The characteristics of Escherichia coli strains and their applications in the biological fermentation industry, as well as the requirements for fermentation tanks

I. Characteristics of Escherichia coli Strains

Escherichia coli (abbreviated as E. coli) is a Gram-negative, spore-free, peritumellar rod-shaped bacterium belonging to the Enterobacteriaceae family. In nature, Escherichia coli is widely present in the intestines of humans and animals and is one of the important intestinal symbiotic bacteria. Although some strains (such as O157:H7) may cause diseases, most Escherichia coli strains are harmless and even have extremely high value in industry and scientific research.

The main species characteristics of Escherichia coli include:

• Rapid growth and reproduction: Escherichia coli has a short growth cycle. Under the optimal temperature of 37℃, its generation time is approximately 20 minutes, making it suitable for efficient industrial cultivation.
• The genetic operation is simple: As one of the model organisms, Escherichia coli has a complete genetic background and a mature operation system, which is convenient for gene editing and recombination.
• The nutritional requirements are simple: It has relatively low requirements for the components of the culture medium. Common simple carbon sources (such as glucose) and inorganic salts can meet the growth needs and reduce the culture cost.
• The expression systems are mature: For instance, the T7 expression system and the pET vector system are widely used for the efficient expression of target proteins.
• It has strong tolerance to environmental changes: It has a certain adaptability to changes in pH, temperature and dissolved oxygen, and is suitable for large-scale application in fermentation tanks.

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II. Application of Escherichia coli in the Biological Fermentation Industry

In the fields of modern biotechnology and industrial fermentation, Escherichia coli, as one of the "factory bacteria", plays an irreplaceable role. Its main application fields include:

1.Recombinant protein expression

Escherichia coli is one of the most commonly used hosts for expressing recombinant proteins. By introducing exogenous genes, various proteins can be expressed efficiently, such as:

• Pharmaceutical proteins (such as insulin, interferon, growth hormone, etc.);
• Industrial enzymes (such as lactase, cellulase);
• Antigen proteins and vaccine precursor substances

Due to its high expression efficiency, short culture period and easy purification, it has become the preferred expression system for biopharmaceutical enterprises.

2. Amino acid and vitamin production

The Escherichia coli strains modified through metabolic engineering can be used to produce a variety of important amino acids and vitamins, such as:

• Essential amino acids such as L-threonine, L-lysine and L-tryptophan
• Vitamin B2 (riboflavin), vitamin B12, etc

This type of product is widely used in the fields of food, feed and medicine.

3. Synthesis of organic acids and metabolites

Escherichia coli can be used to produce various bio-based organic acids and other metabolites:

• Green alternative chemical raw materials such as lactic acid, succinic acid and pyruvic acid
• Precursors of biofuels such as bioethanol and biobutanol
• An intermediate for biodegradable plastics such as polyhydroxybutyrate (PHB)

Such products contribute to achieving clean production and sustainable development.

4. DNA vaccine and plasmid production

E. coli is also an important host for the production of DNA vaccines and engineered plasmids. By using its high-copy plasmid system, large-scale and low-cost vaccine raw material preparation can be achieved.

III. Requirements for Escherichia coli Culture in Fermentation Tanks

High-density culture of Escherichia coli requires a precisely controlled fermentation system. The following are the main requirements that the fermentater should meet in its design and operation:

1. Strong ventilation and efficient stirring system

Escherichia coli is a facultative anaerobic bacterium. During high-density aerobic fermentation, it has an extremely high demand for oxygen. Therefore, the fermentation tank needs to be equipped with:

• High-flow ventilation system (air or pure oxygen)
• Multi-layer mechanical stirring blades (such as Rushton turbines)
• Dissolved oxygen probe and automatic control system
• Efficient oxygen transfer capacity is a key factor in achieving high yields.

2. Strict temperature and pH control

The optimal growth temperature for Escherichia coli is 37℃. However, during the expression of recombinant proteins, expression is often induced at 25-30℃ to enhance protein activity. Therefore, the fermentation tank needs to have:

• High-sensitivity temperature control system
• Online pH monitoring and automatic adjustment device (often maintained at 6.8-7.2)

3. Foam control system

During the culture process of Escherichia coli, there is often a severe foaming phenomenon. The following equipment is required:

• "Foam probe"
• Automatic defoamer addition system
• Window observation and manual adjustment functions
• Foam control is crucial for maintaining ventilation efficiency and avoiding pollution.

4. Sterile system design

The Escherichia coli culture process requires aseptic operation. The fermentation tank should be equipped with:

• The overall CIP (In-situ cleaning) and SIP (in-situ sterilization) functions
• Seal the valve system and sterilization sampling port
• Sterile ventilation and feeding system
• Ensure that the entire production process is carried out under pollution-free conditions.
• 5. Scalability and scalability verification
• From laboratory small-scale trials to pilot-scale trials and industrial scale-up, the fermentation process of Escherichia coli has good scalability. The fermentation tank should have:
• Adjustable stirring and ventilation system
• Modular controllers (PLC/SCADA) to adapt to different scales
• The data collection and batch traceability functions facilitate GMP compliance management

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Iv. Summary

Escherichia coli has become one of the most representative microorganisms in the biological fermentation industry due to its rapid growth, simple operation and high expression efficiency. It is widely applied in multiple fields such as medicine, food and chemical engineering. At the same time, an efficient fermentation process cannot do without scientific design of fermentation tanks and precise process control. With the development of biotechnology, new fermentation equipment and optimized control strategies for Escherichia coli will also continuously promote its industrialization level, contributing to green manufacturing and sustainable development.

On the other hand, when choosing a bioreactor fermenter, it is necessary to find a regular manufacturer with good reputation and strength, so as to ensure the quality of the product. Jiangsu Mike Biotechnology Co., Ltd. was established in 2008, is a focus on biological fermentation equipment research and development, production and sales of high-tech enterprises. Our company has a pilot fermentation platform, which is integrated with intelligence and automation, and has built a mature fermentation system, which can realize the optimization of pilot fermentation process, commissioning development of all process processes from pilot fermentation production to fermentation product separation and purification, and set up a doctor workstation and a modern laboratory.

Our company has a standardized production plant, with complete sets of equipment and tools required for installation, mainly including a variety of machine tools, automatic argon arc welding machine, automatic polishing machine, automatic cutting machine and flaw detection machine and other more than 60 sets of production and testing equipment, the production process all realize modern standard operation, to provide customers with more professional quality and technical support.