Characterization of D-Sorbitol Dehydrogenase Involved in D-Sorbitol Production of a Methanol Yeast, Candida boidinii (Kloeckera sp.) No. 2201

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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 o-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 V_max values were 301 and 384μmol/min/mg, respectively. The enzyme activity was strongly stimulated by Fe³⁺ and significantly inhibited by Pb²⁺, EDTA, and o-phenanthroline.