ARS | Publication request: Conversion of Extracted Oil Cake Fibers into Bioethanol including DDGS, Canola, Sunflower, Seasame, Soy, and Peanut for Integrated Biodiesel Processing

Submitted to: Journal of the American Oil Chemists' Society
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: November 14, 2008
Publication Date: December 18, 2008
Citation: Balan, V., Rogers, C.A., Chundawat, S.P., Sousa, L.D., Slininger, P.J., Gupta, R., Dale, B.E. 2008. Conversion of extracted oil cake fibers into bioethanol including DDGS, canola, sunflower, seasame, soy, and peanut for integrated biodiesel processing. Journal of the American Oil Chemists' Society. 86:157-165.

Interpretive Summary: In the United States, bioethanol is currently produced from starchy biomass, mainly corn. However, with increasing demands for biofuel and the rising corn prices, cheaper renewable biomass feedstocks are desired. Byproducts of the edible oil and corn grain industries, such as extracted oilseed cakes, are potential sources of cheap biomass. Oil seed cakes (e.g., from canola, sunflower, sesame, soybean, and peanut) and distiller¿s grains are rich in proteins and fermentable sugars locked in plant structural material known as cellulose and hemicellulose. In order to aid the release of sugars for fermentation to ethanol, a pretreatment process called AFEX (ammonia fiber exansion) was applied and optimized for several types of oilseed cakes and distillers grain as feed-stocks. The optimized AFEX pretreatment allowed the biomaterials to be enzymatically hydrolyzed to mixed sugars using a synergistic consortium of enzymes including cellulases, beta-glucosidase and pectinase. The freed sugars were efficiently fermented to ethanol by Pichia stipitis a native yeast strain with unique ability to make ethanol from the sugar mixtures derived from low-cost biomass. These findings demonstrate that dried distiller grains with solubles and edible oil cakes such as peanut oilcake have tremendous potential as lignocellulosic feedstocks to produce ethanol. In an integrated biodiesel-oilseed processing plant, the oil and ethanol products could potentially be combined in a reactor to produce biodiesel. These results will be used by others involved in biomass fermentation process technology research and development and the biofuels industry. New knowledge gained from this research is progress toward our national priorities of achieving energy independence, strengthening our rural economy, and preserving our environment.

Technical Abstract: We have come up with a novel integrated approach where biodiesel processing can be potentially done in-house by producing ethanol from edible oilseeds after hexane extraction to remove residual oil. In addition, we have demonstrated how ethanol could be manufactured from widely available oil cakes (such as canola, sunflower, sesame, soy, peanut) and dried distiller grain solid (DDGS). The edible oil cakes and DDGS were hexane extracted, ammonia fiber expansion pretreated, enzymatically hydrolyzed, and fermented to produce ethanol. From all the oil cakes tested in this work, DDGS and peanut oil cake showed the most promising results producing more than 180 g of glucose/kg of oil cake. These two feedstocks were hydrolyzed at 15% solids loading and fermented by a native strain of Pichia stipitis. Most sugars were consumed during the first 24 hours with no pronounced inhibition of P. stipitis by the degradation products in the hydrolyzate. Xylose consumption was more effective in the peanut cake hydrolyzate compared to DDGS.