Effect of probiotic bacteria on the growth and mycotoxin production of two toxigenic fungi

The effect of probiotic bacteria (Lactobacillus delbrueckii and Lactobacillus rhamnosus) on the growth of two toxigenic fungi Aspergillus flavus and Aspergillus parasiticus were investigated in vitro by the well-disc diffusion method. The concentrated and un-concentrated cell-free extracts were examined, and it was found that the effect was non significant on the growth of fungi. The effect of the metabolites produced by the probiotic bacteria affect the growth of, A. flavus on solid medium and exhibited inhibition zone of 16 mm (p ≤ 0.05) in the presence of L. delbrueckii and L. rhamnosus separately. However, the inhibition zone of A. parasiticus varied from 16-17mm (p ≤ 0.05) in the presence of L. delbrueckii and L. rhamnosus, respectively. Also, both bacterial strains showed a reduction of pH in the presence of A. flavus after the addition of L. delbrueckii (4.17-4.00) and L. rhamnosus (4.27-4.09), while in the presence of A. parasiticus, the pH decreased in the existence of L. delbrueckii (4.18-4.01) and L. rhamnosus (4.06-3.96). In addition, the lactic acid concentration of L. delbrueckii and L. rhamnosus were measured in the presence of the two tested fungi individually. It was noted that the acid concentration in the existence of A. flavus was 2.4% while in the existence of A. parasiticus was 2.3%. Furthermore, a significant decrease was observed in the counts of fungal spores of A. flavus and A. parasiticus after the addition of L. rhamnosus and L. delbrueckii, separately. Also, the probiotic strains significantly affect the morphological structure and reduced aflatoxin production of the tested fungi. These probiotic bacteria showed excellent properties for the possibility of using it to prevent fungal contamination to reduce economic loss of agriculture products as well as increase the nutritional value and therapeutic properties of food.