Unveiling the potential of metal-tolerant fungi for efficient enzyme production

The present study first time reports the utilization of metal tolerant fungi as a potential source for efficient enzyme production. The purification and characterization of alkaline protease from an indigenous zinc-metal tolerant fungal isolate Aspergillus flavus NJP08 has been demonstrated. The specific activity of enzyme was determined as 89.1 U mg(-1) which is found to be the highest among the reported Aspergillus flavus isolates so far. The protease was purified 55.87 fold up to homogeneity and identified as alkaline protease with a molecular mass of 33 kDa. The N-terminal sequence was GLTTQKSAPWGLG which showed high similarity with other reported proteases of genus Aspergillus. Physico-chemical characterization of enzyme revealed an estimated half-life of >20 h with aliphatic and GRAVY index values of 79.65 and -0.161 respectively, depicting high thermo-stability and secretory nature of protease. The protease was active within the temperature range of 25-50 degrees C with an optimum temperature of 50 degrees C and was stable in the pH range of 6.0-11.0. The enzyme was activated by Ca2+ and Fe2+ ions, partially inhibited by Cu2+ ions and strongly inhibited by PMSF. High enzyme stability in presence of various detergents further strengthens enzyme applicability in industrial applications. (C) 2014 Elsevier Ltd. All rights reserved.