Enhanced decolourization efficiency of textile dye Reactive Blue 19 in a horizontal rotating reactor using strips of BNC-immobilized laccase: Optimization of conditions and comparison of decolourization efficiency

Abstract The textile dyeing and printing industry has led to extensive environmental pollution and severely threatens ecosystems. Immobilized laccase (IL) is an effective biocatalyst for the biotreatment of dye effluents, but is usually restricted by its aerobic requirements. Thus, it is desirable to design an efficient reactor that will increase the applicability of IL on an industrial scale. Decolourization efficiency of Reactive Blue 19 (RB 19), selected as a model textile dye, was compared between a horizontal rotating reactor (HRR) and a traditional vertical mixing reactor (VMR). The HRR was equipped with strips of bacterial nanocellulose (BNC) immobilized laccase, and the VMR contained wafers of BNC immobilized laccase. The maximum decolourization efficiency of HRR was achieved at the optimized temperature of 55°C, pH of 4.0, and agitation speed of 20 rpm. Advantages of HRR over VMR include a broader range of enzymatic reacting temperatures, greater contact and reacting interfacial area, and higher oxygen availability. After reacting RB 19 at optimized conditions for 5 h, the decolourization ratios of the VMR and HRR were, respectively, 45.7 % and 88.2 %. The HRR provided greater reusability of immobilized enzyme and higher detoxification, removal of chemical oxygen demand, and total organic carbon, indicating great potential in promoted decolourization of dyeing effluents.