Natural sodium lactate for cosmetics and green continuous production method thereof

Abstract

The invention discloses natural sodium lactate for cosmetics and a green continuous production method of the natural sodium lactate, and belongs to the technical field of sodium lactate production.The preparation raw material of the natural sodium lactate is plant source carbohydrate subjected to non-transgenic and organic certification; in the natural sodium lactate, the relative content of L-sodium lactate accounts for more than 99.8% of the total content of sodium lactate, the optical purity is greater than or equal to 99.9%, and the impurity content meets the following limits: the chloride content is less than or equal to 50mg / kg, the sulfate content is less than or equal to 50mg / kg, the total content of heavy metals is less than or equal to 5mg / kg, and the arsenic content is less than or equal to 1mg / kg. According to the invention, non-transgenic and organically authenticated plant-derived carbohydrates are adopted as raw materials, so that the product is ensured to meet the high-standard requirements of cosmetics on nature, safety and traceability from the source, and meanwhile, a green continuous production process is combined; harmful impurities such as benzene series, polycyclic aromatic hydrocarbon and synthetic preservatives which are possibly introduced in the chemical synthesis process are effectively avoided, and the safety and purity of the product are remarkably improved.

Description

A natural sodium lactate for cosmetics and its green continuous production method Technical Field

[0001] This invention relates to the field of sodium lactate production technology, and more specifically, to a natural sodium lactate for cosmetics and a green and continuous production method thereof. Background Technology

[0002] Currently, the cosmetics industry has an increasing demand for natural, safe, and efficient raw materials. Sodium lactate, as a common moisturizer, pH adjuster, and skin conditioning agent, is widely used in various skincare and personal care products. Traditional sodium lactate production processes mostly employ chemical synthesis or batch fermentation methods. The raw materials may originate from non-renewable resources or non-organic crops, and the production process can easily introduce impurities such as heavy metals and residual organic solvents, affecting the safety and purity of the product. In addition, intermittent production processes suffer from low efficiency, high energy consumption, and large fluctuations in product quality, making it difficult to meet the modern cosmetics industry's requirements for high-quality, high-stability, and environmentally friendly raw materials.

[0003] While some existing technologies employ bio-fermentation to prepare sodium lactate, they still suffer from several drawbacks: First, the raw materials lack strict organic and non-GMO certification, making it difficult to guarantee the product's natural properties; second, purification processes often rely on traditional intermittent operations such as filtration and ion exchange, which are inefficient and prone to pollution; third, the production process consumes significant energy and water resources, resulting in insufficient environmental friendliness; and fourth, the product is prone to problems such as decreased light transmittance and yellowing during long-term storage, affecting its application in transparent or light-colored cosmetics.

[0004] Based on this, the present invention designs a natural sodium lactate for cosmetics and a green and continuous production method thereof to solve the above problems. Summary of the Invention

[0005] The purpose of this invention is to provide a natural sodium lactate for cosmetics and a green and continuous production method thereof, so as to solve the problems mentioned in the background art.

[0006] A natural sodium lactate for cosmetics and its green continuous production method are disclosed. The raw material for preparing the natural sodium lactate is a plant-derived carbohydrate that has been certified as non-GMO and organic. In the natural sodium lactate, the relative content of L-sodium lactate accounts for more than 99.8% of the total sodium lactate content, and the optical purity is ≥99.9%. Its impurity content meets the following limits: chloride content ≤50mg / kg, sulfate content ≤50mg / kg, total heavy metal content ≤5mg / kg, arsenic content ≤1mg / kg, and it does not contain detectable benzene compounds, polycyclic aromatic hydrocarbons, or synthetic preservatives. The transmittance of a 1.0g / mL aqueous solution of the natural sodium lactate is ≥99.0% at a wavelength of 450nm, and after being stored for 90 days under accelerated stability test conditions of 40±2℃ and 75±5% relative humidity, the absolute value of the decrease in transmittance does not exceed 2.0%, and the solution color remains stable without obvious yellowing.

[0007] Preferably, the plant-derived carbohydrate is at least one of organic cane sugar, organic beet sugar, organic corn starch saccharification liquid, or organic cassava starch saccharification liquid, and the natural sodium lactate crystals are in the form of regular prismatic or plate-like shapes, with an angle of repose of 28°-35° and a tap density of 0.85-1.05 g / cm³. 3 .

[0008] Preferably, the 1.0 g / mL aqueous solution of the natural sodium lactate has a viscosity of 1.8-2.5 mPa·s at 25°C and a pH value of 6.5-7.0. The microbiological indicators of the natural sodium lactate meet the following requirements: total bacterial count ≤10 CFU / g, total mold and yeast count ≤10 CFU / g, and pathogenic bacteria such as Staphylococcus aureus, Pseudomonas aeruginosa, and Escherichia coli must not be detected.

