Atmospheric and room temperature plasma (ARTP) mutagenesis enables xylitol over-production with yeast Candida tropicalis

Abstract

Xylitol is a sugar alcohol that is used as a sweetener in food and confections. Industrially, xylitol is manufactured by chemical hydrogenation of d-xylose, which requires expensive separation and purification steps as well as high pressure and temperature. The microbial production of xylitol has been examined as an alternative to the chemical process. In this study, a xylitol over-producing strain is breeded by mutagenesis of a newly isolated yeast Candida tropicalis with a new mutation breeding system named atmospheric and room temperature plasma. The highest yield strain T31 was screened among more than 200 mutants with a xylitol yield of 0.61 g/g, which represents a yield increase of 22%. Furthermore, a two-stage dissolved oxygen supply strategy was used in a fermentation process resulting the maximum xylitol yield 0.79 g/g, which makes it a promising candidate for xylitol production. Further biochemical analysis indicating the relative gene expression and the enzyme activity of xylose reductase were higher in mutants than those in the original strain, which partly explained the high yield of xylitol. Thus, this study provides a new strategy to breed the over-producing strains for the xylitol industry.