Astaxanthin crude extract pretreatment process based on multistage membrane filtration technology

Abstract

The present invention discloses an astaxanthin crude extract pretreatment process based on a multistage membrane filtration technology, and relates to the technical field of astaxanthin crude extract, the process comprises the following steps: rotary ceramic membrane dynamic cross flow primary filtration, hollow fiber nanofiltration membrane refining and roll type organic reverse osmosis membrane concentration, the astaxanthin crude extract is firstly screened to remove large particle impurities, and then temperature regulation and stabilization are performed to obtain an astaxanthin feed liquid; carrying out solid-liquid separation on the astaxanthin feed liquid through a tubular ceramic membrane to obtain clear permeate containing an astaxanthin fat-soluble compound; introducing the clarified permeate into a hollow fiber nanofiltration membrane system, and intercepting an astaxanthin lipid complex and free astaxanthin molecules to obtain a refined solution; introducing the refined solution into a roll-type reverse osmosis membrane system, and concentrating to obtain a pretreated concentrated solution; according to three-stage membrane filtration, directional capture of astaxanthin is realized through stepped separation of particle size exclusion, charge interception and molecular sieve separation. The multistage membrane process is obviously superior to the traditional process in core indexes such as astaxanthin recovery rate, purity, activity retention rate and the like.

Description

Technical Field

[0001] This invention relates to the field of astaxanthin crude extract technology, and in particular to a pretreatment process for astaxanthin crude extract based on multi-stage membrane filtration technology. Background Technology

[0002] Astaxanthin, a potent antioxidant, is in high demand in the food, pharmaceutical, and cosmetic industries. However, its production process faces numerous technical bottlenecks in the pretreatment of the crude extract. Currently, the mainstream industrial extraction processes mainly rely on organic solvent extraction and chemical saponification, both of which have significant drawbacks in terms of efficiency and product quality. Organic solvents are consumed in large quantities and pose safety risks: In the extraction of astaxanthin from Phaeformis yeast, dimethyl sulfoxide (DMSO) is required for cell disruption and acetone extraction. After optimization, the astaxanthin concentration in the extract is only 3.145 μg / mL, with solvent accounting for over 99%. Antarctic krill shell extraction uses a mixed solvent of isopropanol and hexane, which not only has low extraction efficiency but also poses flammability, explosiveness, and toxicity risks. These organic solvents are difficult to completely remove in subsequent processes, leading to potential solvent residue hazards in the product.

[0003] Traditional processes require multiple separation steps, including cell wall breaking, extraction, saponification, and concentration. The saponification process can take up to 12 hours (Antarctic krill shell saponification).

[0004] Chinese utility model patent with publication number CN217773295U discloses a high-efficiency extraction device for astaxanthin production. Although it introduces a dual motion mode of centrifugal rotation and reciprocating motion, and enhances mass transfer through the overflow hole of the sieve plate, it still cannot solve the problems of incomplete phase separation and severe emulsification, resulting in low single extraction rate and requiring multiple extractions.

[0005] Astaxanthin has a highly unsaturated structure and is extremely sensitive to light, heat, and oxygen. In existing processes, high-temperature cell disruption at 75.6℃ and high-pressure supercritical extraction at 30MPa lead to intensified isomerization, causing the trans structure to transform into the cis structure, resulting in a 20-40% reduction in biological activity. The saponification process still requires 12 hours at a low temperature (5℃), resulting in significant oxidative losses.

[0006] In addition to astaxanthin, the crude extract also contains impurities such as cell debris, lipoproteins, and free fatty acids. An attempt was made to extract astaxanthin by adding shrimp shells during the fermentation process of rice vinegar brewing, but the resulting product had a low astaxanthin content and introduced a large amount of interfering substances such as organic acids and alcohols, increasing the difficulty of subsequent purification. Summary of the Invention

[0007] To address the aforementioned technical problems, this invention provides a pretreatment process for crude astaxanthin extract based on multi-stage membrane filtration technology. The technical solution is as follows: A pretreatment process for crude astaxanthin extract based on multi-stage membrane filtration technology includes dynamic cross-flow primary filtration with a rotating ceramic membrane, purification with a hollow fiber nanofiltration membrane, and concentration with a spiral wound organic reverse osmosis membrane. The pretreatment process includes the following steps: Step 1: First, large particles of impurities are removed from the crude astaxanthin extract, and then the temperature is adjusted and stabilized to obtain the astaxanthin liquid. Step 2: The astaxanthin solution is separated into solid and liquid phases by passing it through a tubular ceramic membrane to obtain a clarified permeate containing the astaxanthin lipid-soluble complex. Step 3: The clarified permeate obtained in Step 2 is introduced into a hollow fiber nanofiltration membrane system to retain astaxanthin lipid complexes and free astaxanthin molecules to obtain a purified solution. Step 4: The purified solution obtained in Step 3 is introduced into a spiral wound reverse osmosis membrane system for concentration to obtain a pretreated concentrate.

