Aflatoxin (highly toxic and carcinogenic secondary metabolites produced by fingi) contamination is a serious problem worldwide. Modern agriculture and animal production systems need to use high‐quality and mycotoxin‐free feedstuffs. The use of microorganisms to preserve food has gained importance in recent years due to the demand for reduced use of chemical preservatives by consumers. Lactic acid bacteria are known to produce various antimicrobial compounds that are considered to be important in the biopreservation of food and feed. Lactobacillus rhamnosus L60 and Lactobacillus fermentum L23 are producers of secondary metabolites, such as organic acids, bacteriocins and, in the case of L60, hydrogen peroxide. The antifungal activity of lactobacilli strains was determined by coculture with Aspergillus section Flavi strains by two qualitative and one quantitative methods. Both L23 and L60 completely inhibited the fungal growth of all aflatoxicogenic strains assayed. Aflatoxin B 1 production was reduced 95.7–99.8% with L60 and 27.5–100% with L23. Statistical analysis of the data revealed the influence of L60 and L23 on growth parameters and aflatoxin B 1 production. These results are important given that these aflatoxicogenic fungi are natural contaminants of feed used for animal production, and could be effectively controlled by Lactobacillus L60 and L23 strains with probiotic properties.

Lactobacillus fermentum strain L23 and L. rhamnosus strain L60 were selected as an alternative treatment to prevent or treat urogenital infections based on their probiotic properties and production of bacteriocins. The objectives of the present work were to study the inhibitory activities of these two bacteriocin-producing strains, and to analyze the interactions between pairs of bacteriocins that inhibit urogenital pathogens. Antimicrobial activity tests of L23 and L60 were performed by a diffusion method with 207 bacterial strains, isolated from female patients presenting a urogenital infection. Inhibitory substances interaction tests were carried out by using a streak-diffusion method on agar plates. One hundred percent of the clinical isolates showed sensitivity to the antimicrobial substances produced by L23 and L60. The selected lactobacilli produced larger inhibition halos when compared to several antibiotics commonly used for treating these infections. Synergistic interactions and indifferent interactions were recorded in 68.6% and 31.4% of the cases, respectively. No antagonistic interactions were observed. In conclusion, the bacteriocin-producing strains L23 and L60 are potential candidates for probiotic prophylaxis and treatment of urogenital disorders in women.

Group B streptococci (GBS) are bacterial species that colonize the vagina in pregnant women and as such may cause serious infections in neonates that passed through the birth channel. The objective of this work was to study the inhibitory activities produced by each bacteriocin-like inhibitory substance (BLIS) of Lactobacillus rhamnosus L60 and Lactobacillus fermentum L23, and the effects of the combined BLIS-es of these lactobacilli on GBS. The interactions between the BLIS-es were assessed by qualitative and quantitative methods on agar plates. The minimum inhibitory concentrations (MICs) and fractional inhibitory concentrations (FICs) were determined by a modification of the broth microdilution and checkerboard methods, respectively. Antibiotic susceptibilities of all S. agalactiae strains were assayed and the results of these tests were evaluated for statistical significance. A 7.5% of GBS isolates were recovered from 760 pregnant women and 91% of those strains were susceptible to each BLIS produced by L. fermentum, L. rhamnosus, and also to a mixture of them. The comparisons among the BLIS-es showed statistically significant differences, with a combination of the BLIS-es from the two Lactobacillus species being better than the BLIS of each one alone (P < 0.05) as GBS growth inhibitors. Synergistic activities between the BLIS-es were found on 100% of susceptible GBS strains, MICs ranges of BLIS of L23 and L60 were 80-160 and 160-320 UA ml(-1), respectively. By the checkerboard method, the BLIS-es combination showed synergistic effect on all sensitive strains tested, with values of FICs ranging from 0.131 to 0.218. The BLIS-es produced by these lactobacilli of vaginal origin were able to inhibit S. agalactiae isolates. The results indicate that these strains may have probiotic potential for the control of GBS in women and may consequently prevent GBS infections in newborns.