One of the major goals for recombinant protein production in mammalian fed-batch culture is to achieve high titer yield, which can be compromised by cellular metabolic inefficiency leading to early cell apoptosis. To overcome this issue, iterative rounds of basal and feed media optimization is often required during process development. This typically involves a lengthy process using a combination of analytical methods to identify nutrient deficiency and the root cause that triggers cellular apoptosis. In this work, we examined the possibility of utilizing the mitochondrial membrane potential (MMP) as an in-process biomarker for cell metabolism and survival in a recombinant CHO-IgG fed batch culture. In addition, we hypothesized that changes in MMP is mainly induced by signaling information retained in the spent media such as nutrient deficiency and/or accumulation of toxic cell waste. We tested this hypothesis by treating fresh cells with spent media collected at different time points from a fed batch process and probing cellular MMP using a 96-well-plate based fluorescent assay. The results showed significant time point-dependent suppression of MMP by the exposure to spent media as compared to a fresh media-treated control. Interestingly, higher levels of MMP suppression were detected when exposing cells to spent media from later stages of culture from which low viability was triggered in the process. Furthermore, supplementing selective nutrient components to the spent media significantly rescued MMP levels, suggesting that mitochondria activity can be compromised by nutrient deficiency and the MMP assay is sensitive in identifying those limiting nutrients. Current work focuses on verifying whether the key limiting nutrients identified by the MMP assay will translate to improved cell viability and titer yield when included in fed-batch culture media. Overall, this MMP assay provides a high-throughput, fast, and sensitive method and can potentially be implemented as a predictive screening tool to accelerate cell culture media development.

High-throughput screening metabolic assay to improve media design for mammalian fed-batch culture

249th National Meeting (2015)

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