ABSTRACTPluronic® F68 (P‐F68) is an important component of chemically‐defined cell culture medium because it protects cells from hydrodynamic and bubble‐induced shear in the bioreactor. While P‐F68 is typically used in cell culture medium at a concentration of 1 g/L (0.1%), higher concentrations can offer additional shear protection and have also been shown to be beneficial during cryopreservation. Recent industry experience with variability in P‐F68‐associated shear‐protection has opened up the possibility of elevated P‐F68 concentrations in cell culture media, a topic that has not been previously explored in the context of industrial cell culture processes. Recognizing this gap, we first evaluated the effect of 1–5 g/L P‐F68 concentrations in shake flask cultures over ten 3‐day passages for cell lines A and B. Increase in terminal cell density and cell size was seen over time at higher P‐F68 concentrations but protein productivity was not impacted. Results from this preliminary screening study suggested no adverse impact of high P‐F68 concentrations. Subsequently fed‐batch bioreactor experiments were conducted at 1 and 5 g/L P‐F68 concentrations with both cell lines where cell growth, viability, metabolism, and product quality were examined under process conditions reflective of a commercial process. Results from these bioreactor experiments confirmed findings from the preliminary screen and also indicated no impact of elevated P‐F68 concentration on product quality. If additional shear protection is desired, either due to raw material variability, cell line sensitivity, or a high‐shear cell culture process, our results suggest this can be accomplished by elevating the P‐F68 concentration in the cell culture medium without impacting cell culture performance and product quality. Biotechnol. Bioeng. 2015;112: 832–837. © 2014 Wiley Periodicals, Inc.