title: Oxygen transfer in a pressurized airlift bioreactor.
abstract: Airlift bioreactors (ALBs) offer advantages over conventional systems, such as simplicity of construction, reduced risk of contamination, and efficient gas-liquid dispersion with low power consumption. ALBs are usually operated under atmospheric pressure. However, in bioprocesses with high oxygen demand, such as high cell density cultures, oxygen limitation may occur even when operating with high superficial gas velocity and air enriched with oxygen. One way of overcoming this drawback is to pressurize the reactor. In this configuration, it is important to assess the influence of bioreactor internal pressure on the gas hold-up, volumetric oxygen transfer coefficient (k(L)a), and volumetric oxygen transfer rate (OTR). Experiments were carried out in a concentric-tube airlift bioreactor with a 5 dm(3) working volume, equipped with a system for automatic monitoring and control of the pressure, temperature, and inlet gas flow rate. The results showed that, in disagreement with previous published results for bubble column and external loop airlift reactors, overpressure did not significantly affect k(L)a within the studied ranges of pressure (0.1-0.4 MPa) and superficial gas velocity in the riser (0.032-0.065 m s(-1)). Nevertheless, a positive effect on OTR was observed: it increased up to 5.4 times, surpassing by 2.3 times the oxygen transfer in a 4 dm(3) stirred tank reactor operated under standard cultivation conditions. These results contribute to the development of non-conventional reactors, especially pneumatic bioreactors operated using novel strategies for oxygen control.
authors.affiliation: Chemical Engineering Graduate Program, Federal University of São Carlos (PPEQ-UFSCar), São Carlos, Brazil, gilson.campani@yahoo.com.
authors.forename: Gilson
authors.initials: G
authors.lastname: Campani
authors.forename: Marcelo Perencin Arruda
authors.initials: MP
authors.lastname: Ribeiro
authors.forename: Antônio Carlos Luperni
authors.initials: AC
authors.lastname: Horta
authors.forename: Roberto Campos
authors.initials: RC
authors.lastname: Giordano
authors.forename: Alberto Colli
authors.initials: AC
authors.lastname: Badino
authors.forename: Teresa Cristina
authors.initials: TC
authors.lastname: Zangirolami
mesh_terms: D019149:Bioreactors; D008956:Models, Chemical; D010100:Oxygen / Q000737:chemistry*; D011312:Pressure
chemical_list: D010100:Oxygen