Submitted to: Textile Research Journal
Publication Type: Peer reviewed journal
Publication Acceptance Date: 3/12/2007
Publication Date: 5/1/2007
Citation: Cardamone, J.M., Phillips, J.G. 2007. Enzyme-mediated Crosslinking of Wool Part II: Keratin and Transglutaminase. Textile Research Journal. 77(5):277-283. Interpretive Summary: The ARS process involves a bleaching step followed by an enzymatic treatment step for biopolishing and shrinkproofing wool. This process reduces the felting shrinkage of wool fabrics to 3% or less in machine washing. The process has proven to be successful and has met with industry acceptance. However enzymatic digestion is responsible for up to 18% strength loss in fine jersey fabric. To alleviate this problem we replaced the enzyme step with an approach involving the application of solutions and dried powders of keratin obtained by dissolving wool fibers in strong alkali. We applied the keratin solutions and powders together with a non-digestive crosslinking enzyme to wool fabric pretreated by an ARS bleaching method. A set of experiments varying the concentrations of keratin and this enzyme were carried out to predict the optimum conditions for their concentrations that would minimize felting shrinkage and change in fabric weight while maximizing dry burst strength and increase in fabric whiteness. Optimum conditions were found when 5% keratin powder with 5% new enzyme was applied to wool fabric at 30ºC, 30 minutes for this resulted in minimized felting shrinkage, strength loss, loss of whiteness, and weight change. These results are acceptable to the industry and will provide an option to the use of digestive enzyme in ARS shrinkproofing when fine knit fabrics are dictated for military and commercial use.
Technical Abstract: Keratin hydrolysates, KH, and their lyophilized powders, KP, were applied with transglutaminase (amine y-glutamyltransferase EC 188.8.131.52), TG, to fine jersey wool fabric bleached by peroxycarboximide acid in the first step of the ARS process. The full ARS process involving treatment with proteolytic enzyme (ESPERASE) after pretreatment by bleaching can result in up to 18% fabric strength loss in fine-gage jersey knits, yet the ARS process has met with industry acceptance. To alleviate strength loss we applied solutions of KH and KP in combination with TG as a transferase enzyme to catalyze transamidation reactions involving keratin as KH and KP and keratinaceous wool fabric in order to provide crosslinking between and among these keratin constituents. Treatments of KH from 100% to 10% with TG showed that shrinkage could be controlled; application of 6% owf KP and 2% owf TG controlled shrinkage to 4.89% Scanning electron micrographs showed that the keratin material coated the fibers to fill wool’s raised scales. The results of statistical analysis predicted the optimum application conditions of 5% KP and 5% TG. These conditions minimized felting shrinkage to 5.21% and fabric weight change to 0.26% and maximized dry burst strength to 4.7% loss and increase in fabric whiteness to 17.8 whiteness index units. Wool material, including hydrolysates and powders crosslinked by TG enzyme-mediation can provide a rich resource for the production of modified keratin-based biomaterials.