Investigation on Effects of Lactate Adaptation Using Metabolic Indicators and Amino Acids to Explore Cell Metabolism

Biopharmaceutical products are drugs that are made from living cells. One protein type of high importance to biopharmaceuticals is monoclonal antibodies. Monoclonal antibodies allow for highly specific, targeted treatment of diseases and detection of molecules related to diseases. With major roles in detecting and/or treating diseases like human immunodeficiency virus (HIV), coronavirus disease 2019 (COVID-19), and some cancers, monoclonal antibodies are in demand. This demand has led to a need for efficient cell culture systems to produce high yields of protein with minimal waste. The most commonly used cell culture system for these high-value proteins is Chinese hamster ovary (CHO) cells. Understanding and modifying CHO cell culture conditions can improve culture productivity. Previous research by Freund et al. (2018) presented a simple means to adapt cells to elevated lactate concentrations to reduce waste product buildup, increase protein productivity, and improve growth. It was also observed that the lactate-adapted cells had lower lactate accumulation. However, the lactate-adaptation process that Freund et al. (2018) used was stressful, as significant growth retardation was observed during the process. The work presented in this thesis developed a less stressful method to adapt CHO cells to elevated lactate concentrations The lactate adaptation was achieved by serial passages of the CHO cells into incrementally higher lactate concentrations. Batch cultures were used to compare the lactate-adapted cell growth characteristics to unadapted cells. Cell densities, metabolic indicators, and amino acid profiles were obtained daily for two lactate-adapted cell lines and unadapted cells. The lactate-adapted cells were cultured in elevated lactate equal to the final lactate-adaptation levels. Additionally, the unadapted and lactate-adapted cells were cultured in the standard media. It was observed that the elevated lactate was used by the lactate-adapted cells late in the cultures instead of alanine. This alteration in metabolism resulted in lower ammonia levels for the lactate-adapted cultures in elevated lactate compared to both lactate-adapted and the unadapted cultures in standard media. Thus, elevated lactate can have a positive effect on metabolism for lactate-adapted cells