Sunday, April 29, 2007

Removal of inhibitors from biomass sugars using a biological process

Nancy N. Nichols1, C. Kevin Chambliss2, Lekh Nath Sharma2, G. Peter Van Walsum3, and Bruce S. Dien1. (1) National Center for Agricultural Utilization Research, USDA, ARS, Midwest Area, 1815 N. University Street, Peoria, IL 61604, (2) Chemistry and Biochemistry, Baylor University, One Bear Place #97348, Waco, TX 76798-7348, (3) Environmental Studies, Baylor University, One Bear Place #97266, Waco, TX 76798-7266

A major constraint to fermentation of sugars in biomass hydrolysates is the presence of side-products of pretreatment that are toxic to microorganisms.  These chemicals include products of sugar degradation (furfural, 5-hydroxymethylfurfural (HMF), and levulinic acid), organic acids released from hemicellulose side-groups, and aldehydes and phenolics released from lignin.  These products are especially problematic because their inhibitory effects can be synergistic in blocking fermentation.  We are developing a bioremediation strategy to detoxify biomass sugars prior to fermentation.  A fungal strain (Coniochaeta ligniaria NRRL30616), isolated by us from an industrial soil sample, metabolizes furfural and HMF as well as a number of aromatic and aliphatic acids and aldehydes.  When evaluated on corn stover dilute-acid hydrolysates, the fungus was found to readily grow and remove a number of inhibitors, including furfural and HMF.  Analytical extraction of corn stover hydrolysate, followed by HPLC and LC-MS analysis, has been used to further quantitate a wide variety of aromatic acid, aliphatic acid, aldehyde and phenolic compounds, and follow their fate during growth of C. ligniaria in hydrolysate.  Biological abatement of the hydrolysates was determined to improve ethanol yield and productivity of glucose and xylose fermentations.