Optimization of the Cultural Parameters for Improved Production of Antimicrobial Metabolites by Streptomyces gulbargensis DAS 131

Abstract

Aims: To investigate the influence of appropriate culture medium by optimizing the cultural conditions affecting the growth and bioactive metabolite production by Streptomyces gulbargensis DAS 131 under submerged culture conditions in order to reduce the cost of fermentation process to improve the formation of antimicrobial compounds. Place and Duration of Study: Department of Botany and Microbiology, January 2012 to May 2012. Methodology: The impact of environmental parameters such as incubation period, pH, temperature and salt concentration and effect of various nutrients such as carbon and nitrogen sources and minerals on the antimicrobial metabolite production by Streptomyces gulbargensis DAS 131 was evaluated by employing agar well diffusion assay. Growth was measured in the form of dry mycelial weight. Results: The optimum pH and temperature for bioactive metabolite production were 7 and 35°C respectively. Highest antimicrobial metabolite production was found when the strain was inoculated into the medium amended with glucose at the concentration of 2%, soya peptone at the rate of 1% and NaCl at the concentration of 5% and incubated for six days under shaking conditions. The metabolites showed good antimicrobial activity against Gram positive and Gram negative bacteria, as well as unicellular and multicellular fungi. Conclusion: S. gulbargensis DAS 131 isolated from the semi-arid soils of Gulbarga, Northern Karnataka province, India exhibited broad spectrum antimicrobial activity. It was found that the antimicrobial metabolite production by the strain was positively influenced by carbohydrates, nitrogen sources and minerals.