Comparison of chemical composition of hydrolysates produced from five different feedstocks and its effect on microbial responses during the biofuel synthesis

Different biomass feedstocks and high glucan-loading hydrolysates will be necessary for sustainable biofuel production from lignocellulose. Therefore, it is crucial to understand microbial responses to hydrolysates produced from different feedstocks, as well as microbial stress caused by high sugar concentrations and potentially high levels of inhibitors in high glucan-loading hydrolysates. Using AFEX-pretreated biomass, we produced hydrolysates from five different feedstocks, including corn stover, switchgrass, miscanthus, sorghum, and mixed prairie, which all are grown and harvested at the same location and in the same year avoiding effects due to variable weather and growing conditions. We then used a three-tiered strategy to study how feedstock diversity impacts microbial responses. The strategy includes hydrolysate compositional analysis, chemical genomics for fingerprinting of hydrolysates and comparative fermentation. We also compared the hydrolysates that were produced with high-solid loading from pretreated corn stover.  During fermentations with two ethanologens, Saccharomyces cerevisiae and Zymomonas mobilis, we monitored and quantitated cell growth, glucose and xylose utilization, and ethanol production in these different feedstock hydrolysates. RNA samples were collected for RNAseq analysis. Together with chemical compositional analysis, chemical genomics and RNAseq data analysis, these results help us to determine specific microbial stress responses in these different feedstock hydrolysates.