Hydrothermal sterilization method of xanthan gum fermentation system

Abstract

The invention relates to the technical field of biochemical engineering, discloses a hydrothermal sterilization method of a xanthan gum fermentation system, and aims to solve the problems of high steam consumption, non-uniform temperature, material scale residue and the like in the prior art. The method comprises the following specific steps: S1, system inspection and water injection; s2, heating and circulating starting: starting a steam ejector of a maintaining tank, introducing saturated steam, monitoring the temperature of circulating water in real time through a temperature sensor, adjusting the flow of the steam, starting a circulating pump after the target temperature is reached, and controlling the circulating flow rate to be 1.5-2.0 m / s; s3, a constant-temperature sterilization stage: keeping the water temperature at 130 + / -5 DEG C, continuously circulating for 40 minutes, and keeping the system pressure at 0.3-0.4 MPa through a pressure sensor; and S4, completing sterilization and draining. Through the synergistic effect of hydrothermal circulation and steam waste heat, uniform sterilization is achieved, energy consumption is reduced, material scale residues are reduced, and the product quality and the production stability are improved.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of bio-chemical industry, and particularly relates to a hydrothermal sterilization method for a xanthan gum fermentation system. BACKGROUND

[0002] As an important microbial polysaccharide, xanthan gum has a wide range of applications in food, petroleum, medicine and other fields. Its industrial production mainly relies on high-density fermentation process, and the sterile state of the fermentation system is the core prerequisite for ensuring the stability of the fermentation process and the quality of the product. In the existing xanthan gum production process, the sterilization link usually adopts steam direct sterilization (i.e. "steam elimination") method, which kills microorganisms by passing high-temperature saturated steam into the fermentation system. Although this method can achieve basic sterilization, it has multiple technical defects in practical application: first, the steam consumption is large, and the energy utilization rate is low, which does not meet the current industrial orientation of green manufacturing and energy saving and emission reduction; second, the steam condenses unevenly inside the equipment, which easily forms a temperature gradient in areas such as pipe bends, valve gaps and dead corners of heat exchangers, resulting in incomplete local sterilization and the risk of contamination; third, the organic residues attached to the inner wall of the equipment cannot be effectively removed after steam condensation, which easily accumulates dirt during long-term operation, not only reducing the heat transfer efficiency, but also possibly becoming a breeding ground for microorganisms, affecting the fermentation purity and xanthan gum production performance of subsequent batches. The above problems are particularly prominent in continuous and large-scale xanthan gum production, which seriously restricts the stability and economy of the process. Therefore, it is urgent to develop a new sterilization method that can achieve uniform sterilization throughout the system, simultaneously clean the inner wall of the equipment, and significantly reduce energy consumption, in order to break through the inherent limitations of traditional steam elimination technology. SUMMARY

[0003] To solve the above technical problems, the present application provides a hydrothermal sterilization method for a xanthan gum fermentation system, which aims to use water as a heat transfer medium, combined with the synergistic effect of steam waste heat, to optimize temperature and time parameters, and solve the technical problems of high energy consumption, sterilization dead angle and dirt residue in traditional steam elimination technology.

[0004] To achieve the above purpose, the present application provides the following technical solutions:

[0005] The application discloses a hydrothermal sterilization method for a xanthan gum fermentation system, and the method comprises the following steps: step S1, system inspection and water injection: checking the sealing performance of valves in the system and the running state of a circulating pump, closing a system discharge valve, and injecting process water into a maintenance tank and a continuous sterilization pipeline to a liquid level scale line; step S2, heating and circulating start: opening a steam ejector of the maintenance tank, and injecting saturated steam; the circulating water temperature is monitored in real time through a temperature sensor, the steam flow is adjusted so that the water temperature is increased to 130±5 DEG C, the circulating pump is started after the target temperature is reached, and the circulating flow rate is controlled to be 1.5-2.0 m / s; step S3, constant temperature sterilization stage: the water temperature is kept at 130±5 DEG C, and the circulation is kept for 40 min; during the period, the system pressure is kept at 0.3-0.4 MPa through a pressure sensor; step S4, sterilization completion and water drainage: the steam valve is closed, the circulating pump is stopped, the system water drainage valve is opened, and hot water is drained, and compressed air is injected to blow off residual water in the pipeline.

