Study on Preparation and Properties of Immobilized Pectinase from Aspergillus niger on Globular Cross-linked Chitosan

The preparation and properties of immobilized pectinase from Aspergillus niger on globular cross-linked chitosan were investigated.When the concentration of chitosan solution was 2.0%,the composition of coagulation liquid was 15% NaOH∶40% ethanol=4∶1(in Volume),and after being cross-linked with 5.0% glutaraldehyde for 6 hours,globular cross-linked chitosan carrier was successfully made.The optimum conditions for immobilization were investigated,and the results showed that,with ten milligramme pectinase for one gramme carrier,after 40 minute oscillation and mixture of enzyme and carrier,the process time was 12 h at 4 ℃ under pH 3.4 of reaction medium and the recovery rate of enzyme activity was 91.45%,while the strength of immobilized enzyme remained strong enough.The optimum pH and optimum temperature of immobilized pectinase for the hydrolysis of pectin were determined to be pH 3.4 and 45 ℃,respectively.The apparent Michaelis constant of immobilized pectinase Kmapp equaled to 9.97 mg/mL.The stability of immobilized enzyme to pH and temperature was greater than that of the natural enzyme.The recovery activity of immobilized pectinase was more than 53.74% after being repeated seven times.