THE FILTRATION PROPERTIES OF ATROPA-BELLADONNA PLANT-CELL SUSPENSIONS- EFFECTS OF HYDRODYNAMIC SHEAR AND ELEVATED CARBON-DIOXIDE LEVELS ONCULTURE AND FILTRATION PARAMETERS

The filtration properties of Atropa belladonna plant cell suspensions cultured at different bioreactor stirrer speeds and gas-phase carbon d ioxide levels were measured. Cell cake compressibility did not vary si gnificantly with culture time, shear intensity or carbon dioxide conce ntration, Average cell cake permeability decreased by c. 70% with incr easing stirrer speeds between 400 and 1000 rpm, and could be correlate d with concomitant reductions in cell aggregate size. Permeability was more responsible than other culture parameters, such as growth, cell membrane integrity and protein release, to levels of hydrodynamic ener gy dissipation in the range 10(6)-10(9) J m(-3). Cell cake permeabilit y was significantly affected by carbon dioxide levels of 10 and 15%, b ut not 2%. Average permeability at 15% CO2 was reduced by c. 50% compa red with the air-sparged control culture, even though aggregate size, morphological characteristics and filtered cake compressibility were u naltered. A distinctive pattern of permeability change over the course of the cultures was observed when the reactor conditions were not inh ibitory to growth; however, this pattern was destroyed at medium-to-hi gh shear levels and high carbon dioxide concentrations.