Living cell growth process

The process of racemization is important in the survival and growth of living cells and is catalyzed by a group of enzymes called racemases. Alanine racemase. for example, is able to convert n-alanine to DL-alanine if a suitable alpha keto acid is also present. In this reaction the asymmetry of the alpha-carbon atom of alanine is lost as the amino acid is converted to the keto acid and back. This process is analogous to the well-known process of transamination in which racemization seldom occurs. 

The possibility of using an immune-function assay as a potential biomarker for humans exposed to chromium has been examined (Snyder et al. 1996). Isolated mononuclear cells from 46 individuals who lived and/or worked in areas in northern New Jersey at sites contaminated by chromium processing were stimulated by pokeweed mitogen. Rates of stimulated cell growth and production of interleukin 6 (IL-6)... 

The rapid development of biotechnology during the 1980s provided new opportunities for the application of reaction engineering principles. In biochemical systems, reactions are catalyzed by enzymes. These biocatalysts may be dispersed in an aqueous phase or in a reverse micelle, supported on a polymeric carrier, or contained within whole cells. The reactors used are most often stirred tanks, bubble columns, or hollow fibers. If the kinetics for the enzymatic process is known, then the effects of reaction conditions and mass transfer phenomena can be analyzed quite successfully using classical reactor models. Where living cells are present, the growth of the cell mass as well as the kinetics of the desired reaction must be modeled [16, 17]. 

As discussed previously, read time is often a bottleneck in the HCS process and will dictate upstream liquid handling processes unless a pause step (as with fixed cells) is included. Assays with many 384-well plates in live cell mode become difficult, even with a fully integrated robotic system, because the cell growth, cell plating, compound addition, and other steps require precise coordination with imaging that is often not worth the cost. 

All life processes are the result of enzyme activity. In fact, life itself, whether plant or animal, involves a complex network of enzymatic reactions. An enzyme is a protein that is synthesized in a living cell. It catalyzes a thermodynamically possible reaction so that the rate of the reaction is compatible with the numerous biochemical processes essential for the growth and maintenance of a cell. The synthesis of an enzyme thus is under tight metabolic regulations and controls that can be genetically or environmentally manipulated sometimes to cause the overproduction of an enzyme by the cell. An enzyme, like chemical catalysts, in no way modifies the equilibrium constant or the free energy change of a reaction. 

Stages of cell growth in a batch reactor are shown schematically in Figure 7-14. Here, the log of the number of living cells is shown as a function of time. Initially, a small number of cells is inoculated into (i.e., added to) the batch reactor containing the nutrients and the growth process begins. 

Mechanism and kinetics in biochemical systems describe the cellular reactions that occur in living cells. Biochemical reactions involve two or three phases. For example, aerobic fermentation involves gas (air), liquid (water and dissolved nutrients), and solid (cells), as described in the Biocatalysis subsection above. Bioreactions convert feeds called substrates into more cells or biomass (cell growth), proteins, and metabolic products. Any of these can be the desired product in a commercial fermentation. For instance, methane is converted to biomass in a commercial process to supply fish meal to the fish farming industry. Ethanol, a metabolic product used in transportation fuels, is obtained by fermentation of corn-based or sugar-cane-based sugars. There is a substantial effort to develop genetically modified biocatalysts that produce a desired metabolite at high yield. 

A bioreactor is a device that transforms raw materials into products by means of biological processes conducted by enzymes or living cells.Bioreactors are frequently called fermenters when they generate a product by means of microbial cells, because the growth of microbes in a vessel is commonly called fermentation. There are several different bioreactor designs that can be customized to a desired process.The processing conditions in a reactor, such as temperature, pH, and aeration, depend on the aspects of a particular... 

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