Amino acid decarboxylation by Lactobacillus curvatus CTC273 affected by the pH and glucose availability.

ABSTRACT

The aim of the present study was to investigate the aminogenic behaviour of Lactobacillus curvatus strain CTC273, isolated from a fermented pork sausage, and showing its ability to produce tyramine, putrescine, phenylethylamine and lower amounts of cadaverine. Besides the amine production by growing cells under different pH, glucose availability and aero-/anaerobiosis, the effect of these environmental conditions on the activity of decarboxylase enzymes was also studied in resting cells. Tyrosine decarboxylation occurred during the active growth phase and followed the acidification curve. Glucose and oxygen availability had little influence on tyramine production, although anaerobiosis seemed to favour the enzyme activity. The decarboxylation of other amino acids occurred later and was more pronounced during the stationary phase. Compared to aromatic amines, the more acidic pH inhibited the production of putrescine. Slightly higher amounts of putrescine were reached during aerobic growth at lower glucose concentration. Thus, the function of ornithine-decarboxylase in this bacterium would not seem to be a mechanism to neutralise the acid environment, but it may play a role in supplying metabolic energy.