Amino Acid Isomerization in the Production of l-Phenylalanine from d-Phenylalanine by Bacteria1

Abstract

CHIBATA, ICHIRO (Tanabe Seiyaku Co., Ltd., Osaka, Japan), TETSUYA ToSA, AND RYUJIRO SANO. Amino acid isomerization in the production of L-phenylalanine from D-phenylalanine by bacteria. Appl. Microbiol. 13:618-624. 1965.-To establish an advantageous method for the production of L-amino acids, microbial isomerization of D-and DL-amino acids to L-amino acids was studied. Screening experiments on a number of microorganisms showed that cell suspensions of Pseudomonas fluorescens and P. miyamizu were capable of isomerizing D-and DL-phenylalanines to L-phenylalanine. Various conditions suitable for isomerization by these organisms were investigated. Cells grown in a medium containing D-phenylalanine showed highest isomerization activity, and almost completely converted Dor DL-phenylalanine into L-phenylalanine within 24 to 48 hr of incubation. Enzymatic studies on this isomerizing system suggested that the isomerization of Dor DL-phenylalanine is not catalyzed by a single enzyme, (Camino acid isomerase," but the conversion proceeds by a two step system as follows: D-pheylalanine is oxidized to phenylpyruvic acid by D-amino acid oxidase, and the acid is converted to L-phenylalanine by transamination or reductive amination.