Monday, August 13, 2012
Columbia Hall, Terrace Level (Washington Hilton)
To identify and overcome key barriers to the sustainable conversion of lignocellulosic biomass to biofuels, we are studying the effects of lignocellulosic hydrolysates on microbial physiology and gene regulation. We have previously compared the properties of an Escherichia coli ethanologen grown in hydrolysates prepared from corn stover pretreated by AFEX (ACSH) to those of the same strain grown in a synthetic ACSH mimic (SynHv1) that contains similar concentrations of sugars, amino acids, other essential components found in authentic ACSH. Comparative multiomic fermentation of ACSH vs. SynH revealed effects of multiple inhibitors and stress responses in hydrolysate on strain performance in the conversion of lignocellulose to biofuel. To further characterize the stresses associated with growth in ACSH, we have generated a new version of SynH (SynHv3) containing potential lignin-derived inhibitors (phenolic lignotoxins), acetate/acetamide, extra sugars, higher osmolarity, and osmoprotectants (e.g., betaine) at the concentrations detected in authentic ACSH. Our results indicate that these compounds exert synergistic inhibitory effects on cell growth, ethanol synthesis, and xylose conversion. However, at the concentrations present in ACSH, the phenolic amides (feruloyl amide and coumaroyl amide) were the principal inhibitors of growth and xylose utilization, whereas osmotic stress, phenolic acids, and phenolic aldehydes had lesser effects. Comparative multiomic fermentation with the new SynHv3 and ACSH allowed us to identify regulatory and metabolic changes associated with growth in ACSH, and to characterize the effects of single or multiple inhibitory compound(s) on E. coli growth, xylose utilization, and ethanol yield.