The glycoconjugates, herein glyco-proteins, existing in animal skins are closely related to the effectiveness of unhairing and fiber opening-up. Glycosidases have been used in leather making processes to reduce pollutants and improve leather quality. But the selection of glycosidases is still blind because the related mechanisms are not well understood yet. Hence, the animal skin structures and glycoconjugates components, the advances in the methods and mechanisms of removing glycoconjugates related to unhairing and fiber opening-up in leather manufacture, the kinds, compositions, structures and functions of typical glycoconjugates in skin are summarized. Then the approaches to destroy them, possible glycosidases suitable for leather making and their acting sites are analyzed based on the recognition of glycoconjugates in skin and the specificities of glycosidases toward substrates. It is expected to provide useful information for the optimization of glycosidases and the development of new enzymes and the cleaner technologies of unhairing and opening up fiber bundles assisted by glycosidases.
Graphical abstract
Glycoconjugates, herein glyco-protein conjugates, composed of protein and saccharide chains are the main components of the interfibrillar matrix in skin which need to be fully removed in the leather making process. The application of glycosidases can assist unhairing and skin fiber opening-up, resulting in the improvement of leather quality, by breaking the glycoconjugates safely and efficiently in mild conditions. The biotechnology assisted by glycosidases, a big family of over 200 kinds of enzymes, has a great potential but the related mechanisms and the efficiency of different glycosidases are still not clear, which interferes with its wide application. To screen the proper glycosidases, a novel method of evaluating the catalytic hydrolysis properties of glycosidases towards skin glycoconjugates based a special hide powder substrate, simulating the actual leather processing, was established through detecting the produced amount of the total sugar in the solution. The special substrate was prepared, the determination conditions were optimized, then the performances of several typical glycosidases were evaluated and their application effects in soaking process of leather making were also investigated. The results show that the optimum testing conditions are lower than 4 h of the reacting time, optimally 2 h, and lower than 40 U/mL of the enzyme concentration, optimally 0-25 U/mL based on 2 g of the substrate; the results to evaluate the properties of some glycosidases based on the established method are positively related to their applying effects in soaking. The new method with better repeatability can be used as an available tool to correctly select glycosidases and optimize process parameters for correct use.
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