As an important metabolic control fermentation process, glutamate fermentation is not only affected by the characteristics of bacteria, but also restricted by many external factors. The purpose of this paper is to analyze these external factors in depth, in order to provide strong support for the optimization of glutamate fermentation.
1. Effect of oxygen supply concentration on glutamate fermentation
Oxygen supply concentration is one of the key factors affecting glutamate fermentation. Excessive oxygen supply will lead to the enhancement of the reoxidation capacity of NADPH, which will interfere with the reductive amination process of α-KGA, which is not conducive to the formation of glutamate. Conversely, insufficient oxygen supply will lead to a large accumulation of lactic acid, which will reduce the pH value of the fermentation broth, which is also not conducive to the production of glutamate. Therefore, proper control of the oxygen supply concentration is essential for glutamate fermentation.
2. The role of NH4+ concentration
NH4+ concentration plays a dual role in glutamate fermentation. On the one hand, it directly affects the pH of the fermentation broth; On the other hand, it is closely related to the formation of the product. Excess NH4+ inhibits bacterial growth and leads to the conversion of glutamate to glutamine. However, NH4+ deficiency is not conducive to the reductive amination of α-KGA, thereby affecting the accumulation of glutamate. Therefore, it is crucial to strictly control the NH4+ concentration during the fermentation process.
3. The effect of phosphate
Phosphate also plays an important role in glutamate fermentation. Excess phosphate promotes the EMP pathway, upsetting the balance between EMP and TCA, leading to pyruvate accumulation and the production of by-products such as lactate. This not only affects glutamate yield, but also reduces glyco-acid conversion and product yield.
Fourth, the carbon and nitrogen ratio of the fermentation broth
The sugar content in the fermentation broth is closely related to glutamic acid fermentation. Sugar content that is too low can limit glutamate production; Too high a sugar content will lead to excessive osmotic pressure, which is not conducive to the growth of bacteria. Therefore, reasonable control of the carbon and nitrogen ratio of fermentation broth is the key to achieve efficient fermentation.
5. The role of biotin
Biotin, as a trophic factor of glutamate-producing bacteria, has a significant impact on its growth and reproduction and metabolites. Excess biotin leads to the conversion of pyruvate to lactate and affects the excretion of glutamate. The sub-appropriate amount of biotin is conducive to the accumulation of glutamate. Therefore, it is important to control the biotin content reasonably according to the different fermentation periods.
6. Fermentation temperature and pH value
Fermentation temperature and pH value are important environmental factors affecting glutamic acid fermentation. The appropriate temperature and pH range are conducive to the growth of the bacteria and the accumulation of metabolites. Temperatures and pH levels that are too high or too low can adversely affect glutamate fermentation. Therefore, it is essential to monitor and regulate the temperature and pH value in real time during the fermentation process.
7. Ventilation and foam control
Ventilation is an important means of oxygen supply and mixing in glutamate fermentation. A reasonable amount of ventilation can not only ensure the normal growth of bacteria, but also avoid the production of by-products. At the same time, foam control is also a key part of the fermentation process. Too much foam can affect the respiration of bacteria, cause waste and pollution, and even cause bacterial accidents. Therefore, taking effective measures to control the foam is the key to ensuring that fermentation proceeds smoothly.
Glutamate fermentation is a complex metabolic control process that is influenced by a variety of external factors. Through in-depth study of the mechanism of action of these factors and the corresponding regulatory measures, it is expected to further improve the efficiency and yield of glutamate fermentation.
Relationship between fermentation conditions and products of glutamate-producing bacteria
| Control factor | Fermentation product conversion |
| oxygen | Lactic acid or succinic acid (hypoventilation) ←→ glutamate (adequate ventilation) |
| NH4+ | α-Ketoglutarate (deficiency) ←→ glutamate (moderate) ←→ glutamine (excess) |
| pH | N-acetyl glutamine (acidic) ←→ glutamic acid (neutral or slightly alkaline) |
| phosphoric acid | Valine (high concentration) ←→ glutamic acid |
| biotin | Lactic acid or succinic acid (abundant) ←→ glutamate (deficient) |
During glutamate fermentation, the characteristics of the production strains, auxin, fermentation temperature, pH, ventilation and foam produced by fermentation are the main factors affecting glutamate accumulation. In actual production, only by strictly controlling the process conditions for the existing problems can we achieve the purpose of stable and high yield.
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