L’étude de l’activité antifongique des bactéries lactique vis-à-vis des champignons phytopathogènes d’Alternaria alternata.

Abstract

The objective of our work is to test antifungal activity of lactic bacteria against phytopathogenic fungi by studying different parameters that could be at the origin of the increase in the production of bacteriocins.The study of macroscopic characteristics, microscopic, and physiological of our bacteria and fungi. The preservation of foods is essentially based on the delay, or inhibition of the growth of contaminating microorganisms, and the antifungal activity of lactic acid bacteria is one of the desired technological properties. The antifungal effect was investigated by the confrontation method in 5 strains of lactic acid bacteria, isolated from raw camel milk and goat's milk. About 100% of the isolates showed inhibitory activity against Alternaria alternata. Four of them belonged to the genus Eterococcus facium. Strains of Enterococcus facium 35/14.2/ 4.19 and a strain of Enterococcus lactis and a strain Lactobacillus plantarum 4.18 produce antifungal compounds active against Alternaria alternata. A change in the inhibition zones was detected after treatment with proteolytic enzymes, but after heating, by refrigeration and by freezing Inhibition was observed. Total inhibition was observed at pH 7 for all strains and a decrease in inhibition at pH 2, 4 values, these suggest the contribution of bacteriocin in antifungal activity because their activity depends on the neutral pH .pH affects the metabolism of Lb. Plantarum and enterococcus facium that showed maximum production of antifungal compounds when grown at pH 7 and moderate production in pH 9 is minimal at pH 2. Lactobacillus plantarum inhibit spore germination and mycelial growth, and cause malformations in the thallus, conidiophore and Alternaria alternata spore.