[0006] Optionally, in the system inspection and water injection step, the injection amount of the process water accounts for 60%-70% of the total volume of the system, the liquid level range ensures that a continuous water phase is formed in the system, avoids uneven condensation caused by direct contact between steam and the inner wall of the equipment, and provides sufficient heat transfer medium for subsequent heat circulation. Before the water injection operation, it is required to confirm that all the valves are in the closed state, so that liquid leakage does not affect the integrity of the sterilization environment.

[0007] Further, in the heating and circulating start step, the pressure of the saturated steam ranges from 0.8 MPa to 1.0 MPa; under the pressure condition, the steam has a relatively high enthalpy value, and can quickly realize water-steam mixed heat exchange. The temperature sensor adopts a Pt100 platinum resistance probe, the measurement accuracy is ±0.1 DEG C, real-time feedback data are fed back to a control system, the steam valve opening degree is dynamically adjusted through a PID algorithm, and the water temperature is uniformly increased to 130±5 DEG C within 20-30 min. The flow rate of the circulating pump is set to be 1.5-2.0 m / s, the flow rate range ensures that the water flow forms a turbulent flow state in the pipeline, and the scouring capacity of the dead angle of the equipment is enhanced.

[0008] In addition, in the constant temperature sterilization stage, the system pressure is kept at 0.3-0.4 MPa, which is higher than the saturated steam pressure of water at 130 DEG C, and can effectively inhibit the temperature fluctuation caused by water evaporation. The circulating time is 40 min, which is determined based on a microbial heat-induced death kinetics model; for the bacillus commonly seen in the xanthan gum fermentation system, the D value is 1.5-2.0 min under the environment of 130 DEG C, and 40 min can ensure that the residual probability of the microorganism is lower than 10 -6 .

[0009] Optionally, during the sterilization and drainage steps, the compressed air pressure is 0.2-0.3 MPa, and the purging time lasts 3-5 minutes. This removes residual water droplets from pipe bends and valve gaps through airflow shearing, avoiding the risk of secondary contamination. A gradient pressure reduction operation is used during drainage: first, the main pipe drain valve is opened, then the branch valves are opened sequentially, to prevent the formation of negative pressure within the system that could draw in environmental microorganisms.

[0010] Furthermore, the hydrothermal sterilization system includes a holding tank, a steam ejector, a continuous sterilization and feeding pipeline, and a circulating pump. The volume of the holding tank matches the total system volume, and its inner wall is made of 316L stainless steel with a surface roughness Ra≤0.8μm to reduce the probability of scale adhesion. The steam ejector has a venturi structure, with a throat diameter to inlet pipe diameter ratio of 1:2.5, creating a negative pressure ejection effect to promote thorough mixing of steam and water.

[0011] In addition, the circulating pump is a high-temperature resistant centrifugal pump with an open impeller structure, allowing solid particles with a diameter ≤5mm to pass through, thus preventing scale debris from clogging the flow channel. The continuous discharge pipeline layout adopts a large-arc elbow design with a bending radius ≥3 times the pipe diameter. Combined with a circulation velocity of 1.5-2.0m / s, the water flow forms a Dean vortex at the bend, enhancing the mechanical scouring effect on the pipe wall.

[0012] Optionally, the temperature control module integrates multiple temperature sensors, with monitoring points set at key system locations including the bottom of the tank, pipe bends, and the inlet and outlet of the heat exchanger. The temperature difference between each measuring point is controlled within ±2℃ to ensure uniformity of the sterilization temperature field. Pressure control employs a pilot-operated pressure reducing valve with a response time ≤0.5s. When the system pressure exceeds 0.4MPa, it automatically releases pressure to prevent overpressure operation of the equipment.

