S137: New strategies to overcome glucose repression in mixed sugar fermentation in Saccharomyces cerevisiae

Lignocellulosic biomass consisting of cellulose, hemicellulose, and lignin is a potential sustainable source of mixed sugars for fermentation to fuels and chemicals. Co-utilization of all the available sugars including hexose sugars such as glucose and pentose sugars such as D-xylose and L-arabinose present in the lignocellulosic hydrolysates is critical to the overall process economics. Recombinant Saccharomyces cerevisiae strains containing a heterologous pentose utilization pathway can utilize mixed sugars including glucose, D-xylose, and L-arabinose to produce ethanol. However, one of the main limitations in the fermentation of mixed sugars is glucose repression, i.e. utilization of pentose sugars is inhibited by the presence of glucose. This results in delayed utilization of pentose sugars and significantly reduced overall ethanol productivity. In this presentation, I will discuss several new strategies that we have been working on to overcome glucose repression in mixed sugar fermentation.