Optimisation of process parameters for growth and bioactive metabolite produced by a salt-tolerant and alkaliphilic actinomycete, Streptomyces tanashiensis strain A2D

SummaryAn alkaliphilic actinomycete, Streptomyces tanashiensis strain A2D isolated from soil of phoomdi in Loktak Lake of Manipur, India exhibited optimum growth at 2% (w/v) NaCl and pH 8. It is Gram-positive filamentous bacterium which exhibits a broad spectrum of antimicrobial activity against fungi and bacteria. Optimum salt and pH for antibiotic production were 2% (w/v) and 8 respectively. Studies on nutritional factors revealed that highest antibiotic production was obtained when glucose and soyabean meal at 1% (w/v) were used as carbon and nitrogen sources respectively. Seven days of incubation at 28 °C. was found to be the optimum for antibiotic production by the strain. The antimicrobial agent produced by the strain was extracted with ethyl acetate as solvent and purified by TLC. The purified active compound with λmax 241.99 nm has got the lowest minimum inhibitory concentration (MIC) against Staphylococcus aureus (50 μg/ml), whereas highest (100 μg/ml) was recorded against Candida albicans and Fusarium moniliform. So far only few alkaliphilic actinomycetes have been explored for their antimicrobial potential.

RésuméStreptomyces tanashiensis A2D, un actinomycète alcaliphile isolé du sol dans la région du lac Loktak de Manipur (Inde) montre un optimum de croissance pour 2 % (w/v) de NaCl et pH 8. C’est un actinomycète filamenteux Gram positif qui montre un large spectre antimicrobien contre des bactéries et des champignons. La production optimale de métabolites bioactifs est obtenue lorsque le glucose et la farine de soja à 1 % sont utilisés respectivement comme seule source de carbone et d’azote après sept jours d’incubation à 28 °C. Le composé purifié avec un λmax 241,99 nm a donné la plus basse CMI contre Staphylococcus aureus (50 μg/ml) et la plus élevée (100 μg/ml) contre Candida albicans et Fusarium moniliformis. Actuellement, peu d’actinomycètes alcaliphiles ont été testés pour leur activité antimicrobienne.