Support Preparation Of Magnetic Chitosan Microspheres For Pectinase Immobilization And Processing & Properties Of Immobilized Pectinase

Pectinase is one of enzymes to which degrade pectin into galacturonicacid, it was come from the fermentation of Aspergillus Niger. Pectinolytic enzyme was applicated for juice squeeze and clarification in industry of vegetable, fruit juice, wines and liqueurs to improve the yield and steadiness of juice mainly. Pectinase also be used to avoid the phenomenon of "after haze" in vegetable and fruit juice. But in the industry using of pectinase, dissociated enzymes have so many shortcomings, such as large enzyme's amount, high product cost, difficult refined. Those defects affect pectinase's application in food industry greatly. And then immobilized enzyme may avoid the above weakness in some degree. At the same time, immobilized enzyme can decrease product cost and enlarge the enzyme's utilization.There are some studying reports of pectinase immobilization at present in some enterprises and academic institution. But the study for magnetic chitosan microspheres support immobilized pectinase is few. In this paper, the magnetic chitosan microspheres support was prepared, and the conditions of preparation were discussed. On the basis of first studying, the pectinase was immobilized on the magnetic chitosan microspheres support. The optimal conditions of immobilization, characteristics of immobilized enzyme were mainly investigated. The experimental results were as follows:1,With better coprecipitation method, magnetic nanometer Fe3O4 particle was composed, and then using suspension cross-linking technique, the support (magnetic chitosan microspheres) were prepared. The optimal preparation conditions of nanometer Fe3O4 particle were as follow:Fe3+:Fe2+ is 1.7:1, pH 9-10, the temperature of crystallization 80℃, the crystallization time 0.5 h. The optimal preparation conditions of magnetic chitosan microspheres support through orthogonal experiment were as follow:chitosan concentration 1.5%, oil-water ratio 4:1, the amount of emulsifier 4 mL, the amount of crosslinker 1.0 mL, reaction temperature from 50℃to 70℃.2,The support and magnetic core appearance, diameter and size distribution, scrystal strueture and magnetie response properties were characterized by means of Scanning Electron Microscopy,Transmission Electron Microscopy, X-Ray Diffractometer, FT-IR Spectrometers, Ultraviolet Spectrophotometer, Laser Particle Sizer, Vibrating Sample Magnetometer. The results indicate that the magnetic Fe3O4 nanopartieles have narrow size-distribution and fine dispersion stability. Fe3O4 nanopartieles also have fine scrystal strueture and superparamagnetic, their average sizes achieve 14.1nm. The supports (magnetic chitosan microspheres) have fine dispersion and narrow size distribution, average size is about 30μm. Although the surface of magnetic chitosan microspheres presents concavo-convex and the hollows, the support has intact skeleton construeture and has no agglomeration. The FT-IR results of support indicate that the Fe3O4 particle was covered by the chitosan utterly and there is no change in Fe3O4 particle structure. The spectrophotometry results show that magnetic chitosan microspheres have fine magnetic response properties. It is a kind of good carrier of pectinolytic enzyme.immobilization.3,The optimal conditions of pectinase immobilization were investigated through single factor experiment using magnetic chitosan microspheres as supports. The optimum immobilizd conditions were:time 6 h, pH 4.0,40℃,1.25 mL pectniase. Using those optimal conditions, the immobilized pectinase was prepared and its activity recovery will get to the highest.4,The properties of immobilized pectinase and free pectinase were compared. The test results show that immobilized pectinase optimum reacting temperature was 60℃(the free enzyme's 50℃), the immobilization enzyme's thermal stability has increased. The optimum reacting pH of immobilized pectinase was 4.0(the free enzyme's pH 3.5). It indicated that immobilized pectinolytic enzyme had better pH tolerance, its reused times was six and its function is better than free pectinase.5,Self-made immobilized pectinase was applied in apple juice for clarity. The test results show that immobilized pectinase 58mg/L, enzymatic pH4.0, hydrolysis temperature 60℃, time 60min. Under those conditions, the light transmission rate of apple juice get up to 88.7%, and the pectin test was negative.