[0008] Optionally, in step 1, the crude astaxanthin extract is passed through a 140-160 mesh sieve to obtain filtrate. The visual image of the filtrate is captured, and the temperature of the filtrate is regulated to the target temperature by an intelligent temperature controller based on the astaxanthin stability model at the temperature change rate given by the model. After stabilization, the astaxanthin solution is obtained.

[0009] Optionally, the intelligent temperature controller regulates the filtrate temperature by including the following steps: Step a: Enter the source type of astaxanthin raw material. The source types of astaxanthin raw material include Pharbitis fermentation broth, shrimp shell extract, and microalgae cell wall breaking broth. Step b: Call the corresponding sub-model based on the source type of astaxanthin raw materials; Step c: Calculate the rate of temperature change based on the sub-model and real-time data. ; Based on real-time temperature Compared with the target temperature reference The absolute values ​​of the differences are used for tiered calculation: when Then output =2℃ / min; when Then output =1.5℃ / min; when Then output =1℃ / min; Step d, the controller bases the temperature change rate on... The PID algorithm drives the constant temperature heat exchanger to regulate the filtrate temperature to the target temperature. When the astaxanthin solution enters a stable period of 4-6 minutes, the astaxanthin solution is obtained.

[0010] Optionally, sub-models include the Phafedomyelin source sub-model, the shrimp shell extract source sub-model, and the microalgae source model; The Phaef yeast source model uses 34℃-36℃ as the target temperature baseline and incorporates a temperature-related equation for yeast protease activity. The shrimp shell extract source model uses 14℃-16℃ as the target temperature benchmark and integrates the chitin swelling coefficient temperature curve. The microalgae source model uses 24℃-26℃ as the target temperature benchmark and includes a temperature influence function for phycocyanin residue.

[0011] Optionally, in step 1, the viscosity of the filtrate is monitored in real time. If the viscosity of the filtrate exceeds the set viscosity threshold, 0.1wt%-0.3wt% of modified lecithin is added.

[0012] Optionally, in step 2, the tubular ceramic membrane is a tubular type. Ceramic membrane with a surface-grafted dopamine-trehalose composite layer, pore size 0.3-0.6μm; The tubular ceramic membrane adopts a dual-drive rotation structure with a shear rate of 1200-1500. Combined with pulsed electric assisted filtration, charged impurities are repelled by electrostatic discharge; The crossflow velocity of the tubular ceramic membrane is 3.3 m / s-3.7 m / s, the operating pressure is 1.6-2.0 bar, and gas-liquid synergistic backwash is performed every 25-35 minutes. The gas-liquid synergistic backwash first uses a nitrogen pulse of 0.2s-0.4s, followed by a deionized water flush of 0.15s-0.25s.

[0013] Optionally, in step 3, the hollow fiber nanofiltration membrane system uses a gradient pore size PES base membrane with zwitterionic sulfonate betaine grafted on the surface. The zeta potential is dynamically adjusted to -25±3mV. It utilizes a dual mechanism of charge repulsion and molecular sieving to retain astaxanthin lipid complexes and free astaxanthin, while allowing monosaccharides, inorganic ions, and residual solvents to pass through.

[0014] Optionally, in step 4, the spiral wound reverse osmosis membrane uses an asymmetric polyamide active layer, and the flow channel is equipped with a diamond-shaped guide mesh, and the concentration is achieved through segmented pressure swing. The initial pressure is 4.5MPa-5.5MPa, and the subsequent pressure is 5.5-6.5MPa. Combined with the reduced feed temperature gradient, astaxanthin thermal isomerization is suppressed, the concentration factor is stabilized at 5-10 times, and the soluble solids are 15°-20°Brix.

[0015] Optionally, an integrated online high-performance liquid chromatography-ultraviolet spectroscopy system can be used to detect the clarified permeate every 4-6 minutes. When the detected transmittance is greater than 0.5%, the transmembrane pressure difference across the spiral wound reverse osmosis membrane is automatically increased to 0.08MPa-0.12MPa.

[0016] Optionally, the permeate from the dynamic cross-flow primary filtration by rotating ceramic membrane, the purification by hollow fiber nanofiltration membrane, and the concentration by spiral wound organic reverse osmosis membrane is used to recover organic solvents via a composite molecular sieve adsorption tower.

[0017] In summary, the present invention has at least one of the following beneficial technical effects: This invention provides a pretreatment process for crude astaxanthin extract based on multi-stage membrane filtration technology. The three-stage membrane filtration achieves targeted capture of astaxanthin through stepwise separation of particle size exclusion, charge retention, and molecular sieving.

[0018] Multi-stage membrane technology is significantly superior to traditional processes in key indicators such as astaxanthin recovery rate, purity, and activity retention rate, while greatly reducing solvent consumption, energy consumption, and processing time, making it suitable for industrial production of multi-raw material systems. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the pretreatment process of astaxanthin crude extract based on multi-stage membrane filtration technology according to the present invention. Figure 2 This is a schematic diagram of the effect of the clarified permeate obtained by the pretreatment process of astaxanthin crude extract based on multi-stage membrane filtration technology according to the present invention. Figure 3 This is a schematic diagram illustrating the effect of the refined liquid obtained from the pretreatment process of astaxanthin crude extract based on multi-stage membrane filtration technology according to the present invention. Figure 4 This is a schematic diagram illustrating the effect of the pretreated concentrate obtained from the pretreatment process of astaxanthin crude extract based on multi-stage membrane filtration technology according to the present invention. Detailed Implementation

[0020] The present invention will be further described in detail below with reference to the accompanying drawings.

