Co-immobilized spore laccase/TiO 2 nanoparticles in the alginate beads enhance dye removal by two-step decolorization

Combinatorial application of different dye removal methods with specific features can lead to a novel and robust decolorizing system. In this study the bacterial spore laccase and TiO nanoparticles were co-entrapped to enhance dye degradation. The optimum entrapment conditions were achieved in the presence of alginate 2% (w/v) and Ca (0.2M), Cu (0.05M) and Zn (0.25M) as matric polymer and counterions, respectively. Immobilized laccase showed a wide range of pH and temperature stability in comparison to the free spores. The entrapped degradation systems include single laccase, single TiO , laccase + TiO (one-step remediation), TiO /laccase (two-step remediation), and laccase/TiO (two-step remediation) that result to the 22%, 26% 45.6%, 47.6%, and 69.3% indigo carmine decolorization in 60 min. In the kinetic studies, the half-life of indigo carmine (25 mg/l) in the remediation processes containing laccase, TiO , laccase + TiO , TiO /laccase, and laccase/TiO was calculated as 173, 138, 161, 115, and 57 min, respectively. The degradation products by co-entrapped system were not toxic against Sorghum vulgare. The results showed two-step decolorization by co-entrapped spore laccase and TiO nanoparticles, including the pretreatment of dye by laccase, and then, treatment by TiO has potential for degradation of indigo carmine.