S160c: Characterization of Hydrolysate Toxicity on Fermentation of Glucose and Xylose from Lignocellulosic Biomass

Biomass pretreatment is necessary to reduce the recalcitrance of lignocellulosic feedstocks to enzymatic saccharification and to allow the liberation of soluble sugars from plant cell wall carbohydrates, but pretreatment can also release a number of undesirable compounds into the hydrolysate that can inhibit the growth and ethanol productivity of fermentation organisms.  Incomplete utilization of biomass sugars, particularly xylose, consequently lower ethanol yield are often observed in fermentation of hydrolysates especially generated from pretreatment using higher solids loading.  It is critical to understand fermentation inhibition by hydrolysate components/inhibitors at a basic level in order to devise optimal pretreatment processes that maximize sugar yields and minimize the formation of inhibitory compounds or to identify the genes or pathways that provide either resistance to or elimination of toxic components in hydrolysates, and thus eliminate the detoxification (conditioning) step in pretreatment. We conducted systematic study to define the necessary parameters around hydrolysate toxicity in diluted acid pretreatment process using xylose-fermenting Zymomonas mobilis strain 8b and the results of this study will be presented.