The role and influence of pH electrodes, DO probes, temperature probes and air filters in the biological fermentation process

Biological fermentation is a process that utilizes microorganisms to transform organic matter and produce metabolic products under specific conditions. It is widely applied in multiple fields such as food, medicine, agriculture, bio-fertilizers, and chemical engineering. During the fermentation process, the stability of the fermentation environment directly determines the growth rate, metabolic activity of microorganisms, as well as the yield and quality of the final product. In order to achieve real-time monitoring and precise control of the fermentation process, key accessories such as pH electrodes, DO probes, temperature probes and air filters are widely used in the bio fermentation system.

This article will respectively start from the principles, functions and influences on the fermentation process of these four core components, and analyze in detail their importance and synergistic effects in practical applications.

I. pH Electrode: The "Gatekeeper" of Microenvironment Acidity and Alkalinity

1. Principle and Function

The pH electrode is a sensor that can measure the concentration of hydrogen ions (i.e., pH value) in the fermentation broth in real time. During the microbial fermentation process, the change in pH value reflects the metabolic activities of microorganisms. Through the pH electrode:

Monitor the pH of the fermentation broth in real time;

Link the automatic acid or alkali addition system to maintain pH stability;

Determine the fermentation stage. For instance, some strains have different metabolic pathways at different pH values.

2. Impact on fermentation

The growth and metabolism of microorganisms are extremely sensitive to pH. For example:

Yeast has the most vigorous metabolism between pH 4.5 and 5.5.

Nitrifying bacteria require a slightly alkaline environment (pH above 7.5).

Both too low and too high pH values can lead to enzyme inactivation, membrane structure damage, and even the death of bacteria.

Therefore, the accuracy and response speed of the pH electrode are directly related to the activity of the strain, the types and concentrations of metabolic products, as well as the overall stability of the fermentation process.

MIKEBIO bioreactor system for  edible fungi 

II. DO Probe: Real-time Monitor of dissolved Oxygen levels

1. Principle and Function

The DO Probe (Dissolved Oxygen Probe) is used to monitor the dissolved oxygen (DO) concentration in the fermentation broth and is an indispensable device in the aerobic fermentation process. Microorganisms (such as Azotobacter, Pseudomonas, etc.) rely on sufficient oxygen for the synthesis of their metabolites in an aerobic environment. The DO probe measures the oxygen content in the liquid phase to:

Determine the oxygen consumption rate of microorganisms in real time;

Interlinked gas supply systems (such as air compressors, mixed gas systems);

Realize the feedback regulation of dissolved oxygen concentration.

2. Impact on fermentation

Insufficient dissolved oxygen levels will cause microorganisms to enter anaerobic metabolic pathways, generating unwanted by-products and even inhibiting the generation of target products. However, excessive oxygen may cause oxidative stress and damage the cell structure. The DO probe helps maintain dissolved oxygen within the most suitable range (such as 20% to 60% saturation), achieving a dynamic balance between oxygen supply and demand. It is a key means to optimize yield and shorten the fermentation cycle.

III. Temperature Probe: The regulatory core of fermentation thermodynamics

1. Principle and Function

The temperature probe is used for real-time monitoring of the liquid temperature in the fermentation tank. In biological reactions, temperature has a significant impact on the activity, metabolic rate, and enzymatic reaction efficiency of microorganisms. By linking the heater or cooling system with the temperature sensor, it is possible to:

Maintain a constant fermentation temperature;

Prevent the temperature from being too high due to the large amount of heat generated by fermentation;

Set different temperature curves according to different fermentation stages.

2. Impact on fermentation

Microorganisms all have an optimal temperature range for growth:

For example, the optimal temperature range for most mesophilic bacteria is 30 to 37°C;

When the temperature is above 45°C or below 20°C, the metabolism of most bacterial species will significantly decrease or even stop.

In practical applications, temperature probes help achieve precise temperature control, thereby ensuring fermentation efficiency, stabilizing the composition of metabolic products, and enhancing yield and reproducibility.

Iv. Air Filters: Anti-pollution Barriers and Gas Purity Assurance

1. Principle and Function

Air filters, especially HEPA filters (high-efficiency particulate air filters), are used to purify the air in the air supply system, removing contaminants such as bacteria, dust, and mold spores. During the fermentation process, air is continuously injected into the fermentation tank as a source of oxygen. Therefore, its cleanliness is crucial to the aseptic requirements of the fermentation environment. The main functions of the air filter include:

Prevent contamination by exogenous microorganisms;

Ensure the gas quality of the gas supply system;

Improve the purity and safety of the final product.

2. Impact on fermentation

Once miscellaneous bacteria are mixed into the air, it may cause competition among strains, metabolic disorders and even fermentation failure. In addition, for the production of pharmaceutical and food-grade products, it is even more necessary to ensure the microbial control standards of the products through air purification. The efficiency and lifespan of the filter directly affect the stability of the system operation and the product quality.

V. The Overall Impact of the Synergistic Effect of the Four on the fermentation process

In an efficient biological fermentation system, the pH electrode, DO probe, temperature probe and air filter form a closed-loop system of "perception - regulation - protection" :

When these types of devices operate in coordination, the fermentation process can achieve a high degree of automation, precision and repeatability, thereby reducing energy consumption, shortening the fermentation cycle, and increasing product output and purity.

MIKEBIO pilot scale fermentation system 

Conclusion

Today, with the continuous development of modern biological fermentation technology, the degree of intelligence and precision of sensors and accessories directly determines the technological level and industrial competitiveness. The pH electrode, DO probe, temperature probe and air filter, as indispensable core components in the fermentation system, not only achieve real-time monitoring and dynamic control of key parameters, but also play a significant role in ensuring the activity of the strain, increasing the yield and controlling pollution.

In the future, as biomanufacturing moves towards large-scale and intelligent development, the performance of the aforementioned components and their system integration capabilities will become even more crucial, serving as the cornerstone for achieving green, efficient, and biological process control.

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.