Tuesday, April 20, 2010
10-13

Ethanol production from agricultural residues using integrated enzyme production and microbial fermentation system

Kelly C. Williams, Biological Systems Engineering, University of California, Davis, One Shields Ave, 2030 Bainer Hall, Davis, CA 95616, Ruihong Zhang, Biological and Agricultural Engineering, University of California, Davis, One Shields Ave., Davis, CA 95616, and Tina Jeoh, Biological and Agricultural Engineering, University of California Davis, One Shields Ave., Davis, CA 95616.

Ethanol from lignocellulosic biomass can be used as a renewable fuel supplement for gasoline. One of the most expensive steps of lignocellulosic ethanol production is the enzyme production for hydrolysis of complex carbohydrates into simple sugars. A process for glycosyl hydrolase production is being developed for coupling with simultaneous saccharification and fermentation (SSF) by E. coli KO11. A variety of lignocellulosic substrates, including rice bran, wheat bran, sugar beet pulp and grape pomace are tested as carbon sources for enzyme induction by Trichoderma reesei QM9414 and Aspergillus niger. Total protein produced, as well as activities on filter paper, carboxymethyl cellulose (CMC) and pectin, are being quantified for each treatment. It is expected that the activity profiles of the enzymes produced with each substrate will vary with the composition of each of the substrates. Crude enzyme extracts from all treatments are used in SSF of sugar beet pulp, grape pomace or rice straw with E. coli KO11. Ethanol production from these cultures is being quantified by gas chromatrography. It is expected that the SSF with each substrate will be most successful with their corresponding production substrate. Preliminary data show that for A. niger, the highest total protein production is 0.15 g/L on grape pomace. A. niger grown on wheat bran produced enzymes had the highest cellulase activity compared to other substrates. CMC and Filter paper activities were 5.5 and 3.5 g glucose/hr/L, respectively.