Indole-3-acetic acid production by Streptomyces albidoflavus

A terrestrial streptomycete isolate, Streptomyces albidoflavus was screened for plant growth promoters like indole-3-acetic acid (IAA). Streptomyces albidoflavus was found to produce IAA in culture medium supplemented with L-tryptophan. IAA production by the strain initiated after 24 hrs and reached a maximum after 96 hrs of incubation when it reached stationary phase of growth. IAA was extracted with ethyl acetate from a culture filtrate (96 hrs) and it was purified and structurally confirmed by H-1 NMR, C-13 NMR and EI-MS. Cultural and nutritional conditions were optimized for IAA production by this strain. The strain produces high amounts of IAA when cultured in a medium containing glucose (1%) and yeast extract (0.5%) as carbon and nitrogen sources respectively, along with L-tryptophan (0.5%). The optimum pH and temperature for IAA production were 7 (at 30 degrees C) and 35 degrees C (at pH = 7), respectively. The strain, S. albidoflavus might be useful for plant growth promoters like IAA beside antimicrobial metabolites.