Cultivation of CHO-A. A commercial process of a CHO cell line, referred to as the A cell for the purpose of this paper. Details of the cultivation
parameters are not given because of confidentiality. The CultiBag was compared to four 2-L stirred-tank bioreactors and Wave
Cellbags on Wave rocking machines. Seed cultivation was performed in shake flasks and Wave Cellbags. The inoculum conditions
and feed-control strategy in the CultiBag and the Wave bioreactors was similar to the conventional stainless-steel tank bioreactors.
The operational parameters of the CultiBag were similar to those for the Wave Bioreactor. The pH and DO set points for the
CultiBag were similar to those for the stirred-tank bioreactors. For the stirred-tank bioreactors, pH was controlled by automatic
addition of 1 M NaOH and sparging CO2 on demand. DO was controlled by sparging pure O2 on demand. For the CultiBag bioreactor, pH was controlled by continuous automatic surface aeration of CO2 automatic addition of 1 M NaOH. DO was controlled by continuous automatic surface aeration with the four-stage cascade control
system. Cell culture performance was analyzed using CEDEX Cell Counter (Innovatis AG) for cell density and viability; YSI
analyzer 2700 Select (YSI, Inc.) for cell culture metabolites: glucose/lactate and L-glutamine/L-glutamate; NOVA BioProfile
100 Analyzer (Nova Biomedical) for ammonium level; ABL-5 radiometer (Radiometer Medical) for pH/pO2/pCO2; and RP HPLC for productivity (titer).
Cultivation of CHO-S and CHO-K1. Two different CHO sub clones, CHO-S and CHO-K1, were compared for their growth characteristics and metabolic profiles. The
cells were cultured in repeated batch mode in the reusable bioreactor (Sartorius-Stedim Biotech Biostat B-DCU 2; 10-L UniVessel
with pitched three-blade impellers and ring sparger) as well as in the single-use CultiBag RM 20-L. The CHO-S cultivations
were run in a head-to-head comparison, while for the comparison of CHO-K1, two similar bioreactor runs were assessed. The
CHO-S seed culture was grown in a stirred-tank bioreactor and 2,000 mL of the seed were used to inoculate the Biostat B-DCU
reusable stirred tank bioreactor as well as the Biostat CultiBag RM. The final volume inside both bioreactors was 10 L of
Power-CHO 2 (0.1% Pluronic, 6 mM L-glutamine, Lonza) media. The initial cell density was ~1 x 106/mL. The process parameters used are listed in Table 1.
Table 1. Process parameters used to compare B-DCU STR and CultiBag RM20
After 72 h of cultivation, the culture was divided 1:5 in the same cultivation vessel, i.e., a repeated batch process was
carried out. Eight L of media containing the cell suspension were harvested and replaced with 8 L of fresh media. Samples
were taken in regular intervals and the viable cell number was determined. Lactate and glucose levels were measured using
the Glucose/Lactate Analyzer YSI 7100. The cultivation of CHO-K1 was carried out in a similar manner. The only difference
was that the B-DCU STR and the CultiBag RM were inoculated from individual seed cultures to an initial cell density of 5 x
105/mL in the STR and 1 x 106/mL in the CultiBag, respectively. The temperature in the CultiBag was set to 37 °C.