The Properties Of Acid Protease And Its Application In The Bating Process Of Wet-blue

Chrome tanned leather has good stability to wet heat,good fullness,softness and good mechanical properties,etc.Therefore,the chrome tanning is the mainly tanning method in leather industry.However,with the increasing strict environmental protection laws,chrome pollution has brought severe challenges to the leather industry,which restricts the development of the leather industry.In order to reduce the cost of pollution treatment,most tanneries at home and abroad directly purchase wet blue as raw material to produce different finished leather.However,there are some problems in the actual production: for example,there are great differences in fiber dispersion and tanning degree between different regions and batches of wet blue,and some wet blue still have problems such as insufficient pretreatment,resulting in poor uniformity of leather quality;in addition,during the transportation and long-term storage of wet blue,not only the grain defects increase,but also the collagen fibers will bond,which will affect the subsequent chemical materials to penetrate into the skin,so the quality of finished leather is decreased.Therefore,it is very important to improve the quality of finished leather by pretreatment.In practice,it is found that the treatment of wet blue with acid protease,as a supplementary means of bating process,can play an obvious role in making up for the inconsistencies in the previous process,reducing the defects of grain surface and improving the product quality.But at present,there is blindness in the application and the selection of acid protease in the bating process of wet blue;on the other hand,the mechanism of action between acid protease and wet blue in the bating process is still lack of in-depth study.In this paper,four kinds of acid protease from different strains(Aspergillus niger,Aspergillus oryzae and Bacillus subtilis)were applied to the bating process.By comparing the chromium resistance and the bating effect,and the L1 acid protease which is most suitable for the bating process get slected.Taking L1 as the main research object,the enzymatic properties of it were analyzed.By observing the dispersion of L1 acid protease on collagen fiber and elastic fiber in the bating process and analyzing the degradation condtion of collagen and elastin in the wet blue by L1 acid protease,the mechanism of acid protease in the process on wet blue was clarified.The results showed that the resistance of acid protease from Aspergillus niger and Aspergillus oryzae to chromium was better than that from Bacillus subtilis.Acid protease has no strong destructive effect on collagen,among which acid protease from Aspergillus oryzae and Aspergillus niger is the weakest.The results of technological application showed that the hygienic property,handness and mechanical strength of the crust leather were significantly improved after bating treatment,and the L1 acid protease from Aspergillus oryzae showed better effect.The study of enzymatic properties shows that the acid protease has high stability and the molecular weight of L1 is 48000 D,which has the advantages of small molecular weight and easy penetration;acid protease does not have a strong destructive effect on collagen,so it has a high safety when applied to the bating process of wet blue.In addition,acid protease from Aspergillus niger and Aspergillus oryzae had better chromium resistance than that from Bacillus subtilis,and acid protease from Aspergillus oryzae showed better bating effect.The results showed that two main structural proteins,collagen and elastin,were degraded under the action of acid protease,and the degradation rate of elastin was 100 times of that of collagen.Therefore,the degradation of elastin by acid protease during the bating process was the main reason to improve the performance of wet blue,and it can promote the further dispersion of collagen fibers by properly degrading the collagen,which plays an auxiliary role in improving the performance of the wet blue.On the basis of the above research,on the one hand,this paper also carried out the acid enzyme treatment for the blood vessel tissues on the wet blue.The results showed that 1% acid protease treatment for 4 hours had obvious treatment effect on the defects.In addition,on the basis of acid protease treatment,collagen based retanning filling material can promote the reduction of the blood vessel tissues.On the other hand,the synergistic effect of protease and lipase in the bating process of wet blue was also studied.It was found that the synergistic effect of protease and lipase was good in the bating process:The simultaneous use of both of them could improve degreasing efficiency in the bating process and promote the absorption of chrome tanning agent in the retanning process,and improving the cleanliness of the grain surface.At the same time,they have a good synergistic effect on the stability to wet heat of wet blue and the mechanical strength of crust leather.This paper has important theoretical significance and application value for further exploring the theoretical problem of acid enzyme acting on wet blue and exploring the solution of leather defects in bating process by acid protease.