Résumé:
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.
