Direct conversion of xylan to butanol by a wild‐type Clostridium species strain G117

Lignocellulosic biomass has great potential for use as a carbon source for the production of second‐generation biofuels by solventogenic bacteria. Here we describe the production of butanol by a newly discovered wild‐type Clostridium species strain G117 with xylan as the sole carbon source for fermentation. Strain G117 produced 0.86 ± 0.07 g/L butanol and 53.4 ± 0.05 mL hydrogen directly from 60 g/L xylan provided that had undergone no prior enzymatic hydrolysis. After process optimization, the amount of butanol produced from xylan was increased to 1.24 ± 0.37 g/L. In contrast to traditional acetone‐butanol‐ethanol (ABE) solventogenic fermentation, xylan supported fermentation in strain G117 and negligible amount of acetone was produced. The expression of genes normally associated with acetone production ( adc and ctfB2 ) were down‐regulated compared to xylose fed cultures. This lack of acetone production may greatly simplify downstream separation process. Moreover, higher amount of butanol (2.94 g/L) was produced from 16.99 g/L xylo‐oligosaccharides, suggesting a major role for strain G117 in butanol production from xylan and its oligosaccharides. The unique ability of strain G117 to produce a considerable amount of butanol directly from xylan without producing undesirable fermentation byproducts opens the door to the possibility of cost‐effective biofuels production in a single step. Biotechnol. Bioeng. 2016;113: 1702–1710. © 2016 Wiley Periodicals, Inc.