[0021] This invention discloses a pretreatment process for crude astaxanthin extract based on multi-stage membrane filtration technology.

[0022] Reference Figures 1-4 Example 1: A pretreatment process for crude astaxanthin extract based on multi-stage membrane filtration technology, comprising dynamic cross-flow primary filtration with a rotating ceramic membrane, purification with a hollow fiber nanofiltration membrane, and concentration with a spiral wound organic reverse osmosis membrane. The pretreatment process includes the following steps: Step 1: First, large particles of impurities are removed from the crude astaxanthin extract, and then the temperature is adjusted and stabilized to obtain the astaxanthin liquid. Step 2: The astaxanthin solution is separated into solid and liquid phases by passing it through a tubular ceramic membrane to obtain a clarified permeate containing the astaxanthin lipid-soluble complex. Step 3: The clarified permeate obtained in Step 2 is introduced into a hollow fiber nanofiltration membrane system to retain astaxanthin lipid complexes and free astaxanthin molecules to obtain a purified solution. Step 4: The purified solution obtained in Step 3 is introduced into a spiral wound reverse osmosis membrane system for concentration to obtain a pretreated concentrate.

[0023] By adopting the above technical solution, the three-stage membrane filtration achieves the targeted capture of astaxanthin through a stepwise separation of particle size exclusion, charge retention, and molecular sieving. The rotating ceramic membrane pre-filtration can retain more than 99% of large particulate impurities such as bacterial fragments and chitin, preventing astaxanthin from being lost with the solid phase; Hollow fiber nanofiltration membranes retain astaxanthin-lipid complexes and free astaxanthin through charge repulsion and molecular sieving. The high-efficiency concentration of spiral-wound reverse osmosis membranes further reduces the loss of target substances, and the final total recovery rate of astaxanthin is significantly improved compared with traditional processes.

[0024] The entire process is controlled at low temperatures, avoiding astaxanthin isomerization caused by high temperatures in traditional processes. The trans structure is retained at a very high rate, and the loss of bioactivity is significantly reduced compared to traditional processes.

[0025] Through precise separation using hollow fiber nanofiltration membranes, small molecule impurities (monosaccharides, inorganic ions, residual solvents, etc.) in the crude extract can be efficiently removed, with a monosaccharide removal rate of over 90% and inorganic ions ( , The removal rate is greater than 90%, and the content of residual solvents such as acetone in the permeate is extremely low; the purity of astaxanthin in the final purified solution is greatly improved, meeting the feed requirements for downstream chromatography purification.

[0026] It integrates online ultraviolet spectroscopy, HPLC, viscometer and other monitoring systems, which can provide real-time feedback on parameters such as astaxanthin transmittance and concentration, and dynamically adjust key parameters such as transmembrane pressure difference and temperature to ensure process stability and avoid product fluctuations caused by human operation errors.

[0027] It can process crude extracts from different sources, such as Pharbitis fermentation broth, shrimp shell extract, and microalgae cell wall breaking liquid. By adjusting the parameters accordingly, it can meet the characteristic requirements of different raw materials, solve the dependence of traditional processes on a single raw material, and is suitable for industrial promotion.

[0028] In Example 2, in step 1, the crude astaxanthin extract is passed through a 140-160 mesh sieve to obtain filtrate. The visual image of the filtrate is captured, and the temperature of the filtrate is regulated to the target temperature by an intelligent temperature controller based on the astaxanthin stability model at the temperature change rate given by the model. After stabilization, the astaxanthin solution is obtained.

[0029] Example 3: The intelligent temperature controller regulates the filtrate temperature by including the following steps: Step a: Enter the source type of astaxanthin raw material. The source types of astaxanthin raw material include Pharbitis fermentation broth, shrimp shell extract, and microalgae cell wall breaking broth. Step b: Call the corresponding sub-model based on the source type of astaxanthin raw materials; Step c: Calculate the rate of temperature change based on the sub-model and real-time data. ; Based on real-time temperature Compared with the target temperature reference The absolute values ​​of the differences are used for tiered calculation: when Then output =2℃ / min; when Then output =1.5℃ / min; when Then output =1℃ / min; Step d, the controller bases the temperature change rate on... The PID algorithm drives the constant temperature heat exchanger to regulate the filtrate temperature to the target temperature. When the astaxanthin solution enters a stable period of 4-6 minutes, the astaxanthin solution is obtained.

[0030] Example 4, the sub-models include the Phaefoetida source sub-model, the shrimp shell extract source sub-model, and the microalgae source model; The Phaef yeast source model uses 34℃-36℃ as the target temperature baseline and incorporates a temperature-related equation for yeast protease activity. The shrimp shell extract source model uses 14℃-16℃ as the target temperature benchmark and integrates the chitin swelling coefficient temperature curve. The microalgae source model uses 24℃-26℃ as the target temperature benchmark and includes a temperature influence function for phycocyanin residue.

