Effect of production parameters and inhibitory activity of antimicrobial compounds produced by co-cultured strains of Streptomyces xinghaiensis-OY62 and S. rimosus-OG95

Abstract

Due to emergence and re-emergence of resistant pathogenic microorganisms, there is need to develop more potent antimicrobial metabolites with broad spectrum antimicrobial activity. Hence, the strains of Streptomyces xinghaiensis-OY62 (KU934248) and Streptomyces rimosus-OG95 (KU934251) were co-cultured for the production of antimicrobial metabolites using starch casein broth by submerged fermentation. Effect of production parameters on antimicrobial activity was studied using standard methods. Purification of the antimicrobial extract was carried out using column and thin layer chromatography. The Minimum Inhibitory Concentration was done by macro broth dilution method. Bioactive compounds were characterized using thin layer chromatography; Fourier transformed infraRed spectrophotometer and gas chromatography-mass spectrophotometer. The best antimicrobial activity was observed at pH 8.0, temperature of 45 °C, in starch casein broth supplemented with sodium chloride concentration of 0.6% (w/v), casein + KNO3 as nitrogen source, in the presence or absence of carbon source and a period of fifteen days of incubation. The retention factor of the partially purified antimicrobial extract was 0.97. Functional groups such as hydroxyl, aromatic rings, carboxylic acid, amides and carbonyls were detected. Eight different antimicrobial metabolites were identified and characterized. Higher quantity (41.4%) of dibutyl phthalate was produced by the co-cultured strains of the Streptomyces. The antimicrobial metabolites produced by co-cultured strains of Streptomyces xinghaiensis-OY62 and Streptomyces rimosus-OG95 exhibited broad spectrum antimicrobial activity against indicator strains. The MIC and MBC ranged between 3.12 mg/L to 6.25 mg/L and 12.5 mg/L to 25.0 mg/L respectively. Keywords: Effect of production parameters, Broad spectrum antimicrobial activity, Chemical characterization, Minimum Inhibitory Concentration (MIC)