Synergistic effect of choline chloride/ethylene glycol deep eutectic solvent with protease for eco-friendly leather dehairing.

Environmental pollution from the leather manufacturing process, particularly from the dehairing operations involving sodium sulfide and lime, poses significant ecological threats. Although enzymatic dehairing offers a cleaner alternative, it often results in incomplete hair removal and collagen damage due to poor enzyme penetration and specificity. This study introduces a novel dehairing process that combines neutral protease with a choline chloride/ethylene glycol deep eutectic solvent (DES) to address these issues. This DES-protease (DES-P) system has been shown to significantly improve key protease properties, increasing activity by 8.4 % while also enhancing stability and hide penetration. This synergy facilitated more efficient hydrolysis of keratin and proteoglycans. The DES-P process achieved complete dehairing within 3 h, produced leather with a tensile strength 13.3 % higher than that produced by the conventional protease method, while maintaining comparable hydrothermal stability. Furthermore, it reduced the levels of ammonia nitrogen and suspended solids in the effluent by 9.5 % and 22.5 %, respectively. By eliminating the need for deliming and softening, the process also reduces overall pollution. These results demonstrate that the DES-protease synergistic system is an efficient, sustainable, and eco-friendly technology for leather dehairing.