Monday, July 25, 2011: 9:00 AM
Oak Alley, 4th fl (Sheraton New Orleans)
Lignocellulosic biomass represents a potential feedstock for microbial conversion into fuels or value-added chemicals. Low concentrations of furan derivatives such as furfural and 5-hydroxymethylfurfural are formed by the dehydration of sugars during dilute acid pretreatment of lignocelluloses that significantly inhibit growth and fermentation. Developing biocatalysts that are furfural tolerant is essential for future process simplification. Gene array experiments comparing the parent and a furfural-resistant mutant suggested silencing NADPH-dependent furfural reductase such as YqhD is a beneficial genetic change for furfural resistance under xylose fermentation condition. Oxidoreductase YqhD is proposed to contribute to furfural inhibition by depleting the pools of NADPH and starving biosynthesis. Deletion of yqhD increased furan tolerance. We also found that increasing the availability of NADPH by genetic (pntAB) or metabolic approaches maked cells more tolerant to furfural, confirming the linkage between furfural inhibition on cell growth and NADPH starvation. We recently identified an NADH-dependent oxidoreductase (FucO) that can reduce furfural without competing for NADPH. Overexpression of fucO increased furfural tolerance. These discoveries have been used to develop a general model for metabolic engineering furfural tolerant E. coli strains for ethanol production and organic acid production.