title: Stereoselective biotransformation of racemic mandelic acid using immobilized laccase and (S)-mandelate dehydrogenase.
abstract: OBJECTIVE
  (S)-Mandelate dehydrogenase (SMDH) and laccase were immobilized on chitosan. The bi-enzymatic system with immobilized SMDH and immobilized laccase was taken to catalyze the stereoselective transformation of racemic mandelic acid and (R)-mandelic acid was obtained from its racemic mixture.
  
  
  RESULTS
  Characteristics of the immobilized enzymes were valuated. The optimum pH and temperature of the immobilized SMDH were found to be pH 3.4 and 45 °C, and these of the immobilized laccase were about pH 6.0 and 55 °C, respectively. TheKmvalue of the immobilized SMDH for racemic mandelic acid was 0.27 mM and that of the immobilized laccase for ferrocyanide was 0.99 mM. The thermal and storage stabilities of these enzymes were improved with immobilization. The enantiomeric purity of the bi-enzymatically produced (R)-mandelic acid was determined to be over 99%.
  
  
  CONCLUSIONS
  The immobilized bi-enzymatic system for the stereoselective transformation of racemic mandelic acid showed higher productivity, faster reaction velocity, and more stable catalytic ability.Graphical abstract.
authors.affiliation: Department of Bioengineering, Nanjing University of Science and Technology, Xiaolingwei 200, Nanjing, 210094 People's Republic of China.
authors.forename: Xing
authors.initials: X
authors.lastname: Chen
authors.affiliation: Department of Bioengineering, Nanjing University of Science and Technology, Xiaolingwei 200, Nanjing, 210094 People's Republic of China.
authors.forename: Chengli
authors.initials: C
authors.lastname: Yang
authors.affiliation: Department of Bioengineering, Nanjing University of Science and Technology, Xiaolingwei 200, Nanjing, 210094 People's Republic of China.
authors.forename: Peng
authors.initials: P
authors.lastname: Wang
authors.affiliation: Department of Bioengineering, Nanjing University of Science and Technology, Xiaolingwei 200, Nanjing, 210094 People's Republic of China.
authors.forename: Xuan
authors.initials: X
authors.lastname: Zhang
authors.affiliation: Department of Bioengineering, Nanjing University of Science and Technology, Xiaolingwei 200, Nanjing, 210094 People's Republic of China.
authors.forename: Bingxin
authors.initials: B
authors.lastname: Bao
authors.affiliation: Department of Bioengineering, Nanjing University of Science and Technology, Xiaolingwei 200, Nanjing, 210094 People's Republic of China.
authors.forename: Dali
authors.initials: D
authors.lastname: Li
authors.affiliation: Department of Bioengineering, Nanjing University of Science and Technology, Xiaolingwei 200, Nanjing, 210094 People's Republic of China.
authors.forename: Ruofu
authors.initials: R
authors.lastname: Shi
keywords: (S)-Mandelate dehydrogenase; Bi-enzymatic system; Biocatalysis; Chitosan; Immobilization; Laccase