GENERAL MICROBIOLOGY - T.P. Pirog - 2004

6. MICROBIAL GROWTH

6.4. GROWTH PHYSIOLOGY

6.4.6. Growth Curve Parameters

The Main parameters of the growth curve (Fig. 6.9) include the biomass yield (biomass), growth rate, and the duration of the lag phase (provided that batch culture growth is analyzed based on the increase in biomass rather than Cell number).

Biomass yield (biomass level) is the difference between the maximum and initial bacterial biomass:

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This value is expressed in grams of dry weight. An important indicator is The ratio of cell yield to The amount of substrate consumed — X/S. When both quantities are expressed in units of weight, the X/S ratio is referred to as the yield coefficient (Y). If the yield in grams is related to the number of moles of substrate consumed, the resulting value is called the molar yield coefficient.

The exponential growth rate is a measure of The rate of cell growth during the exponential phase. It is calculated using the formula based on the initial and final biomass X₀ and X_t at times t₀ and t:

д· Ig_e = 0,43420.

The generation time is determined by the formula

For "standard" Cells μ = ln 2v and t₀ = g.

The duration of the lag phase (T₁) is defined as the time interval between the moment t₀, at which the culture reached a certain biomass X₀, and the moment t_t, at which it would have reached the same biomass if exponential growth had started immediately after inoculation.

Fig. 6.9. Growth parameters:

A - cell yield (biomass); B - growth rate; C - duration of the lag phase