Batch fermentation is a fermentation operation where the medium is added to the fermenter in a single batch, followed by sterilization, inoculation, and fermentation, after which the fermentation broth is discharged in one go. In batch fermentation, apart from continuous aeration and the addition of acid or base solutions to maintain the environment, there is no material exchange with the external environment, reducing the risk of contamination. The defining characteristic of batch fermentation is that all process variables change over time.

The metabolic changes during batch fermentation can be divided into three stages: cell growth, product synthesis, and cell autolysis.

1. Cell Growth Stage

The cell growth stage occurs in the early phase of fermentation, where the cells adapt to the new environment, begin to grow and multiply, and increase in number until the critical cell concentration is reached. To minimize adaptation time after transferring the seed solution to the fermentation medium, the composition of the seed medium should closely match that of the fermentation medium.

At this stage, metabolic changes primarily involve the catabolism of carbon and nitrogen sources in the medium and the anabolism of intracellular substances. Nutrients are continuously consumed, new cells are synthesized, and dissolved oxygen levels decline. When one of these factors becomes limiting, the growth rate of the cells slows to a critical threshold, marking the transition from the growth stage to the product synthesis stage.

2. Product Synthesis Stage

The product synthesis stage occurs in the middle of fermentation, when cell density stabilizes, metabolism shifts toward product synthesis, and the product generation rate reaches its peak. Parameters such as pH, temperature, and dissolved oxygen in the fermentation broth influence metabolic changes, increasing by-product formation and affecting yield. Baoxingsaisi's bioreactor system detects and monitors a range of parameters to assess cell growth and optimize the fermentation environment.

3. Cell Autolysis Stage

The cell autolysis stage occurs in the late phase of fermentation, characterized by cell aging, autolysis, reduced product synthesis capacity, increased amino nitrogen content, and a gradual rise in pH. At this point, fermentation must be terminated to avoid compromising the product and increasing the complexity of downstream processing.

With the appropriate hardware configuration, the advanced monitoring software generates metabolic curves based on data such as amino nitrogen, cell concentration, and fermentation units. Analysis of metabolic curves helps identify patterns in metabolic changes and uncover issues in process operations, enabling process improvements and increased yield.