Effect of laccase on dyeing properties of polyphenol-based natural dye for wool fabric

Chemical mordants are generally used during the dyeing process, to increase the uptake of natural dyes. Traditional mordants include metal salts, such as copper, iron, aluminum, chromium, and other metal ions. Continuous developments in bio-engineering technology focus on methods that lower the impact on the environment. In this regard, enzymatic processes show great promise in textile field, due to their efficacy, mild conditions, and environment friendly nature. Laccase is a multicopper oxidoreductase that catalyzes in-situ polymerization of small phenolic monomers to form a colorful polymer. In this study, effects of laccase treatment on the dyeing properties of wool fabrics, dyed with natural dyes (turmeric, grape seed extract, and Chinese gallnut), were investigated. The dyeing properties of the dyed wool fabrics were evaluated under different conditions, including laccase stoichiometry, temperature, pH, and reaction time. The structural changes of natural dyes, due to laccase catalyst were also examined by FT-IR. The results showed that laccase greatly influenced the dyeing performance of Chinese gallnut. Moreover, dyeing effects of the samples using post-mordanting method was better than the other two methods, under the same conditions. After laccase treatment, the dyeing properties of Chinese gallnut improved. Finally, factors affecting the dyeing process with Chinese gallnut were studied and the optimized conditions were determined through single-factor experiments.