Production of xylitol by a Coniochaeta ligniaria strain tolerant of inhibitors and defective in growth on xylose.

Abstract

In conversion of biomass to fuels or chemicals, inhibitory compounds arising from physical-chemical pretreatment of the feedstock can interfere with fermentation of the sugars to product. Fungal strain Coniochaeta ligniaria NRRL30616 metabolizes the furan aldehydes furfural and 5-hydroxymethylfurfural, as well as a number of aromatic and aliphatic acids and aldehydes. Use of NRRL30616 to condition biomass sugars by metabolizing the inhibitors improves their fermentability. Wild-type C. ligniaria has the ability to grow on xylose as sole source of carbon and energy, with no accumulation of xylitol. Mutants of C. ligniaria unable to grow on xylose were constructed. Xylose reductase and xylitol dehydrogenase activities were reduced by approximately two thirds in mutant C8100. The mutant retained ability to metabolize inhibitors in biomass hydrolysates. Although C. ligniaria C8100 did not grow on xylose, the strain converted a portion of xylose to xylitol, producing 0.59 g xylitol/g xylose in rich medium and 0.48 g xylitol/g xylose in corn stover dilute acid hydrolysate. 2016 American Institute of Chemical Engineers Biotechnol. Prog., 2016 © 2016 American Institute of Chemical Engineers Biotechnol. Prog., 32:606-612, 2016.