[0031] In Example 5, in step 1, the viscosity of the filtrate is monitored in real time. If the viscosity of the filtrate exceeds the set viscosity threshold, 0.1wt%-0.3wt% of modified lecithin is added.

[0032] By adopting the above technical solution, the 140-160 mesh sieve filter specifically removes large particulate impurities in the crude extract, such as shrimp shell fragments, intact bacterial cells, and microalgae cell wall residues. The sieve aperture is adapted to the typical large particle size in the astaxanthin crude extract, with a particle size greater than 100μm and a rejection efficiency of ≥99%. This can avoid flux attenuation caused by large particle blockage in the subsequent tubular ceramic membrane and extend the service life of the membrane module.

[0033] Meanwhile, visual monitoring of the filtrate is achieved by capturing images of the pretreatment effect. By analyzing RGB values ​​or correlating turbidity, it is possible to quickly determine whether the screening is thorough. If there are no obvious suspended particles in the image, it is considered qualified, providing an intuitive basis for subsequent process parameter adjustments, reducing manual sampling errors, and improving the consistency of pretreatment.

[0034] By precisely matching raw material type, sub-model, and target temperature, targeted temperature control is achieved for crude astaxanthin extracts from different sources, solving the problem that traditional single temperature control cannot adapt to the characteristics of multiple raw materials. For the crude extract of Pharrellis, the target temperature of the Pharrellis sub-model is 34-36℃, preferably 35℃. By inhibiting the activity of yeast protease, based on the temperature-protease activity correlation equation, astaxanthin degradation caused by high temperature activation of protease is avoided. The temperature-dependent equation for yeast protease activity was established based on the Arrheniuse equation, which describes the quantitative relationship between the chemical reaction rate constant and temperature. This equation is applicable to the regulation of protease activity by temperature in enzymatic reactions. Equation form: ; Where k is the protease activity rate constant, and A is the pre-factor, reflecting the collision frequency of enzyme molecules. It is the activation energy, which characterizes the temperature sensitivity of protease activity; It is the gas constant, and T is the absolute temperature.

[0035] For the shrimp shell extract, the target temperature for the shrimp shell source model is 14-16℃, preferably 15℃. Based on the chitin swelling coefficient-temperature curve, the swelling of chitin at high temperatures can be reduced, and the impurities released during swelling can be prevented from combining with astaxanthin to form difficult-to-separate complexes. The swelling coefficient (Q) of chitin is defined as the ratio of the volume after swelling to the initial volume. The chitin swelling coefficient-temperature curve can be obtained through experimental fitting.

[0036] The mathematical expression is: ; in It is the initial swelling coefficient. It is the linear expansion coefficient. It is a nonlinear correction coefficient. It is the reference temperature.

[0037] For the microalgae cell wall disruption solution, the microalgae source model uses a target temperature of 24-26℃, preferably 25℃. The precipitation of phycocyanin is controlled by the temperature effect function of phycocyanin residue, which reduces membrane fouling caused by precipitation and avoids oxidation of microalgae-derived astaxanthin caused by high temperature.

[0038] The temperature effect function of phycocyanin residue is described using an sigmoid curve (Logistic function) to represent the change of phycocyanin residue with temperature. This model is applicable to the thermal denaturation process of protein secondary structure, and its mathematical expression is as follows: ; in It's the residual amount. is the half-deactivation temperature, which is the temperature at which the residual amount drops to 50%. b is the slope parameter, which reflects the temperature sensitivity. The smaller b is, the steeper the curve.

[0039] The temperature change rate is calculated in stages based on temperature difference, avoiding localized temperature fluctuations caused by traditional uniform heating or cooling. When the temperature difference is small, a higher rate of 2℃ / min is used to shorten the temperature control time and reduce the exposure of astaxanthin in non-optimal temperature ranges; When there is a large temperature difference, a lower rate of 1℃ / min is used to avoid temperature overshoot caused by rapid temperature control. For example, if the target temperature is 15℃, the astaxanthin lipid complex will aggregate due to rapid cooling to 12℃. The trans-astaxanthin isomerization rate can be controlled to less than 1%. The stabilization period is 4-6 minutes, preferably 5 minutes, to stabilize the molecular structure of astaxanthin, providing a uniform feed solution for subsequent membrane filtration and improving the stability of membrane retention efficiency.

[0040] Real-time viscosity monitoring and the addition of modified lecithin solved the flowability problem of high-viscosity liquids, such as concentrated yeast fermentation broth and low-temperature shrimp shell extract. When the viscosity exceeds the viscosity threshold, the viscosity threshold is typically set to... Adding 0.1-0.3 wt% modified lecithin, preferably 0.2 wt%, (hydroxylation modification increases its affinity for astaxanthin) can reduce the viscosity by decreasing the friction within the liquid. This ensures that the cross-flow velocity of the subsequent tubular ceramic membrane is stable at 3.3-3.7 m / s, avoiding concentration polarization caused by insufficient flow rate due to high viscosity; The addition of modified lecithin does not affect the activity of astaxanthin. HPLC analysis shows that there is no significant loss of astaxanthin content after addition, and it can reduce protein adsorption on the membrane surface and lower the membrane fouling index.

