Stability and decolourization ability of trametes villosa laccase in liquid ultrasonic fields

We report in this study that the sonication of laccase from Trametes villosa and bovine serum albumin promotes the formation of protein aggregates with high molecular weight. The formation of aggregates leads to the deactivation of the enzyme, fact that was confirmed by the analysis of the enzyme stability (half-life time) upon ultrasound treatment. This inactivation was mainly caused by the radicals formed by the cavitation phenomenon. It was verified that the addition of polyvinyl alcohol to laccase had a protecting effect against enzyme inactivation. The performance of laccase in the decolourization of indigo carmine was studied. It was observed that the best results were attained when the dye solution was treated with ultrasound and enzyme stabilized with polyvinyl alcohol, where more than 65% of decolourization was achieved. This value is remarkably higher than that attained for the enzyme alone, which was only able to decolourize 20% of the dye solution within 1 h of treatment. These results have important implications for the exploitation of sonication in textile industry, where the pollution caused by the release of dyes into effluents is one of the major concerns.Fundação para a Ciência e a Tecnologia (FCT) - SFRH/BD/8651/2002União Europeia - Projecto ULTRATEC (NMP2- CT-2003-505892)