Application of Acid Protease for Eco-friendly Pre-treatment of Goat Skin to Improve Antimicrobial Finish Using Herbal Natural Extracts

Abstract

Due to its moisture retention capacity and huge surface area, leather is highly prone to microbial proliferation and biodeterioration; hence, leather products desired have an antimicrobial finish. In this study, acid protease enzyme pre-treatment of goat skin was utilized as an eco-friendly substitute for conventional wet-chemical processing. The treatment can impart the desired surface properties to improve the antimicrobial finish with natural extracts obtained from leaves of Azadirachta indica (Neem Tree), Ocimum sanctum (Holy Basil, Tulsi), and Camellia sinensis (Green Tea). The procedure was optimized for different process parameters, including enzyme concentration, pH, material to liquor ratio (MLR), treatment time, and temperature. The effect of the treatment on bulk and surface properties of the skin was characterized by weight loss analysis, X-Ray Diffraction (XRD), Thermal Gravimetric Analysis (TGA), and Attenuated Total Reflectance Fourier Transform Infrared Spectroscopy (ATR-FTIR), X-Ray Photoelectron Spectroscopy (XPS), Water contact angle measurement, Scanning Electron Microscopy (SEM) respectively. The effect of the enzymatic treatment on organoleptic properties and the mechanical strength of the skin was also studied. The enzymatic treatment resulted in weight loss, and removal of non-collagen components, thus opening the fibrous collagen matrix of the skin. Hence, the skin treated with acid protease enzyme provides better affinity and accessibility for phytoactive compounds from the natural extracts and better attachment by electrostatic attachment due to an increase in surface functional groups after the enzymatic treatment compared to untreated skin. The effectiveness of the antimicrobial finish was measured as a zone of inhibition and with a modified Hohenstein test against test microorganisms E. coli and S. aureus.Azadirachta indica (Neem Tree) extract showed the highest inhibitory activity (97%) against E. coli, while the Ocimum sanctum (Holy Basil, Tulsi) extract exhibited the highest inhibitory activity (95%) against S. aureus.