Characterization of the sugar alcohol-producing yeast Pichia anomala

Sugar alcohols have been widely applied in the field of food and medicine for their unique properties. Compared to chemical production, microbial production of sugar alcohol has become attractive for its environmental and sustainable pattern. In this study, a potential yeast isolated from soil of Beijing suburbs was identified as Pichia anomala TIB-x229, and its key enzyme of d-arabitol dehydrogenase for microbial production of sugar alcohols was functionally characterized. This yeast could simultaneously produce d-arabitol, xylitol, and/or ribitol from a different ratio of sugar substrates at a high efficiency by bioconversion, and no glucose repression happened when mixed sugars of xylose and glucose were used as the substrates during the bioconversion. This yeast could also efficiently convert complicated feedstock such as xylose mother liquor to d-arabitol, xylitol, and ribitol with 55 % yields. To elucidate the conversion relationship of the sugar alcohols, especially d-arabitol and xylitol, the key d-arabitol dehydrogenase gene from P. anomala was cloned, expressed and purified for further in vitro characterization. The results showed that this d-arabitol dehydrogenase could catalyze arabitol to xylulose further, which is significant for xylitol production from glucose. Our study laid the foundation for improving the production of sugar alcohols by metabolic and fermentation engineering strategies.