Cell growth decelerating phase

After nutrients and substrate begin to diminish, cell growth decelerates and enters a period of no apparent growth. This phase is known as the stationary phase. In the stationary phase, the rate of growth equals the rate of cell death and no net change in cell mass concentration occurs. Fermentation products produced during the stationary phase are known as non-growth associated products. 

In case the Monod equation holds for the rates of cell growth in the exponential growth, with decelerating and stationary phases in a uniformly mixed fermentor operated batchwise, a combination of Equations 4.2 and 4.6 gives... 

Cells growth is described as an autocatalytic reaction. All growth requires an initial seed or inoculum of cells. As the cells are given nutrients, they metabolize this food to make more cells. The nutrient requirements vary considerably with cell type, but all cells undergo the growth phases shown in Fig. 1—stationary, exponential, deceleration, stationary, and death phases. 

After the exponential growth phase, the cell growth is limited by the availability of nutrients and the accumulation of waste products of metabolism. Consequently, the growth rate gradually decreases, and this phase is called the decelerating phase. 

The onset of the deceleration phase is identified as the time when the net rate of cell growth decreases. Decreases observed in the rate of increase of the number of cells are a direct consequence of the effects enumerated in Section 13.1.1. The point at which the net rate of cell growth becomes zero marks the onset of the stationary phase. 

---