Factors influencing leucine catabolism by a strain of Staphylococcus carnosus

The metabolism of leucine by resting cells of Staphylococcus carnosus 833 w as studied according to three physicochemical factors: pleculture condition (defined medium: complex medium), nitrate concentration (0% and 0.03%) and stirring condition (static or shaking). A factorial design was set up to t est the effects of these factors, each at two levels. The results showed th at resting cells of S. carnosus 833 produced 3-methyl butanal, 3-methyl but anol and 3-methyl butanoic acid from leucine. Whatever the incubation condi tions, there was greater quantity of 3-methyl butanoic acid than 3-methyl b utanal and 3-methyl butanol. The preculture and incubation conditions influ enced the: level of production of the 3 metabolites. The highest overall pr oduction of the 3 metabolites was observed when cells were incubated withou t nitrate in the reaction mixture. 3-methylbutanoic acid production was enh anced when S. carnosus 833 was precultivated in complex medium. 3-methylbut anal was only detected when cells were precultivated in defined medium. Sti rring condition had no effect on leucine catabolism of S. carnosus 833. (C) 1999 Elsevier Science B.V. All rights reserved.