Bio-Adhesive Magnetic Nanoparticles:Preparation And Applied For Immobilization Of Gluconobacter Oxydans

Gluconobacter oxydans is a gram-negative bacterium, shaped in ellipsoidal to rod. It has been widely used to oxidize sugar, alcohol, and aldehyde to produce aldehyde, ketone, and acid by its dehydrogenases connected to the respiratory chain. However, the small size caused the difficulty in the reuse and cycling of G.oxydans in industrial application. Immobilization plays an important role in cell catalysis, it can improve cells reusability and save costs significantly in production processes.In this study, we propose a new approach to immobilize G. oxydans in situ via a synthetic adhesive biomimetic material inspired by the protein glues of marine mussels. The optimum immobilization conditions were studied as well as the valuation of the catalytic activity of the immobilized cells. Our study included three aspects:(1) Preparation and Characterization of PD-IONPs. The magnetic nanoparticles (IONPs) were prepared using co-precipitation method. Dopamine is easy to undergo self-polymerization to produce an adherent polydopamine coating on IONPs. The prepared PD-IONPs were characterized with TEM, XPS, TGA, VSM, XRD.(2) Immobilization of G.oxydans onto PD-IONPs. The immobilization was carried out by mixing cells with PD-IONPs. The immobilized cells were separated by a magnetite. The optimum immobilization conditions were determined.(3) Valuation of the immobilized cells. The catalytic activity, stability and reusability of the immobilized cells were determined compared to the free cells.Our immobilization experiments show that PD-IONPs exhibit high G. oxydan loading capacity due to high surface area and strong adhesive interactions between the cells and PD. Immobilization does not affect the activity of G. oxydan for the catalytic oxidation of glycerol, and the G. oxydan aggregates show high specific activity and good reusability due to the convenience of the magnetic recovery method facilitated by binding of PD-IONPs onto cells. Cells immobilized by the optimized protocol show better stability than free cells, leading to maintenance of high cell biocatalytic activity over more cycles.These results demonstrate that immobilization of cells is facile, and efficient. This strategy could be used in the future as a convenient technique for immobilization of enzymes, DNA, antibodies and other biomolecules onto magnetic nanoparticles.