Ahleboot Zohreh, Khorshidtalab Mahdi, Motahari Paria, Mahboudi Rasoul, Arjmand Razieh, Mokarizadeh Aram, Maleknia Shayan
Biopharmaceutical Research Center, Aryogen Pharmed Inc., Alborz University of Medical Sciences, Karaj, Iran.
Avicenna J Med Biotechnol. 2021 Jul-Sep;13(3):123-130. doi: 10.18502/ajmb.v13i3.6365.
Drastic pH drop is a common consequence of scaling up a mammalian cell culture process, where it may affect the final performance of cell culture. Although CO sparging and base addition are used as common approaches for pH control, these strategies are not necessarily successful in large scale bioreactors due to their effect on osmolality and cell viability. Accordingly, a series of experiments were conducted using an IgG1 producing Chinese Hamster Ovary (CHO-S) cell culture in 30 bioreactor to assess the efficiency of an alternative strategy in controlling culture pH.
Factors inducing partial pressure of CO and lactate accumulation (as the main factors altering culture pH) were assessed by Plackett-Burman design to identify the significant ones. As culture pH directly influences process productivity, protein titer was measured as the response variable. Subsequently, Central Composite Design (CCD) was employed to obtain a model for product titer prediction as a function of individual and interaction effects of significant variables.
The results indicated that the major factor affecting pH is non-efficient CO removal. CO accumulation was found to be affected by an interaction between agitation speed and overlay air flow rate. Accordingly, after increasing the agitation speed and headspace aeration, the culture pH was successfully maintained in the range of 6.95-7.1, resulting in 51% increase in final product titer. Similar results were obtained during 250 scale bioreactor culture, indicating the scalability of the approach.
The obtained results showed that pH fluctuations could be effectively controlled by optimizing CO stripping.
在扩大哺乳动物细胞培养过程中，pH值急剧下降是常见的结果，这可能会影响细胞培养的最终性能。尽管使用二氧化碳鼓泡和添加碱作为控制pH值的常用方法，但由于它们对渗透压和细胞活力的影响，这些策略在大规模生物反应器中不一定成功。因此，使用中国仓鼠卵巢细胞（CHO-S）在30L生物反应器中进行了一系列实验，以评估一种替代策略在控制培养pH值方面的效率。
通过Plackett-Burman设计评估诱导二氧化碳分压和乳酸积累（作为改变培养pH值的主要因素）的因素，以确定显著因素。由于培养pH值直接影响工艺生产率，因此将蛋白质滴度作为响应变量进行测量。随后，采用中心复合设计（CCD）来获得一个模型，用于预测产物滴度作为显著变量的个体和相互作用效应的函数。
结果表明，影响pH值的主要因素是二氧化碳去除效率低下。发现二氧化碳积累受搅拌速度和顶空空气流速之间相互作用的影响。因此，在提高搅拌速度和顶空通气后，培养pH值成功维持在6.95-7.1范围内，最终产物滴度提高了51%。在250L规模生物反应器培养过程中也获得了类似结果，表明该方法具有可扩展性。
所得结果表明，通过优化二氧化碳汽提可以有效控制pH值波动。
