GENETIC AND BIOCHEMICAL CHARACTERIZATION OF AROMA COMPOUNDS BIOSYNTHETIC PATHWAY IN NON-STARTER LACTIC ACID BACTERIA

GUIBERT, LM; SUÁREZ, CA; REPIZO, GD; BLANCATO, VS; MAGNI, C

Rosario - Argentina

Congreso; V Congreso Argentino de Microbiología General. SAMIGE; 2008

Sociedad Argentina de Microbiología General

The utilization of starter cultures in the production of fermented foods allows obtaining reproducible quality. However, the use of non-sterilized raw materials let to the growth of a microflora that could result beneficial or detrimental for human consumption. A desirable characteristic of these microorganisms is its capability of catabolizing citrate, which leads to the production of aroma compounds. By contrast, the production of metabolism by-products such as biogenic amines that could affect human health should be avoided. In this work, we analyzed the bacterium Enterococcus faecalis which is present in cheese as a non-starter microorganism. Our aim was to study the contribution of E. faecalis to the organoleptic properties of diary products. In the first place, we isolated and identified this bacterium from traditional regional fermented foods. We evaluated then, the presence of genes involved in citrate fermentation (transporter, citH; citrate lyase, citDEF; oxaloacetate decarboxylases, citM and oad; as well as the transcriptional activator, citO) and aroma neutral compounds synthesis (alsSD). We also detected the presence of these genes in laboratory strains originally isolated from clinical sources. Interestingly, we determined that genes involved in citrate catabolism and aroma production are present in strains from both origins. Finally, we studied the resistance to acidic pHs of culture medium of a wild type strain compared to an alsSD deficient strain, demonstrating that the aroma synthesis route constitutes a mechanism of resistance to acidic stress due to production of neutral compounds.