Removal of Proteoglycans in Animal Hides by Glycosidase to Promote Opening-Up of Collagen Fiber Bundles

Abstract

The degree of proteoglycan removal from animal hides is closely related to the opening-up of collagen fibers and the properties of leather, but conventional leather-making processes are not very effective at removing proteoglycans. By rationally selecting and utilizing glycosidases during the leather-making process, proteoglycans can be efficiently removed without causing collagen damage due to glycosidases specifically hydrolyzing glycosidic bonds. In spite of this, glycosidases are highly specific and come in a wide variety of types. To solve the blindness of optimizing glycosidases and its application in the soaking process, in this study, seven typical commercial glycosidases capable of hydrolyzing β-glycosidic bonds were selected according to the types of major glycosidic bonds in animal hide proteoglycans. The basic properties of the selected glycosidases and its effectiveness in removing proteoglycans from the hide during the soaking process were investigated. Then, the effects of the dosage of the two optimal glycosidases on the dissolution of polysaccharide, total soluble protein and hydroxyproline, as well as the properties of leather during the soaking process were further studied. The results showed that although the optimal pH of the selected glycosidases was between pH 5 - 7, they maintained more than 50% of their activity under weak alkaline conditions and could be applied to the soaking process. The removal of proteoglycan by different glycosidases is closely related to their specificity for glycosidic bonds, and the penetrability of the enzyme proteins, namely the molecular weight and isoelectric point of the enzymes. Among them, β-Mannase-AKT and Xylanase-AKT are more effective in removing proteoglycans. When the dosage of β-Mannase-AKT and Xylanase-AKT reached 47 U/mL, almost all the glycosaminoglycan was removed from the hide, the opening-up of collagen fibers and the softness and physical properties of the crust leather were significantly improved without damage to the structural proteins.