Cell growth phases Stationary phase

Batch fermentation is the most widely used method of amino add production. Here the fermentation is a dosed culture system which contains an initial, limited amount of nutrient. After the seed inoculum has been introduced the cells start to grow at the expense of the nutrients that are available. A short adaptation time is usually necessary (lag phase) before cells enter the logarithmic growth phase (exponential phase). Nutrients soon become limited and they enter the stationary phase in which growth has (almost) ceased. In amino add fermentations, production of the amino add normally starts in the early logarithmic phase and continues through the stationary phase. 

Mulder. K.M., Levine, A.E. Hinshaw, X.H. (1989) Up-regulation of z-myc in a transformed cell line approaching stationary phase growth in culture. Cancer Res., 49, 2320-2326... 

By contrast, growth studies of B. subtilis ATCC 21332using established potato media evidenced cells reaching early stationary phase whithin 12 h (23). The addition of mineral salts to potato media resulted in a prolongation of the lag phase, the stationary phase being reached only 48 h after inoculation. 

Cell growth phases comprise lag phase, exponential or log growth phase, stationary or plateau phase, and senescence or death phase, as shown in Figure 2.5. Cell growth can be mathematically represented by the following general equation ... 

For cells in the stationary phase, where there is no growth, cell maintenance and product formation are the only reactions to consume the substrate. Under these conditions the substrate balance, Equation (7-118), reduces to... 

For maximal production of extracellular virus by TPA induction of B95-8 or P3F1R-1 cells (see Appendix 3), harvest cells at the stationary phase of growth by centrifugation, resuspend in the same volume of fresh medium containing TPA, and incubate for 10 d without additional medium. 

Granot, D. and Snyder, M. 1993. Carbon source induces growth of stationary phase yeast cells, independent of carbon source metabolism. Yeast 9, 465-479. 

CBH has been reported to be synthesized constitutively in most intestinal bacteria. However, Hylemon and Stellwag [20] detected a 300-fold increase in total units of activity in B. fragilis after the cells entered the stationary phase of growth. CBH activity was detected in the periplasmic space, membrane fraction and soluble extracts. Hence, the synthesis of this enzyme in B. fragilis appears to be under genetic regulation. 

Alternative oxidase activity in plants and fiingi is dependent on environmental, developmental, nutritional, and other signals (30). We found that while the total level of oxygen uptake (mmol O2 min mg cells ) was relatively constant during the growth cycle of P. rhodozyma, cyanide-insensitive O2 uptake became dominant as the cell population entered stationary phase (Fig. 2). This shift in respiration and probable increased formation of excited oxygen species correlated with an increase in pigmentation of the cells (31). 

It is a simple matter to ensure that cells enter the stationary phase of growth as a result of the exhaustion of a constituent of the medium. This is achieved by designing a medium such that all nutrients except one (the... 

When A. brasilense was cultured in Luria-Bertani rich medium, the surface composition varied during growth, as illustrated by Fig. 40. Modeling the composition in terms of molecular compounds indicated that the protein concentration increased, from 30 (exponential phase cells) to 50% (stationary phase cells), concomitantly with a decrease in the polysaccharide concentration, from 60 to 35%. These modifications were related to a change in cell-surface hydrophobicity, the water contact angle measured on cell lawns increasing from 20 to 60° (Fig. 40). No difference of electrophoretic mobility was detected between cells harvested in the exponential... 

Stationary growth phase Duringthis phase, specific growth rate reaches zero as equilibrium is established between the cells reproducing and cells that are no longer viable or lose their capacity to reproduce. 

Figure . Field dependence of 50% suspension of yeast cells in their stationary phase of growth. (A) Spectrum taken at 40.5 MHz by pulsed Fourier transform NMR 12-mm sample tube, pH 6.4. This spectrum was recorded after 2924 accumulations with a repetition time of 2 sec/pulse and an H2O lock, and without proton decoupling. (B) Spectrum taken at 145.7 MHz by pulsed Fourier transform NMR 10-mm sample tube, pH 3.5,4800 accumulations with a repetition time of 0.6 s. The sample contained about 10% D2O to lock the magnetic field. (C) Same spectrum as B, after turning up the gain a factor of 8. From Salhaney et al (1975).

Once there is an appreciable amount of cells and they are growing very rapidly, the cell number exponentially increases. The optical cell density of a culture can then be easily detected that phase is known as the exponential growth phase. The rate of cell synthesis sharply increases the linear increase is shown in the semi-log graph with a constant slope representing a constant rate of cell population. At this stage carbon sources are utilised and products are formed. Finally, rapid utilisation of substrate and accumulation of products may lead to stationary phase where the cell density remains constant. In this phase, cell may start to die as the cell growth rate balances the death rate. It is well known that the biocatalytic activities of the cell may gradually decrease as they age, and finally autolysis may take place. The dead cells and cell metabolites in the fermentation broth may create... 

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