Amine-producing bacteria are undesired strains for the food industry because of the toxic effects that amine cause to consumers (headaches, hypertension, hypotension, allergies) and for the alteration of organoleptic properties of most fermented foods, chiefly wine and cheese. The origin of such compounds lies in the decarboxylative activity of the fermenting microflora over amino acids present in foods. Three parallel techniques were enployed to detect amine production in LAB: 1) detection of the decarboxylases genes by PCR; 2) HPLC and TLC analysis of culture broths; 3) proteomic analysis on the cellular extracts. These last two experiments were performed in a time-course investigation in both control (MRS medium without amino acid) and stimulated condition (MRS medium with amino acid). We studied an amine producing collection strain, Lactobacillus 30 a (ATCC 33222) and Lactobacillus w53 isolated from an amine contaminated Italian red wine. Both LAB posses the genetic determinants for the amino-acid decarboxylase system which enables them to convert histidine into histamine (HDC) and ornithine into putrescine (ODC). Our results indicate that differences between the proteome of stimulated cultures and controls, are not restrained to induction of the decarboxylating enzymes (HDC and ODC) but also to modulation of the biosynthesis of other proteins indirectly involved in amine production. Among these a membrane Opp transporter was overexpressed while GADPH isoenzymes seem to be downregulated in the amine producing conditions. While the enviromental pH does not affect either amine product or decarboxylase biosynthes these biosynthetic pattern is strongly dependent upon the growth phase (stationary phase).
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