ABSTRACT
Standard cultivation protocols for high cell-density cultures of recombinant E. coli rely on air enrichment with oxygen to prevent oxygen limitation. This way of increasing oxygen supply impacts on process economics due to the high cost of pure oxygen. Reactor pressurization is an alternative approach to improve oxygen mass transfer. In the present study, the performance of pressurized airlift bioreactor in growing rE. coli cells was evaluated. Experiments were performed in a pressurized internal-loop airlift bioreactor (ALB) and in a non-pressurized stirred tank reactor (STR), both with 5 L working volume, equipped with a system for automatic control and monitoring of pressure, temperature, pH, and dissolved oxygen. Pressurization showed to be crucial to improve ALB performance in biomass formation (29 g(DCW) L-1) and protein production (201 mg(protein) g(DCW)(-1)), resulting in protein productivity (240 mg(protein)(-1) h(-1)) and energy efficiency (11 g(protein) kWh(-1)) similar to the achieved in STR (200 Mg-protein L-1 h(-1) and 13 g(protein) kWh(-1), respectively). Due to the high cost of pure oxygen, air enrichment revealed to be economically unfeasible for ALB. By pressurizing the bioreactor up to 0.41 MPa, without pure oxygen supply, an 8.7-fold increase in economic efficiency is estimated, what shows the potential of this innovative strategy for aerobic cultures. (C) 2015 Elsevier B.V. All rights reserved.
