A New Method To Produce ?-arbutin By Using Chitosan-coated Magnetic Microspheres As Carriers Of Hydroquinone

a-Arbutin,a glycosylated Hydroquinone(HQ),is widely present in animals,plants and microbial cells.The chemical structure of a-arbutin is 4-Hydroxybenzene-?-D-glucopyranoside.Because of the Hydrophilic property of the glucosyl group and the tyrosinase inhibition of the phenolic hydroxyl group,a-arbutin has effects of moisturizing,whitening and preventing melanin production.But there are some questions in its production,the toxic effect of the substrate Hydroquinone damages cells and reduces the production of a-arbutin.In order to reduce the concentration of isolated HQ,a carrier slowly releasing the substrate was developed.Magnetic nanoparticles(MNPs)are of growing interest in the biochemical industry because of some important properties they exhibit,such as nanometer size,superparamagnetism,high surface area,low cytotoxicity.In this study,chitosan-modified magnetic nanoparticles(MNPs/CTS)were used as the carrier of Hydroquinone(HQ),the acceptor of glycosyl transfer,which could be cata-lyzed by the glycosyltransferase of Xanthomonas maltophilia BT112 to synthetise a-arbutin.The four major results are listed as follows:1.Large-sacle hydrophilic Fe3O4 nanoparticles(NPs)were prepared in the presence of citrate and sodium nitrate via a facile method.The Fe3O4 NPs are quite stable and can be freely dispersed in water.The diameter of 40-50nm particles was obtained in 0.1M Fe2+.The Fe3O4 NPs trended to be more regular when the reaction time was over 1 h.2.Magnetic chitosan microspheres were prepared with a reversed-phase suspension method using glutaraldehyde as cross-linking reagent for the hydroquinone HQ immobilization.The microspheres had well-shaped spherical form with smooth surface,and its mean particle size was 1.0um with a narrow size distribution.The most optimization condition of the emulsion was established by the experiments.The diameter of Fe3O4 NPs is 30-40nm and molecular weight of chitosan is more than 400,the mass ratio of the two is 1:1.The reaction time is 4h.3.Magnetic chitosan microspheres possess the ability to adsorb hydroquinone and adsorption conditions were optimized.The initial concentration of HQ is 7g/L,the optimum temperature for adsorption is 28 ?,the rotational speed is 120rpm.The amount of HQ adsorption on the modified-MNPS could reach 314 mg/g MNPs/CTS.4.The immobilized hydroquinone could be re-leased in the broth and glycosylated to product a-arbutin.The a-arbutin yield is 7.96 g L-1 and conversion of HQ is 56.3%.The optimum concentration of immobilized HQ is 25g/L,the optimum temperature is 32 ?,the rotational speed is 180rpm.This new method for a-arbutin production involves the novelty of a slow release of the immobilized HQ so that the content of the system could not damage the cell.The magnetic nanoparticles could moreover be efficiently separated from the broth and recycled several times.Furthermore,this new method hold great promise for using magnetic nanoparticles in fermentation process.