Biodegradation of hair waste for keratinase production using Bacillus altitudinis VK-1120 and its application in enzymatic dehairing.

The leather industry impacts the environment through the use of hazardous chemicals for dehairing and the improper disposal of waste from these processes. In this study, a newly isolated Bacillus altitudinis VK-1120 was utilized for hair waste valorization and keratinase production. The keratinase production was optimized, and the maximum activity of 220.82 U/mL was achieved at 40 °C, pH 8.0, and 100 rpm after 48 h. The activity of purified enzyme was inhibited by PMSF and EDTA, suggesting that the enzyme functions as a serine-metalloprotease. SDS-PAGE results revealed a molecular weight of ~25 kDa for the purified keratinase. The optimum temperature and pH for the purified keratinase were 50 °C and 9.0, respectively. The keratinase solution was applied to the dehairing of goatskins using the industrial drum-based method, and complete dehairing was observed within 5 h. The enzymatic treatment significantly improved the waste liquor quality, reducing Biochemical Oxygen Demand (BOD) by 38.67%, Chemical Oxygen Demand (COD) by 50.16%, Total Dissolved Solids (TDS) by 65.25%, and Total Solids (TS) by 52.22%. The physical and organoleptic properties of enzymatically dehaired leather were comparable to those processed by the conventional lime and sulfide method. Additionally, the recyclability of the dehairing enzyme for up to 3 cycles enhanced the application of the keratinase for industrial-scale depilation. Therefore, this study could pave the way for more environmentally responsible solid waste management and depilation practices in the leather industry.