Protease from new isolate Bacillus subtilis E6-5 strain: Optimization of production conditions, partial purification, characterization, potential applications in leather industry

In this study, Bacillus subtilis E6-5 strain was used as a protease source and tested for protease production capacity in different media. Optimization of the medium for protease production was obtained by modifying nutritional and physical conditions. Maximum protease production has achieved using sucrose (carbon source), tryptone (nitrogen source) and BaCl2 + CaCl2 (metal ions) in medium composition. The optimal physical parameters for maximum protease production were determined as 35°C, pH 8.0, 150 rpm agitation rate, 4% inoculum size, 72 hours inoculum age. In the new modified medium obtained by combining optimal nutritional and physical parameters, a 5-fold increase in protease production was achieved. The optimal temperature and pH of the purified protease were determined as 60°C and 7.0, respectively. Thermostability studies have shown that the enzyme is thermostable. The purified enzyme was active in the presence of Ca2+, K2+ and Mn2+. The enzyme was a metalloprotease. Vmax and Km kinetic values of the enzyme were determined as 3333 U/mL and 1 mM, respectively. The molecular weight was determined about 51.5 kDa. The activity of the enzyme was found to be stable up to 45 days at -20ºC. The enzymatic treatment was found to be more effective than the chemical treatment for hair removal from the skin. Histological analyses revealed that the protease has enhanced the quality of skins. The protease of Bacillus subtilis E6-5 strain may have the potential to be used in the leather industry.