Brunner Matthias, Doppler Philipp, Klein Tobias, Herwig Christoph, Fricke Jens
Research Division Biochemical Engineering Vienna University of Technology Vienna Austria.
CD Laboratory on Mechanistic and Physiological Methods for Improved Bioprocesses Vienna University of Technology Vienna Austria.
Eng Life Sci. 2017 Dec 19;18(3):204-214. doi: 10.1002/elsc.201700131. eCollection 2018 Mar.
The shift from lactate production to consumption in CHO cell metabolism is a key event during cell culture cultivations and is connected to increased culture longevity and final product titers. However, the mechanisms controlling this metabolic shift are not yet fully understood. Variations in lactate metabolism have been mainly reported to be induced by process pH and availability of substrates like glucose and glutamine. The aim of this study was to investigate the effects of elevated pCO concentrations on the lactate metabolic shift phenomena in CHO cell culture processes. In this publication, we show that at elevated pCO in batch and fed-batch cultures, the lactate metabolic shift was absent in comparison to control cultures at lower pCO values. Furthermore, through metabolic flux analysis we found a link between the lactate metabolic shift and the ratio of NADH producing and regenerating intracellular pathways. This ratio was mainly affected by a reduced oxidative capacity of cultures at elevated pCO. The presented results are especially interesting for large-scale and perfusion processes where increased pCO concentrations are likely to occur. Our results suggest, that so far unexplained metabolic changes may be connected to increased pCO accumulation in larger scale fermentations. Finally, we propose several mechanisms through which increased pCO might affect the cell metabolism and briefly discuss methods to enable the lactate metabolic shift during cell cultivations.
在CHO细胞代谢中，从乳酸生成向乳酸消耗的转变是细胞培养过程中的一个关键事件，并且与延长培养寿命及提高最终产物滴度相关。然而，控制这种代谢转变的机制尚未完全明确。乳酸代谢的变化主要据报道是由工艺pH值以及葡萄糖和谷氨酰胺等底物的可用性所诱导的。本研究的目的是调查升高的pCO₂浓度对CHO细胞培养过程中乳酸代谢转变现象的影响。在本出版物中，我们表明，在分批培养和补料分批培养中，与较低pCO₂值的对照培养相比，升高pCO₂时不存在乳酸代谢转变。此外，通过代谢通量分析，我们发现乳酸代谢转变与细胞内产生和再生NADH的途径比例之间存在联系。该比例主要受到升高pCO₂时培养物氧化能力降低的影响。所呈现的结果对于大规模和灌注过程尤其有趣，因为在这些过程中可能会出现升高的pCO₂浓度。我们的结果表明，迄今为止无法解释的代谢变化可能与大规模发酵中pCO₂积累增加有关。最后，我们提出了几种升高的pCO₂可能影响细胞代谢的机制，并简要讨论了在细胞培养过程中实现乳酸代谢转变的方法。
