The Impact of Proteases on Elastin in Leather Manufacture

摘要

In recent years, tanners have payed more attention to biotechnology in leather-making, so proteases are more generally used to reduce pollution in various process stages, such as soaking, unhairing and bating, instead of traditional chemicals. But excessive enzyme treatment will cause loose grain and even damaged grain, especially in enzyme-unhairing. One of the keys to successfully carry out bioprocesses of leather-making is in the control of the balance between the desirable effect and the degree of proteolytic effect of enzymes on structural proteins in skins and hides. Elastin is an important fibrous protein, especially for the grain layer, and the excessive degrading of elastin is an important factor causing grain damage. Elastin is sensitive to proteases, so our series of investigations is focussed on evaluating the impacts of commercial proteases for leather manufacture on Elastin and leather quality. This paper reports on the evaluation of the specificity of typical and widely used proteases on elastin. Firstly, a suitable and sensitive method for determining elastase activity at the broad pH spectrum, was established based on Remazol Brilliant Blue Elastin powder (Elastin-RBB) substrate. The main commercial proteases were selected, including microorganism and pancreatic, alkaline, acid and neutral proteases widely used in soaking, unhairing, liming and bating, for assaying elastin activity. The specificities of these proteases to collagen were also evaluated, based on hide powder-RBB substrate. The results show that most commercial alkaline and neutral proteases exhibit elastase activity, while acid proteases show very low activity against elastin. The optimum pH of elastase activity of these proteases is about 9.0. The optimum temperature is about 65℃, and the activity linearly increases with temperature rise from 30-65℃. Compared to bacterial enzymes, pancreatic proteases show lower activity against elastin, especially, a purified trypsin. Most bacterial proteases show higher activity against elastin, and several alkaline proteases used in soaking and liming exhibit much a higher ratio of activity to elastin against collagen. Thus, care is needed to select proteases for leather-making processes to avoid grain loosening and damage from the excessive removal of elastin.