Decolorization of melanoidins from simulated and industrial molasses effluents by immobilized laccase

Dark brown color of molasses effluents is mainly due to the presence mainly of recalcitrant, high-molecular-weight compounds such as melanoidin. Microbial enzymes including laccase degrade persistent molecules in contrast to the conventional biological process. To overcome the loss of enzyme activity during catalysis of the process, their immobilization is often a successful strategy. In this study laccase was covalently immobilized on alumina or controlled pore glass-uncoated particles. The immobilization yield (IY) was 87.5 and 69%, respectively. The immobilized enzyme on both supports showed higher tolerance to pH (4-6.5), to temperature (35-60 degrees C) and improved thermostability maintaining at 80 degrees C the 55% and 80% of its initial activity, respectively. The kinetic parameters of K-m and V-max for immobilized and free laccase were determined. Immobilized laccase displayed operational stability (11 cycles for syringaldazine and 4 cycles for melanoidin). Degradation of simulated molasses wastewaters after 48 h with immobilized laccase on glass and alumina reached 74% and 71%, respectively. Whereas degradation of baker's yeast effluents by immobilized laccase on glass reached 68% within 24 h at pH 4.5 and 28 degrees C for a melanoidin solution 1% v/v. (C) 2016 Elsevier Ltd. All rights reserved.