Performance Assessment of Kert Protease Treatment for the Sustainable Management of the Unhairing System in Tannery

Pollution management has received significant critical attention in the leather industry, and effective solutions involve minimizing pollutant discharge during production and optimizing waste utilization through reuse and recycling. This study focused on developing an enzyme unhairing system to reduce sulfide pollution in leather production, which utilized recombinant KerT protease with minimal collagenolytic activity to avoid over-degrading the hide collagen fibers. The properties of the recombinant protease were systematically analyzed to ensure efficient complete hair removal by degrading the soft keratin of hair roots. A comprehensive pollution management strategy for the unhairing system encompassed both wastewater reuse and solid waste hair recovery. The concentrations of chemical oxygen demand (COD), total suspended solids (TSS), ammonia-nitrogen (NH3-N), and sulfide in the wastewater notably decreased during the liming processes to 74%, 38%, 30%, and 0%. After five unhairing-liming wastewater cycles, the quality of the finished leather remained uncompromised, with the highest tear strength reaching 117.2 N/mm. Additionally, waste hairs generated by this system could be collected to produce regenerated protein, containing approximately 70% total protein. This industrial-scale enzyme unhairing system for cowhide contributed to cleaner leather production and effectively addressed challenges associated with waste management, including wastewater recycling and protein regeneration from waste hairs.