KINETIC-ANALYSIS OF ALKALINE PROTEASE ACTIVITY, RECOMBINANT PROTEIN-PRODUCTION AND METABOLITES FOR INFECTED INSECT (SF9) CELLS UNDER DIFFERENT DO LEVELS

An analysis of protease activity, recombinant protein yield (beta-gala ctosidase and epoxide hydrolase) and metabolite concentration (glucose , glutamine, ammonia, and lactate) for Sf9 cells under varied dissolve d oxygen tension and before and after viral infection are reported, Di fferent levels of bulk proteolytic activity were found under three dif ferent dissolved oxygen (DO) levels (50%, 25%, and 15% of air saturati on). The culture with lowest protease activity had the highest specifi c recombinant protein yield, suggesting a negative correlation and an appropriate timing for cell harvest. At low dissolved oxygen tension ( 15% of air saturation), epoxide hydrolase production was lowest and th e lactate/glucose yield, Y-lac/gla, was highest, marking low glucose u tilization efficiency. Ammonia and lactate were consumed by cells at 2 5% DO, but not at low and high DO. Thus, the possibility that ammonia and lactate exert an inhibitory effect on protein production is very l ow given an appropriate DO setpoint. Our results facilitate systematic development of optimized media formulations and reactor operating str ategies for maximizing protein yield in insect cell systems.