Polydopamine tethered CPO/HRP-TiO2 nano-composites with high bio-catalytic activity, stability and reusability: Enzyme-photo bifunctional synergistic catalysis in water treatment

摘要

An enzyme-TiO2 composite with high catalytic activity, stability at harsh reaction condition, and good reusability was prepared via modification of TiO2 by polydopamine (PDA) to tethering with chloroperoxidase (CPO) or horseradish peroxidase (HRP) through glutaraldehyde. TiO2 played both roles of solid carrier and photocatalyst in the application of soluble dyes decolorization, and in this way, the loss of enzymatic activity during enzyme immobilization can be compensated. Because the enzyme and TiO2 were included in same composites, an enzyme-photo bifunctional synergistic catalysis was observed due to the interaction between enzyme and TiO2, resulting in that the formation of catalytic intermidiate, center dot OH, increased and the band gap energy of TiO2 became narrow. The light absorption by TiO2 was extended from the UV region to the visible region through coated by PDA and CPO/HRP so as that CPO/ HRP-TiO2@PDA can be used under visible light irradiation instead of ultraviolet light irradiation, which can avoid the decrease of enzyme activity by ultraviolet light irradiation. HRP-TiO2@PDA composite had even the best resuability of enzyme immobilized on solid support compared with the data in reference, in our best knowledge. There was no activity loss of HRP-TiO2@PDA after 15 times use, and more than 90% activity can be remained after 25 times use. Even after 40 times use, the relative activity of HRP-TiO2@PDA was 63.6% of that in the first run. The difference of reusability between CPO and HRP have relationship with the distribution of function group among the surface of enzyme molecule.