Xylose reductase and xylitol dehydrogenase activities of D‐xylose‐xylitol‐fermenting Candida guilliermondii

The effect of the inoculum age and initial xylose concentration on the activities of xylose reductase (XR) and xylitol dehydrogenase (XD) of Candida guilliermondii FTI 20037 were investigated. Under the experimental conditions used, the XR and XD activities were, respectively. NADPH and NAD or NADP dependent. The NADP/NADPH ratio for XR was not substantially influenced by the age of inoculum or the initial xylose concentration. The Km of XR (0.18 M) was about 4‐folds smaller than the Km of XD NAD‐dependent. A renewable xylose‐xylitol conversion was obtained with 40 h aged inoculum of Candida guilliermondii FTI 20037 grown in a medium containing an initial xylose concentration of 120g/l.