2.4 Chemostat cultivations
Chemostat cultivations were run at a density of 30 g/L CDM and a dilution rate of D = 0.1/h in a working volume of 0.67 L. The starting batch process was followed by a fed-batch phase. The batch volume was set to 400 mL and the batch medium allowed production of 4.72 g CDM; the feed volume was set to 270 mL with medium designed to produce another 15.4 g of CDM, which corresponds to a final CDM concentration of 30 g/L. In the next step, the bioreactor was shifted to chemostat mode with a dilution rate of 67 mL/h. The medium was used as continuous feed to the reactor to provide nutrients to maintain a CDM concentration of 30 g/L. The temperature was decreased to 30°C and recombinant protein production induced with 10 µmol IPTG/g CDM. Volume was kept constant via an immersion tube adjusted to the right height of the liquid surface, ensuring that the bleed pump was working at a higher rate than the feed pump.