The influence of dissolved oxygen tension on the metabolic activity of an immobilized hybridoma population.

In the study presented here a laboratory scale (150 ml) fluidized bed bioreactor was used as a tool for making kinetic measurements on the production of monoclonal antibodies (MAb) with a hybridoma cell line. We determined the influence of dissolved oxygen tension (DOT) on the metabolic activity of a hybridoma population immobilized in macroporous collagen microspheres. The data obtained showed a reduction of the metabolic activity of the immobilized population at reduced DOT, the total number of immobilized cells, however, remained constant. At decreasing DOT an increasing lactate yield from glucose at reduced glutamine consumption was noticed, indicating a shift in the pattern of substrate usage. A mathematical description of maintenance metabolism was formulated and the parameters of growth and maintenance requirements were calculated. A growth associated MAb production was determined under the conditions applied leading to space time yields of 225 mg MAb per liter of total reactor volume and day.

The importance of cell physiology to the performance of animal cell bioreactors.

This report has pointed out the following: (1) the new animal cell products that will be produced commercially will have large dollar markets and will, together with cost containment and competitive pressures, place a greater emphasis on the reduction of the cost of production through the selection of appropriate culture technology; (2) the benefits to be gained by working with basic biological processes in animal cell culture that will increase cell density, cell productivity, and product quality; (3) the need to work with reactor technologies that can affect the basic biology of the cell in these positive ways; (4) it appears worthwhile to explore immobilized, high cell density culture technologies as a possible means to achieve the objectives by affecting the basic regulation of the cell through fundamental cell/cell environment biological processes.

Optimization of the microenvironment for mammalian cell culture in flexible collagen microspheres in a fluidized-bed bioreactor.

Flexible, three-dimensional, collagen Microspheres have been developed to actively promote a natural, optimal microenvironment for large-scale tissue culture of mammalian cells. The transport of nutrients into and cell products out of the Microspheres is enhanced by forced convective flow, which is the result of the tumbling of Microspheres and the dynamic properties of media flow in the fluidized-bed bioreactor. The collagen Microspheres have important characteristics of composition and morphology essential for optimal cell-matrix and cell-cell interactions. These interactions lead to high cell density and productivity through the dynamic modification of the microenvironment by cell-derived extracellular constituents. The collagen and Microsphere/fluidized-bed system provides the means to control and optimize the diffusive and contact components of the cells' microenvironment. Adaptation of cells to this microenvironment often results in dramatic increases in cell-specific productivity. Production of biotherapeutics in this process can be routinely performed in serum-free media, often leading to high productivity and product quality.

Cultivation of hybridoma cells in continuous cultures: kinetics of growth and product formation.

Mouse hybridoma cells were grown in suspension in continuous stirred bioreactors. Cell growth, substrate utilization, and monoclonal antibody (MAb) production were studied using serum-free medium. Steady-state data were obtained at different dilution rates, between 0.012 and 0.039 h(-1) Viability was profoundly affected by dilution rate, particularly near the lower end of the dilution-rate range investigated. MAb concentration and productivity went through a maximum with respect to dilution rate. Lactate yield on glucose declined with increasing dilution rate. Experiments were carried out to study the effects of medium glucose concentration on cell growth, product formation, and lactate yield on glucose. Reduction of glucose concentration in the feed medium did not considerably affect cell density and MAb concentration in the culture, but lactate levels dropped sharply; lactate yield on glucose declined substantially, indicating alterations in cell metabolic path ways for energy metabolism. Optimization strategy for continuous cell culture is discussed.