Antifungal and antimycotoxigenic effect of Lactobacillus plantarum CRL 778 at different water activity values

Ochratoxin A (OTA) is a mycotoxin produced by filamentous fungi with high impact in food safety due to its toxicity. In the last decade, the presence of OTA was widely reported in different foods. In this study, the ability of Lactobacillus (L.) plantarum CRL 778 to control growth and OTA production by Aspergillus (A.) niger 13D strain, at different water activity (a_w) values (0.955, 0.964, 0.971, 0.982, and 0.995) was determined in vitro. Both parameters were significantly (p<0.05) reduced by the lactobacilli and the effect depended on a_w. Greatest growth rate inhibition (46.9%) was obtained at a_w=0.995, which is the most suitable value for growth and production of antifungal metabolites (lactic acid, acetic acid, phenyllactic and hydroxyl-phenyllactic acids) by L. plantarum CRL 778. Besides, morphological changes and inhibition of melanin synthesis were observed in colonies of A. niger 13D in presence of L. plantarum CRL 778 at a_w ranged between 0.971 and 0.995. In addition, maximum reduction (90%) of OTA production took place at a_w=0.971, while inhibition of fungi growth was more evident at a_w=0.995. These findings suggest that L. plantarum CRL 778 could be used for control of ochratoxigenic fungal growth and OTA contamination in different fermented foods with a_w values between 0.971 and 0.995.