[0041] Through the synergistic optimization of precise screening, raw material matching temperature control, and dynamic viscosity adjustment, the targeting and stability of astaxanthin crude extract pretreatment are significantly improved, providing high-quality and uniform feed for subsequent multi-stage membrane filtration. Ultimately, this helps to improve astaxanthin recovery rate and activity retention rate, reduce the risk of process fluctuations, and has strong industrial application value.

[0042] Example 6, in step 2, the tubular ceramic membrane is tubular. Ceramic membrane with a surface-grafted dopamine-trehalose composite layer, pore size 0.3-0.6μm; The tubular ceramic membrane adopts a dual-drive rotation structure with a shear rate of 1200-1500. Combined with pulsed electric assisted filtration, charged impurities are repelled by electrostatic discharge; The crossflow velocity of the tubular ceramic membrane is 3.3 m / s-3.7 m / s, the operating pressure is 1.6-2.0 bar, and gas-liquid synergistic backwash is performed every 25-35 minutes. The gas-liquid synergistic backwash first uses a nitrogen pulse of 0.2s-0.4s, followed by a deionized water flush of 0.15s-0.25s.

[0043] In Example 7, in step 3, the hollow fiber nanofiltration membrane system uses a gradient pore size PES base membrane with zwitterionic sulfonate betaine grafted on the surface. The zeta potential is dynamically adjusted to -25±3mV. It utilizes a dual mechanism of charge repulsion and molecular sieving to retain astaxanthin lipid complexes and free astaxanthin, while allowing monosaccharides, inorganic ions, and residual solvents to pass through.

[0044] By adopting the above technical solution, the dopamine-trehalose composite layer is formed through mussel-inspired biochemical grafting. Dopamine self-polymerizes to form an adhesive layer, while trehalose is covalently bonded via ether bonds, exhibiting both hydrophilicity and resistance to biofouling. The hydroxyl groups of trehalose form transient hydrogen bonds with astaxanthin molecules, reducing the irreversible adsorption of astaxanthin on the membrane surface. The hydration layer formed on the surface of the composite layer effectively repels macromolecular impurities such as proteins and polysaccharides, thus reducing the membrane fouling rate.

[0045] The gradient pore size distribution of 0.3-0.6μm (inner 0.6μm support layer + outer 0.3μm separation layer) enables efficient retention of yeast fragments and chitin particles, while ensuring smooth permeation of astaxanthin lipid complexes.

[0046] In Example 8, step 4, the spiral wound reverse osmosis membrane uses an asymmetric polyamide active layer, and the flow channel is equipped with a diamond-shaped guide mesh. It is concentrated through segmented pressure swing. The initial pressure is 4.5MPa-5.5MPa, and the subsequent pressure is 5.5-6.5MPa. Combined with the reduced feed temperature gradient, astaxanthin thermal isomerization is suppressed, the concentration factor is stabilized at 5-10 times, and the soluble solids are 15°-20°Brix.

[0047] By adopting the above technical solution, the spiral wound reverse osmosis membrane employs an asymmetric structure with a dense surface layer and a porous support layer: The dense surface layer can completely retain astaxanthin-lipid complex (molecular weight of about 800 Da) and free astaxanthin (596.8 Da) through molecular sieving effect, preventing the target substance from being lost with the permeate; The porous support layer reduces the mass transfer resistance between water and solvent, achieving a permeation flux of 25-30 L / ( This shortens the processing time and reduces the exposure time of astaxanthin in the membrane system at the same concentration factor.

[0048] The flow channel is designed with a diamond-shaped guide net, which is different from the traditional straight-line guide net: The rhomboid structure causes the liquid to form a spiral turbulence in the flow channel, which disrupts the concentration polarization layer on the membrane surface and prevents astaxanthin from polymerizing due to excessively high local concentrations. The rhomboid mesh fluid distribution design ensures that the flow velocity deviation within the channel is less than 5%, avoiding the deposition of impurities (such as inorganic salts and small molecule sugars) caused by local dead volumes, and reducing the membrane fouling rate.

[0049] A segmented pressure strategy is adopted, with an initial pressure of 4.5-5.5 MPa (preferably 5 MPa) and a subsequent pressure of 5.5-6.5 MPa (preferably 6 MPa), to precisely match the changes in solution characteristics during concentration. Low-pressure energy saving in the early stage: The viscosity of the solution is low in the initial stage of concentration, and the mass transfer requirements can be met by a pressure of 5MPa, which reduces energy consumption compared to the high pressure of 6MPa throughout the process. High-pressure concentration in the later stages maintains efficiency: During the later stages of concentration, the solution viscosity increases to... Mass transfer resistance increases significantly, but a pressure of 6 MPa can maintain a stable permeation flux, ensuring that the concentration factor remains stable at 5-10 times.

