Location: Bioenergy ResearchTitle: Production of xylitol by a Coniochaeta ligniaria strain tolerant of inhibitors and defective in xylose metabolism
Submitted to: Biotechnology Progress
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/3/2016
Publication Date: 5/17/2016
Citation: Nichols, N.N., Saha, B.C. 2016. Production of xylitol by a Coniochaeta ligniaria strain tolerant of inhibitors and defective in growth on xylose. Biotechnology Progress. 32(3):606-612. doi: 10.1002/btpr.2259.
Interpretive Summary: Xylitol is a five-carbon sugar alcohol that has been shown to improve dental health and prevent ear infections. With 40% fewer calories per gram than sucrose, it is used in pharmaceuticals and personal-care products and as an alternative sweetener in gums and mints. Xylitol is difficult to extract from natural sources and, because the current chemical method of production has high energy and cost demands, a biological route to xylitol is desirable. NCAUR scientists developed a microbe that makes xylitol from a sugar, xylose, found in biomass. The microbe has intrinsic resistance to inhibitors of the types encountered in conversion of biomass to fuels and chemicals, and produced up to 0.48 grams of xylitol per gram of xylose from corn stover.
Technical 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 hyrdrolysate.