THE STEREOSELECTIVITY OF THE USE OF LACTIC-ACID BY CLOSTRIDIUM-TYROBUTYRICUM

A study of the factors influencing Clostridium tyrobutyricum growth is necessary to improve the control of butyric fermentation and avoid la te blowing during cheese making. Lactic acid, one of the substrates of this fermentation is present in two optical forms in cheeses and thei r relative amounts may be a controlling factor. in order to determine whether these proportions could influence C. tyrobutyricum growth, the micro-organism was inoculated in culture media containing different p roportions of these isomers. In the racemic mix, the results show the consumption of 90% of D(-) and 25% of L(+) lactic acid during the expo nential growth phase. When both isomers are present, C. tyrobutyricum preferentially uses the D(-) lactic acid, and if only one of the two i somers is present ifs growth rate is three times higher with the D(-) than with the L(+) isomer. (C) 1997 Academic Press Limited.