Understand one article! Control of Fermentation Feeding
1、 The purpose of supplementing materials
The concentration of inhibitory substrates can be controlled: substrate concentration and precursors can relieve or weaken the inhibition of decomposition products; metabolic inhibition can optimize the fermentation process: carbon sources, nitrogen sources, inorganic salts
2、 The content of supplementary materials
The need to supplement microbial energy and carbon sources. Supplement the nitrogen source required by the bacterial cells. Supplement trace elements or inorganic salts. Supplement precursors, accelerators, etc.
3、 Principle of supplementing materials
Control the intermediate metabolism of microorganisms to promote the accumulation of products. To achieve this goal, appropriate feedback control parameters and feeding rates must be selected during intermediate feeding control.
5、 Strategy for material replenishment control
Most batch fermentation with supplementary materials is supplemented with growth limiting substrates.
Control flow with empirical or predictive data; Indirectly control the flow rate with parameters such as pH, exhaust gas, dissolved oxygen, and product concentration;
By using the material balance equation, the concentration of the restrictive matrix is indirectly controlled by measuring some parameters online through sensors; Directly measure the concentration of restrictive matrix using sensors and control the flow rate.
6、 Selection of feeding control parameters
In order to effectively carry out intermediate feeding, it is necessary to select appropriate feedback control parameters and understand the relationship between these parameters and microbial metabolism, bacterial growth, substrate utilization, and product formation.
The adoption of the optimal supplementary program also depends on factors such as the morphology of the growth curve, the rate of product generation, and the initial conditions of fermentation.
Therefore, in order to establish a mathematical model for batch feeding cultivation and select the optimal control program, it is necessary to fully understand the metabolic laws of microorganisms in the fermentation process and their requirements for environmental conditions.
7、 Determination of replenishment rate
Optimizing the feeding rate is also a crucial aspect of feeding control, as nutrients and precursors need to be maintained at appropriate concentrations, which are consumed at different rates.
Therefore, the feeding rate should be determined based on the microbial consumption rate of nutrients and the minimum maintenance concentration set in the culture medium.
For example, the continuous cultivation method was used to determine the carbon, chlorine, oxygen, phosphorus, sulfur, and acetate salts of penicillin producing bacteria producing Penicillium flavum at different specific growth rates, as well as the feeding rates of various substrates required for the optimal growth of the bacteria.
Example: Control of sugar supplementation
Early timing of sugar supplementation stimulates growth and accelerates sugar utilization. Too late, the required energy cannot keep up.
Add sugar to determine the conditions of the culture medium, bacterial species, fermentation status (residual sugar, pH, bacterial morphology, etc.), and add it as needed. Continuous sugar supplementation method: Each infusion can be divided into fast infusion, constant infusion, exponential infusion, and variable infusion.
A small amount of intermittent replenishment, a large amount of intermittent replenishment.
Multi component feeding can be carried out together with other components.
The principle of sugar supplementation is based on the premise of not causing drastic fluctuations in the components of the fermentation broth, balancing the addition and consumption, and maintaining a stable sugar concentration.
