PHENYLLACTIC ACID PRODUCTION BY ANTIFUNGAL LACTIC ACID BACTERIA

A:M. DALLAGNOL; C. CATAL¨¢N; M.I.MERCADO; G.FONT DE VALDEZ; G.C. ROLLAN

San Miguel de Tucuman

Simposio; Simposio Internacional de Bacterias Lácticas; 2009

CERELA-CONICET

Lactobacillus (L.) plantarum CRL 778, isolated from wheat dough, has antifungal activity with potential applications in bakery products. The antimicrobial effect was correlated to acetic, phenyllactic (PLA) and hydroxyphenyllactic (OH-PLA) acid production, being PLA the most effective. This organic acid results from phenylalanine (Phe) catabolism while OH-PLA originates from tyrosine (Tyr). In lactic acid bacteria (LAB), the biosynthetic pathways to these metabolites are correlated and may be influenced by different compounds that are present in the culture media. The aim of this work was to evaluate the effect of some selected compounds on the production of PLA by L. plantarum CRL 778. The LAB strain was grown in a chemically defined medium (CDM) at 30 °C for 24 h to assess the following compounds: 1) amino acids (Phe, Tyr, tryptophan [Trp], glutamate [Glu]) 2) carbohydrates (glucose, fructose, sucrose, lactose); 3) electron acceptores (fructose, citrate, oxalacetate); amino group acceptors (α-ketoglutarate, oxalacetate). The concentration of PLA, OH-PLA, acetate, lactate, ethanol and mannitol were determined by HPLC in the cell free supernatants. Results shown that the major PLA and OH-PLA production took place through the exponential growth phase reaching 0.09 and 0.11 mM, respectively, after 24 h of fermentation. Phenylalanine was an important inductor of PLA while Tyr inhibited its production. Fructose fermentation decreased PLA concentration by 22.2 % but increased (45.5 %) the synthesis of OH-PLA. The presence of lactose as the only carbon source reduced the production of both metabolites probably due to the low cell growth attained. Citrate did not affect the growth of L. plantarum CRL 778 but its absence in the culture medium produced a decrease in the concentration of both PLA and OH-PLA. The ethanol production was detected only in media without citrate while mannitol was not observed under the assayed conditions. On the basis of these results, the optimization of the parameters for the production of PLA and OH-PLA are being carried out.