Bioreactors plant cell cultures

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). 

The problems with jojoba as a commercial crop are the usual ones of domestication and cultivation. It is a slow-growing plant, available only in the wild and therefore has very wide genetic variabiUty. Efforts are underway to select the most promising variants and cultivate these as a crop in the southwestern United States deserts (7). A possible alternative for producing jojoba oil is to culture plant embryos in bioreactors (see Cell culture technology). 

Bramble, J. L., Graves, D. J., and Brodelius, P., Plant Cell Culture Using a Novel Bioreactor The Magnetically Stabilized Fluidized Bed, Biotechnol. Prog.,... 

Breuling, M., Alfermann, A. W. and Reinhard, E. 1985. Culivation of cell cultures of Berberis wilsoniae in 20-1 airlift bioreactors. Plant Cell Reports, 4 220-223. 

As de novo synthesis has been proven unsuccessful in most cases, biotransformation of added precursors has been studied extensively. There is evidence that plant cell cultures retain an ability to transform specifically exogenous substrates administered to the cultured cells. Therefore, plant cell cultures are considered to be useful for transforming cheap and plentiful substances into rare and expensive compounds by using the cell culture as a bioreactor. For instance, cofactor dependent specific conversions of terpenoids in suspension cultures of aromatic plants often proceed with high yields and negligible amounts of byproducts. In Fig. (1), three examples of biotransformations of terpenes by plant cell cultures are shown (after [6]). 

Such information about shear effects in plant cell suspension cultures as given above is useful for bioreactor design and operation as well as the optimization of bioreactor environments for plant cell cultures. It may also be beneficial to bioreactor scale-up and high-density cultivation of plant cells for production of useful plant-specific chemicals (pharmaceuticals). In addition, because different cell suspensions can show different degrees of cell sensitivity to shear stress, and shear affects culture viability, cell lysis, and even metabolite secretion, as demonstrated in various cases like cell cultures of tobacco, Catharanthus roseus and Perilla frutescens [17, 54, 61], detailed studies are required for individual cases. 

Various adsorbents have been examined for their potential to increase in situ product separation in plant cell culture. Suspended solid adsorbents were popular, and the use of immobilized adsorbent has been investigated recently [17-20]. The advantages of immobilized adsorbent are that it is easy to use in a bioreactor operation and that it allows adsorbents to be easily separated from culture broth for the repeated use of cells and adsorbents [21, 22]. The design and optimization of in situ separation process for phytochemicals using immobilized adsorbent required a detailed mathematical model. It was difficult to achieve an optimal design based on purely empirical correlations, because the effects of various design parameters and process variables were coupled. 

To increase metabolite production in plant cell culture, various adsorbents have been used for the solid/liquid two-phase system. Activated charcoal, lipophilic carrier (RP-8), zeolite, nonionic exchange resin (Amberlite XAD-2, XAD-4, XAD-7, XAD-8), acidic cationic exchange resins (Dowex 50 W, Amberlite IRC-50, IRC-200), basic anion exchange resin (Dowex i 1X4-50, Amberlite IRA-93, IRA-400), mixed bed resin (TMD-8), and wofatite have all been examined as shown in Table 2. Before adsorbent is introduced to a vessel or bioreactor for this purpose, it should be pre-treated to activate the surface. As an example, the preparation of XAD-7 is detailed as follows. 

Integrated bioprocesses can be used to enhance the production of valuable metabolites from plant cell cultures. The in situ removal of product during cell cultivation facilitates the rapid recovery of volatile and unstable phytochemicals, avoids problems of cell toxicity and end-product inhibition, and enhances product secretion. In situ extraction, in situ adsorption, the utilization of cyclodextrin, and the application of aqueous two-phase systems have been proposed for the integration of cell growth and product recovery in a bioreactor. The simultaneous combination of elicitation, immobilization, permeabilization, and in situ recovery can promote this method of plant cell culture as a feasible method to produce various natural products including proteins. 

Keywords. Plant cell culture, Micropropagation, Bioreactor design, Embryogenic callus, Hairy root, Image analysis, Plant factory... 

One reason for interest in plant cell culture is that over 20,000 different chemicals are produced from plants, with about 1600 new plant chemicals added each year. Also, 25% of all prescribed drugs come from plants. These chemicals can be produced in a bioreactor through suspension culture. Advantages of plant cell suspension culture, as compared to agriculture, are that plant cell suspension culture can be carried out independently of weather conditions and political problems, it does not compete with other agricultural products for land use, and it is done in a controlled environment which minimizes contamination and provides easier product validation and assurance. 

To estimate what conditions need to be met to make plant cell culture economical, I have utilized Professor Cooney s economic analysis of fermentation systems (see Table 1). Professor Cooney concluded after examining a number of fermentations that 12 cents per liter per day of product value must be achieved in the bioreactor to have an economical process. The... 

Bioreactors employing plant cell cultures have use in chemicals production systems and in micropropagation (biomass) systems, as well. Factors related to the performance of these reactors from an engineering point of view have been addressed in this paper. Some preliminary data from our laboratory suggest how mass... 

The first plant product commercially produced by plant cell culture was the prenylated anthraquinone shikonin 16, from the boraginaceous plant Lithospermum erythrorhizon Sieb. et Zucc. (Mitsui Petrochemical Industry Company) in 1983.25 Shikonin is used as a dye in cosmetics (lipsticks, soaps and lotions) and its production yield from cell cultures was over ten-fold its isolation yield from the intact plant.25 In practice, eight runs of two weeks each in a 200 L bioreactor could afford the amount of shikonin produced in four years by a 1 ha field of L. erythrorhizon 25 Shikonin has an interesting and pleiotropic biological profile, which includes insulin mimicry and interference with protein-protein interactions, but it has not yet found medicinal application.26... 

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