This guide aims to break down the inherent logic of maintenance techniques, ensuring that fermenters are always in optimal condition to guarantee the value of core equipment.
1. Daily Cleaning and Sterilization
After each fermentation cycle, thorough cleaning and sterilization are the primary defenses against microbial contamination. Residual nutrients provide a breeding ground for bacteria, while stubborn biofilms can harbor pathogens. High-frequency CIP (Cleaning in Place) procedures are initiated immediately after fermentation, using a fixed temperature, concentration of cleaning agent, and cleaning flow rate. Periodic SIP (Sterilization in Place) procedures maintain a 121°C and 0.11 MPa steam environment to thoroughly remove all active microorganisms from the tank.
(1) Stainless Steel Fermenters: Focus on the coverage of CIP/SIP balls/nozzles to ensure no blind spots. High tolerance allows for the use of broader-spectrum or slightly higher concentration cleaning/disinfectants.
(2) Laboratory Fermenters: Extra caution must be taken when selecting cleaning and disinfectants to avoid strong alkalis, hydrofluoric acid, etc., which can corrode glass or silicone seals. Manual cleaning is more common, requiring gentle handling to avoid scratching the inner glass wall. During sterilization, pay attention to the rate of temperature rise and fall to avoid thermal shock causing glass breakage. Neglecting any step can lead to future contamination.
(3) Dead-end cleaning: Pay attention to areas with weak fluid dynamics, such as sampling valves, inoculation ports, exhaust filter interfaces, and the area around the agitator shaft seal. Manual disassembly and cleaning may be necessary.
2. Sealing Inspection
Fermentation tanks need to operate stably under positive and negative pressure. Even a small leak can lead to culture medium leakage, gas leakage, or contamination. We must focus on key connection points such as tank flanges, sampling valves, inoculation ports, and electrode interfaces, and regularly check the integrity, elasticity, and signs of aging of O-rings, gaskets, and other seals. Pressure holding tests during tank pressurization (empty or full sterilization) are an effective way to verify overall sealing.
(1) Stainless steel fermentation tanks: Flange surface flatness and bolt tightening torque are key inspection points. A wide range of seal materials can be selected.
(2) Laboratory Fermentation Tanks: Due to their glass construction, laboratory fermentation tanks are prone to leaks at the top cover connection and electrode ports. Sealing rings are also susceptible to aging and deformation, requiring more frequent inspection and replacement. Pressure holding tests must be conducted under the guidance of professionals, equipped with protective equipment (explosion-proof covers, safety gloves, goggles, etc.), and the test pressure must be strictly controlled within the safe range of the glass tank; overpressure is absolutely prohibited.
3. Sensor Calibration
Temperature, pH, dissolved oxygen (DO), and pressure sensors are the "eyes" of the fermentation process. Data deviations will lead to uncontrolled process parameters, affecting yield and quality at best, and causing batch failures at worst. Calibration plans must be strictly developed based on manufacturer recommendations and process requirements. Temperature probes require periodic multi-point calibration in standard solutions; pH electrodes typically have the highest calibration frequency, ideally calibrated using standard buffer solution each time; dissolved oxygen electrodes require zero-point and full-point calibration.
(1) General Principle: Calibration frequency depends on usage intensity, process criticality, and sensor stability.
(2) Differences: Laboratory glass jars often require frequent disassembly and reassembly of electrodes for offline calibration or replacement. Aseptic operation and interface sealing checks during disassembly and reassembly are particularly important. Stainless steel jars tend to be used for in-situ calibration or quick-connect designs to reduce the risk of contamination.
4. Preventive Maintenance and Monitoring
In addition to the above-mentioned fixed maintenance plans, regular checks of the condition of mechanical components are crucial. Proactive intervention is better than reactive maintenance.
(1) Stirring System: Monitoring bearings and shafts can detect early mechanical problems such as shaft misalignment and bearing wear. Check the impellers for deformation, corrosion, or biofouling.
(2) Valves and Piping: Confirm the accuracy and response time of valve opening and closing, and check the stability of pipeline supports.
(3) Regular Replacement: Regularly replacing consumables such as air pre-filters and respirator filters is key to maintaining a sterile barrier.