Growth rate specific

Measurement of specific growth rate of the microorganism is necessary for the kinetic study of the fermentation process. 

Specific growth rate can be defined by the following equation  

The kinetic pattern of microbial growth goes through different phases. These phases are known as growth phases, and are as follows  

Lag phase This is a stage in which microbes do not start to multiply and the specific growth rate is practically nil. Duration of lag phase depends on factors such as physiology of microorganism, environment, type of inoculum, and so on. 

Accelerated growth phase In this phase, microbes start dividing and new cells will be synthesized. This is an intermittent phase and is found for a relatively short period. 

---

Loop reactors are particularly suitable as bioreactors to produce, for example, single-cell protein (96). In this process, single yeast or bacteria ceUs feeding on methanol multiply in aqueous culture broths to form high value biomass at 35—40°C, 20 kg/m ceU concentrations, and specific growth rates of... 

Table 2. Relation of Generation Time to Hourly Growth Rate and Specific Growth Rate ...

Generation time, h Hourly growth rate, CJ Cq Specific growth rate, )J., h ... 

A plot of the specific respiration rate ( 02 versus the specific growth rate coefficient [L is linear, with the intercept on the ordinate equal to the oxygen uptake rate for cell maintenance. A formulation of this is ... 

In these equations, [L = specific growth rate coefficient, v = specific rate of substrate uptake, t = time, x = biomass concentration, Sj = intracellular substrate, and Cj = concentration of intracellular substrate. Several examples where these equations can be applied include nitrogen hmitations in M. citrifolia cultures and phosphate hmited growth in C. roseus, N. tahacum, a.nd Papaver. somniferum. 

Two types of interac tion, competition, and predation are so important that worthwhile insight comes from considering mathematical formulations. Assuming that specific growth-rate coefficients are different, no steady state can be reached in a well-mixed continuous culture with both types present because, if one were at steady state with [L = D, the other would have [L unequal to D and a rate of change unequal to zero. The net effect is that the faster-growing type takes over while the other dechnes to zero. In real systems—even those that approximate well-mixed continuous cultures—there may be profound... 

Specific growth rate coefficient, I The rate of ehange of mierobial eell mass eoneentration per unit eell eoneentration p = (l/C )(dC /dt) (where C, = eell mass eoneentration, g/1). 

In practice, carbon limited chemostat cultures are used to estimate the P/O quotient These conditions are used because they favour the most efficient conversion of the carbon substrate into cellular material, ie the highest efficiency of energy conservation. The steady state respiration rate (qo,) is measured as a function of dilution rate (specific growth rate) and Yq can be obtained from the reciprocal of the slope of the plot. qo, is also known as the metabolic quotient for oxygen or the specific rate of oxygen consumption. 

Productivity. The continuous system operates such that the biomass concentration remains constant (specific growth rate = dilution rate). Productivity is therefore given by the biomass concentration x the dilution rate. 

Using the Monod rate for the specific growth rate in (3.11.9), it is reduced to following equation ... 

Flow rate) (Cell in Cell out) + Rate of cell generation = 0 Let us define /a, which is known as specific growth rate... 

Substituting the specific growth rate into (3.11.2.28) leads to the following differential equation. 

Since there are various specific growth rates and different values of rate constants while substrate concentration varies, therefore mix inhibition exists. Andrew26 incorporated a substrate inhibition model27 in the Monod equation the modified Monod equations with second-order substrate inhibition are presented in (3.14.5.1) and (3.14.5.2).16,17... 

Table 3.1 shows the kinetic parameters for cell growth, rate models with or without inhibition and mass transfer coefficient calculation at various acetate concentrations in the culture media. The Monod constant value, KM, in the liquid phase depends on some parameters such as temperature, initial concentration of the carbon source, presence of trace metals, vitamin B solution, light intensity and agitation speeds. The initial acetate concentrations in the liquid phase reflected the value of the Monod constants, Kp and Kp. The average value for maximum specific growth rate (/xm) was 0.01 h. The value... 

Circulation time Precursors Specific growth rate... 

There is no cell removal from the batch vessel and the cell propagation rate is proportional to specific growth rate, /jl (h 1), using the differential growth equation the cell concentration with respect to the time is ... 

At steady-state condition, the biomass concentration remains constant, that is, dX/dt = 0, and (5.6.1.3) concludes to /x = /) therefore the specific growth rate is equal to the dilution rate. 

The effect of substrate concentration on specific growth rate (/i) in a batch culture is related to the time and p,max the relation is known as the Monod rate equation. The cell density (pcell) increases linearly in the exponential phase. When substrate (S) is depleted, the specific growth rate (/a) decreases. The Monod equation is described in the following equation ... 

For quasi-steady state, the specific growth rate reaches the media dilution rate, /l D. If Fm>F[Pg.97]

Comparison of the ordinary Michaelis-Menten relation with (5.108) shows that the inhibitor did not influence specific growth rate, vmgx, but the Michaelis-Menten constant was affected by the inhibitor and resulted in a constant, known as the apparent Michaelis constant. 

The maximum specific growth rate is retarded with non-competitive inhibitor. The apparent specific growth rate, vgr > is smaller than the ordinary specific growth rate, umax. 

Rate of product formation, g-11 - h 1 j Specific growth rate, h 1... 

Kfvv Appai-ent Michaelis constant, g-l1 umS Apparent maximum specific growth rate constant, li 1... 

---