Characteristics of immobilized dye-decolorizing peroxidase from Bacillus amyloliquefaciens and application to the bioremediation of dyeing effluent

Abstract

Dyeing effluent is a major source of aquatic pollution, necessitating novel remediation techniques. In this paper, dopamine-modified, chitosan-coated, halloysite nanotube (HNT) porous microspheres, which are biomimetic entities with a 3D nest-like architecture, were used as a matrix to immobilize dye-decolorizing peroxidase from Bacillus amyloliquefaciens (BaDyP). The porous HNT microspheres showed excellent loading capacity for BaDyP—as high as 250.8 mg/g. Compared with free BaDyP, immobilized BaDyP exhibited better stability over a wide range of pHs and temperatures. At 25 ℃, pH 4.5, and with 2, 2′-azinobis (3-ethylbezthiazoline-6-sulfonate) (ABTS) as an oxidation substrate, the Michaelis constant of immobilized BaDyP was 0.70 mM. The reusability of BaDyP is enhanced by immobilization and approximately 57.6% of the initial activity was retained after six recycling batches. Immobilized BaDyP showed great ability to decolorize various dyes and remediate dyeing effluents. It removed 52.77% of the chemical oxygen demand (COD) and provided 93.93% decolorization (Hazen Units; 89.96% in terms of ADMI), accompanied by significant detoxification within a 72-h incubation period. These results demonstrate the feasibility of using immobilized BaDyP on modified HNTs for the bioremediation of dyeing wastewater. The application of HNT-immobilized BaDyP to the continuous treatment of dyeing effluents in fixed bed reactors will be the next focus of research.