CONVERSION OF MESO-2,3-BUTANEDIOL INTO 2-BUTANOL BY LACTOBACILLI - STEREOCHEMICAL AND ENZYMATIC ASPECTS

A number of strains of Lactobacillus spp. from foods were screened for their ability to convert meso-2,3-butanediol into 2-butanol. Only thr ee strains of L. brevis transformed the meso-diol into the secondary a lcohol. These strains as well as the others unable to metabolize meso- 2,3-butanediol exhibited the capacity to hydrogenate 2-butanone to 2-b utanol. In both types of lactobacilli, an inverse relationship was obs erved between the diol or ketone concentration and the abundance of th e 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 diff erent kinetic parameters and opposite enantioselectivities. These resu lts represent a further support to the assumption that 2-butanol prese nt in distillates originates from the enzymatic activity of lactobacil li growing on mashes and give the most likely explanation of the enant iomeric excess of (R)-2-butanol generally found in distillates.