Bioreactors mixing

Bae, T.H. and Tak, M.T. (2005) Interpretation of fouling characteristics of ultrafiltration membranes during the filtration of membrane bioreactor mixed liquor. Journal of Membrane Science, 264 (1-2), 151-160. 

Ognier, S., Wisniewski, C. and Grasmick, A. (2002) Influence of macromolecule adsorption during filtration of a membrane bioreactor mixed liquor suspension. Journal of Membrane Science, 209, 27-37. 

Continuous SSF processes are usually operated in plug flow mode. Such processes will require pasteurization or sterilization of the substrate as it enters the bioreactor, mixing with an inoculum, and at the outlet end of the bioreactor, continuous removal of spent substrate. Such a process was operated on a pilot scale for the production of ethanol from fodder beets by Saccharomyces cerevisiae [81,82]. The bioreactor had a screw within a 4.7 m long and 15.25 cm diameter tube. The screw was rotated intermittently to mix the substrate and move it along the tube. At the front end was a hammer-mill and a pasteurization chamber for substrate preparation and a port for inoculation. New substrate was added, inoculated, and the screw rotated at 12-h intervals, resulting in a residence time of 72 h. 

Delvigne, F., Boxus, M., Ingels, S., and Thonart, P. (2009) Bioreactor mixing efficiency modulates the activity of a prpoS GFP reporter gene in E. coli. Microb. Cell Fact., 8, 15. 

Gelbgras, V.G., Wylock, C.E., Drugmand, J., and Haut, B. (2011) Computational fluid dynamics characterization of a bioreactor mixing device for the animal cell culture. 

Brannock, M, Wang, Y and Leslie, G (2010a), Evaluation of Full-Scale Membrane Bioreactor Mixing Performance the Effect of Membrane Configuration , Journal of Membrane Science, 350 101-108. 

Wang, Y (2010b). Evaluation of Membrane Bioreactor Mixing Performance via Computational Fluid Dynamics Modelling, UNESCO Centre for Membrane Science Technology, School of Chemical Engineering,The University of New South Wales, PhD thesis, Sydney, Australia. 

Provided this equaHty is satisfied and the dissolved oxygen concentration in the weU-mixed Hquid is greater than the critical concentration throughout the bioreactor, then the maximum oxygen demand of the species should be met satisfactorily. Design of the bioreactor must ensure that the above requirements are achieved economically and without damaging the biological species. 

In a stirred bioreactor the Hquid is generally considered weU-mixed, ie, is spatially constant. The gas phase too may be weU-mixed (19) so that... 

Activities associated with bioreactors include gas/hquid contacting, on-hne sensing of concentrations, mixing, heat transfer, foam control, and feed of nutrients or reagents such as those for pH control. The workhorse of the fermentation industry is the conventional batch fermenter shown in Fig. 24-3. Not shown are ladder rungs inside the vessel, antifoam probe, antifoam system, and sensors (pH, dissolved oxygen, temperature, and the like). Note that coils may lie between baffles and the tank wall or connect to the top to minimize openings... 

Bubble behaviour was studied in the pilot-scale bioreactor so that a complete model of flow, OTR, mixing, cooling, energy requirement and disengagement could be developed for this system and larger production-scale vessels of similar type. 

Batch mixed reactor There are three principal modes of bioreactor operation (a) batch (b) fed batch (c) continuous. 

Industrial bioreactors can withstand up to 3 atmospheres positive pressure. Large fermenters are equipped with a lit vertical sight glass for inspecting the contents of the reactor. Side parts for pH, temperature and dissolved oxygen sensors are a minimum requirement. A steam sterilisation sample port is provided. Mechanical agitators are installed on the top or bottom of the tank for adequate mixing. 

In low shear, there is low mixing which means the bioreactor can be used for growing plant and animal cells. 

One problem mentioned earlier is that certain animal cells are anchorage-dependent. Also, plant and animal cells are easily raptured by mechanical shear. Bioreactors for handhng such cells must be designed so that the contents of the reactor can be mixed without disrupting the cells. A similar problem exists in the design of systems to transfer the cells from one vessel to another. 

The flow of jets becomes turbulent at much lower Re numbers than channel flows. Calculating the stress from the mean velocity profiles does not reflect the true situation in turbulent flow. As in the case in most bioreactors, the maximum turbulent stress is determined by the turbulence, which can be calculated using Eqs. (2)-(4). It occurs in free jets after the nozzle, at the edge of the mixing zone. The following is generally valid ... 

Biichs J, Zoels B (1999) Evaluation of the Maximiun Specific Power Consumption in Shaking Bioreactors, Proceedings of 3th International Symposium on Mixing in Industrial Processes (ISMlP-3) 19-22 Sept 1999 Japan... 

Figure 2.27. Mixing, mass transfer and oxygen consumption in a bubble column bioreactor (Oosterhuis, 1984). Tj - reaction time constant, Xmt - ass transfer time constant, tmix -mixing time constant. ro2 - oxygen consumption rate, Vs - superficial gas velocity.

Mixing tank Slurry Bioreactors Slurry Dewatering... 

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