Minimization of by-product formation during D-amino acid oxidase catalyzed racemate resolution of D/L-amino acids

摘要

D-Amine acid oxidase (DAAO, EC 1.4.3.3) was applied to biotransformations of D-methionine or D-phenylalanine to the corresponding #alpha#-keto acids starting with the racemic mixtures as substrates. Hydrogen peroxide is formed as by-product in the DAAO-catalyzed reaction. This reactive species is disadvantageous for the racemate resolution process due to the chemical decarboxylation of the #alpha#-keto acids as well as the inactivation of the DAAO. To immediately remove the generated H_2O_2 during the biotransformations three different commercially available catalyses (bovine liver Aspergillums niter or Micrococcus lysodeikticus) were tested. By external addition of catalase from Micrococcus lysodikticus an #alpha#-keto acid yield of 100% was obtaind after complete conversion of the D-phenlalanine The space-time yield of the #alpha#-keto acid production increased up to 8.26 g l~9-1) h~(-1) compared to the process without addition of catalase (0.14 g l~(-1) h~(-1)). Another observation was a relationship between #DELTA#-redoxpotential and H_2O_2 concentration which should be the basis for an automated catalase feeding in the amino acid resolution process using DAAO in the future.