rhamnosus L60 and L. fermentum L23 on aflatoxigenic fungal isolates. Nevertheless, Lumacaftor in vivo L. rhamnosus L60 was the most effective strain in inhibiting growth of all Aspergillus section Flavi strains assayed in vitro. Our results agree with those reported by Vanne et al. (2000), who assayed the effects of Lactobacillus casei on growth and aflatoxin production by A. parasiticus. Onilude et al. (2005) demonstrated that Lactobacillus plantarum, L. fermentum, Lactobacillus brevis and Lactococcus spp. have in vitro antifungal effects on aflatoxigenic fungal isolates in similar proportions to those detected in this study. The results obtained in the present study agree with those
of other researchers, who assayed Lactobacillus species similar to those used in this study but with other LAB strains in the in vitro growth control of Aspergillus spp. and other fungal strains (Magnusson & Schnürer, 2001; Zara et al., 2003; Kam et al., 2007; Muñoz et al., 2010; Voulgari et al., 2010). The growth rate inhibition by lactobacillus strains on fungal species may be caused by production of secondary metabolites. Lactobacillus rhamnosus L60 and L. fermentum L23 are producers of organic acids, bacteriocins and, in the case of L. rhamnosus L60, hydrogen peroxide (Pascual et al., 2008a ,b; Ruiz et al., 2009). The presence of these substances in culture media could inhibit the
fungal development of Aspergillus section Flavi species, as observed in our assays. Lactic and acetic acids are the main products of the fermentation of carbohydrates Selleck EPZ5676 by LAB. These acids diffuse through the membrane of target organisms in their hydrophobic undissociated form and then reduce cytoplasmic pH, thereby causing loss of viability and cell destruction (Gerez et al., 2009; Dalié et al., 2010). Although there is no clear evidence of the role of protein compounds in the inhibition of mould growth, several authors have reported that some lactic strains produced
antifungal metabolites that were sensitive to proteolytic enzymes (Magnusson & Schnürer, 2001; Rouse et al., 2008). On the other hand, the strong inhibitory activity can be attributed Erastin cell line to competition between LAB and Aspergillus section Flavi species in batch conditions. However, the observed reduction of the lag phase is probably due to rapid adaptation of fungal strains to the culture medium but LAB may have advantages over fungi as they are simpler organisms with a faster metabolim. Therefore, bacteria can utilize the original substrate earlier to produce more cell biomass, while fungi develop later after nutrient levels are lower. We have clearly demonstrated here the inhibitory effect of growth of Aspergillus section Flavi strains by secondary metabolites of LAB. However, future studies will need to determine the optimal concentration of pure organic acid, bacteriocins and hydrogen peroxide that inhibit fungal growth.