Laccase-catalyzed simultaneous dye synthesis and cotton dyeing by using plant extracts as dye precursor

Natural dyes are gaining importance in recent years due to their advantages in terms of ecology, but the need of heavy metal salt (mordant) usage is an important limitation for their use. For this reason, it is very important to find alternative methods for textile dyeing with industrial dye plants. At this point, enzymatic processes are an important alternative. One of the most recent applications of enzymes in textile dyeing is laccase assisted coloration of textile materials. In this study, laccase-catalyzed enzymatic dye synthesis was used to dye cotton fabrics with St. John's wort and white onion peel extracts as an alternative to conventional mordants. For this aim, experiments were conducted at various laccase enzyme concentrations, plant extract solution concentrations, temperatures and times and results of color yield values were evaluated statistically. Furthermore, effect of enzymatic dyeing on the fastness values of these natural dyes was also investigated. According to the experimental results it was observed that enzyme concentration, plant extract concentration, time and temperature parameters on enzymatic dyeing with both St. John's wort and onion peel extract was statistically significant (p < 0.05). The optimum conditions were 1 g/L enzyme, 40 g/L plant extract, 60 degrees C, 3 h for St. John's wort. On the other hand, for white onion peel, optimum results were obtained with 1 g/L enzyme and 40 g/L plant extract at 80 degrees C for 2 h. Besides, in the natural dyeings made by adding laccase enzyme to the dye bath, the colors obtained are darkened and washing, rubbing and light fastness values were improved.