Feedback Control of Redox Potential in Hybridoma Cell Culture

Abstract

Culture redox potential (CRP) is an easily measured variable and its utility in hybridoma culture has been recently shown. Nevertheless CRP is scarcely measured as a routine variable in cell culture and very few reports exist of its proper control. In this work we describe, for the first time, a proportional feedback control algorithm based on manipulation of oxygen partial pressure for maintaining CRP at a constant and predetermined value in hybridoma cultures. A broad spectrum of reducing and oxidizing conditions, in the range of −140 mV to 100 mV with respect to the initial CRP, was evaluated by maintaining CRP constant. Cultures were performed in 1-Lt instrumented and computerized stirred bioreactors operated in batch mode. It was observed that cell and MAb concentrations, and specific growth and thiol production rates increased with decreasing CRP. Maximum concentration of ammonium and lactate remained constant at all CRP values tested. Apoptotic cell death was present in the early stage of cultures at oxidative conditions, whereas at a reduced environment it was triggered only until nutrient depletion during late culture stages. Accordingly, oxidative stress was found to be an inducer of apoptosis. The results of this study show that CRP control in animal cell cultures can be exploited to increase productivity, opening a new way to optimize hybridoma cultures.