Engineering aspects of improved antibody production by hybridomas

摘要

This study has been an investigation of bioreactor performance with an emphasis on growth and antibody productivity of hybridomas in membrane systems. The goal of the work was to explore ideas for optimizing bioreactor operation and design with the intent of improving yield and lowering downstream processing costs. Model equations of substrate uptake and diffusive mass transfer in microcapsules, hollow fiber and flat membrane bioreactors were formulated and used to generate simulated concentration profiles of oxygen and glucose. For use in the model, diffusivity and uptake rates of these substrates in a packed bed of hybridomas were measured aseptically with a temperature-controlled diffusion cell. Equations describing convective leakage flows in the extracapillary space of a hollow fiber reactor were also developed and the resulting theoretical velocity profiles were found to closely approximate actual measurements obtained using magnetic resonance flow imaging.;From a more biological perspective, specific cellular productivity was investigated in a cell sorting study using flow cytometry and in a study comparing growth and productivity in serum-reduced and serum-free media. Live hybridomas, sorted on the basis of high surface antibody, demonstrated an enhanced total cellular antibody content compared to an unsorted population; however the difference between the two cultures disappeared after several generations. The serum study showed that cells grown in a defined serum-free medium have similar growth rates but higher antibody productivity than those grown in medium containing 10% serum. Hybridomas grown in medium with different levels of serum content (10, 5.5, 1, 0.5%) exhibited increases in both the duration of the lag phase and the specific IgG production rate as serum levels were decreased. Antibody production for the three cultures with higher serum content were nearly the same indicating that serum levels can be reduced to approximately 1% without loss in reactor yield. Individually, each of these studies provides recommendations for optimizing bioreactor operation and protein production by mammalian cells. Used together, significant improvements in efficiency and economy should result.