Batch culture growth

A batch culture is a closed-culture system which contains an initial, limited amount of nutrients, hence the exponential growth is limited to a few generations.

Figure 1: Yeast growth phases.

The phase of microbial growth in a batch culture is generally divided into four phases; the lag phase, log phase or exponential phase, stationary phase and death phase. During the lag phase, microbes are growing and adapting to the new environment so the biomass does not increase significantly. During the exponential phase, the cells are at their most active and consume large amounts of nutrients, hence maximum biomass is achieved.

The limited amount of nutrients will eventually lead to nutrient depletion and growth rates will decrease and become zero. When the number of dying cells is greater than the number of cells generated, the biomass will decrease. This is the death phase.

Saccharomyces cerevisiae grown with excess sugar will show two distinct exponential phases with different growth rates. This phenomenon is called the diauxic shift.