What is the air saturation during anaerobic fermentation tank cultivation

Official instructions on air saturation during anaerobic fermentation tank cultivation

In the anaerobic fermentation process, air saturation is a key environmental parameter that directly affects microbial metabolic activity and product synthesis efficiency. After laboratory research and industrial practice verification, the relevant technical parameters and control points are explained as follows:

1. Core parameter standards
Anaerobic fermentation environments need to maintain extremely low levels of dissolved oxygen concentrations and usually require:

1. dissolved oxygen threshold: ≤0.5% air saturation (conventional fermentation process)
2. limit control value: ≤0.1% air saturation (exclusive anaerobic culture)

2. Parameter control principle

1. inhibition of microbial metabolism：
   • Metabolism inhibition occurs in aerobic bacteria at 0.2% air saturation
   • Obligate anaerobic bacteria (e.g. methanogens) stagnate growth in an environment above 0.5% dissolved oxygen
2. Design code for fermentation tanks：
   • Tank sealing level ≥0.5MPa, oxygen permeability ≤0.01cm³/(m²·d·atm)
   • Equipped with dual mechanical sealing system, residual oxygen permeability ≤0.05mL/min
3. gas displacement process：
   • The pretreatment stage requires more than 3 nitrogen replacement cycles
   • Real-time monitoring by tail gas oxygen analyzer to ensure that residual oxygen content is ≤0.1%

3. Detection and control technology

1. on-line monitoring system：
   • Use fluorescence method to dissolve oxygen probe, response time ≤5 seconds
   • Equipped with automatic calibration device, zero-point calibration is carried out every 24 hours
2. dynamic control strategy：
   • When the dissolved oxygen concentration exceeds 0.3%, start nitrogen pulse air filling
   • Equipped with oxygen mass flow controller, adjustment accuracy ±0.01L/min
3. Exception handling plan：
   • When the dissolved oxygen suddenly increases ≥0.5%, the emergency pressure relief procedure will be started immediately
   • Investigate hidden dangers such as damage to the intake filter and leakage of the mixing shaft seal

4. Process verification requirements

1. Strain adaptability test：
   • Anaerobic acclimation culture was carried out for 24 hours before inoculation
   • Test the redox potential of the bacteria and confirm that it is ≤-300mV
2. Batch stability verification：
   • Dissolved oxygen fluctuation during 3 consecutive batches of fermentation is ≤±0.1%
   • Standard deviation of key metabolite yield ≤2%

V. Equipment maintenance specifications

1. Seal cycle management：
   • Mechanical seals are replaced every 5000 hours
   • Inspection of tank flange gaskets after production of each batch
2. Test device calibration：
   • Monthly zero/range calibration for dissolved oxygen probes
   • The oxygen analyzer is sent to the metering institution for verification every quarter

When enterprises carry out anaerobic fermentation processes, they should establish a three-dimensional monitoring system including dissolved oxygen, pH value, and temperature, and configure independent and redundant sensors for cross-verification. It is recommended to use an intelligent expert control system and use fuzzy algorithms to achieve dynamic balance of environmental parameters. While ensuring maximum microbial activity, the dissolved oxygen concentration is strictly controlled within the range of process requirements to ensure efficient and stable operation of the fermentation process.