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.