Scale-up of a high cell density continuous culture with Pichia pastoris X-33 for the constitutive expression of rh-chitinase.

The feasibility of large-scale production of recombinant human chitinase using a constitutive Pichia pastoris expression system was demonstrated in a 21-L continuous stirred tank reactor. A steady-state recombinant protein concentration of 250 mg/L in the supernatant was sustained for 1 month at a dilution rate of 0.042 h -1 (equivalent to one volume exchange per day), enabling a volumetric productivity of 144 mg/L d (240 U/L d). The steady-state dry cell weight concentration in this high cell density culture reached 110 g/L. Considering safety and economical aspects, all large-scale cultivations were conducted without molecular oxygen supplementation. Conventional air sparging was used instead. The oxygen demand of the process was determined by off-gas analysis (OUR = 4.8 g O 2 L -1 h -1 with k L a = 846 h -1 ) and evaluated with regard to further reactor scale-up.