A simple method for control of lactate accumulation in suspension cultures of Chinese hamster ovary (CHO) cells based on the culture's pH was developed. When glucose levels in culture reach a low level (generally below 1 mM) cells begin to take up lactic acid from the culture medium resulting in a rise in pH. A nutrient feeding method has been optimized which delivers a concentrated glucose solution triggered by rising pH. We have shown that this high-end pH-controlled delivery of glucose can dramatically reduce or eliminate the accumulation of lactate during the growth phase of a fed-batch CHO cell culture at both bench scale and large scale (2,500 L). This method has proven applicable to the majority of CHO cell lines producing monoclonal antibodies and other therapeutic proteins. Using this technology to enhance a 12-day fed-batch process that already incorporated very high initial cell densities and highly concentrated medium and feeds resulted in an approximate doubling of the final titers for eight cell lines. The increase in titer was due to additional cell growth and higher cell specific productivity.

Chinese hamster ovary (CHO) cells in culture are known to consume large amounts of nutrients and divert most of them toward byproducts, some of which, including lactate and ammonia, are known to be toxic in nature. Glucose limitation strategies can successfully control lactate accumulation in fed-batch cultures yielding higher peak cell densities and titers. Interestingly, even in such optimized cultures, cell growth slows and eventually stops, indicating the emergence of other factors that negatively affect cell growth. In this study, we employed omics techniques to identify and quantify nine compounds that are intermediates or byproducts of amino acid metabolism, and accumulate in fed-batch cultures. Treatment with these compounds either individually or in a combined fashion resulted in partial or complete cell growth inhibition. Careful control of selected amino acid concentrations between one-half and one millimolar during the growth phase of fed-batch cultures reduced accumulation of the inhibitory metabolites and allowed for higher peak cell densities and increased productivity. Biotechnol. Bioeng. 2017;114: 1779-1790. © 2017 Wiley Periodicals, Inc.

The steady-state metabolic parameters for a hybridoma cell line have been determined in continuous suspension-perfusion culture over a wide range of perfusion rates and cell bleed rates. Significant increases in viable cell concentrations and volumetric productivities were achieved at high perfusion rates and low cell bleed rates. At the low growth rates examined in this study, cellular metabolism shifted to become more oxidative, and as a result, the fraction of consumed substrate converted to inhibitory metabolic by-products was reduced. Specific antibody productivity was found to be non-growth associated.