Production and biochemical characterization of keratinase enzyme from <i>Bacillus subtilis</i> ES5 and its potential application in leather dehairing process: a clean leather tanning process

The traditional leather industry releases different chemical wastes into the environment, which calls for the use of alternative, nonpolluting processes. The use of biological catalysts in industrial processing has received a great deal of attention in recent years, mainly for environmental reasons. The main objective of this study was to produce and characterize keratinase enzyme from Bacillus subtilis ES5 and evaluate its potential application for leather dehairing. The gene encoding keratinase was validated with a fragment length of approximately 1100 bp. The keratinase exhibited maximum activity at temperature and pH of 45 °C and 8, respectively. Among the tested metal ions, Ca2+ and Mg2+ improved keratinase activity by 132.56 and 111.78%, respectively, at concentrations of 5 mM. β-mercaptoethanol enhanced keratinolytic activity. However, ethylenediaminetetraacetic acid (EDTA) significantly inhibited it, indicating that the enzyme is a member of the metalloprotease family. It completely dehaired goat/sheep skins within 14 h, resulting in decreased biochemical oxygen demand (BOD5), chemical oxygen demand (COD), total dissolved solids (TDS), total suspended solids (TSS), and overall pollution load by 57.39, 70.53, 93.59, 94.90, and 79.10%, respectively. The results demonstrated the pivotal advantages of this keratinase, addressing environmentally friendly processing and sustainable solid waste management. The improved properties of enzyme-treated dehaired pelts suggest that crude keratinase could be used in ecologically friendly holistic leather manufacturing to avoid the pollution issues associated with the use of chemicals.