Abstract
A unit process packed bed reactor system for the growth of anchorage dependant cells and the production of animal viruses has been developed and studied. The technique is based on a static bed of 3mm diameter glass spheres with medium circulation provided by an airlift pump. The efficiency of this arrangement was assessed by comparison with the model process of the production of foot and mouth disease virus from BHK monolayer cells in Roux flasks. The physical parameters of the substrate bed and the critical rate of medium circulationn were established at the 100 ml scale. A linear flowrate of 2 cm/min down uniformly-shaped beds of glass speheres was used for the design of larger propagators of 1, 10 and 100 litres (equivalent to 10, 100 and 1,000 Roux flasks). These confirmed the observations from the prototype reactors and enabled new process strategies to be developed. Cell growth in glass sphere propagators was monitored from the level of glucose in the culture medium. A fall to less than 2 g/litre corresponded to the time of maximum cell growth. Biochemical analysis of culture fluid was also used to follow virus replication. The level of lactate dehydrogenase reached maximum at the time of maximum infectivity and the level of enzyme started to decline at the time of maximum antigenicity. The optimum levels of pH and dissolved oxygen for cell growth in glass sphere propagators were determined. There was no critical upper limit for dissolved oxygen. The combined use of both optima enabled the incubation period to be reduced from 96 to 72 hours. A study was made of cell distribution and growth in models of very deep beds of glass spheres. High cell concentrations were recovered from packed bed reactors supplied with tenfold increases of culture medium. The novel unit process has been exploited for the growth of a variety of anchorage dependant cells and the production of different animal viruses. Glass sphere propagators are particularly effective where rapid and repeated changes of process fluids are required. In addition these packed bed reactors provide reliable and acceptable substrate (glass) for cell growth. The technique is capable of further technological and biological development.