Engineered Furfural Tolerance in Caldicellulosiruptor bescii, a Consolidated Bioprocessing Thermophile


Harsh pretreatments are often used to make lignocellulose sugars more accessible for conversion to biofuels. These pretreatments can cause problems for subsequent stages of biofuel production. For example, dilute-acid pretreatment of lignocellulosic biomass creates potent inhibitors of microbial growth and fermentation such as furfural and 5-hydroxymethyl-furfural (5-HMF). The enzymatic reduction of these furan aldehydes to their corresponding less toxic alcohols is an engineering approach that has been successfully implemented in both Saccharomyces cerevisiae and ethanologenic Escherichia coli. However, this approach has not yet been investigated in thermophiles relevant to biofuel production through consolidated bioprocessing (CBP), such as Caldicellulosiruptor bescii. To test if C. bescii could be engineered to be more tolerant of these inhibitors, researchers from the Department of Energy’s BioEnergy Science Center (BESC) constructed a strain of C. bescii using a butanol dehydrogenase encoding gene from Thermoanaerobacter pseudethanolicus 39E (BdhA), which had previously been shown to have furfural and 5-HMF reducing capabilities. Heterologous expression of the NADPH-dependent BdhA enzyme conferred increased resistance of the engineered strain to both furfural and 5-HMF relative to the wild-type and parental strains. Further, when challenged with 15 mM concentrations of either furan aldehyde, the ability to eliminate furfural or 5-HMF from the culture medium was significantly improved in the engineered strain. This study represents the first example of engineering furan aldehyde resistance into a CBP-relevant thermophile and further validates C. bescii as being a genetically tractable microbe of importance for lignocellulosic biofuel production.


Chung, D., T. J. Verbeke, K. L. Cross, J. Westpheling, and J. G. Elkins. 2015. “Expression of a Heat-Stable NADPH-Dependent Alcohol Dehydrogenase in Caldicellulosiruptor bescii Results in Furan Aldehyde Detoxification,” Biotechnology for Biofuels 8,102. DOI: 10.1186/s13068-015-0287-y.