Nutritional requirements for the production of antimicrobial metabolites from Streptomyces

The objective of this study was to optimize the nutritional and cultural conditions of Streptomyces strain ERI-1, ERI-3 and ERI-26 for the production of antimicrobial metabolites under shake-flask conditions. Effect of eight fermentation medium, different temperature, pH, incubation time, different carbon and nitrogen sources and different concentration of sodium chloride on production of antimicrobial metabolites were studied. Antimicrobial activity of the fermentation medium was evaluated by cup plate method by measuring the zone of inhibition. Nutritional and cultural conditions for the production of antimicrobial metabolites by Streptomyces strain ERI-1, ERI-3 and ERI-26 under shake-flask conditions have been optimized. Modified nutrient medium was found to be good base for fermentation. Glucose and ammonium nitrate were identified as best carbon and nitrogen sources, respectively for growth and production of more antimicrobial compounds. Similarly, initial production medium pH of 7.0, incubation temperature of 30°C and incubation time of 96 h was found to be optimal. Optimization of medium and cultural conditions resulted in better antibacterial and antifungal activity. The zone of inhibition of ERI-26 against Aspergillus niger was 25 and 20 mm for Curvularia lunata, respectively. It is clear that novel Stretomyces strains ERI-1, ERI-3 and ERI-26 produced extra cellular antimicrobial metabolites effective against pathogenic bacteria and fungi, moreover the medium and cultural conditions for better antimicrobial metabolites production have been optimized.   Key words: Streptomyces, antimicrobial activity, nutritional requirements, cultural conditions, optimized media.