansasSorghum

Commission

Thanks