[0013] Furthermore, the process water is deionized water with a conductivity ≤10μS / cm, reducing the risk of electrochemical corrosion between ions in the water and equipment materials at high temperatures. During the process of raising the water temperature to 130±5℃, the mass flow ratio of steam to water is controlled at 1:8-1:10. This ratio ensures heating efficiency while avoiding excessive steam condensation that could lead to system water imbalance.

[0014] On the other hand, a hydrothermal sterilization system for xanthan gum fermentation using the above-mentioned sterilization method is also provided. This system includes the following components: a holding tank with a steam inlet and a water inlet at the top, and a circulating pump connected to the bottom via a pipe; a steam ejector with its inlet connected to the steam pipe of the holding tank and its outlet extending below the liquid surface of the holding tank; a continuous sterilization and feeding pipeline, including a main pipeline and several branch pipelines, with the branch pipelines respectively connected to a heat exchanger and a valve group; a circulating pump with its inlet connected to the bottom outlet of the holding tank and its outlet connected to the inlet of the continuous sterilization and feeding pipeline; a temperature sensor with its probe arranged inside the holding tank and at key nodes of the pipeline; a pressure sensor with its interface located on the outlet pipeline of the circulating pump; and a control system that receives signals from the temperature and pressure sensors and outputs control commands to the steam valve and the circulating pump.

[0015] Compared with the prior art, the present invention has the following advantages:

[0016] 1. This invention utilizes the synergistic effect of hydrothermal circulation and waste steam heat to achieve a uniform temperature field distribution within the system. Water flow can penetrate complex structures such as pipes and valves, enabling sterilization without dead zones and reducing the contamination rate to 0%.

[0017] 2. This invention uses water as a heat transfer medium to reduce direct steam emission losses. Experiments have verified that steam consumption is reduced by 20%, and the steam consumption per batch is reduced from 1.5t to 1.2t.

[0018] 3. The circulating water flow of this invention generates a mechanical scouring effect during the sterilization process, removing residual scale from the inner wall of the equipment, reducing the amount of residual scale by more than 85%;

[0019] 4. This invention optimizes the temperature parameter of 130±5℃ and the time parameter of 40min, resulting in a stable xanthan gum yield of 4.2-4.25% on a dry basis, a product viscosity of 1200-1300 cP, and a purity of over 99.5%, ensuring production continuity and product consistency. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the overall architecture of the hydrothermal sterilization method for the xanthan gum fermentation system of the present invention. Detailed Implementation

[0021] To make the objectives, technical solutions, and advantages of this application clearer, the technical solutions of this application will be clearly and completely described below in conjunction with specific embodiments and corresponding drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0022] Example 1

[0023] In industrial xanthan gum fermentation production workshops, hydrothermal sterilization of the fermentation system is a core step in ensuring a sterile environment during the fermentation process. (See also...) Figure 1 This system includes core components such as a holding tank, steam ejector, continuous sterilization and feeding pipeline, and circulating pump. Before starting the system inspection and water injection process, operators must thoroughly check the sealing performance of all valves in the continuous sterilization system, confirming that the valve seats and valve core contact surfaces of ball valves, gate valves, and butterfly valves are intact. Simultaneously, the insulation resistance value of the circulating pump motor must be tested to be no less than 50MΩ, and the grease filling level in the bearing housing must reach two-thirds of its volume. After confirming that the system is in normal condition, close the discharge valve at the end of the system to prevent media leakage during water injection. Inject process water into the system through the inlet at the top of the holding tank. During water injection, observe the magnetic level gauge on the side wall of the holding tank. Stop water injection when the liquid level rises to the 65% mark of the total system volume. This liquid level range ensures that a continuous and complete aqueous phase medium is formed inside the system, avoiding direct contact between steam and the equipment's inner wall, thus preventing localized condensation hotspots, and providing sufficient heat carrier for subsequent thermal circulation processes. After the water injection operation is completed, the closed status of all manual and pneumatic valves must be verified a second time. Special attention should be paid to checking whether the sealing gaskets at the pipe flange connections are tightened to ensure that the system's sealing integrity meets the sterilization process requirements.

