Characterization of D-sorbitol dehydrogenase involved in D-sorbitol production of a methanol yeast, Candida boidinii (Kloeckera sp.) No. 2201.

Abstract

d-Sorbitol (sorbitol) production from d-glucose could be achieved by initial isomerization of d-glucose to d-fructose via xylose isomerase, then reduction to sorbitol via sorbitol dehydrogenase coupled with NADH regeneration from the methanol oxidative enzymes system by an intact cell system of a methanol yeast, Candida boidinii (Kloeckera sp.) No. 2201. Sorbitol dehydrogenase was purified 351-fold from a cell-free extract of d-xylose-grown cells and characterized. It oxidized preferably d-mannitol besides sorbitol, and reduced preferably d-xylulose and d-ribulose, besides d-fructose. Km values for sorbitol and d-fructose were 7.7 and 263 mM, and Vmax values were 301 and 384 μmol/min/mg, respectively. The enzyme activity was strongly stimulated by Fe3+ and significantly inhibited by Pb2+, EDTA, and o-phenanthroline.