36 h when co-culturing Aspergillus strains with L60 and between 20.63 and 22.31 h see more in presence of L23. The lag phase prior to growth of all fungal strains was significantly (P < 0.05) reduced by L. rhamnosus L60 compared with L. fermentum L23. In all Aspergillus section Flavi strains assayed, growth rate decreased significantly (P < 0.05) when coculturing with L60 and L23. Lactobacillus rhamnosus L60 significantly reduced (P < 0.05) the growth rate from 77% to 96%, while L. fermentum L23 significantly reduced (P < 0.05) the growth rate from 36% to 50%, with respect to control (Fig. 2). The highest reduction
of growth rate was observed with both bacterial strains on A. flavus RC2054. Lactobacillus rhamnosus L60 was most effective in reducing the growth rate on all Aspergillus section Flavi strains assayed when compared with L. fermentum L23. The effect of L60 and L23 on inhibition of AFB1 production is shown in Fig. 3. In general, AFB1 production exhibited a similar pattern to growth rate, when the fungal
strains were cocultured with L60 and L23. The presence of L60 and L23 did not stimulate the production of AFB1 in any of the Aspergillus section Flavi strains assayed. Lactobacillus fermentum L23 was able to inhibit AFB1 production of A. flavus RC2053 and A. flavus RC2055. Aspergillus section Flavi strains showed a significant reduction (P < 0.05) in AFB1 production when grown in the presence of L60 and L23, with decreased production of the toxin between 96% and 99% and 73% and 99%, respectively. Toxin production of Aspergillus section Flavi was significantly reduced Erastin (P < 0.05) by both lactobacilli strains assayed compared with control. The Lactobacillus strains used were previously characterized by Pascual et al. (2008a ,b and Ruiz et al. (2009) as presenting probiotic properties: colonization, self-aggregation, adherence to epithelial cells
and coaggregation with bacterial pathogens. Lactobacillus rhamnosus L60 and L. fermentum L23 are producers of secondary active metabolites, such as organic acids, bacteriocins and, in the case of L. rhamnosus L60, hydrogen peroxide. Bacteriocin production was PR-171 ic50 previously characterized and the substance was purified (Pascual et al., 2008a ,b). The two strains showed a wide spectrum of antimicrobial activity against Gram-positive and Gram-negative bacteria, some being human and animal pathogens. The present study shows the potential of L. rhamnosus L60 and L. fermentum L23 in control of Aspergillus section Flavi growth and AFB1 production in vitro. Biopreservation, the use of microorganisms to preserve food and feed stuffs, has been gaining increasing interest due to consumers’ demand for reduced use of chemical preservatives (Prema et al., 2010). As LAB are ‘generally recognized as safe’ organisms (Hoque et al., 2010), they could have useful application in the prevention of fungal contamination in raw materials, food and feed, and in reducing the health hazards associated with mycotoxins.