食品安全国家标准食品中镉的测定_等13项食品安全国家标准发布_.pdf

第 卷 第 期 15 2 海藻酸钠-聚乙烯醇- 活性炭共固定化重组大肠杆菌细胞 27 Co-immobilized Recombinant Escherichia coli Cells with Sodium Alginate-PVA-Activated Carbon Sun Lihui Shen Aiping He Baolong Zheng Yuguo* （Institute of Bioengineering ， Zhejiang University of Technology ， Hangzhou 310032 ） Abstract Objective ： To investigate immobilization of acid phosphotransferase of recombinant Escherichia coli BL21 （ ） ， ： DE3 /pET28b -AP/PT and enzyme characteristics of immobilized cells. Methods Suitable carrier of sodium alginate - （ ） PVA-activated carbon for the immobilization of recombinant E. coli BL21 DE3 /pET28b-AP/PT was selected by the com- ， parison of nine immobilization methods. The optimal immobilization conditions such as gel constitution cells embedded and crosslinking time were determined ， and the enzyme characteristics of immobilized cells and free cells were also com- pared. Results ： The optimized preparation conditions were as follows ： activated carbon concentration 1.0% ， sodium algi- nate concentration 2.0% ， polyvinyl alcohol concentration 6.0% ， CaCl2 concentration 2.0% ， embedded cell amount 6 g/100 mL gel solution ， and crosslinking time 6 h. The optimum temperature of acid phosphotransferase from the immobilization cells was 35 ℃ ， 5 ℃ higher than free cells. The optimum pH values both immobilization cells and free cells were 5.0. Immobilized cells possessed excellent operation stability. After 12 cycles ， 54.5% of activity stil