Continuous hybridoma suspension cultures with and without cell retention: kinetics of growth, metabolism and product formation.

A laboratory scale bioreactor was constructed from glass and polycarbonate materials whereby a track-etch membrane (3 microns pore diameter) was integrated into its two-part bottom flange. The reactor performance was evaluated for continuous hybridoma suspension cultures under various conditions of cell retention. A total retention experiment demonstrated that this type of stirred tank reactor cannot be operated at near zero growth rate conditions. Instead, at steady viable cell concentrations of congruent to 3 x 10(6) cells per ml, specific growth and death rates were estimated at 0.60 +/- 0.06 d-1. Specific substrate (glucose, glutamine, O2, amino acids) consumption, by-product (ammonia, alanine, amino acids) and product (antibody) production rates as well as various apparent molar yield coefficients were obtained and are compared to metabolic quotients and yield coefficients previously calculated from standard continuous culture experiments, i.e., without cell retention, at specific growth rates of 0.63 and 1.24 d-1. Furthermore, steady-state data on viable cell and antibody concentrations, spec. mAb productivities, and space-time yields determined before and after a step change (2.5-fold increase) in dilution rate at identical specific growth rates mu are presented.