Biodegradation of a simulated textile effluent by immobilised-coated laccase in laboratory-scale reactors

Abstract

Laccase from Trametes pubescens was immobilised on alumina pellets and coated with polyelectrolytes. It was shown that this approach enhanced both laccase stability and reusability. Further, the immobilised-coated laccase was applied to the decolouration of a simulated textile effluent in laboratory-scale reactors. The simulated textile effluent was based on the recalcitrant diazo dye Reactive Black 5 (0.5 g/L). It was found that the decolouration was due to two processes: dye adsorption on the immobilisation support and coating and dye degradation by the laccase enzyme. The adsorption process represented less than 10% of colour removal for all cases, so decolouration was mainly due to laccase action. The decolouration was performed in both batch and continuous modes. A complete decolouration of the effluent was obtained in 30–36 h for the former and 48 h for the latter without the addition of redox mediators. In addition, the decolourised effluent showed lower phytotoxicity than the original one. These encouraging results make the process suitable for its potential implementation at industrial scale.