Cells, surface area/volume ratio

Conditions. Table II provides temperature, pressure, and other conditions for the experiments. The surface area/volume ratio for all experiments was 2.7 x 103 cm 1. The hydrothermal apparatus was a Dickson-type sampling autoclave with a gold-titanium reaction cell, a gold-lined sampling tube, and a titanium sampling valve block (11). Samples of the reacting fluid could be taken over time without disturbing the pressure-temperature conditions of a run. The autoclaves were rocked 180 at about 4 cycles/min. 

In industrial (e.g. recombinant protein) and medical (e.g. bioartificial organ) fields 3D cultures can be used to improve the surface area/volume ratio compared with 2D cultures, which is a useful feature where cells are used as the machinery for biological production. Such approaches promote high cell yield and increased production of cellular or recombinant proteins. 

Lowering the surface to volume ratio of a cell is another method of reducing the impact of electroosmosis on separations. Widening the apparatus will accomplish this. It has been shown (30,34) that rectangular channels are much more suitable for this kind of manipulation than circular channels. The disadvantage of widening a channel lies in reduction of the surface area/volume ratio, and hence, reduced heat dissipation. At the same time, power requirements are increased, due to the cell s wider cross section. 

A. Because of the small sizes of many microbial cells, especially bacterial cells, compared with those of plants and animals, micro-organisms are able to grow relatively quickly. This is because small cells have a high surface-area volume ratio, which in turn influences the potential to take up nutrients from the environment. A necessary corollary to promote rapid growth is that microbial cells have high rates of cellular metabolism, leading to fast rates of biotransformation of substrates undertaken by whole cells of micro-organisms. 

The thin-film media in fuel cells have a very large surface area-volume ratio, so that interfacial effects not dealt with in bulk flow theory become very important. 

As indicated earlier, insect cells have been cultured either as attached or suspension cultures. For scale-up purposes, systems where cells grow attached to surfaces are less suitable because of the fundamental limitation in surface area upon further increase in reactor volume (surface-to-volume ratio decreases as volume increases) unless microcarriers are utilised, which increases complexity and cost. In contrast, suspension systems are easily scalable and therefore their use is widespread since insect cells, like Sf9, have already been well adapted to suspension systems. 

Bacteria can grow incredibly fast. Under some conditions, it takes a bacterial cell only 10-20 min to double its size and to divide to form two cells.4 An animal cell may take 24 h for the same process. Equally impressive are the rates at which bacteria transform their foods into other materials. One factor contributing to the high rate of bacterial metabolism may be the large surface to volume ratio. For a small spherical bacterium (coccus) of diameter 0.5 xm, the ratio of the surface area to the volume is 12 x 106 m , while for an ameba of diameter 150 xm the ratio is only 4 x 104 m 1 (the ameba can increase this by sticking out some pseudopods). Thimann33 estimated that for a 90-kg human, the ratio is only 30 m 1. 

The active surface to volume ratio of the tubular arrangements previously described is approximately 1 cm2/l cm3. This parameter could be increased with corresponding increases in both volume power density and area power density. New concepts for solid state electrochemical reactors have been proposed based on more or less planar cell structures which can be integrated to make blocks. 

Increasing surfactant concentrations in the aeration cell has been found to decrease bubble diameter, bubble velocity, axial diffusion coefficient, but increase bubble s surface-to-volume ratio, and total bubble surface area in the system. The effect of a surface-active agent on the total surface area of the bubbles is also a function of its operating conditions. The surfactant s effect is pronounced in the case of a coarse gas diffuser where the chances of coalescence are great and the effectiveness of a surface-active solute in preventing coalescence increases with the length of its carbon chain. 

In the above equation, q represents the specific growth rate (d ), Cg is external CO2 (aq) concentration (pM/kg), V is cell volume (pm ) and A is the cell surface area (pm ). Popp et al. (1998) estimated surface area to volume ratios for cells of different geometry, with cell dimensions ranging from a radius of 0.68 pm (Synechococcus sp.) to 14 pm Porosira glacialis). Isotopic fractionation for the prokaryotic species Synechococcus sp.) employed in this study exhibited little variation with growth conditions, and did not conform to the relationship observed for the eukaryotic species. Thus, Synechococcus was not included in the development of Equation (2) data from this study are shown in Figure 2. 

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