Growth exponential phase

In unicellular organisms, the progressive doubling of cell number results in a continually increasing rate of growth in the population. A bacterial culture undergoing balanced growth mimics a first-order autocatalytic chemical reaction (Carberry, 1976 Levenspiel, 1972). Therefore, the rate of the cell population increase at any particular time is proportional to the number density (CN) of bacteria present at that time  

Therefore, the specific growth rate p is equal to ln2 times of the division rate, 8. 

If jl is constant with time during the exponential growth period, Eq. (6.5) can be integrated from time t1 to t as 

The time required to double the population, called the doubling time (td), can be estimated from Eq. (6.9) by setting CN = 2CNq and t1 = 0 and solving for t  

The doubling time is inversely proportional to the specific growth rate and is equal to the reciprocal of the division rate. 

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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... 

The objective of a good process design is to minimise the lag phase period and maximise the length of exponential growth phase. 

Place the flask in a temperature-controlled shaker at 37 °C. The exponential growth phase will last from 2 to 24 hours after inoculation. The exact time and duration depend on the physiological condition of the inoculum. The data in Table 10.1 are plotted and a growth curve will be obtained for an exponentially growing culture. Figure 10.2 shows the typical growth curve obtained for a viable organism. 

Exponential growth occurs after cell metabolisms have adjusted and before a key nutrient becomes limiting or toxic products accumulate. In the exponential growth phase, the total cell mass will increase by a fixed percentage during each time interval, typically doubling every few hours. Ultimately, however, the... 

The bacterium acts through a 4S metabolic pathway and it has been found that it expresses its maximum enzymatic activity after over halfway of the exponential growth phase (i.e., approximately 28 hours),... 

The cultures grew at 18-20°C under a constant illumination (150 pmol photons m 2-s 1) provided by cool-white fluorescence lamps. For the anaerobic induction, cells were harvested by centrifugation (5 min, 3000xg) in the exponential growth phase at an approximate culture concentration of2><106 cells ml 1 and afterwards resuspended in fresh TAP medium. 

An exponential growth phase (c-d). When the growth conditions are... 

Most of the studies05,20 271 show that a correlation between culture fluorescence and biomass concentration can be obtained mainly in the exponential growth phase. In addition, in order to obtain reproducible correlations, all of the fermentation conditions such as initial substrate concentration, pH, dissolved oxygen level, temperature, and agitation rate have to be the same. However, once the culture is past exponential growth, biomass measurement by following culture fluorescence is no longer accurate. 

Note that this equation will only apply during the initially exponential growth phase. As the number of cells becomes much greater, the daughter cells compete for limiting quantities of one or more nutrients. This will reduce the efficiency of cell division, and the proliferation curve will reach a plateau that is often called the stationary growth phase. 

Figure 1 Absorbed dose necessary to produce a given biological effect on a given system, in the present case 50% inactivation of V79 hamster cells in exponential growth phase. The dose needed depends on the type of the particles (photons, alpha particles, or uranium ions) and on their energy. (From Ref 15.)...

In a well mixed bioreactor a homogeneous suspension exists and typical growth kinetics an be observed as illustrated in Figure 5.17. Six phases can be distinguished the lag phase acceleration phase the exponential growth phase the deceleration phase the stationary phase and the phase at which death/decline occurs. 

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