The Effect Of Salt-Enzyme Solution Systems On The Hide And Collagen

In leather making,liming could remove the interfibrillar substance of hide,open the collagen fiber bundles,expose the active groups,and provide the suitable condition for subsequent tanning.In conventional liming,plenty of water resources and chemicals are used,such as sodium sulfide,lime,and surfactants,causing much wastewater and serious environment pollution.Hence,how to achieve the cleaner production in leather manufacturing has always become one of the main research directions of many researchers.Enzyme,a kind of biocatalyst,is an ideal alternative to traditional high pollution chemicals for its excellent characteristics.In this thesis,the effect of different salt-enzyme solutions on hide and structure of collagen is studied,with the thermal stability and physical properties of the final leathers analyzed.The aim of the present work is to explore the interaction between the salt-enzyme solution components and the influence on hide and collagen fiber bundles,so as to provide the necessary theoretical support for scientific and reasonable search of environment-friendly liming method and the realization of cleaner production of leather industry.The effect of different anions and cations to assist protease solution systems on hide and collagen fibers are studied.The Folin method was used to study the effect of different anions and cations on protease activity.After liming,the released protein and proteoglycan from hide and the hydroxyproline content in wastewater were investigated.H&E and EVG staining methods were used to analyze the sections of hide after liming.Scanning electron microscopy(SEM)was used to observe the cross-section of crust leather.The colorimetry was to calculate the tannic acid absorption by hide.The shrinkage and physical properties of crust leathers was tested by shrinkage instrument and texture analyzer.The results showed that most salts have little effect on protease activity.Enzyme liming system has better removal of interfibrillar substance,compared with conventional one,wherein hydrogen phosphate,sulfate,ammonium and magnesium obviously promote than other ions.The absorption of tannic acid by hides treated by enzyme liming systems are improved better,compared with conventional one,and the collagen fiber bundles are also opened well.Besides,the shrinkage temperature and physical properties are also improved with the assistance of ions.The effect of different concentrations of salts assisted enzyme on removal of interfibrillar substance and the dispersion of collagen fiber bundles were studied.The protein released from hide at different liming time and the proteoglycan contents in wastewater after liming were determined.Histological staining and SEM were used to analyze the removal of interfibrillar substance and collagen fiber dispersion.The results showed that different salt concentration has different efficiency in promoting the removal of interfibrillar substance.At the magnesium chloride concentration of 0.4 wt%,the efficiency in promoting the interfibrillar substance releasing is better than others.Compared with sodium sulfate and sodium chloride,magnesium chloride has the better effect on fiber opening,and the tannic acid absorption by hide is also stronger.The effect of different salts/?-amylase solutions on hide and collagen fibers were studied.The effect of different salts on ?-amylase solution activity and p H values were investigated.After liming,the effect of different solutions on protein and proteoglycan released from hide were determined,and the damage degree of collagen was studied.The SEM was used to observe the cross-section of crust leather.Finally,the shrinkage and physical properties of crust leather were evaluated.The results showed that ?-amylase activity is nearly unaffected by salts,while the p H values of ?-amylase solution are a little fluctuated due to the week hydrolysis of ammonium,magnesium,hydrogen phosphate and calcium.Calcium chloride might promote the dissolution of protein and proteoglycan better than other salts,and the damage of collagen is also higher due to the strong capacity of calcium.The tannic acid absorption by hide by ?-amylase systems are improved compared with conventional one,and the final crust leather have better shrinkage properties.Magnesium chloride can improve the tensile strength of crust leather,while disodium hydrogen phosphate can improve the toughness and softness.