Secondary feed filtration and storage conditions influence trace element availability and process performance at 2000  <scp>L</scp> scale

Achieving consistent CHO cell culture performance during process scale-up is critical but often challenged by subtle changes in operational parameters. This study investigates how differences in feed media filtration and storage during scale-up can impact CHO cell culture performance. A 70% reduction in titer and a 25% drop in peak viable cell density (VCD) were observed at 2000 L scale. Root cause analysis revealed that the secondary filtration of feed media was likely a contributing factor. Trace element analysis confirmed significant copper(II) ions (Cu²⁺) loss in feed media at 2000 L, likely due to precipitation during storage and subsequent removal by secondary sterile filtration. This resulted in continued lactate accumulation and reduced titer. Feed storage conditions had an impact on Cu²⁺ stability, with room temperature storage accelerating Cu²⁺ loss when compared to storage at 2 to 8°C. By eliminating the secondary filtration step and optimizing feed media storage conditions, process performance was successfully restored at 2000 L scale, matching smaller scale performance. This study highlights how feed filtration and storage critically affect micronutrient stability and availability during scale-up. While secondary filtration may be used for additional microbial control, it can inadvertently alter feed composition, affecting cell metabolism and productivity. Thorough evaluation of feed stability, filtration, and storage strategies is therefore key to ensuring consistent bioreactor performance across scales.