PHENYLLACTIC ACID PRODUCTION BY ANTIFUNGAL LACTIC ACID BACTERIA

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

Tucumán

Simposio; III International Symposium on Lactic Acid Bacteria II Argentinean LAB Net Meeting; 2009

Lactobacillus plantarum CRL 778, a lactic acid bacterium isolated from wheat dough, has antifungal activity with potential application in bakery products. The antimicrobial effect was correlated with acetic, phenyllactic (PLA) and hydroxyphenyllactic (OH-PLA) acid production, being PLA the most effective. This metabolite is a product from phenylalanine (Phe) while OH-PLA results from tyrosine (Tyr) catabolism. The biosynthetic pathways of both metabolites are linked in lactic acid bacteria (LAB) and may be influenced by different compounds present in the culture media. The aim of this work was to optimize the PLA production by L. plantarum CRL 778 evaluating the effect of different biomolecules. The LAB strain chemically defined medium (CDM) at 30ºC for 72 h containing different concentrations of the following compounds: 1) amino acids (Phe, Tyr, tryptophan [Trp], glutamate [Glu]) 2) carbohydrates (glucose, fructose, sucrose and lactose); 3) electron acceptors (fructose, citrate, oxalacetate); amino group acceptors (alfa ketoglutarate, oxalacetate). PLA; OH PLA, acetate, lactate, ethanol and mannitol concentrations were determined in cell free supernatant from samples taken at different periods by HPLC. The results show that the highest PLA (0.09 mM) and OH-PLA (0.11 mM) production occurred during the exponential growth phase after 24 h of fermentation. Phe was an important inductor of PLA while Tyr inhibited the synthesis of this antifungal compound. The assayed carbohydrates affected the antifungal compounds production; fructose decreased 22,2 % PLA and increased 45,5 % OH-PLA respect to the control with glucose. The presence of lactose reduced the production of both metabolites, which was correlated with the lowgrowth. Citrate did not affect the growth of L. plantarum CRL 778, but its absence decreased about 50% the concentration of both antifungal metabolites evaluated. Ethanol production was detected only in media without citrate while mannitol was not observed under any assayed condition.