Isolation and characterization of l ‐valine‐degrading Candida maltosa DLPU‐zpb for d‐ valine preparation from dl ‐valine

To develop a practical process for d‐ valine preparation from dl‐ valine, l ‐valine was used as a sole source of carbon and nitrogen in basal minimal medium to isolate l ‐valine‐degrading micro‐organisms. A yeast strain DLPU‐zpb was obtained, which showed asymmetric degrading activity against dl‐ valine. Based on the morphology, physiological and biochemical characteristics, and 26S rDNA D1/D2 domain sequence, strain DLPU‐zpb was identified as Candida maltosa . The cells of this strain were used as a biocatalyst for eliminating the l ‐isomer from dl‐ valine. The l ‐isomer was completely degraded within 72 h under the conditions of 30°C, pH control at 6·0, 200 rev min −1 and 50 g l −1 dl‐ valine. The strain DLPU‐zpb degraded l ‐valine effectively but not d‐ valine, and thus d‐ valine could be easily isolated from the resultant reaction mixture, which provides a new method for d‐ valine preparation from dl‐ valine. Significance and Impact of the Study d‐ valine is an important raw material for medicines and its demand is increasing year by year. Several approaches for d‐ valine preparation have been reported, but none of them are likely to provide product at low cost. A newly isolated l ‐valine‐degrading yeast strain Candida maltosa DLPU‐zpb was described, which showed asymmetric degrading activity against dl‐ valine. Thus, a new and practical process for d‐ valine preparation from dl‐ valine could be developed. This is the first report of the asymmetric degrading ability of C. maltosa against dl‐ valine and d‐ valine preparation from dl‐ valine.