Fermentation animal/plant cell cultures

Animal and Plant Cell Cultures. Bioprocess engineering incorporating animal cell culture is used primarily for the production of health care products such as viral vaccines or antibodies in traditional fermenters or bioreactors with immobilized cells. Antibodies, for example, are produced in bioreactors with hoUow-fiber immobilized animal cells. Plant cell culture is also an important target of bioprocess engineering. However, only a few processes have been successfully developed. One successful process is the production of the pigment shikonin in Japan. Shikonin is used as a dye for coloring food and has applications as an anti-inflammatory agent. 

In airlift bioreactors the fluid volume of the vessel is divided into two interconnected zones by means of a baffle or draft-tube (Fig. 5). Only one of these zones is sparged with air or other gas. The sparged zone is known as the riser the zone that receives no gas is the downcomer (Fig. 5a-c). The bulk density of the gas-liquid dispersion in the gas-sparged riser tends to be less than the bulk density in the downcomer consequently, the dispersion flows up in the riser zone and downflow occurs in the downcomer. Sometimes the riser and the downcomer are two separate vertical pipes that are interconnected at the top and the bottom to form an external circulation loop (Fig. 5c). External-loop airlift reactors are less common in commercial processes compared to the internal-loop designs (Fig. 5a, b). The internal-loop configuration may be either a concentric draft-tube device or an split-cylinder (Fig. 5a, b). Airlift reactors have been successfully employed in nearly every kind of bioprocess—bacterial and yeast culture, fermentations of mycelial fungi, animal and plant cell culture, immobilized enzyme and cell biocatalysis, culture of microalgae, and wastewater treatment. 

Modern in vitro fermentation technologies can compete with in vivo production of antibodies regarding concentration and purity of the produced material. In fact, a number of more sophisticated methods of antibody expression have been developed in the last decade the most important are cell culture in protein-free media and the expression in the milk of transgenic animals, in transgenic plants, and in egg yolk. 

Microbial enzymes produced by fermentation under controlled conditions constitute now the most relevant option for enzyme synthesis. Microbial strains can produce not only the enzyme proteins coded by their own genetic information, but also those produced by the expression of foreign genes as recombinant proteins. As analyzed before, microorganisms are ideal hosts for enzyme synthesis and only those glycoenzymes which cannot be properly produced in microbial hosts are to be produced in plant (Ma et al. 2003) or animal cell culture (Altamirano et al. 2004 Wurm 2004). 

One major advantage of monoclonal antibodies from plants is the potential low cost of large-scale production. There are commercial companies (such as EPIcyte Pharmaceutical Inc) who are planning clinical dials for plant-produced secretory antibodies for human therapy. These so-called plantibodies can be produced at an estimated cost of 0.01 to 0.1/mg as opposed to 1 to 5/mg for production from cell culture processing of animal-derived hybridomas. The cost of microbial fermentation is lower than that of mammalian cell culture but bacteria lack the ability for efficient multimeric protein assembly and of any post-translational modification. A further potential advantage of the plantibodies is delivery by consumption of plant tissue and thus avoiding any need of purification. These possibilities are particularly applicable in certain cases such as the previously shown ability of a plant-produced... 

Some mycehal fermentations exhibit early sporulation, breakup of mycehum, and low yields if the shear is excessive. A tip speed or 250 to 500 cm/s (8 to 16 ft/s) is considered permissible. Mixing time has been proposed as a scale-up consideration, but httle can be done to improve it in a large fermenter because gigantic motors would be required to get rapid mixing. Culturing cells from plants or animals is beset by mixing problems because these cell are easily damaged by shear. 

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