Aflatoxins are a large group of highly toxic, mutagenic, and carcinogenic mycotoxins produced by specific species of fungi. Potential contamination of food commodities by these compounds causes extensive damage that lead to great economic losses. This study explored the potential use of antifungal compounds, produced by Lactobacillus brevis and Lactobacillus paracasei, for growth inhibition and subsequent aflatoxin B1 production from select strains of Aspergillus flavus and Aspergillus parasiticus. Lactobacilli strains were isolated from traditional Egyptian dairy products, whereas fungal strains were isolated from infected cereal seeds. There were noticeable decreases in mycelium biomass and aflatoxin production as well. L. brevis exhibited the highest reduction of aflatoxin B1 production by A. flavus and A. parasiticus, 96.31 and 90.43%, respectively. The concentrations of amino acids of the antifungal compound produced by L. brevis were significantly higher than that produced by L. paracasei. Asparagine, glutamine, glycine, alanine, and leucine were the most concentrated amino acids for both strains. The antifungal compounds produced by L. brevis and L. paracasei were active in a wide range of pH, heat stable and inactivated by proteolytic enzymes (protease K and trypsin A). The expression of Omt-A gene that involved in the later step of aflatoxin production was evaluated by real-time PCR. There was a vigorous reduction at transcriptional level of Omt-A gene observed in A. flavus that is treated by L. brevis and L. paracasei (80 and 70%, respectively). However, the reduction of Omt-A gene observed in A. parasiticus that is treated by L. brevis and L. paracasei was 64.5 and 52%, respectively. Treating maize seeds with antifungal compounds exhibited great efficiency in controlling fungal infection and increasing seed germination. The results confirmed that lactic acid bacteria are a promising strategy to control food contamination of fermented food and dairy products.
Entomopathogenic nematodes (EPNs) of families Heterorhabditidae and Steinernematidae are known to be effective against a variety of pests. In the present work, different EPNs that are isolated from the Egyptian environment were tested against the onion thrips, Thrips tabaci Lindeman (Thysanoptera: Thripidae), under field conditions. The Egyptian EPNs were tested at different concentrations and against different onion thrips stages (adult and nymph). When used as a foliage spray, the tested EPN isolates were efficient against both adult and nymph stages. Differences in pathogenicity were observed within the same EPN species as in Heterorhabditis indica (EGAZ3) that caused higher reduction in population of T. tabaci (adult and nymph) after 24 and 48 h at a concentration of 10,000 infective juveniles (IJs)/ml compared to H. indica (EGAZ2) after 24 h post treatment at a concentration of 15,000 IJs/ml. The same pattern was observed with Heterorhabditis bacteriophora (HP88), where a higher reduction percent was recorded after 24 h at a concentration of 20,000 IJs/ml. On the other hand, Steinernema carpocapsae (All), S. carpocapsae (EGAZ9), and S. carpocapsae (BA2) isolates were less effective in controlling onion thrips (adult and nymph) population. In general, controlling T. tabaci at the nymphal stage was more efficient than at the adult stage (12-73% reduction at the nymph stage compared to 6-65% at the adult stage). It was also found that increasing inoculation concentration above 15,000 IJs/ml had no significant difference in controlling onion thrips populations.
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