Isolation and characterization of L-valine-degrading Candida maltosa DLPU-zpb for D-valine preparation from DL-valine

摘要

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 degrees 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.