Optimization of cultural conditions affecting growth and improved bioactive metabolite production by a subsurface aspergillus strain TSF 146.

The aim of this study was to optimize cultural conditions for optimum growth and bioactive metabolite production by Aspergillus strain TSF 146, isolated from the subsurface soils of Brahmaputra plains, Assam, India. Agar disc diffusion assay was used to examine the antagonistic activity of the strain. The effect of different culture media, temperature, pH, incubation period, shaking, inoculum size and various carbon and nitrogen sources on the mycelial growth and bioactive metabolite production in a fixed volume of culture broth were studied. Aspergillus strain TSF 146 grew well and produced optimum bioactive metabolites in Potato dextrose broth medium at 25 °C on the 14th day of the incubation. The optimal mycelial growth, however, was obtained at pH 5.5. Sucrose (2.0 g/l) and asparagine (1.0 g/l) were the best carbon and nitrogen sources respectively for optimum growth and production of active metabolites by the isolate. Inoculum size of 2x1010 spores/ml with periodic shaking at 150 rpm optimized production of bioactive molecules. The results of the present investigation indicated that cultural conditions like carbon, nitrogen and mineral sources as well as physical factors such as temperature, pH, incubation period, inoculum size and shaking greatly affected the growth and production of bioactive metabolites by Aspergillus strain TSF 146.