5. Optimization of yeast culture conditions
Recovering functional protein from recombinant host cells is dependent upon their capacity to synthesize an authentically-folded polypeptide. This requires the proper functioning of the transcription, translation and folding pathways [62]. During a recombinant protein production experiment, the maintenance and processing of an expression plasmid places a substantial metabolic burden on a cell, which means that these pathways must operate under abnormally stressful conditions [3]. A popular strategy to mitigate this burden is to decrease culture temperature; however, transcription, translation, polypeptide folding rates and membrane composition are also affected by low temperature stress [63]. This probably explains why increased yields are not always observed experimentally using that approach. Furthermore, many other variables are likely to affect yields including the composition of the growth medium, the pH and oxygenation of the culture, the inducer concentration and the point of induction.