Air-lift bioreactors

Plant Cell Culture. Air-lift bioreactors have been favored for plant cell systems since these cultures were first studied (4). However, they can give rise to problems resulting from flotation of the cells to form a meringue on the top. It is interesting to note that some reports indicate that stirred bioreactors do not damage such cells (4). 

Single-Cell Protein. Systems involving single-cell proteins are often very large throughput, continuous processing operations such as the Pmteen process developed by ICI. These are ideal for air-lift bioreactors of which the pressure cycle fermenter is a special case (50). 

The calculation of heat transfer film coefficients in an air-lift bioreactor is more complex, as small reactors may operate under laminar flow conditions whereas large-scale vessels operate under turbulent flow conditions. It has been found that under laminar flow conditions, the fermentation broths show non-Newtonian behaviour, so the heat transfer coefficient can be evaluated with a modified form of the equation known as the Graetz-Leveque equation 9... 

The high sulfur-containing feedstock and the biocatalyst, usually suspended in the aqueous phase have to be contacted with each other in a bioreactor. A homogeneous, continuous phase would be preferred, which would imply formation of an emulsion, preferably a microemulsion. Several bioreactor designs have been suggested for biodesulfurization of petroleum feedstocks including impeller-mixed systems [65,202], electro-spray bioreactor [220,261,262], and draft tube air-lift bioreactor [263],... 

Sajc, L., Obradovic, B., Vukovic, D., Bugarski, B., Grubisic, D., and Vunjak-Novakovic, G., Hydrodynamics and Mass Transfer in a Four-Phase External Loop Air Lift Bioreactor, Biotechnol. Prog., 11 420 (1995)... 

The dye Poly R-478 was decolorized to a much greater extent and at slightly faster rate when the culture was supplemented with Mn(II), while the opposite was obtained for Poly S-119. They found a correlation between polymeric dye decolor-ization and peroxidative activity of fungus under static or immobilized condition in air-lift bioreactor. Immobilized culture produced LiP and MnP enzymes over a longer time than static cultures. 

Frmdamentally, air-lift bioreactors are a modification of the bubble colunms that generate air-flow for medium circulation unidirectionally by having at least two columns—a raiser column and a downer column. They are either a draft tube or an external loop bioreactor. The bubbles sparged into a draft tube generate upward flow and medium pours into the annular space between the draft tube and bioreactor vessel and flows downwards. An essential design feature to consider is the bioreactor ratio of the height (H) to the diameter (D). Values of H/D of five or more are needed for sufficient mixing (18). Efficiency of medium circulation depends on the rate of aeration and on the ratio of the cross-sectional area of the draft tube to the total... 

Stirred-tank bioreactors Air-lift bioreactors Wave bioreactors Microcarrier-based systems Packed-bed bioreactors Fluidized-bed bioreactors Hollow-fiber bioreactors Bioreactors providing surfaces for attached cell growth (roller bottles, CellCube , Cell Factory)... 

These bioreactors are characterized by low levels of cell damage and can also be operated in perfusion mode. However, the main limitation of this type of equipment is related to its scale-up air-lift bioreactors up to only 5000 L have been described so far. 

Air-lift bioreactors were popular in the 1990s, but currently their large-scale use is limited. Only the company Lonza (originally Celltech) uses this type of bioreactor on a large scale, for the production of monoclonal antibodies (mAbs) and other therapeutic proteins (Lonza, 2006). 

Bellco (Appendix 3) produce a 3 1 air lift bioreactor designed initially for use with hybridoma cells entrapped within alginate macro beads ( 3.6.4). In this system the rate of antibody production was over 10 times that achieved in a spinner culture (Familletti, 1987). 

Yahiro et al. [115] conducted itaconic acid production from glucose using stirred-tank and air-lift reactors. Results indicate that the air-lift reactor has a much higher productivity (0.64 g/l/h) than the stirred-tank reactor (0.48 g/l/h). Final itaconic acid concentration reached 65 g/1 after 96 h of fermentation. Likewise, Okabe et al. [116] used an air-lift bioreactor using a modified draft tube for itaconic acid production and obtained an enhanced itaconic acid yield. 

Figure 19. Comparison of yield and productivity for cell mass and anthraquinones in various bioreactor systems, Shake Flask. Flat Blade Turbine. (3 Perfolated Disk Impeller. (4) Draft Tube Bioreactor with Kaplan Turbine. (5) Air-lift Bioreactor.

Breuling, M., Alfermann, A. W., and Reinhard, E., Cultivation of cell cultures of Berberis wilsonde in 20-1 air-lift bioreactor. Plant Cell Report, 4 220-223 (1985)... 

Agrobacterium radwbacter, 206 Agrobacterium rhuogenes, 284 air-lift bioreactor design of, 94 air-lift bioreactors, 7,95 air-lift pressure-cyde reactor, 94 alanine, 240,280,288 alcalase, 285... 

Figure 6.2 Cultivation of adventitious roots in liquid-phase air-lift bioreactors (20-10 000 L). Adventitious roots of Echinacea purpurea-. 20 L, 500 L (A and B) and 1000 L (C and D) Hypericum perforatum-. 500 L (E and F) Ginseng 10 000 L(G and I).

Yin P, Nishina N, Kosakai Y, Yahiro K, Park YS, Okabe M. (1997). Enhanced production of L(-l-)-lactic acid from corn starch in a culture of Rhizopus oryzae using an air-lift bioreactor. J Ferment Bio eng, 84, 249-253. 

Vunjak-Novakovic G, KimY.Wu X, Berzin I, MerchukJC. Air-lift bioreactors for algal growth on flue gas mathematical modeling and pilot-plant studies. Ind Eng Chem Res 2005 44 6154. 

Fluidized-bed bioreactors (FBRs). (d) Air-lift bioreactors (ALRs). (e) Hoilow fiber membrane bioreactors (HFMRs). 

In an air-lift bioreactors (ALRs) (Figure 7.7d), the culture medium is kept mixed and gassed by the introduction of air or other gases (e.g., CO2 at the bottom of the reactor equipped with either an inner draught tube or an external tube [1]). Liquid circulates in an ALR as a result of the density difference between the riser and downcomer to prevent particles from sedimenting. 

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