Submitted to: Biocatalysis and Agricultural Biotechnology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/7/2020
Publication Date: 9/13/2020
Citation: Saha, B.C., Kennedy, G.J. 2020. Production of xylitol from mixed sugars of xylose and arabinose without co-producing arabitol. Biocatalysis and Agricultural Biotechnology. 29. Article 101786. https://doi.org/10.1016/j.bcab.2020.101786.
DOI: https://doi.org/10.1016/j.bcab.2020.101786

Interpretive Summary: Xylitol is a natural food sweetener, dental caries reducer and sugar substitute for diabetics. Production of xylitol from a sugar (xylose) by fermentation from waste biomass has become attractive due to problems associated with its production chemically. During fermentation, another sugar (arabinose) commonly present in waste biomass is converted to a product (arabitol) which is difficult to separate in a cost-effective way. There is a strong interest to find a naturally occurring yeast for production of arabitol free xylitol. In this work, a total of 99 yeast strains from ARS Culture Collection were evaluated for production of arabitol free xylitol from biomass derived sugars. The results are very encouraging to warrant developing bioprocess technology for production xylitol from biomass.

Technical Abstract: Xylitol, a five-carbon sugar alcohol, is a natural food sweetener, dental caries reducer and sugar substitute for diabetics. Production of xylitol by fermentation from hemicellulosic hydrolyzates has become attractive due to problems associated with its production using chemical hydrogenation. During fermentation, L-arabinose present in hemicellulosic hydrolyzates is converted to L-arabitol which is difficult to separate in a cost-effective way. A total of 99 yeast strains (NRRL numbered) were evaluated for production of arabitol free xylitol and vice versa from a mixture of xylose and arabinose (10 g L-1 each). The five best xylitol producers (3.35 – 4.96 g L-1) with least arabitol production (0.10 – 0.55 g L-1) were: Barnettozyma populi Y-12728, Bar. californica Y-1680, Bar. californica Y-11750, Cyberlindnera mrakii Y-1364 and Bar. salicaria NRRL Y-6780. The five best arabitol producers (5.70 – 9.65 g L-1) with little or no xylitol production (0.00 – 0.49 g L-1) were: Kluyveromyces wickerhamii Y-8286, Galactomyces geotrichum Y-17569, Metschnikowia pulcherrima Y-7111, Candida homilentoma Y-10941 and Can. lyxosophila Y-17539. Ten selected xylitol producing strains with the ability to produce little or no arabitol were evaluated for xylitol production from undetoxified corn stover hemicellulosic hydrolyzate containing 20 g xylose, 3.5 g arabinose, 3.5 g glucose and 1.5 g galactose per L. Among these strains, Petrozyma xylosa YB-2349 produced 7.20±0.19 g xylitol per L without producing detectable arabitol from the hydrolyzate. A number of these strains showed promise to be used for production of arabitol free xylitol from hemicellulosic hydrolyzate.