Effect of induction temperature on the production of malaria antigens in recombinant E. coli

As part of a process development campaign, studies have been conducted to determine the influence of induction temperature on the expression of two different malaria antigens, RN1 and RT2. Single-step temperature inductions, in which growth at 32.0 degrees C is followed by a shift in temperature to a desired setpoint, show that there exists an optimum duration and temperature of induction which is product specific. Between an induction temperature of 39.5 and 44.5 degrees C RN1 yield is constant at ca. 0.20 g/g total soluble protein (TSP). RT2 yield approaches 0.20 g/g TSP only at elevated induction temperatures. The optimum temperature of induction for RN1 production is 39.5 degrees C, whereas, that for RT2 production is 41.0 degrees C. Above the optimum temperature of induction antigen concentration decreases owing to decreases in biomass. Furthermore, the maximum concentration of these two antigens differ by a factor of four. With increasing temperature of induction the extent of proteolysis of the products also appears to increase.