Nystatin Production by a Local Streptmyces sp. Isolated from Egyptian Soil

Various soil samples were randomly collected at different places in south Delta, Egypt. A total of 105 Streptomyces isolates, were selected according to their morphological characteristics. Antifungal activity was assessed by agar well diffusion assay. Ten isolates showed antifungal activity against various reference strains of yeast and fungi. The maximum zone of inhibition was detected for Aspergillus niger and Candida albicans using cell homogenate of isolate N5. This potential isolate was identified on the bases of the International Streptomyces Project (ISP) as Streptomyces noursei. ِ◌ ِ ◌ ِ ◌ Accordingly the name Streptomyces noursei sp.N5 was proposed. Maximum antifungal productivity was observed on the 5 day of incubation at 30C and at initial pH 7.0 in starch nitrate medium. The production medium was optimized to attain maximum productivity. Starch 1.0% (w/v), potassium nitrate 0.25% (w/v) and dipotassium hydrogen phosphate 0.1% (w/v) as carbon, nitrogen and phosphorus sources, respectively, were proved to give the highest significant antifungal productivity. Maximum antifungal production was detected at inoculum size of 2 % (v/v) in shake flasks containing 20 % (v/v) culture medium. The antifungal metabolite was efficiently extracted by methanol and was successfully recovered and purified by HPLC procedure. The spectral examination of the compound by Ultraviolet, Infrared, H-NMR, C-NMR and Mass spectra (MS), suggested that it was Nystatin A3.