Effects of Culture Conditions on the Antimicrobial Activity of Streptomyces spp. LTB08

The aim of the present study was to find out the optimal culture conditions for Streptomyces spp. LTB08 which previously showed strong antimicrobial activity to exert high antimicrobial activity. The effect of each parameter viz., incubation time, pH, sodium chloride concentration, and added carbon on antimicrobial activity was studied by varying single parameter of standard culture condition at a time. The result showed that antimicrobial activity reached the peak after 4 days of culture and remained relatively constant until day 7. Among different tested pHs and salinities, highest antimicrobial activity was obtained at pH 7.0 in comparison to pH 6 and 8 and at the salinity of 0.5% in comparison to 1 and 2%. In contrast, when different carbon sources (glucose, fructose, sucrose, and starch) were supplemented to the culture medium (MHB), there was a marked decrease in the antimicrobial activity of Streptomyces spp. LTB08 in comparison to non-supplemented condition which indicated that the production of antimicrobial compounds seemed to be more preferable in restricted media. In summary, 4 days of incubation at pH 7.0; 0.5% NaCl and non-supplemented MHB are optimal conditions to achieve maximum yield of antimicrobial activity of Streptomyces in general and of isolate LTB08 in particular.