Expression of a heat-stable NADPH-dependent alcohol dehydrogenase fromThermoanaerobacter pseudethanolicus39E inClostridium thermocellum1313 results in increased hydroxymethylfurfural resistance.
BACKGROUND
Resistance to deconstruction is a major limitation to the use of lignocellulosic biomass as a substrate for the production of fuels and chemicals. Consolidated bioprocessing (CBP), the use of microbes for the simultaneous hydrolysis of lignocellulose into soluble sugars and fermentation of the resulting sugars to products of interest, is a potential solution to this obstacle. The pretreatment of plant biomass, however, releases compounds that are inhibitory to the growth of microbes used for CBP.


RESULTS
Heterologous expression of theThermoanaerobacter pseudethanolicus39EbdhAgene, that encodes an alcohol dehydrogenase, inClostridium thermocellumsignificantly increased resistance to furan derivatives at concentrations found in acid-pretreated biomass. The mechanism of detoxification of hydroxymethylfurfural was shown to be primarily reduction using NADPH as the cofactor. In addition, we report the construction of new expression vectors for homologous and heterologous expression inC. thermocellum.These vectors use regulatory signals from bothC. bescii(the S-layer promoter) andC. thermocellum(the enolase promoter) shown to efficiently drive expression of the BdhA enzyme.


CONCLUSIONS
Toxic compounds present in lignocellulose hydrolysates that inhibit cell growth and product formation are obstacles to the commercialization of fuels and chemicals from biomass. Expression of genes that reduce the effect of these inhibitors, such as furan derivatives, will serve to enable commercial processes using plant biomass for the production of fuels and chemicals.
Department of Genetics, University of Georgia, Athens, GA USA.|BioEnergy Science Center, Oak Ridge National Laboratory, Oak Ridge, TN USA.
Sun-Ki
SK
Kim
Department of Genetics, University of Georgia, Athens, GA USA.|BioEnergy Science Center, Oak Ridge National Laboratory, Oak Ridge, TN USA.
Joseph
J
Groom
Biosciences Center, National Renewable Energy Laboratory, Golden, CO USA.|BioEnergy Science Center, Oak Ridge National Laboratory, Oak Ridge, TN USA.
Daehwan
D
Chung
Biosciences Division, Oak Ridge National Laboratory, Oak Ridge, TN USA.|BioEnergy Science Center, Oak Ridge National Laboratory, Oak Ridge, TN USA.
James
J
Elkins
Department of Genetics, University of Georgia, Athens, GA USA.|BioEnergy Science Center, Oak Ridge National Laboratory, Oak Ridge, TN USA.
Janet
J
Westpheling
5-hydroxymethyl-2-furfural; Butanol dehydrogenase; Clostridium thermocellum; Consolidated bioprocessing; Furfural