[0024] During the heating and circulation start-up phase, the steam ejector control valve at the top of the holding tank is opened, introducing saturated steam at a pressure of 0.9 MPa. The steam generates a negative pressure effect as it passes through the throat of the Venturi-structured ejector, drawing surrounding liquid into the mixing chamber for efficient heat exchange. A Pt100 platinum resistance temperature sensor is used, with its probe directly immersed in the flowing liquid layer in the middle of the holding tank to monitor the circulating water temperature changes in real time. The control system collects temperature data every 200 ms and dynamically adjusts the opening of the electric regulating valve on the steam pipeline using a proportional-integral-derivative algorithm. Initially, the opening is slowly increased to 30%, gradually increasing to 60% once the temperature reaches 100 degrees Celsius, ensuring the water temperature is uniformly raised to within 130 ± 5 degrees Celsius within 25 minutes. Specifically, the steam valve opening is dynamically adjusted using a PID algorithm to control the steam flow rate. Once the target temperature is reached, the circulation pump is immediately started. This high-temperature centrifugal pump uses an open impeller structure, and its flow channel design allows solid particles up to 5 mm to pass through. Adjust the pump outlet valve opening to stabilize the fluid velocity in the pipeline at 1.8 m / s. Under this velocity condition, the fluid Reynolds number exceeds 4,000, forming a fully developed turbulent state in the pipeline and enhancing the scouring ability of the equipment dead zone area.

[0025] During the isothermal sterilization stage, the system temperature was maintained within the range of 130±5℃ for 40 minutes. The temperature control module set up multiple monitoring points at key parts of the system, including the sedimentation zone at the bottom of the tank, the outside of the 90° bend in the pipeline, and the inlet and outlet positions of the heat exchanger. The temperature difference between each measuring point was strictly controlled within ±2℃. The system pressure was maintained at 0.35MPa through a pilot-operated pressure reducing valve. This pressure value is significantly higher than the saturated vapor pressure of water at 130℃ (270kPa), effectively suppressing temperature fluctuations caused by water evaporation. The 40-minute circulation time was determined based on a microbial thermal lethality kinetic model. For *Bacillus stearothermophilus*, a common bacterium in xanthan gum fermentation systems, its D-value is 1.8 min at 130℃. Calculations based on the 12D sterilization standard showed that 40 minutes ensures a microbial survival probability of less than one in a million. During circulation, a flow velocity of 1.8 m / s generated Dean vortices at the large-arc bend in the continuous sterilization and feeding pipeline. The secondary flow effect enhanced the shearing action on microorganisms attached to the pipe wall.

[0026] During the sterilization and drainage phases, the main shut-off valve of the steam pipeline is first closed to stop the steam supply. Then, after a 30-second delay, the circulating pump is stopped, utilizing the system's residual heat to maintain a brief circulation. The drain valves at the lowest point of the system are opened, using a gradient pressure reduction operation mode. First, the main drain valve (100mm diameter) on the main pipeline is opened. Once the system pressure drops to 0.1MPa, the auxiliary drain valves (50mm diameter) on the branch pipelines are opened sequentially. Simultaneously, the compressed air purging system is activated during drainage. The pressure reducing valve is adjusted to stabilize the air pressure at 0.25MPa, and the purging time lasts for 4 minutes. Compressed air is injected into the pipeline system through a ring distributor, achieving an airflow velocity of 15m / s. The shearing action of the gas-liquid two-phase flow effectively removes residual water droplets from pipe bends and valve gaps. After purging, an endoscope is used to inspect critical connections to confirm the absence of visible water film residue, avoiding the risk of secondary contamination.

