Oxygen Mass Transfer Rate in a Pressurized Lab‐Scale Stirred Bioreactor

In industrial biotechnology, microbial cultures are exposed to different local pressures inside bioreactors. Depending on the microbial species and strains, the increased pressure may have detrimental or beneficial effects on cellular growth and product formation. In this review, the effects of increased air pressure on various microbial cultures growing in bioreactors under moderate total pressure conditions (maximum, 15 bar) will be discussed. Recent data illustrating the diversity of increased air pressure effects at different levels in microbial cells cultivation will be presented, with particular attention to the effects of oxygen and carbon dioxide partial pressures on cellular growth and product formation, and the concomitant effect of oxygen pressure on antioxidant cellular defense mechanisms.

Section: Introductionsupporting

confidence: 50%

OTR = α {true(\frac{P_{normalg}}{V} true)}^{δ} {(v_{normals})}^{γ} (P {false)}^{β}

being the exponent of pressure close to unit, the specific power input P g / V exponent δ around 0.7 and the ν s exponent γ around 0.48 . Based on Eq.…”

Section: Introductionmentioning

confidence: 99%

Over‐pressurized bioreactors: Application to microbial cell cultures

Lopes

Belo

Мота

2014

“…The sodium sulfite oxidation method was used to determine k L a values as previously described . The method is based on the reaction of sodium sulfite, a reducing agent, with dissolved oxygen in the presence of a catalyst, usually a divalent cation such as Cu 2+ or Co 2+ , to produce sulfate.…”

Section: Methodsmentioning

confidence: 99%

Studies on fluid dynamics of the flow field and gas transfer in orbitally shaken tubes

Zhu

Wang

Monteil

et al. 2016

Orbitally shaken cylindrical bioreactors [OrbShake bioreactors (OSRs)] without an impeller or sparger are increasingly being used for the suspension cultivation of mammalian cells. Among small volume OSRs, 50-mL tubes with a ventilated cap (OSR50), originally derived from standard laboratory centrifuge tubes with a conical bottom, have found many applications including high-throughput screening for the optimization of cell cultivation conditions. To better understand the fluid dynamics and gas transfer rates at the liquid surface in OSR50, we established a three-dimensional simulation model of the unsteady liquid forms (waves) in this vessel. The studies verified that the operating conditions have a large effect on the interfacial surface. The volumetric mass transfer coefficient (k a) was determined experimentally and from simulations under various working conditions. We also determined the liquid-phase mass transfer coefficient (k ) and the specific interfacial area (a) under different conditions to demonstrate that the value of a affected the gas transfer rate more than did the value of k . High oxygen transfer rates, sufficient for supporting the high-density culture of mammalian cells, were found. Finally, the average axial velocity of the liquid was identified to be an important parameter for maintaining cells in suspension. Overall these studies provide valuable insights into the preferable operating conditions for the OSR50, such as those needed for cell cultures requiring high oxygen levels. © 2016 American Institute of Chemical Engineers Biotechnol. Prog., 33:192-200, 2017.

“…Jin et al stated that with oxygen‐enriched air (50% O 2 ), the effective porcine interferon‐alpha (pIFN‐α) production period by recombinant P. pastoris KM71H (IFNα‐pPICZαA) could be prolonged, resulting in a further enhancement in pIFN‐α antiviral activity, comparatively to the strategy without DO control. An increase of the oxygen mass transfer rate, by raising the air pressure inside the bioreactor, is an interesting alternative to overcome oxygen limitation . For instance, and according to the q O 2 on methanol (64 mg O 2 /g h −1 ) reported in literature for the P. pastoris GS115 strain, for the cell densities reached in this work (around 15 g /L of cell dry mass), the OTR needed to supply to the culture (960 mg O 2 /L h −1 ) is significantly higher than that obtained at 1 bar (Table ).…”

Section: Resultsmentioning

confidence: 47%

Enhanced heterologous protein production in Pichia pastoris under increased air pressure

Lopes

Oliveira

Domingues

et al. 2014

Pichia pastoris is a widely used host for the production of heterologous proteins. In this case, high cell densities are needed and oxygen is a major limiting factor. The increased air pressure could be used to improve the oxygen solubility in the medium and to reach the high oxygen demand of methanol metabolism. In this study, two P. pastoris strains producing two different recombinant proteins, one intracellular (β-galactosidase) and other extracellular (frutalin), were used to investigate the effect of increased air pressure on yeast growth in glycerol and heterologous protein production, using the methanol AOX1-inducible system. Experiments were carried out in a stainless steel bioreactor under total air pressure of 1 bar and 5 bar. The use of an air pressure raise of up to 5 bar proved to be applicable for P. pastoris cultivation. Moreover, no effects on the kinetic growth parameters and methanol utilization (Mut) phenotype of strains were found, while an increase in recombinant β-galactosidase-specific activity (ninefold) and recombinant frutalin production was observed. Furthermore, the air pressure raise led to a reduction in the secreted protease specific activity. This work shows for the first time that the application of an air pressure of 5 bar may be used as a strategy to decrease protease secretion and improve recombinant protein production in P. pastoris.