[0050] By reducing the feed temperature gradient, the heat sensitivity of astaxanthin is specifically addressed. Astaxanthin is prone to trans- and cis-isomerization at high temperatures, but a temperature gradient of 20-25℃ can control the isomerization rate to less than 3%. At low temperatures, the molecular motion rate of astaxanthin decreases, weakening its interaction with the membrane surface. Combined with the forced retention by segmented high voltage, this further reduces permeation loss caused by changes in molecular configuration.

[0051] Example 9: An integrated online high-performance liquid chromatography and ultraviolet spectroscopy system was used to detect the clarified permeate every 4-6 minutes. When the detected transmittance was greater than 0.5%, the transmembrane pressure difference across the spiral wound reverse osmosis membrane was automatically increased to 0.08 MPa-0.12 MPa.

[0052] By adopting the above technical solution, online high performance liquid chromatography can accurately quantify the absolute content of astaxanthin in the permeate, and ultraviolet spectroscopy (475nm) can quickly reflect the concentration change through the intensity of characteristic peaks. The combination of the two achieves dual verification of qualitative and quantitative results, which improves the accuracy by 30% compared with a single detection method.

[0053] Detection every 4-6 minutes can capture process fluctuations, such as sudden changes in raw material concentration or early-stage membrane fouling, while avoiding the waste of system resources caused by overly frequent detection. This frequency ensures that astaxanthin permeability is detected within one detection cycle when it exceeds 0.5%, improving response speed compared to traditional offline detection and reducing target material loss.

[0054] When the permeate rate exceeds 0.5% (i.e., the astaxanthin loss with the permeate exceeds 0.5% of the total feed), the transmembrane pressure differential is automatically increased by 0.08-0.12 MPa, preferably 0.1 MPa, to enhance the membrane's mechanical retention and charge repulsion effect. The increased pressure differential makes the membrane pores more compact, strengthening the repulsion force against the astaxanthin-lipid complex. This can reduce the permeate rate to below 0.3% within 10 minutes, and a single adjustment can reduce astaxanthin loss by approximately 2-3 kg / ton of feed.

[0055] The 0.1MPa differential pressure adjustment range has been optimized to avoid the problem that too small an adjustment cannot effectively improve retention, while preventing membrane compaction or energy consumption surge caused by too large an adjustment, thus balancing retention efficiency and membrane life.

[0056] In Example 10, the permeate from the dynamic cross-flow primary filtration by a rotating ceramic membrane, the purification by a hollow fiber nanofiltration membrane, and the concentration by a spiral wound organic reverse osmosis membrane was used to recover the organic solvent via a composite molecular sieve adsorption tower.

[0057] By employing the above technical solution, the composite molecular sieve possesses precise pore size matching and surface polarity control capabilities, enabling it to specifically adsorb residual organic solvents in the permeate, such as ethanol, acetone, and ethyl acetate commonly used in astaxanthin extraction, while effectively adsorbing water molecules or inorganic ions (e.g., water molecules or inorganic ions in the permeate)... , With an adsorption rate of less than 5%, targeted adsorption is achieved. Compared with traditional activated carbon adsorption, the organic solvent recovered by the composite molecular sieve can reach a purity of over 95%, meeting the recycling requirements of the astaxanthin extraction process. The solvent recycling rate is greatly improved, and the amount of new solvent used is reduced compared with the non-recovery process.

[0058] The following describes the implementation principle of the present invention using specific embodiments: Multi-stage membrane process steps for Pharf yeast fermentation broth: The Fabry yeast fermentation broth (initial astaxanthin concentration 12.5 μg / mL) was filtered through a 150-mesh sieve, and the filtrate was photographed to confirm that there were no obvious particles. The intelligent temperature control system uses the Phaefoetida source model, with a target temperature of 35℃, an initial temperature of 20℃, a temperature difference of 15℃, and a heating rate of 1℃ / min, stabilizing for 5 minutes, during which the viscosity is monitored. The value is within the threshold, so there is no need to add modified lecithin. Rotating ceramic membrane, 0.5μm, dopamine-trehalose composite layer, dynamic cross-flow primary filtration, rotation speed 2000rpm, cross-flow velocity 3.5m / s, pressure 1.8bar, gas-liquid backwash every 30min; Hollow fiber nanofiltration membrane, 500 Da cutoff, Zeta potential -25 mV, purified, pressure 1.0 MPa, 25 °C, online HPLC-UV monitoring showed a transmittance of less than 0.3%; Spiral wound reverse osmosis membrane, polyamide active layer segmented concentration, 5.0 MPa in the front section and 6.0 MPa in the back section, temperature reduced from 25℃ to 20℃, concentrated to 18°Brix; Acetone was recovered from the liquid via a composite molecular sieve adsorption tower, with a recovery rate of 96%.

[0059] Multi-stage membrane processing steps for Antarctic krill shell extract: Antarctic krill shell extract (initial astaxanthin concentration 8.2 μg / g) was filtered through a 140-mesh sieve. The viscosity of the filtrate was... Adding 0.2wt% modified lecithin reduced the ; The intelligent temperature control system calls the shrimp shell source model, with a target temperature of 15℃, an initial temperature of 30℃, a temperature difference of 15℃, and a cooling rate of 1℃ / min, stabilizing for 5 minutes. Rotating ceramic membrane pre-filtration, 0.5μm, dopamine-trehalose composite layer, dynamic cross-flow pre-filtration, rotation speed 2000rpm, cross-flow velocity 3.5m / s, pressure 1.8bar, gas-liquid backwash every 30min, retaining chitin particles; Hollow fiber nanofiltration membrane refining, pressure 0.9MPa, 25℃, to remove saponification residue NaOH and free fatty acids; Reverse osmosis concentration to 16°Brix, with 95% isopropanol recovery from the permeate.

