Evaluation of antifungal activity of novel marine actinomycete, Streptomyces sp. AA13 isolated from sediments of Lake Oubeira (Algeria) against Candida albicans

A new actinomycete strain, designated AA13 was isolated from a marine sediment sample obtained from Lake Oubeira, in the North-East of Algeria and selected for its antifungal activities against Candida albicans. Morphological, physiological and biochemical properties and 16S rRNA gene sequencing strongly suggested that this strain was a new species, which belonged to the genus Streptomyces. Study of the influence of different nutritional compounds and culture conditions on growth and production of compounds with antifungal activity by the Streptomyces sp. strain AA13 indicated that the highest biomass and biological activities were obtained by utilizing the glycerol and peptone as carbon and nitrogen sources, respectively, with pH 7.0 and incubation temperature of 30°C. Two bioactive spots were detected by analysis of the ethyl acetate extract by thin-layer chromatography (TLC) and bioautography analyses. Among these bioactive compounds (antibiotics), a complex AA13-B that showed the interesting antifungal activity, was selected and purified by high performance liquid chromatography (HPLC), which indicated the presence of three peaks. Interestingly, the infrared spectroscopy (IR) studies showed that the molecule AA13-B2 contain an aromatic ring substituted by aliphatic chains. However, the investigations which determine the structure of the antifungal molecule are in progress.