The Preparation Of Amino Modified Fe₃O₄@SiO₂ Nanoparticles And Its Immobilized Pectinase Research

Fe₃O₄@SiO₂-NH2 was prepared by sol-gel method,experimental study using single factor analysis of the amino-modified process affects the concentration of TEOS,APTES content,temperature and time on the content of amino,magnetic immobilized carrier with a higher amino content was obtained and the products of each stage were characterized.The optimum reaction time was 8 h during the sol-gel method,and the effect of prolonging the reaction time on the content of amino groups was not significant.The amino content of the magnetic nanocarriers prepared at the reaction temperature of 80?,the TEOS content of 2m L and the APTES content of 5 mL can reach the highest value of 1.22 mmol/g.TEM and SEM analysis showed that the prepared magnetic nanocarrier had a diameter of 20-40 nm,the results of VSM analysis show that the saturation magnetization of magnetic Fe₃O₄@SiO₂-NH2 composite particles is about 49 emu/g,with superparamagnetic properties,and the results of XRD,FI-IR and TG also show that the magnetic nano-particles have been successfully prepared.The effects of glutaraldehyde concentration,pectinase content,pH,temperature and crosslinking time on the activity of immobilized pectinase were studied by univariate analysis and orthogonal analysis.The optimal immobilization conditions of the immobilized enzyme were obtained,The four factors which affect the immobilization effect of immobilized pectinase were determined,the order of it was: glutaraldehyde concentration> pH>temperature> crosslinking time,The optimum experimental conditions were as follows:0.2g of magnetic nano-carrier and 3% concentration of glutaraldehyde 2 mL for the reaction,then adding 20 mL of 32.4 U/mL pectinase,at 50?,pH 8.0 and the crosslinking time was 8 hours,the recovery rate of the enzyme activity of the immobilized pectinase was73.5%.The results of VSM analysis show that the saturation magnetization of magnetic Fe₃O₄@SiO₂-NH2 immobilized pectinase particles was about 32 emu/g,and it has good magnetic recovery performance.Characterization of magnetic immobilized pectinase by SEM,XRD,TG,VSM and FT-IR showed that pectinase had been successfully immobilized.The results of enzymatic studies show that optimum reaction pH of the free enzyme and immobilized pectinase was 8.5,the optimum reaction temperature of free enzyme was 50?,and the immobilized pectinase was 55 ?.The optimal pH stability of free enzyme and immobilized pectinase was 8.5,and the temperature stability of immobilized pectinase was slightly higher than that of free enzyme.In the range of 30-70?,The enzyme activity of the enzyme decreased by 46.5%,while the immobilized pectinase decreased by 41.4%.The freeenzyme lost about 18.5% of the enzyme activity after 30 days of storage,but only about10.4% of the enzyme activity of the immobilized pectinase was lost.After 7 times of continuous use of pectinase,64.4% of pectinase activity remained.K_m=6.11 mg / mL for free enzyme,K_m=7.42 mg / mL for immobilized pectinase,and free enzyme?Vm=2.41 mg /m L?min?with immobilized pectinase?Vm=2.53 mg/mL min?was not much difference.