Abstract:The immobilized Candida antarctica lipase B(CALB) was prepared by physical adsorption, and the effects of different environmental factors(buffer ionic strength, drying method, enzyme-to-carrier ratio, carrier type and enzyme pretreatment method) on the immobilization were explored. The results indicated that under high ionic strength conditions (1 mol/L), epoxy resins ECR8215 and ECR8285 demonstrated 92.2% and 232.2% increases in enzymatic activity, respectively, compared to low ionic concentration conditions (0.1 mol/L). Conversely, macroporous adsorbent resins (ECR1030, ECR8806, VPOC1600, and PCG900C) exhibited optimal performance under low ionic strength (0.02 mol/L), showing activity enhancements of 209.8%, 13.2%, 74.2%, and 15.3%, respectively, compared to high ionic conditions (0.1 mol/L). Drying methodology substantially affected enzyme performance. All six immobilized enzyme formulations (ECR8215-CALB, ECR8285-CALB, ECR1030-CALB, ECR8806-CALB, VPOC1600-CALB and PCG900C-CALB) displayed superior activity with blast drying compared to vacuum drying, demonstrating increases of 11.2%, 12.3%, 16.3%, 12.6%, 182.2%, and 65.8%, respectively. Increasing the ratio of enzyme-to-carrier from 50 mg/g to 100 mg/g enhanced esterification activity by 17.1%, 7.6%, 8.2%, 27.2%, 6.8%, and 26.5% for the respective formulations. However, further increase to 150 mg/g resulted in activity reductions of 8.6%, 14.2%, 1.4%, 12.8%, 3.8%, and 12.2%, suggesting potential carrier saturation or mass transfer limitations. The activity of the immobilized enzyme exhibits a positive correlation with the specific surface area of the carrier, while the mechanical stability of the carrier also significantly influences its performance. Notably, solvent pretreatment of free CALB prior to immobilization substantially enhanced catalytic activity. The effects of pretreatment on the structure of CALB were further analysed by circular dichroism and fluorescence spectroscopy, and the results showed that the secondary structure content of CALB changed after pretreatment and that there was a positive correlation between its α-helix content and immobilisation enzyme activity. The final immobilized CALB was prepared by using ECR1030 resin with a buffer ionic strength of 0.02 mol/L, and the CALB enzyme solution was pretreated with n-hexane, the ratio of enzyme to carrier was 100 mg/g, and the immobilized CALB was dried in a blast at 40 ℃ for 8 h. The activity of immobilized CALB reached (13 960.3±81.8) U/g, which is 25.6% higher than Novozym 435, and the activity of the immobilized CALB was still maintained at 70.5% after 60 days of sealed storage at 4 ℃. This study provides a theoretical basis and technical reference for the independent development of immobilised enzyme in China.