El-Sayed A H, Mahmoud W M, Coughlin R W
Department of Chemical Engineering and Biotechnology Center, University of Connecticut, Storrs, Connecticut 06268, USA.
Biotechnol Bioeng. 1990 Aug 5;36(4):338-45. doi: 10.1002/bit.260360404.
In batch fermentation Leuconostoc mesenteroides immobilized in calcium alginate beads produced a total dextransucrase activity equal to about 93% of that by free, suspended bacterial cells under comparable conditions in a bubble column reactor. Continuous sucrose feeding (5 g/L h) to the immobilized-cell culture in the airlift bioreactor increased production of enzymatic activity by about 107% compared with ordinary batch operation of this reactor. About 14% of the enzymatic activity produced by the immobilized cells appears as soluble activity in the cell-free broth compared with about 40% in case of free cells. In an airlift bioreactor, both the soluble and the intact (sorbed and entrapped) enzymatic activity produced by the immobilized bacterial cells was about 34% greater under automatic pH control, compared to that produced in a bubble column reactor with only manual pH control. During formation of dextran by intact enzyme within cells and beads, declines are observed in apparent enzymatic activity.
在分批发酵中，固定在海藻酸钙珠中的肠系膜明串珠菌在气泡柱反应器中，在可比条件下产生的总葡聚糖蔗糖酶活性约等于游离悬浮细菌细胞的93%。与该气升式生物反应器的普通分批操作相比，向气升式生物反应器中固定化细胞培养物连续添加蔗糖（5 g/L·h）使酶活性产量提高了约107%。固定化细胞产生的酶活性中约14%以可溶性活性形式存在于无细胞肉汤中，而游离细胞的这一比例约为40%。在气升式生物反应器中，与仅采用手动pH控制的气泡柱反应器相比，在自动pH控制下，固定化细菌细胞产生的可溶性和完整（吸附和截留）酶活性均高出约34%。在细胞和珠子内完整酶形成葡聚糖的过程中，观察到表观酶活性下降。
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