Physiological responses to mixing in large scale bioreactors
Physiological responses to mixing in large scale bioreactors
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DOI：
10.1016/s0168-1656(00)00365-5
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发表时间：
2001-02-13
影响因子：
4.1
通讯作者：
Manelius, Å
中科院分区：
文献类型：
--
作者：
Enfors, SO;Jahic, M;Manelius, Å
将22 m3规模的大肠杆菌补料分批培养与相应的实验室规模工艺和培养进行了比较，所述工艺和培养使用配备有高葡萄糖浓度区以模拟大型生物反应器的进料区中的条件的按比例缩小的反应器。甲酸盐在大反应器中积累，表明存在氧限制区。有人建议，在大规模的生物量产量减少部分是由于重复生产/再同化的乙酸盐从溢流代谢和混合酸发酵产物，由于局部移动区与氧气的限制。在按比例缩小的反应器中产生混合酸发酵的条件也诱导了许多应激反应，通过分析选定的应激诱导基因的mRNA来监测。当细胞返回到反应器的底物限制和氧气充足的隔室时，应力响应被放松。在大型反应器中的相应分析表明，在离进料区最远的取样口，4个胁迫诱导基因的mRNA浓度最低。据推测，在大型生物反应器中反复诱导/松弛应激反应可能有助于改变在大规模生物反应器中生长的细胞的生理特性。流式细胞仪分析显示，在大规模反应器和缩小规模反应器的动态环境中生长的细胞中，细胞质膜电位和完整性的损伤减少。(C)2001 Elsevier Science B. V.保留所有权利。
Escherichia coli fed-batch cultivations at 22 m(3) scale were compared to corresponding laboratory scale processes and cultivations using a scale-down reactor furnished with a high-glucose concentration zone to mimic the conditions in a feed zone of the large bioreactor. Formate accumulated in the large reactor, indicating the existence of oxygen limitation zones. It is suggested that the reduced biomass yield at large scale partly is due to repeated production/reassimilation of acetate from overflow metabolism and mixed acid fermentation products due to local moving zones with oxygen limitation. The conditions that generated mixed-acid fermentation in the scale-down reactor also induced a number of stress responses, monitored by analysis of mRNA of selected stress induced genes. The stress responses were relaxed when the cells returned to the substrate limited and oxygen sufficient compartment of the reactor. Corresponding analysis in the large reactor showed that the concentration of mRNA of four stress induced genes was lowest at the sampling port most distant from the feed zone. It is assumed that repeated induction/relaxation of stress responses in a large bioreactor may contribute to altered physiological properties of the cells grown in large-scale bioreactor. Flow cytometric analysis revealed reduced damage with respect to cytoplasmic membrane potential and integrity in cells grown in the dynamic environments of the large scale reactor and the scale-down reactor. (C) 2001 Elsevier Science B.V. All rights reserved.