This study evaluates the potential of using ultrasound to enhance the bleaching efficiency of laccase enzyme on cotton fabrics. Ultrasound of low intensity (7 W) and relatively short reaction time (30 min) seems to act in a synergistic way with the enzyme in the oxidation/removal of the natural colouring matter of cotton. The increased bleaching effect could be attributed to improved diffusion of the enzyme from the liquid phase to the fibres surface and throughout the textile structure. On the other hand inactivation of the laccase occurred increasing the intensity of the ultrasound. However, at the ultrasound power applied in the bleaching experiments the loss of enzyme activity was not significant enough to justify the use stabilizer such as polyvinyl alcohol. Furthermore, the polyvinyl alcohol appears to be a substrate for the laccase.
Calafell, M.; Diaz, C.; Hadzhiyska, H.; Gibert, J.; Daga, J.; Tzanov, T. Biocatalysis and biotransformation Vol. 25, num. 2-4, p. 336-340 DOI: 10.1080/10242420701379874 Data de publicació: 2007-03 Article en revista
Cotton fabrics were dyed with dyes generated in situ by laccase-catalyzed oxidative coupling of the colorless 2,5-diaminobenzenesulfonic acid (2,5-DABSA) and 1-hydroxyphenol (catechol). The enzymatic oxidation of the dye intermediates led to cross-coupling reaction products when the reaction was conducted with an excess of catechol. At least fourfold excess of catechol was necessary to achieve satisfactory dye fixation on cotton. Formation of the same colored product using either an equimolar ratio of the reagents or tenfold excess of catechol was observed. Most probably, homo-molecular reactions predominate over the cross-coupling at equimolar ratio of the precursors, while with an excess of catechol, the cross-coupling occurs in higher yield. The reaction was followed using UV-Vis spectroscopy, HPLC, FTIR and MALDI-TOF MS. A reaction pathway for laccase-induced cross-coupling of catechol and 2,5-DABSA yielding a major colored product was proposed.