ARS | Publication request: Culture conditions supporting inhibitor tolerance and rapid production of ethanol from natural xylose-fermenting yeasts presented mixed sugars

Submitted to: Society for Industrial Microbiology News
Publication Type: Abstract Only
Publication Acceptance Date: July 30, 2009
Publication Date: July 26, 2009
Citation: Slininger, P.J. 2009. Culture conditions supporting inhibitor tolerance and rapid production of ethanol from natural xylose-fermenting yeasts presented mixed sugars [abstract]. Society for Industrial Microbiology. p. 116.

Technical Abstract: Efficient fermentation processes to produce ethanol from low-cost lignocellulosic biomass are sought to support the expansion of the biofuels industry. Stress-tolerant microorganisms are needed that are able to consume both hexose and pentose sugars and also to withstand, survive, and function in the presence of stress factors common to fermentations of lignocellulose hydrolyzates, including inhibitors such as furfural and hydroxymethylfurfural (HMF) and high concentrations of mixed sugars and ethanol. Using optimal nitrogen and mineral sources for inhibitor tolerance, the utility of priming inocula with high xylose concentrations to induce faster fermentation rates in ethanol production fermentors and to eliminate diauxic lag during mixed sugar conversion was observed for Pichia stipitis NRRL Y-7124 as well as the more acid-tolerant Pachysolen tannophilus Y-2460. Under optimal conditions, P. stipitis Y-7124 yielded 66 g/L ethanol, 0.44 g ethanol/g sugar, in 48 h when grown on 150 g/L xylose and then resuspended to A620 ~40 in 95 g/L of glucose and 55 g/L xylose. Implications of these findings on process-based strategies to produce a tolerant initial population and then to foster and maintain an efficient viable population during subsequent ethanol fermentation on lignocellulosic biomass are investigated.