Bioadhesion Inspired Enzyme Immobilization In Magnetic Iron Oxide

Recent years,soluble enzyme as biocatalyst has been applied into many fields for the advantages of high efficiency, excellent specificity and high stereoselectivity, and could catalyze the reaction under mild conditions. However, soluble enzyme encounters several limitations which leads to the low efficiency of industrial processes. Firstly, the majority of natural enzymes tend to be instable once they break away from physiological environments.Secondly, the factors of physics, chemistry and biology can damage the activity of enzymes due to the environmental sensitivity of the advanced enzyme structure. Thirdly,most of the natural enzymes were water soluble and it was difficult to purify products and recover enzymes. To overcome these disadvantages, different strategies including enzyme immobilization methods have been envisioned. In this study, the magnetic Fe3O4-PDA was applied for immobilization gelase enzyme and its' performance was investigated. In addition, CaCO3 was selected as template to prepare Fe3O4-PDA composite with neat spherical morphology and homogeneous particle size.Firstly, Fe3O4 was prepared by the chemical co-precipitation method. The magnetism of Fe3O4 was analyzed qualitatively with magnetic response time. Fe3O4 was characterized by FT-IR, XRD, LS and SEM-EDS and the effects of reaction temperature, time, pH and atmosphere on the performance of Fe3O4 were investigated. It indicated that there is no significant effect of different reaction conditions on the crystal structures and particle distribution of Fe3O4. Reaction time and temperature have slight influence on the magnetism of Fe3O4 and the pH of 9.0 is optimum to produce the strongest magnetic Fe3O4.Secondly, Fe3O4-PDA composite was prepared and identified by FT-IR, XRD, LS and SEM-EDS. It was shown that Fe3O4 and PDA combined into Fe3O4-PDA composite.Besides, the addition of PDA prevented the agglomeration of Fe3O4 in drying process to some extent. In addition, Fe3O4-PDA composite with neat spherical morphology was prepared using CaCO3 as a template and the morphologies of products prepared in different reactant adding orders were studied. It indicated that CaCO3-PDA was microsphere whose diameter was about 3?5?m, but the neat spherical morphology disappeared once it mixed with Fe3O4. CaCO3/Fe3O4 prepared from PEI-treated Fe3O4 was microsphere whose diameter was about 3?5?m and it was porous while the regular morphology disappeared when it reacted with PDA.Finally, the optimal order and ratio of reactants on immobilized BSA using Fe3O4-PDA composite were investigated. Fe3O4-PDA was used to immobilize gelase enzyme and it was illustrated that the immobilized enzyme has better mechanical stability and environment tolerance compared to the free gelase enzyme. The activity of the immobilized enzyme maintains higher than 50% after reuse for 5 times and it still remains higher than 27% after 9 times reuse, which indicates the immobilized gelase enzyme is of great reusability.