Preparation And Characterization Of The Support Grafting Polyethylene Imine For Reversible Immobilization Of Enzymes

Immobilized enzyme is extremely active in research of the field of chemical biology, bio-engineering, medicine, environmental engineering and food industries. the most critical for Immobilized enzyme technology is the choice of the immobilized enzyme carrier. Graft polyethylene imine on an epoxy-based carrier has some special advantages compared with the general epoxy based carrier. We synthesized carrier grafted with polyethylene imine, and using this carrier immobilized lactase, and the nature of the immobilized enzyme were also studied.Hydroxyethyl methacrylate (HEMA), glycidyl methacrylate (GMA) as the monomer, ethylene glycol dimethacrylate (EGDMA) as crosslinker, then Potassium peroxydisulfate were anded to initiate the suspension polymerization reaction in NaCl solution, After polymerization, the epoxy-based carrier were synthetized. The carrier have a good dispersion, and the surface is smooth, spherical, monodisperse particles with average diameter of200μm. The epoxy group of the carrier is8.745mmol/g carrier measured with EDTA Method.Epoxy-based carrier is easy to be modified, can react with an amino, to form a strong, stable covalent bond. Therefore, under certain conditions, the epoxy-based carrier and polyethylene imine solution were mixed, to obtain an epoxy-based carrier grafted with polyethylene imine. The particle size distribution of the carrier is relatively narrow, an average diameter of400nm. In addition, the carrier does not have any of the aggregation phenomenon, showed very good characteristics of the single dispersion. Compared with the conventional carriers in the immobilized enzyme process, it can provide a larger surface area for the adsorption of enzyme. Hydrochloride titration Determination of the amino group content of the carrier was0.25mmol/g carrier.We studed the influence of immobilized pH value, temperature and the immobilization time to lactase immobilization and found that the initial enzyme concentration of4mg/ml, immobilized time of8h, the reaction medium at pH7.0, the best effect of the immobilized enzyme got. PEI-carrier of various enzymatic properties of the immobilized lactase was also studied, such as the optimum pH value, the thermal stability of the immobilized enzyme and repeat operability. Compared to the free enzyme, immobilized enzyme optimum pH alkaline, the thermal stability increases and after20times of using, it still be able to maintain900%of the original adsorption capacity.Study of the influence factors of the immobilized enzyme catalyzed synthesis of galactooligosaccharides indicated that the concentration of the substrate, reaction time have important effects to GOS yield. The GOS yield increased with lactose concentration increasing, when lactose as the substrate concentration of150g/L, the reaction for4hours, the GOS maximum yield,40g/L.