ANTIFUNGAL AND ANTIOXIDANT ACTIVITIES OF ACTINOBACTERIA ISOLATED FROM ALGERIAN DESERT SOILS

Actinomycetes are gram-positive filamentous bacteria that are thought to be the best candidates for producing biologically active secondary metabolites. Our research aims to identify antifungal and antioxidant activity, as well as purify and characterize the components involved in this phenomenon in isolated actinomycetes derived from the Algerian desert soil. Eighteen isolates were studied. The antagonism tests are performed by the agar cylinder technique against two gram-positive bacteria, Staphylococcus aureus and Listeria monocytogenes, and five fungi, which are known for their importance in human infectious pathologies. 14 isolates showed inhibitory activity against the two bacteria, and 15 isolates showed antifungal activity against the five fungal species: Fusarium graminearum, Aspergillus flavus, Aspergillus ochraceus, Penicillium expansum, and Aspergillus parasiticus. The results allowed us to choose two strains of Actinomycetes coded A10 and A7, both of which have strong inhibitory abilities. That was used for solid-state fermentation (AF). After 14 days of incubation at 28 °C, methanol is used for the extraction of the metabolites produced in the medium. The methanolic extract was effective against the five target fungi species targets even at low doses of 2 mg/ml. The ergosterol degradation test revealed that strain A7 generates an antifungal agent capable of changing membrane sterols, but strain A10 had no impact. A characterization of the inhibiting agent using chromatographic techniques was carried out. The antioxidant activity of the two crude extracts was measured using DPPH radical scavenging. The results demonstrate that the A10 strain extract has good activity, with a percentage inhibition of 58% and an IC50 test of 8.10. The study of the morphological, cultural, physiological, and biochemical characteristics of the two isolates, A7 and A10, allowed us to link them to the genus Streptomyces