Co-immobilized spore laccase/TiO2nanoparticles 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(2)nanoparticles were co-entrapped to enhance dye degradation. The optimum entrapment conditions were achieved in the presence of alginate 2% (w/v) and Ca2+(0.2M), Cu2+(0.05M) and Zn2+(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 TiO2, laccase + TiO2(one-step remediation), TiO2/laccase (two-step remediation), and laccase/TiO2(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, TiO2, laccase + TiO2, TiO2/laccase, and laccase/TiO(2)was calculated as 173, 138, 161, 115, and 57 min, respectively. The degradation products by co-entrapped system were not toxic againstSorghum vulgare.The results showed two-step decolorization by co-entrapped spore laccase and TiO(2)nanoparticles, including the pretreatment of dye by laccase, and then, treatment by TiO(2)has potential for degradation of indigo carmine.

Automated summary

The combination of co-entrapped spore laccase and TiO(2) nanoparticles led to efficient degradation of dye with good stability and high decolorization efficiency. Analysis of the half-life of indigo carmine in different remediation systems showed that the laccase/TiO2 combination exhibited the best degradation effect in this study.