The characteristics and applications of lactic acid bacteria strains and the requirements for fermentation tanks

Lactic acid bacteria are a type of beneficial microorganisms widely used in multiple fields such as food, medicine, and agriculture. They generate lactic acid by fermenting sugars, which not only improves the flavor of food but also plays an important role in inhibiting harmful bacteria, promoting nutrient absorption and enhancing immunity. With the popularization of the concept of healthy consumption, the industrial application of lactic acid bacteria is becoming increasingly widespread. To achieve stable, safe and efficient lactic acid bacteria fermentation, higher requirements are also put forward for the characteristics of the strains themselves and hardware equipment such as fermentation tanks.

I. Characteristics of Lactic Acid Bacteria Strains

Lactic acid bacteria, in a broad sense, include multiple groups such as Lactobacillus, Bifidobacterium, Streptococcus, Streptococcus thermophilus, and Lactococcus. Although there are differences among them, they generally share the following common characteristics:

1. Anaerobic or facultative anaerobic

Most lactic acid bacteria are anaerobic or facultative anaerobic bacteria, which ferment sugars to produce lactic acid in low-oxygen or anaerobic environments. This means that the oxygen level needs to be controlled during the production process to avoid affecting its growth activity.

2. Temperature sensitive

Different lactic acid bacteria have different temperature adaptation ranges. Most grow well at 30 to 40° C. For instance, Streptococcus thermophilus has an optimal temperature of around 42°C, while some Lactobacillus species are suitable for 37°C. Deviation of temperature from the optimal range will lead to a decrease in fermentation efficiency and even the death of the strain.

3. pH adjustment ability

Lactic acid bacteria lower the environmental pH by secreting lactic acid, thereby inhibiting putrefactive bacteria. The optimal growth pH for most lactic acid bacteria is 5.5 to 6.5. However, a pH that is too low will inhibit their own growth. Therefore, the pH value needs to be dynamically adjusted during the cultivation process.

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4. Dependence on nutrients

Lactic acid bacteria require rich nutrients during their growth process, such as amino acids, B vitamins, carbon sources (glucose, lactose, etc.), which means that the formula of the culture medium has a significant impact on their activity.

5. Acid and bile salt resistance (partial)

Especially probiotic lactic acid bacteria, after entering the human digestive tract, need to tolerate gastric acid and bile salts. Therefore, screening strains with tolerance is an important indicator.

II. Main Application Fields of Lactic Acid Bacteria

The wide application of lactic acid bacteria is attributed to their safety, progenicity and functionality. The main applications are as follows:

1. Food fermentation field

Lactic acid bacteria are the core strains of various traditional fermented foods, such as yogurt, kimchi, cheese, and pickles. They not only improve the flavor and extend the shelf life, but also inhibit pathogenic bacteria and enhance food safety.

2. Functional health supplements

By precisely screening strains with specific functions (such as enhancing immunity, improving intestinal flora, and regulating blood lipids) and making them into capsules, powders, beverages, etc., it has become an important growth point in the probiotics industry.

3. Animal feed and agriculture

Adding lactic acid bacteria in animal husbandry can promote the intestinal health of animals and reduce the use of antibiotics. In agriculture, lactic acid bacteria are also used in composting fermentation and the production of bio-organic fertilizers to increase crop yields and quality.

4. Medical adjuvant therapy

Some lactic acid bacteria have the functions of regulating immunity, alleviating irritable bowel syndrome, and assisting in the treatment of Helicobacter pylori infection, and are increasingly used in the auxiliary treatment of intestinal-related diseases.

III. Basic Requirements for Fermentation Tanks in Lactic Acid Bacteria Fermentation

The large-scale cultivation of lactic acid bacteria must rely on highly automated fermentation equipment with precise temperature and oxygen control. High-quality fermentation tanks not only ensure the activity of the bacteria but also enhance production capacity and quality stability.

1.Material requirements: Resistant to acid corrosion and easy to clean

Due to the significant acid production of lactic acid bacteria, the inner wall of the tank should be made of corrosion-resistant stainless steel (such as 316L stainless steel), and it should have CIP/SIP (in-situ cleaning/sterilization) functions to ensure sterility and ease of maintenance.

2. Temperature control system: High temperature control accuracy

The temperature control during the fermentation process is directly related to the activity of the bacteria. It is required that the temperature control system has a control capability with an accuracy of ±0.1° C. Meanwhile, a water bath or jacket temperature control structure should be configured to achieve stable heating or cooling.

3. Dissolved oxygen control: Precise adjustment in a low-oxygen environment

For most lactic acid bacteria fermentation, a low dissolved oxygen or oxygen-free state should be maintained. Therefore, the tank needs to be equipped with a gas regulating valve system and negative pressure control equipment to precisely regulate the gas environment.

4. Stirring system: Moderate stirring to prevent shear damage

Appropriate stirring is beneficial for the uniformity of the culture medium and the consistency of the temperature, but excessive stirring can cause shear damage to the bacteria, especially for the small Lactococcus. It is recommended to use low-speed propellers or magnetic stirring systems.

5. Automatic pH adjustment system

Due to the continuous generation of lactic acid during the fermentation process, the pH of the culture medium drops. It is necessary to be equipped with an online pH monitoring and automatic alkali solution addition system to maintain the optimal fermentation pH range and increase the yield and survival rate.

6. Foaming control

Foam often occurs during lactic acid bacteria fermentation, so it is necessary to be equipped with foam sensors and automatic defoamer addition devices to prevent foam overflow and contamination.

Iv. Development Trends and Challenges

• With the rapid growth of the probiotics market, the lactic acid bacteria industry is upgrading towards "high activity, high functionality, and industrial automation". The key challenges in the future include:
• Precise strain screening and functional verification
• Intelligent and modular fermentation equipment system
• Greening of raw materials and optimization of low-carbon fermentation processes;
• Product form innovation (such as the combined application of probiotics with dietary fiber and peptides);

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Conclusion

Lactic acid bacteria, as a highly functional microbial resource, are empowering the development of multiple industries. Starting from the characteristics of the strain, to the process standards of industrial fermentation, and then to the precise release of the product, the requirements for technology and equipment throughout the entire chain are getting higher and higher. In the future, with the integration of bioengineering and intelligent fermentation equipment, the application of lactic acid bacteria will become more widespread, and it will also bring more assistance to human health and sustainable agricultural 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.