[0027] The process water used is ultrapure water produced by a deionized water preparation system, with a conductivity ≤10μS / cm and a chloride ion concentration below 0.1mg / L, significantly reducing the risk of chloride ion pitting corrosion on stainless steel equipment under high-temperature conditions. During the heating process, the mass flow ratio of steam to water is monitored in real time by a flow meter and maintained at an optimal ratio of 1:9. This ratio ensures heating efficiency while avoiding excessive steam condensation that could lead to system water imbalance. The holding tank is made of 316L stainless steel, with an inner surface mechanically polished to a surface roughness Ra value ≤0.8μm, reducing the probability of protein-based scale adhesion. The continuous discharge piping layout adopts a large-arc elbow design with a pipe diameter three times the pipe diameter, combined with a circulation velocity of 1.8m / s, forming a stable Dean vortex at the bend, enhancing the mechanical scouring effect on the pipe wall.

[0028] The temperature control module integrates six temperature sensors, with three measurement levels (upper, middle, and lower) along the axial direction of the holding tank. Two measuring points are evenly distributed circumferentially on each level to comprehensively monitor the temperature field distribution. Pressure control employs a pilot-operated pressure reducing valve with a diaphragm actuator response time ≤0.5s. When the system pressure exceeds 0.4MPa, the pressure relief valve automatically opens to prevent overpressure operation. The circulating pump's mechanical seal uses a hard alloy and silicon carbide friction pair, and the cooling water system ensures the sealing chamber temperature is ≤80℃, guaranteeing pump reliability under high-temperature conditions. The ratio of the steam ejector throat diameter to the inlet pipe diameter is 1:2.5, and the mixing chamber length is designed to be five times the throat diameter, ensuring thorough mixing of steam and liquid.

[0029] Example 2

[0030] In the sterilization process following a regular overhaul of the xanthan gum fermentation system, an enhanced sterilization procedure is implemented to address any persistent biofilm within the system. During system inspection and water injection, after injecting the standard process water, an additional 0.5% food-grade hydrogen peroxide solution is added as a sterilization enhancer. The total water volume is controlled to 70% of the system's total volume to provide ample mixing space for the chemical additives. During heating and circulation start-up, the time to reach 130±5℃ is extended to 35 minutes to ensure sufficient activation of the hydrogen peroxide during the heating phase. The circulation pump flow rate is adjusted to 2.0 m / s to enhance the mechanical removal of the attached biofilm.

[0031] The constant-temperature sterilization phase was maintained for 45 minutes, with the system pressure controlled at 0.35 MPa. Hydrogen peroxide decomposed at 130°C to generate hydroxyl radicals, which, in synergy with heat sterilization, effectively destroyed the protective outer layer of spores. During the circulation process, the residual concentration of hydrogen peroxide in the water was checked every 10 minutes to ensure it remained within the effective range of 0.3% to 0.5%. In the drainage phase after sterilization, the sterilized liquid containing hydrogen peroxide was first discharged, followed by two system flushes with deionized water, each flushing using 50% of the system volume at a flow rate of 1.5 m / s. Finally, compressed air purging was performed, with the purging pressure increased to 0.3 MPa and the duration extended to 5 minutes, ensuring no chemical residue remained in the system.

[0032] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. A method for hydrothermal sterilization of a xanthan gum fermentation system, characterized in that, The method includes the following steps: S1, System Inspection and Water Injection: Check the sealing of the valves in the continuous disinfection system and the operating status of the circulating pump. Close the system discharge valve and inject process water into the holding tank and continuous disinfection pipeline up to the liquid level mark. S2, Heating and Circulation Start-up: Turn on the steam injector of the holding tank, introduce saturated steam, monitor the circulating water temperature in real time through the temperature sensor, adjust the steam flow rate to raise the water temperature to 130±5℃, start the circulation pump after reaching the target temperature, and control the circulation flow rate to 1.5-2.0m / s. S3, Constant Temperature Sterilization Stage: Maintain water temperature at 130±5℃ and circulate continuously for 40 minutes, during which the system pressure is maintained at 0.3-0.4MPa by a pressure sensor; S4, Sterilization complete and drainage: Close the steam valve, stop the circulation pump, open the system drain valve to drain the hot water, and at the same time, introduce compressed air to purge the residual moisture in the pipes; In step S1, the injection volume of process water accounts for 60%-70% of the total system volume. In step S2, the pressure range of saturated steam is 0.8-1.0 MPa, and a Pt100 platinum resistance probe is used as the temperature sensor with a measurement accuracy of ±0.1℃. Real-time data feedback is sent to the control system, and the steam valve opening is dynamically adjusted using a PID algorithm to uniformly raise the water temperature to 130±5℃ within 20-30 minutes. The flow rate of the circulating pump is set to 1.5-2.0 m / s. In step S3, the system pressure is maintained at 0.3-0.4 MPa, and the circulation time of 40 minutes is determined based on a microbial thermal lethality kinetic model. For Bacillus, a common bacterium in xanthan gum fermentation systems, the D value is 1.5-2.0 min at 130℃. Calculations using the 12D sterilization standard show that 40 minutes can ensure a microbial survival probability of less than 10%. -6 In step S4, the pressure of the compressed air is 0.2-0.3 MPa, and the purging time lasts for 3-5 minutes.

