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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. [ABSTRACT FROM AUTHOR]

Leather is made from animal hides and skins that have passed through several stages of processing, from soaking to finishing. Unhairing is a crucial processing stage in which hair is removed from the animal hide or skin through open up the hair and it facilitates subsequent operations. The conventional sodium sulfide-based unhairing process generates a high volume of effluent, which accounts for 50 to 70% of the total biochemical oxygen demand (BOD) and chemical oxygen demand (COD) load in the tanneries' effluent. This study aimed to investigate the potential of unhairing agents prepared from locally available plants. The research employed qualitative methods. Plant materials are collected, dried, and ground. In different proportions, unhairing extracts were obtained from Phytolacca dodecandra leaves, Cucurbita foetidissima fruits, and Solanum incanum fruits. In the conventional soaking process, plant extracts were applied in various concentrations to sheepskin. The physical parameters of conventionally processed (control) and experimentally treated leather were examined using FTIR, SEM, tear strength, percentage of elongation, and organoleptic tests. The unhairing solution was prepared from a mixture of 0.5% S. incanum extract, 0.5% P. dodecandra extract, 0.6% C. foetidissima extract, and 260 g/L lime powder lime, and this solution effectively removed the hair from the sheepskin in both hairs saving and hair burning unhairing process. The study revealed that the sheepskin treated with the plant extracts based on an unhairing agent and the conventional unhairing agent showed a comparable tensile strength (42.3 kg/cm and 45.2 kg/cm), tear strength (140.1 kg/cm2 and 143.5 kg/cm2), and percent elongation at break (40.2 and 42.3), respectively, which were above the permissible limit for leather production making. According to the study findings, the plant extracts have a good potential for removing hair from sheepskin, and they are eco-friendly and cost-effective compared to unhairing chemicals such as sodium sulfide. [ABSTRACT FROM AUTHOR]