Effects of environmental factors on leucine catabolism by Carnobacterium piscicola

The metabolites from leucine degradation are involved in dry fermented sausage aroma. The catabolism of leucine by a strain of Carnobacterium piscicola was studied directly in the growth medium with 3H-labelled leucine to investigate the effect of five parameters: phase of growth, pH, oxygen, glucose and alpha-ketoisocaproic acid. Resting cells (RC) were also incubated with 3H-labelled leucine. The radioactive metabolites from leucine catabolism were analysed by high performance liquid chromatography (HPLC). At pH 5.4 and 7.2, the main metabolites detected were 3-methyl butanal, 3-methyl butanol and alpha-ketoisocaproic acid. At pH 6.5, the leucine catabolism was maximum and was characterised by a high production of 3-methyl butanoic acid. Leucine catabolism was most important during the exponential phase of growth. The addition of alpha-ketoisocaproic acid at 1%, glucose at levels of 0.5% to 2% and shaking of the growth medium increased leucine catabolism.