(643e) A Native S. Cerevisiae Fermentation Methodology for Converting Glucose and Xylose From Biomass Hydrolysate to Ethanol

Saccharomyces cerevisiae, better known as baker's yeast, has traditionally been used in large-scale ethanol fermentation of starch-based raw materials. In order to use the same species in second generation bioethanol production, both hexose and pentose sugars derived from lignocellulosic biomass need to be fully utilized. Unfortunately, S. cerevisiae is unable to ferment xylose, the major pentose sugar released from the hydrolysis of hemicellulose, to ethanol. Much effort has focused on the genetic modification of ethanologens to incorporate genes for xylose utilization into the metabolic pathways of yeast and bacteria. However, one of the rate limiting steps in the utilization of xylose appears to be the isomerization of xylose to xylulose. In our approach reported previously, we conduct the isomerization step extracellularly using commercially available immobilized xylose isomerase (XI) to yield hydrolysates significantly enriched in xylulose. In this presentation, ethanol productivity of baker's yeast on pre-isomerized mixed sugars and biomass hydrolysate will be presented.