Biocontrol Effect of Lactobacillus delbrueckii on Aflatoxin Expression in Aspergillus parasiticus

Background and Aim : Background: Recent studies demonstrated that some of the lactic acid bacteria (LAB) strains have great inhibitory effects on fungal growth as well as aflatoxin production. Aspergillus (Asp.) species are pathogenic fungi caused invasive aspergillosis. Aflatoxins are extremely toxic secondary metabolites which contaminate food products. Several investigations have been performed on the removal of aflatoxin. The aim of this study was evaluation of the effect of L. delbrueckii on Asp. parasiticus growth as well as aflatoxin production.Methods : Material and Methods: In this study assessed Lactobacillus delbrueckii subsp. Bulgaricus (PTCC ۱۷۳۷) in controlling the Asp. parasiticus (ATCC ۱۵۵۱۷) growth and aflR and Nor۱ genes expression. Broth microdilution method (CLSI, M۲۷-A۳) was applied to identify the antifungal activity of L.bulgaricus and examined by exposing Asp. parasiticus to different amounts of L.bulgaricus. A suspension of ۱.۵×۱۰۸ CFU/ml of L. delbrueckii was diluted to ۷.۵×۱۰۷ CFU/ml in Potato Dextrose Broth medium. Analysis of the aflR and Nor۱ genes expression was performed by measuring the genes mRNA levels with Real Time PCR assay. β-actin was used as housekeeping gene.Results : Results: In the presence of ۲ × ۱۰۳ CFU/ml of L.bulgaricus, the relative expression of aflR gene significantly reduced when compared to control. There were statistically significant differences in aflR and Nor۱ gene expressions after treated with L.bulgaricus (P=۰.۰۰۱). The aflR mRNA expression levels were down regulated by ۹۰% whereas the Nor۱ mRNA expression level was down regulated by ۳۰% (P<۰.۰۰۱).Conclusion : Conclution: According of our results, L.bulgaricus could be suitable LAB against toxigenic effects of mouldy human foods and animal feeds.

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Key words: Aspergillus (Asp.) , Aflatoxin , lactic acid bacteria