[On-line monitoring of oxygen uptake rate and its application in hybridoma culture].

On-line analysis and control are critical for the optimization of product yields in animal cell culture. The close monitor of viable cell number helps to gain a better insight into the metabolism and to refine culture strategy. In this study, we use the oxygen uptake rate (OUR) to estimate the number of viable cell and the OUR-based feed-back control strategy for nutrients feeding to improve the efficiency of cell culture. A hybridoma cell line (HAb18) was cultured in fed-batch and perfusion model using serum free medium in 5L CelliGen Plus bioreactor (NBS Co., American) and 5L Biostat B bioreactor (Braun Co., Germany). The system and the method for online monitoring OUR in bioreactors, based on the dynamic measurement of dissolved oxygen (DO), were developed. The method of on-line cell concentration estimation was established based on the relationship between the growth of the hybridoma and the uptake rate of oxygen. This method was then used to determine OUR and the concentrations of cell, antibody, glucose, lactate, glutamine and ammonia in the bioreactors at given times. The relationship between OUR and nutrients metabolism was studied and OUR-based feed-back control strategy, which used the state deltaOUR = 0 as the regulation point, was established and used to control the rates of nutrients or medium feeding rate in the perfusion culture. The results showed that there was close relationship between OUR, concentration of live cells, productivity of antibody and consumption of glutamine. The sudden decrease in OUR may be caused by glutamine depletion, and with different delay times, the viable cell concentration and antibody productivity also decreased. The further analysis revealed the linear relationship between OUR and the density of live cells in the exponential growth phase as qOUR = (0.103 +/- 0.028) x 10(-12) mol/cell/h. These findings can be applied to the on-line detection of live cell density. Our study also indicated that by adjusting the perfusion rate with OUR-based feed-back control strategy, it is feasible to continuously increase in viable cell density and antibody concentration in the perfusion culture.