Optimization of medium components for the production of antimicrobial and anticancer secondary metabolites from Streptomyces sp. AS11 isolated from the marine environment

Abstract

In this study, 102 actinomycetes were isolated from the marine environment from three different locations at Saudi Arabia. Among the actinomycetes isolates, Streptomyces sp. AS11 showed significant activity against methicillin-resistant Staphylococcus aureus (MRSA) was selected for further studies. It has grown well at pH 7.3, 29 °C and with 34% seawater. Based on colony morphology, biochemical, and 16S rDNA sequencing the selected organism was identified as Streptomyces sp. AS11. Among the selected culture medium, ISP4 showed more activity against S. aureus and the zone of inhibition was 29 ± 2 mm. The factors such as, pH and temperature of the culture medium significantly affected secondary metabolite production. Secondary metabolite production was found to be maximum at pH 7.5 (31 ± 1 mm) and marginal decrease in antibiotics production was observed at pH 8.0 (27 ± 1 mm). Antibiotics production was found to be high at 38 °C and the zone of inhibition was 32 ± 2 mm. Among the carbon sources tested, supplementation of glucose and starch enhanced antibiotics production and the zone of inhibition was 31 ± 2 mm and 30 ± 3 mm, respectively. Among the nitrogen sources tested, sodium nitrate enhanced antibiotics production. The secondary metabolite concentration at 2× minimum inhibitory concentration (MIC) and 4× MIC was effectively reduced MRSA. 4× MIC concentration was found to be effective than 2× MIC values and reduced bacterial count considerably. In our study, the crude extract showed cytotoxic effect against cancer cell line and the IC50 value was 0.250 mg/ml. The crude extract acts on HeLa and abnormal cell morphology was observed due to cytotoxic effect. Keywords: Streptomyces sp. AS11, Secondary metabolites, Anti-MRSA, Optimization, Cytotoxicity