Chemical Modification Of Savinase By Dextran For Wool Anti-felting Finishing

During the current anti-felting process of protease, proteases will diffuse inside the fibre surface and hydrolyze the cell membrane complex(CMC), causing unacceptable strength loss. Therefore, it is considered to enlarge the molecular size of the enzyme so that the hydrolytic attack can be limited to the fibre surface, achieving machine-washable wool without significant fibre damage.In this work, Savinase is chemically modified using oxidised dextran. The optimum reaction conditions (temperature37℃,pH7) are selected, in terms of the residual activity, and the highest residual enzyme activity is 31.54%. GPC results show that the molecular size of the protease increased after chemical modification. CD and Fluorescence spectra reveal the difference between native and modified Savinase, which further demonstrate the conjugate of oxidized dextran and Savinase.Comparing with the native Savinase, the modified one has higher affinity to casein. The optimum reaction temperature for both of the proteases is 40℃, and the modified Savinase has better thermal stability at 30℃-50℃. The stability of modified Savinase is better than the native one at pH8.5-9.5.To study the enzymatic shrink-resist process based on modified Savinase, the process has been optimized (H₂O₂ concentration:10mL/L, time:120min; modified Savinase concentration:3%(o.w.f), temperature:50℃, time:120min). The wool fabric was treated with the native and modified Savinase under the same enzyme activity and then the properties of wool have been compared. It is found that although the area shrinkage of wool treated with the modified Savinase is slightly higher than the native one, it has reach the requirement of"machine washable". Furthermore, the modified Savinase treatment could obviously decrease the strength loss of wool compared with the native one. After the treatment with modified enzyme, the strength loss is 22.64%, much better than the native one of 7.74%. In addition, the two treatments also cause different change to the dye ability of wool. The results of ATR-FTIR show that the pretreatment of H₂O₂ can oxidize the cystine disulfide which is favorable for the hydrolytic attack of the enzyme to the wool. Both modified and native proteases can change the secondary structure of keratin, but the former has lower-efficiency. SEM shows that the scales of wool are damaged by the H₂O₂-protease treatment, while the modified protease cause lower fibre loss than the native one.