Conversion of<i>meso</i>-2,3-Butanediol into 2-Butanol by Lactobacilli. Stereochemical and Enzymatic Aspects

Abstract

A number of strains of Lactobacillus spp. from foods were screened for their ability to convert meso-2,3-butanediol into 2-butanol. Only three strains of L. brevis transformed the meso-diol into the secondary alcohol. These strains as well as the others unable to metabolize meso-2,3-butanediol exhibited the capacity to hydrogenate 2-butanone to 2-butanol. In both types of lactobacilli, an inverse relationship was observed between the diol or ketone concentration and the abundance of the R form of 2-butanol. This fact has been interpreted in terms of a co-occurrence of two dehydrogenases, both acting on the ketone with different kinetic parameters and opposite enantioselectivities. These results represent a further support to the assumption that 2-butanol present in distillates originates from the enzymatic activity of lactobacilli growing on mashes and give the most likely explanation of the enantiomeric excess of (R)-2-butanol generally found in distillates. Keywords: 2-Butanol; meso-2,3-butanediol; lactobacilli; diacetyl; acetoin; dehydrogenases