1-02: Understanding the physiology of Thermoanaerobacter thermohydrosulfuricus WC1 through genomic, proteomic and metabolic analysis for its usefulness in cellulolytic biofuel producing co-cultures

The inability of the cellulolytic specialist, Clostridium thermocellum, to ferment hemicellulose constituent sugars is a major limitation in achieving the complete conversion of lignocellulosic biomass to biofuels.  Thermoanaerobacter thermohydrosulfuricus WC1, which has been shown to ferment a broad range of lignocellulose constituent sugars, is being investigated as a potential co-culture partner for purposes of improving lignocellulose hydrolysis rates, extent of degradation and total biofuel yield.  We have recently determined the draft genome sequence of T. thermohydrosulfuricus WC1 and performed pangenomic analysis of all sequenced Thermoanaerobacter strains.  Of the sequenced Thermoanaerobacter strains, T. thermohydrosulfuricus WC1 has one of the most extensive and diverse enzymatic suites capable of hydrolyzing and fermenting the heterogeneous hemicellulose matrix.  However, a cellobiose specific phosphotransferase system (csPTS) as well as a carbon catabolite repression (CCR) network is encoded in the T. thermohydrosulfuricus WC1 genome, thus potentially limiting pentose utilization in the presence of cellulose hydrolysis products.  To evaluate substrate usage patterns we have analyzed the metabolic profiles and conducted gene expression profiling supported by RP-HPLC-MS/MS proteomic analysis.  Cultures grown on the cellobiose-xylose combination were found to ferment both sugars simultaneously despite proteomic evidence identifying synthesis of both the csPTS and CCR networks when grown on cellobiose alone.  Thus, xylose utilization does not seem to be under the regulatory control of a potential cellobiose-induced regulatory network and T. thermohydrosulfuricus WC1 may be well suited for C. thermocellum based co-cultures fermenting lignocellulosic biomass.