2. The hydrothermal sterilization method for the xanthan gum fermentation system according to claim 1, characterized in that, In step S1, all valves must be confirmed to be closed before water injection; in step S2, the circulation flow rate ensures that the water flow forms a turbulent state in the pipeline; in step S3, the system pressure value is higher than the saturated vapor pressure of water at 130℃; in step S4, a gradient pressure reduction operation is adopted during drainage, first opening the main pipeline drain valve, and then opening the branch valves in sequence.

3. The hydrothermal sterilization method for the xanthan gum fermentation system according to claim 1, characterized in that, The process water is deionized water with a conductivity ≤10μS / cm; during the process of raising the water temperature to 130±5℃, the mass flow ratio of steam to water is controlled at 1:8-1:

10.

4. The hydrothermal sterilization method for the xanthan gum fermentation system according to claim 1, characterized in that, The temperature sensor has monitoring points set at key parts of the system, including the bottom of the tank, pipe bends, and the inlet and outlet of the heat exchanger. The temperature difference between each measuring point is controlled within ±2℃. The pressure control adopts a pilot-operated pressure reducing valve with a response time of ≤0.5s. When the system pressure exceeds 0.4MPa, it automatically releases pressure.

5. A hydrothermal sterilization system employing the hydrothermal sterilization method for xanthan gum fermentation systems according to any one of claims 1-4, characterized in that, The system comprises the following components: a holding tank with a steam inlet and a water inlet at the top, and a circulating pump connected to the bottom via a pipe; a steam ejector with its inlet connected to the steam pipe of the holding tank and its outlet extending below the liquid level in the holding tank; a continuous discharge and feeding pipeline, including a main pipeline and several branch pipelines, which are respectively connected to a heat exchanger and a valve assembly; a circulating pump with its inlet connected to the bottom outlet of the holding tank and its outlet connected to the inlet of the continuous discharge and feeding pipeline; temperature sensors with probes arranged inside the holding tank and at key nodes of the pipeline; a pressure sensor with its interface located on the outlet pipeline of the circulating pump; and a control system that receives signals from the temperature and pressure sensors and outputs control commands to the steam valves and the circulating pump.

6. The hydrothermal sterilization system for the xanthan gum fermentation system according to claim 5, characterized in that, The volume of the maintenance tank is matched with the total volume of the system, and its inner wall is made of stainless steel with a surface roughness Ra≤0.8μm; the steam injector is a venturi structure with a throat diameter to steam inlet pipe diameter ratio of 1:2.

5.

7. The hydrothermal sterilization system for xanthan gum fermentation according to claim 5, characterized in that, The circulating pump is a high-temperature centrifugal pump with an open impeller that allows solid particles with a diameter of ≤5mm to pass through. The continuous discharge and feeding pipeline adopts a large-arc elbow design with a bending radius ≥3 times the pipe diameter.

8. The hydrothermal sterilization system for xanthan gum fermentation according to claim 5, characterized in that, The temperature control module integrates multiple temperature sensors; the pressure control uses a pilot-operated pressure reducing valve; and the process water is deionized water.

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