Factors influencing leucine catabolism by a strain of Staphylococcus carnosus

The metabolism of leucine by resting cells of Staphylococcus carnosus 833 was studied according to three physico-chemical factors: preculture condition (defined medium; complex medium), nitrate concentration (0% and 0.03%) and stirring condition (static or shaking). A factorial design was set up to test the effects of these factors, each at two levels. The results showed that resting cells of S. carnosus 833 produced 3-methyl butanal, 3-methyl butanol and 3-methyl butanoic acid from leucine. Whatever the incubation conditions, there was greater quantity of 3-methyl butanoic acid than 3-methyl butanal and 3-methyl butanol. The preculture and incubation conditions influenced the level of production of the 3 metabolites. The highest overall production of the 3 metabolites was observed when cells were incubated without nitrate in the reaction mixture. 3-methylbutanoic acid production was enhanced when S. carnosus 833 was precultivated in complex medium. 3-methylbutanal was only detected when cells were precultivated in defined medium. Stirring condition had no effect on leucine catabolism of S. carnosus 833.