Tuesday, May 1, 2012
Napoleon Ballroom C-D, 3rd fl (Sheraton New Orleans)
Resistance mechanisms for biomass-derived pretreatment inhibitors such as furfural have been characterized in Saccharomyces cerevisiae and ethanologenic Escherichia coli but parallel responses in cellulolytic thermophiles are poorly described. Saccharolytic thermophiles from the genera Thermoanaerobacter and Caloramator, including a novel isolate from our laboratory, readily grow in the presence of biomass hydrolysates and demonstrate conversion of furan and aromatic aldehydes to less-toxic alcohols. The enzymes responsible for detoxification are unknown but once identified, could potentially be expressed in Clostridium thermocellum or Caldicellulosiruptor sp. to improve growth on cellulose in the presence of pretreatment inhibitors. Thermoanaerobacter pseudethanolicus 39E and Caloramator proteoclasticus ALDO1 displayed rapid reduction of 15 mM furfural to furfuryl alcohol during growth on glucose. As an initial screen to identify upregulated enzymes potentially involved in furfural detoxification, we employed multidimensional liquid-chromatography mass spectrometry to survey the proteome during growth in the presence of furfural. While the two strains showed similarities in their respective physiological response to the inhibitor, distinct differences were also apparent. Both organisms displayed increases in ABC transporter-related proteins for sugar uptake by two orders of magnitude. T. pseudethanolicus 39E upregulated a number of enzymes involved in purine, pyrimidine, and amino acid biosynthesis while C. proteoclasticus ALDO1 showed increases in proteins encoded by a large operon responsible for lipid production. Several enzymes involved in redox reactions were also upregulated in both strains and their role in aldehyde reduction is under investigation.