Pretreatment and conversion of distiller's dried grains with solubles for acetone-butanol-ethanol (ABE) production

Distillers dried grains with solubles (DDGS) is a low-value co-product from dry grind ethanol production. Due to its high fiber content, DDGS is used primarily as a feed for ruminant animals. Conversion of the carbohydrate components in DDGS to biofuel would improve the overall economics of dry grind ethanol production. The effect of solids loading oil pretreatment of DDGS and oil subsequent acetone-butanol-ethanol (ABE) fermentation was examined. DDGS samples were subjected to six pretreatments, involving acidic and alkaline electrolyzed water, at three solids loadings (20%, 30%, and 40% w/w). After a 72 h hydrolysis, the highest glucose yield was obtained from the sulfuric acid pretreated samples. In fermentation tests using Clostridium acetobutylicum P260 for ABE production, the highest ABE concentration was similar to 17 g L-1, which was achieved from alkaline electrolyzed water pretreated samples at 30% (w/w) solids loading. The solids loading in a pretreatment significantly affected both the sugar yield from enzymatic hydrolysis and the ABE yield from fermentation of DDGS hydrolysates. The hydrolysate from alkaline electrolyzed water pretreatment at 30% (w/w) solids was found to be most favorable to ABE production, while that from sulfuric acid pretreatment was the least fermentable, although it produced the highest sugar yield