Simultaneous Application of Acid Protease and Transglutaminase on Wool and its Optimisation to Achieve Machine Washable Care Claim

Abstract

In the previous work by the same authors, optimisation of sequential application of acid protease and transglutaminase was carried out to achieve Woolmark specification AW-1 for the machine washable care claim, that is, less than 3% total shrinkage. As a result of optimisation, the total warp shrinkage reduced to 2.64% with only 2.82% loss in warp tensile strength. In this work, simultaneous application of acid protease and transglutaminase was explored and optimised using Box–Behnken design of experiment. The optimisation was carried out using two criteria. In the first criterion, the model was used to predict treatment parameters for minimum total warp shrinkage with minimum loss in warp tensile strength. Taking these predicted treatment parameters, wool was treated with acid protease (1%, owf) and transglutaminase (2.8%, owf) at pH ∼5.3 and 50°C for 60 min. After treatment, the total warp shrinkage reduced to only 4.32% with 4.65% loss in warp tensile strength. This was not only higher than the optimised sequential application of both the enzymes but also failed to meet the Woolmark specification for machine washable care claim. So, the second criterion was used in which the prediction was taken for treatment parameters to achieve the minimum total warp shrinkage without any constraints on loss in warp strength. Again, taking these predicted treatment parameters, wool was treated with acid protease (1.3%, owf), transglutaminase (1.6%, owf), pH ∼4.7 at 55°C for 85 min. Under these treatment conditions, the total warp shrinkage reduced to 2.89% with 10.1% loss in warp strength. Furthermore, interaction between the enzymes also plays a role in the outcomes of the treatment. It was evident that there was a loss in transglutaminase activity as a result of acid protease digestion. However, there was no loss in the activity of acid protease, indicating that transglutaminase did not have any negative influence on the activity of acid protease.