title: Isolation and characterization of L-valine-degrading Candida maltosa DLPU-zpb for D-valine preparation from DL-valine.
abstract: 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.
  
  
  CONCLUSIONS
  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.
authors.affiliation: School of Biological Engineering, Dalian Polytechnic University, Dalian, China.
authors.forename: C H
authors.initials: CH
authors.lastname: Zhang
authors.affiliation: School of Biological Engineering, Dalian Polytechnic University, Dalian, China.
authors.forename: W T
authors.initials: WT
authors.lastname: Xin
authors.affiliation: School of Biological Engineering, Dalian Polytechnic University, Dalian, China.
authors.forename: M
authors.initials: M
authors.lastname: Chen
authors.affiliation: School of Biological Engineering, Dalian Polytechnic University, Dalian, China.
authors.forename: Y
authors.initials: Y
authors.lastname: Bi
authors.affiliation: School of Biological Engineering, Dalian Polytechnic University, Dalian, China.
authors.forename: Z Q
authors.initials: ZQ
authors.lastname: Gao
authors.affiliation: School of Biological Engineering, Dalian Polytechnic University, Dalian, China.
authors.forename: J
authors.initials: J
authors.lastname: Zhang
mesh_terms: D055162:Biocatalysis; D002175:Candida / Q000302:isolation & purification / Q000378:metabolism*; D004275:DNA, Ribosomal / Q000235:genetics; D007218:Industrial Microbiology / Q000379:methods*; D008969:Molecular Sequence Data; D014633:Valine / Q000737:chemistry / Q000378:metabolism*
chemical_list: D004275:DNA, Ribosomal; D014633:Valine
keywords: Candida maltosa; characterization; d-valine; isolation; l-valine-degrading; preparation