Subtilisin Carlsberg immobilization and its application for eco-friendly leather processing

Conventional dehairing based on application of huge amount of chemicals is the most polluting process of all leather manufacturing processes. In this study, Subtilisin Carlsberg (SC) was immobilized on magnetic chitosan (mCTS) using two different crosslinkers: 2% glutaraldehyde (GA) and 0.5% genipin (GE). The reaction medium for SC immobilization consisted of 500 mg carrier and 5 ml (1 mg/ml) enzyme solution. Also, the immobilization conditions were pH 8, 25 °C and 2 h incubation period. The hydrolysis activity of immobilized SC has been extensively investigated. The structure and surface morphology of the prepared carriers were characterized by Scanning Electron Microscop (SEM), Thermogravimetric Analyzis (TGA) and Energy Dispersive X-Ray Spectroscopy (EDX). Optimum temperature and pH values of SC activity were found to be 50 °C and pH 8.0, respectively for free and immobilized SC. Higher activity of SC at around pH 8 and 50 °C makes it suitable for industrial applications. Thermal stability of immobilized SC was found greater than free SC. At the end of 4 h of exposure to high temperature, while the immobilized enzyme can maintain its activity around 50%, the free enzyme can maintain around 20%. Enzymatic hair removal from leather skin with SC was carried out as an alternative eco-benign deharing process. In enzymatic hair removal, a softer and smoother skin surface was obtained compared to the chemical method. Leather skins was characterized by SEM images. •Enzyme immobilization is important to improve its catalytic activity against environmental condition.•Magnetite enhances the mechanical and thermal stabilization of chitosan.•The main process that creates contaminants in leather processing is the removal of fibrillar proteins from the skin surface.•Enzymes can present a greener alternative process to the traditional chemical method.