4.5 Effect of Temperature
The cell cultivation temperature is crucial for optimal cellular metabolism, protein production, and processing. The temperature modulation strategy is often applied to alter the cell metabolism, production of glycoprotein variants, and their processing. The insect cells are reported to best grow at temperature between 27°C to 30°C[62]. In addition, no heat shock protein expression has been reported at a temperature below 37°C[63]. However, there are reports available with varying conclusions on protein expression yield at various temperatures[64]–[67]. Some reports suggest better protein processing at temperature lower than 27°C (20°C -24°C) without any effect on the overall yield. Aucoin et al. reported AAV production in Sf9 cells using a triple BV co-infection strategy at various temperatures[68]. Across different temperature range tested (°C:21, 24, 27, 30 and 33), the highest yield of AAV functional particle was achieved at 30°C which was 2.5X and 5X more than at 27°C and temperatures below it, respectively. At the temperature below 27°C, the cells show reduced growth rate and lower protein expression; however, the cell viability was maintained in the post-infection phase. There was no significant decrease in overall maximum cell density achieved at various temperatures. Interestingly, the temperature above 27°C showed a significant effect on the kinetics of AAV helper protein expression.