[0060] Multi-stage membrane process steps for Haematococcus pluvialis cell wall disruption solution: The Haematococcus pluvialis cell wall disruption solution (initial astaxanthin concentration 15.8 μg / mL) was filtered through a 160-mesh sieve. The intelligent temperature control called the microalgae source model, with 25℃ as the target temperature, an initial temperature of 10℃, a temperature difference of 15℃, and a temperature increase rate of 1.5℃ / min, and stabilized for 5min. Rotating ceramic membrane primary filtration, 0.5μm, dopamine-trehalose composite layer, dynamic cross-flow primary filtration, rotation speed 2000rpm, cross-flow velocity 3.5m / s, pressure 1.8bar, gas-liquid backwash every 30min, retaining unbroken algal cells; Hollow fiber nanofiltration membrane is refined at a pressure of 1.1 MPa and a temperature of 25°C to remove residual phycocyanin. The solution was concentrated to 20°Brix by reverse osmosis, and ethyl acetate was recovered from the permeate with a recovery rate of 97%.

[0061] Table 1 shows a comparison of the detection results of key indicators such as astaxanthin recovery rate, purity, and activity retention rate between multi-stage membrane process and traditional solvent extraction method: Table 1 detection indicators Raw material type Traditional crafts Multi-stage membrane process Improvement effect Astaxanthin recovery rate Favour yeast 72% (DMSO cell disruption + acetone extraction) 94% Increased by 22% Antarctic krill shells 68% (isopropanol-hexane extraction + saponification) 93% Increase by 25% Haematococcus pluvialis <![CDATA[75% (supercritical CO2 extraction, 30 MPa / 50 °C)]]> 95% Increase by 20% Product purity Favour yeast 63% (including yeast protein impurities) 88% Increase by 25% Antarctic krill shells 60% (including chitin degradation products) 86% Increased by 26% Haematococcus pluvialis 65% (containing phycocyanin) 89% Increased by 24% Inverse structure retention rate Favour yeast 75% (isomerization caused by cell wall disruption at 75.6℃) 97% Increased by 22% Antarctic krill shells 80% (oxidation loss after 12 hours of saponification) 96% Increase by 16% Haematococcus pluvialis 70% (supercritical extraction at 50℃) 98% Increased by 28% Solvent consumption Favour yeast 77.4 mL / g dried bacterial cells (acetone) 5.4 mL / g dry bacterial cells (acetone, recovery rate 96%) Reduced by 93% Antarctic krill shells 50 mL / g shrimp shell (isopropanol-hexane) 3.5 mL / g shrimp shell (isopropanol, recovery rate 95%) Reduced by 93% Haematococcus pluvialis 30 mL / g algae (ethyl acetate) 2.1 mL / g algae (ethyl acetate, recovery rate 97%) Reduced by 93% Energy consumption Favour yeast 0.8kWh / m³ 0.3kWh / m³ Reduced by 62.5% Antarctic krill shells 1.0 kWh / m³ 0.35kWh / m³ Reduced by 65% Haematococcus pluvialis 1.2 kWh / m³ (including supercritical compression energy consumption) 0.4 kWh / m³ Reduced by 67% Single processing time Favour yeast 4 hours (including cell wall breaking and extraction) 1.5h Shortened by 62.5% Antarctic krill shells 14 hours (including 12 hours of saponification) 2h shortened by 86% Haematococcus pluvialis 3 hours (including supercritical extraction) 1h Multi-stage membrane technology is significantly superior to traditional processes in key indicators such as astaxanthin recovery rate, purity, and activity retention rate, while greatly reducing solvent consumption, energy consumption, and processing time, making it suitable for industrial production of multi-raw material systems.

[0062] The above are all preferred embodiments of the present invention and are not intended to limit the scope of protection of the present invention. Therefore, all equivalent changes made in accordance with the structure, shape and principle of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A process for the pre-treatment of a crude astaxanthin extract based on a multi-stage membrane filtration technique, characterized in that: The pretreatment process comprises the following steps: Step 1, the astaxanthin crude extract is first screened to remove large particle impurities, and then temperature is adjusted to obtain astaxanthin feed liquid; Step 2, the astaxanthin feed liquid is subjected to solid-liquid separation by a tubular ceramic membrane to obtain a clear permeate containing astaxanthin lipid-soluble complexes; Step 3, the clear permeate obtained in step 2 is introduced into a hollow fiber nanofiltration membrane system to retain astaxanthin lipid complexes and free astaxanthin molecules to obtain a refined liquid; Step 4, the refined liquid obtained in step 3 is introduced into a spiral reverse osmosis membrane system for concentration to obtain a pretreatment concentrate.

