Thursday, July 30, 2009 - 10:00 AM
S135
Ethanol Production from Pine Using Modified Yeast and Bacteria
Joy Doran-Peterson, Amruta Jangid, Divya Bansal, and Matthew Hawkins. Microbiology, University of Georgia, 204 Biological Sciences, Athens, GA 30602-2605
Softwood is a major source of lignocellulosic biomass and contains about 44% cellulose, 22% hemicellulose and 28% lignin (dry wt basis). Conversion of softwood to ethanol is challenging due to high lignin and extractables content. Problematic compounds also result from chemical pretreatments designed to break down the plant cell wall in softwoods. Compounds potentially inhibitory to microorganisms include: furfural, 5-hydroxymethylfurfural (HMF), levulinic acid, acetic acid, formic acid, uronic acid, 4-hydroxybenzoic acid, vanillic acid, vanillin, phenol, cinnamaldehyde, formaldehyde 2-furoic acid, 3,4-dihydroxybenzoic acid, 3,4-dihydroxybenzaldehyde, salicylic acid, homovanillic acid, benzoic acid, and ferulic acid. Using commercially available ethanologenic yeasts with increasing solids concentrations of pretreated pine resulted in increased lag times. A modified yeast, AJP50, has recently been developed for fermentation of softwood biomass at high solids concentrations. AJP50 reached over 40 g/L ethanol after 72 h in 17.5% w/v solids fermentations. At the same inoculum level, the parent strain only produced 7 g ethanol/L after 72 h of fermentation. With a 100X increase in inoculum, the parent produced 18 g ethanol/L by 72 hours and 40 g ethanol/L by 144h fermentation. In contrast, AJP 50 produced 95-85% of maximum theoretical yield (MTY) of ethanol by 48h fermentation in 12-15% w/v solids of pine subjected to a harsher pretreatment. The parent yeast was unable to survive in the more severely pretreated pine at the same inoculum level. In 12% w/v solids concentrations, increasing the inoculum 100X resulted in 21% of MTY by 48 hours and 95% of MTY by 120h.