BIOCONVERSION OF 2-AMINO ACIDS TO 2-HYDROXY ACIDS BY CLOSTRIDIUM-BUTYRICUM

Analysis by gas chromatography-mass spectrometry (GC-MS) of 24-h cultu res of Clostridium butyricum type strain in synthetic BMG medium suppl emented with various 2-amino acids (10 mM) revealed the presence of th e corresponding 2-hydroxy acids. C. butyricum was able to bioconvert L -valine, DL-norvaline, L-leucine, DL-norleucine, L-methionine and L-ph enylalanine as well as unusual 2-amino acids, i.e,, L-2-aminobutyric a cid, L-2-amino-4-pentenoic acid, DL-2-aminooctanoic acid, and DL-2-ami no-4-phenylbutanoic acid. L-Isoleucine and cycloleucine were not conve rted into their corresponding 2-hydroxy acids. The bioconversion rate was maximal with DL-norvaline (6.2%). Chiral GC analysis demonstrated that only D-2-hydroxy-4-methylpentanoic acid is formed from L-leucine, indicating that the bioconversion is stereospecific, with inversion o f configuration. D-Leucine and D-methionine were also converted to the corresponding 2-hydroxy acids. This observation opens new aspects in the study of C. butyricum and raises questions about the amino acid me tabolism by this species. (C) 1998 Federation of European Microbiologi cal Societies. Published by Elsevier Science B.V. All rights reserved.