Impact of culture nutrition on the tolerance of furan inhibitors and the conversion of high xylose concentrations to ethanol by Pichia Stipitis Nrrl Y-7124

Efficient fermentation processes to produce ethanol from both the hexose and pentose sugars available in low-cost lignocellulosic biomass are sought to support the expansion of the biofuels industry. Furfural and hydroxymethylfurfural are key byproducts of the dilute acid pretreatment hydrolysis of lignocellulosic biomass, the most economical method of releasing hemicellulosic sugars for fermentation to ethanol biofuel. The availability of tolerant microbial catalysts would allow efficient fermentation of low-cost acid hydrolysates despite the presence of inhibitory byproducts. Data showing the impact of mineral and nitrogen source composition on the ability of yeast Pichia stipitis to survive and detoxify furan inhibitors and to convert high xylose concentrations efficiently to ethanol are presented. Implications of these findings in context of the current literature on biomass to ethanol conversion and stress tolerance are discussed. Process-based strategies to produce a tolerant initial population and then to foster and sustain tolerance during growth and ethanol fermentation are considered. This is an abstract of a paper presented at the 2006 AIChE Annual Meeting (San Francisco, CA 11/12-17/2006).