Defined medium

Achieving optimal concentrations is difficult because components in the medium and the biomass itself may neutralise the inhibitory effects of these reagents. This is especially true if complex, non-defined media, such as comsteep liquor, are used. 

The chemical environment of the cells has to be considered very carefully. Animal cells do not need only a carbon and nitrogen source. They are dependent on a variety of other compounds (amino acids, vitamins, growth factors etc.).This complexity of requirements of the culture medium and the complexity of the metabohsm hamper not only the development of defined media but... 

There are other, nonhydrogel, new materials for chromatographic and electrophoretic separations [7,8,103,164,199,214,377,407], Eor example, Volkmuth and Austin [407] proposed electrophoretic studies in microlithographic arrays of posts and channels etched into sihcon wafers. This material may be useful for studying fundamental transport characteristics of macromolecules in defined media, and many recent studies have been conducted to develop chromatography and electrophoresis on silicon wafers with micron-scale channels... 

The four antigens are produced in a fermentation process using the yeast Saccharomyces cerevisiae grown in chemically defined media. The purified antigens are formulated in aluminum-containing adjuvant in sterile liquid suspension. 

Selection of putative positive clones on synthetic defined media... 

Onoue, Y. and Mori, M., Amino acid requirements for the growth and enterotoxin production by Staphylococcus aureus in chemically defined media, Int. J. Food Microbiol., 36, 77-82, 1997. 

Immortalization of human hepatocytes would help to overcome the hmited availability of human cells, thereby avoiding the use of mahgnant-derived cell hnes however, care will still be required with these cells. A better approach would be to develop methods for the culture of primary human hepatocytes using hormonally defined media containing growth factors in which cells are stimulated to undergo division. 

Hence, if the composition of the organism (i.e., /phase values) and if the various partition coefficients in Eq. 10-4 can be estimated, we can calculate an approximate value for the KMa. As we saw in discussing organism compositions (Table 10.1) and defined media-water partition coefficients (Table 10.2), the uncertainties in the inputs to Eq. 10-4 imply that such calculations can be expected to provide only an order of magnitude estimate. 

C. bifermentam strain CYS-1 was also isolated from our anaerobic bioreactor. Shin Crawford (1995) examined the ability of CYS-1 to degrade TNT cometabolically in various defined media. This strain could overcome the toxicity of and degrade >150 ppm TNT in liquid media supplemented with a rich cosubstrate such as yeast extract or trypticase soy, given an appropriate inoculum ( 107 CFU/ml). Furthermore, it was found that CYS-1 could degrade TNT which contaminated a sandy loam soil. The degradation of TNT proceeded through the transient intermediates 4-amino-2,6-dinitrotoluene and 2,4-diamino-6-nitrotoluene. 

To cultivate microorganisms, culture medium has to be prepared in one of the commonly employed culture vessels a test tube, a flask, a Petri dish, or a fermenter. There are two main types of culture media natural (or empirical, or complex) and synthetic (or chemically defined) media. They vary widely in form and composition, depending on the species of organism to be cultivated and the purpose of the cultivation. 

Cells in suspension may be maintained for a limited period of time in defined media or for longer periods in nutrient, but less well-defined, media. In either case these cultures are often used for studies of xenobiotic metabolism. 

N Madry, R Zocher, H Kleinkauf. Enniatin production by Fusarium oxysporum in chemically defined media. Eur J Appl Microbiol Biotechnol 17 75-79, 1983. 

The need to deal with some of these differences demands enormous efforts for the development of culture media (chemical environment) or shear, mixing, viscosity and bubbling conditions (physical environment), which should be optimized to result in an industrial process that can be validated. Requirements to avoid contamination have led to the formulation of serum-free media or even of protein-free, chemically defined media for the production of biopharmaceuticals (Griffiths, 1988). 

While some culture media are formulated to promote cell multiplication (growth media), others only maintain cell structural and metabolic integrity (maintenance media), but do not stimulate cell division. Media prepared with highly purified compounds and with known composition are designated chemically defined media. These are particularly attractive for biopharmaceutical production, because they are less vulnerable to contamination and quality control is easier. Nevertheless, these media can be expensive. 

Different media have been developed for specific cell lines in order to obtain optimal growth or in an attempt to grow cells in defined media without the addition of serum. 

Two major disadvantages in the use of serum (lack of reproducibility in quality and possible risk of contamination) are avoided by using serum-free medium. In addition, it is possible to culture a wider variety of differentiated cells using defined media. 

Different selective media may enhance growth of different sorts of epithelial cells from such cultures (Chung et al., 1982) but the differentiated functions are rapidly lost if serum is added to the medium (Lieberman and Ove, 1958 Becker and Willis, 1979). The selectivity of particular defined media can be a disadvantage in that each individual cell type requires a different defined media. 

---