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Growth law of bacteria in batch fermentation

Data: 2020-11-19

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Growth law of bacteria in batch fermentation

Fermentation tanks for batch fermentation are closed systems. After inoculating the strains into the fermentation culture media, apart from inputing sterile air into the bioreactor, add acid and alkali to adjust the pH of the fermentation broth, generally no substances are added or removed from the system. 

Therefore, batch fermentation can only support the growth, reproduction and accumulation of metabolites of microorganisms for a limited period of time. The growth of microorganisms is growth under restrictive conditions.

The whole process can be divided into 5 stages.

1. Lag phase.

Lag phase is an adaptation phase of microbial cells in a new culture environment. Cells need to synthesize related enzymes to utilize nutrients in the new environment, resulting in lag phase.

2. Exponential phase

At the end of the delay period, since the nutrient substances in the medium are relatively sufficient, the target product has not yet begun to accumulate, and there are few harmful metabolites, so the growth of the cells is not restricted, and the cell concentration increases exponentially with the culture time.

3. Deceleration phase

With the massive multiplication of cells, the nutrients in the culture medium are rapidly consumed. While the target product accumulates in large quantities, harmful metabolites also gradually accumulate. The growth rate of cells gradually decreases and enters a deceleration phase.

4. Stable phase

Due to the exhaustion of nutrients or the accumulation of harmful substances, the cell concentration no longer increases, and this stage becomes a stable period. The concentration of cells reaches a maximum in the stationary phase.

5. Decline phase

As the environment deteriorates, cells begin to die and the concentration of living cells continues to decrease. This stage is called the decline phase.

The Paragon bio-engineering company provides high-quality fermentation equipment and corresponding auxiliary equipment to help customers produce high-quality product