Cell culture
A proprietary DG44 Chinese Hamster Ovary (CHO) cell line engineered to
produce a full monoclonal antibody was used. These cells were cultivated
for 14 days in 2L glass bioreactors (Sartorius) with dissolved oxygen
and pH control. Bioreactors were inoculated on day 0 at a seeding
density of 0.35x106 cells/mL. Cells were cultivated in
fed-batch mode with addition of feeds from day 3 to day 12. Viable cell
concentration (VCC) and viability were measured using a Vi-Cell analyzer
(Beckman Coulter). Recombinant protein titer was measured by
immunoturbidimetry using a Cedex Bio HT analyzer (Roche) in supernatant.
Two processes have been assessed to produce this recombinant protein:
Process 1 and Process 2. In the upstream part, Process 2 has a less
concentrated feed medium especially with less cysteine. To mimic an
oxidative stress during the culture, L-buthionine sulfoximine (BSO)
(Sigma) was spiked on day 3 to a final concentration of 0.5 mM in the
bioreactor. All conditions have been performed in triplicates. One
bioreactor cultivated with Process 2 and without BSO has been excluded
from the data set due to pump failure during the culture.