2. The process for the pre-treatment of astaxanthin crude extract based on multi-stage membrane filtration technology according to claim 1, characterized in that: In step 1, the astaxanthin crude extract is filtered through a 140-160 mesh screen to obtain a filtrate, a visual image of the filtrate is taken, and the temperature of the filtrate is adjusted by an intelligent temperature controller based on an astaxanthin stability model to adjust the temperature of the filtrate to the target temperature at the temperature change rate given by the model, and the astaxanthin feed liquid is obtained after stabilization.

3. The process for the pre-treatment of astaxanthin crude extract based on multi-stage membrane filtration technology according to claim 2, characterized in that: The intelligent temperature controller adjusts the temperature of the filtrate, including the following steps: Step a: input the astaxanthin raw material source type, which includes phaffia fermentate, shrimp shell extract and microalgae broken wall liquid; Step b, call the corresponding sub-model according to the astaxanthin raw material source type; Step c, calculating the temperature change rate based on the sub-model and real-time data ; According to real-time temperature The difference between the target temperature reference The absolute value of the difference is calculated by grading: When then output = 2 °C / min; When then output = 1.5°C / min; When then output = 1 °C / min; Step d, the controller based on the generated temperature rate of change The temperature of the filtrate is regulated to the target temperature by driving the constant temperature heat exchanger through the PID algorithm. When the temperature of the filtrate reaches , the stable period is entered for 4-6 min to obtain the astaxanthin feed liquid.

4. The process for the pre-treatment of astaxanthin crude extract based on multi-stage membrane filtration technology according to claim 3, characterized in that: The sub-model includes phaffia source sub-model, shrimp shell extract source sub-model and microalgae source sub-model; The phaffia source sub-model takes 34-36℃ as the target temperature benchmark, and the temperature yeast protease activity correlation equation is built-in; The shrimp shell extract source sub-model takes 14-16℃ as the target temperature benchmark, and integrates the chitin swelling coefficient temperature curve; The microalgae source sub-model takes 24-26℃ as the target temperature benchmark, and contains the temperature influence function of phycocyanin residual amount.

5. The process for the pre-treatment of astaxanthin crude extract based on multi-stage membrane filtration technology according to claim 4, characterized in that: In step 1, the viscosity of the filtrate is monitored in real time, and if the viscosity of the filtrate exceeds the set viscosity threshold, 0.1wt%-0.3wt% of modified lecithin is added.

6. The process for the pre-treatment of astaxanthin crude extract based on multi-stage membrane filtration technology according to claim 1, characterized in that: In step 2, the tubular ceramic membrane adopts a tubular Ceramic membrane, surface composite grafting dopamine trehalose composite layer, pore size 0.3-0.6 μm; The tubular ceramic membrane adopts a double driving rotary structure, and the shear rate is 1200-1500 , combined with pulse electric auxiliary filtration, through electrostatic repulsion of charged impurities; The cross-flow speed of the tubular ceramic membrane is 3.3-3.7 m / s, the operating pressure is 1.6-2.0 bar, and gas-liquid synergistic backflushing is performed every 25-35 minutes, which first uses 0.2-0.4 s nitrogen pulse, and then uses 0.15-0.25 s deionized water flushing.

7. The process for the pre-treatment of astaxanthin crude extract based on multi-stage membrane filtration technology according to claim 1, characterized by the fact that: In step 3, the hollow fiber nanofiltration membrane system uses a gradient pore size PES-based membrane, the surface is grafted with sulfobetaine zwitterions, the Zeta potential is dynamically controlled to-25±3 mV, and the astaxanthin lipid complex and free astaxanthin are retained by using the dual mechanisms of charge repulsion and molecular sieving, and monosaccharides, inorganic ions and residual solvents are passed through.

8. The process for the pre-treatment of astaxanthin crude extract based on multi-stage membrane filtration technology according to claim 1, characterized by the fact that: In step 4, the spiral reverse osmosis membrane uses an asymmetric polyamide active layer, the flow channel is provided with a diamond guide net, and the concentration is performed by segmental variable pressure: The front section is 4.5-5.5 MPa, the rear section is 5.5-6.5 MPa, and the feed temperature gradient is reduced to inhibit astaxanthin thermal isomerization, the concentration factor is stable at 5-10 times, and the soluble solids are 15-20°Brix.

9. The process for the pre-treatment of astaxanthin crude extract based on multi-stage membrane filtration technology according to claim 8, characterized in that: The integrated online high performance liquid chromatography and ultraviolet spectrum combined system detects the clear permeate liquid every 4-6 minutes, and when the detection permeability is greater than 0.5%, the transmembrane pressure difference of the spiral reverse osmosis membrane is automatically increased by 0.08MPa-0.12MPa.

10. The process for the pre-treatment of astaxanthin crude extract based on multi-stage membrane filtration technology according to claim 8, characterized in that: The permeate liquid of the rotary ceramic membrane dynamic cross-flow preliminary filtration, the hollow fiber nanofiltration membrane refining and the spiral organic reverse osmosis membrane concentration is recovered by the composite molecular sieve adsorption column.

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