Hydrolysis of proteinaceous tannery solid waste for the production of extracellular acidic protease by Selenomonas ruminantium

Abstract

The objective of this study was to produce protease from Selenomonas ruminantium using animal fleshing (ANFL), an untanned tannery solid waste as the sole protein source. Optimization of the minimal medium composition for the production of protease was carried out by a statistical approach using response surface methodology (RSM) which includes the variables such as NH₄Cl, K₂HPO₄, KH₂PO₄ and NaCl. The isolate was found to produce maximum protease at pH 6 and at a temperature of about 40°C. Protease was purified 56 fold with a total yield of 28.14%. The enzyme was found to be monomeric having a molecular weight around 53 kDa. The purified enzyme was stable at a pH of about 4 revealing its acid protease nature and was also found to be stable up to 40°C. The enzyme was activated by divalent cations like Ca²⁺ and Mg²⁺ and inhibited by dithiothreitol (DTT), where the latter suggested its cysteine protease nature. The enzyme had good stability in the presence of non-ionic surfactants like tween 20, tween 40, tween 80 and triton X100 and also in the presence of solvents like methanol, ethanol and isopropanol. These characteristics reveal the potential of the enzyme for different industrial applications.

Keywords: Acid protease, animal fleshing, optimization, response surface methodology (RSM), Selenomonas ruminantium