[0009] A green and continuous production method for natural sodium lactate for cosmetics includes the following steps: S1, continuous fermentation: A sterile culture medium prepared from plant-derived carbohydrates that has been certified as non-GMO and organic is continuously pumped into a series of bioreactors containing immobilized lactic acid bacteria at a constant flow rate for fermentation. The pH of the fermentation broth is monitored and adjusted in real time to 5.5-6.0, and the temperature is 37-40℃. The fermentation broth containing natural L-lactic acid is continuously collected; S2, continuous membrane integrated purification: The fermentation broth collected in step S1 is first passed through a continuous ceramic membrane microfiltration system. Under cross-flow velocity of 3-6 m / s and operating pressure of 0.2-0.6 MPa, bacteria and insoluble impurities are removed. The resulting microfiltration permeate then enters a spiral wound nanofiltration membrane system. Under operating pressure of 2.0-3.0 MPa and temperature of 25-40℃, the permeate is purified. Continuous decolorization and removal of small molecule impurities are performed at 0℃ to obtain a high-purity lactic acid solution; S3, continuous ion exchange and online neutralization: The high-purity lactic acid solution obtained in step S2 is continuously passed into a continuous ion exchange device consisting of at least three ion exchange columns. Food-grade hydrogen-form cation exchange resin adsorbs lactic acid and replaces hydrogen ions to obtain a purified lactic acid solution. This purified lactic acid solution is then continuously neutralized with a food-grade sodium hydroxide solution from a membrane electrolysis device through an online precision metering and dynamic mixing system. The acid and alkali flow rates are adjusted in real time to control the pH value at the neutralization endpoint to 6.8-7.2, generating a sodium lactate solution; S4, continuous energy-saving concentration: The sodium lactate solution generated in step S3 is introduced into a multi-effect evaporation system using mechanical vapor recompression technology for continuous concentration at a vacuum degree of -0.08. -0.095MPa, final evaporation temperature not exceeding 60℃, to obtain a concentrated solution with a sodium lactate mass fraction of 70%-80%; S5, continuous crystallization and separation: the concentrated solution obtained in step S4 is pumped into a continuous cooling crystallizer, and the temperature is gradually reduced at a rate of 0.5-1.5℃ / min according to a preset program to induce the nucleation and growth of sodium lactate crystals. The slurry containing crystals is continuously fed into a piston pusher centrifuge for solid-liquid separation to obtain wet sodium lactate crystals. The mother liquor is returned to step S4; S6, continuous drying and processing: the wet sodium lactate crystals obtained in step S5 are fed into a continuous vibrating fluidized bed dryer. A segmented temperature control method is adopted. The temperature of the drying section is 60-75℃, and the cooling section is circulated with sterilized and filtered room temperature air to cool the product to below 35℃, finally obtaining natural sodium lactate crystals with a moisture content ≤0.5%.

[0010] Preferably, in step S1, the immobilized lactic acid bacteria are prepared by embedding and immobilizing Lactobacillus plantarum or Lactobacillus acidophilus using calcium alginate, κ-carrageenan or polyvinyl alcohol as carriers, and the series of bioreactors are connected in series or parallel, with a total average hydraulic retention time of 18-36 hours.

[0011] Preferably, in step S2, the membrane pore size of the continuous ceramic membrane microfiltration system is 0.05-0.2 micrometers; the membrane molecular weight cutoff of the spiral wound nanofiltration membrane system is 200-300 Da, and its rejection rate for pigments and divalent or higher metal ions in lactic acid solution is ≥95%.

[0012] Preferably, in step S3, the continuous ion exchange device operates in a simulated moving bed or multi-column alternating adsorption / regeneration cycle mode; the membrane electrolysis device uses refined brine as raw material, and the resulting food-grade sodium hydroxide solution is used for neutralization in step S3, while the byproduct hydrochloric acid and chlorine are used for the regeneration of the cation exchange resin and system disinfection, respectively.

[0013] Preferably, in step S4, all the high-purity condensate generated by the multi-effect evaporation system of the mechanical vapor recompression technology is recycled and used as water for culture medium preparation or system cleaning in step S1.

[0014] Preferably, in step S5, the continuous cooling crystallizer is equipped with an ultrasonic seed generator or a multi-point seed injection device, and the gradient cooling procedure is as follows: cool down from 60°C to 40°C at a constant rate, then maintain the temperature at 40°C for 30-60 minutes to grow crystals, and then continue to cool down at a constant rate to 20-25°C to discharge the material.

[0015] Preferably, in step S6, the product exiting the continuous vibrating fluidized bed dryer immediately enters the online metal detection and rejection system, and is sealed and packaged using an automatic metering and packaging system with nitrogen protection.

[0016] Compared with existing technologies, the advantages of this invention are as follows: 1. By using plant-derived carbohydrates that have been certified as non-GMO and organic as raw materials, this invention ensures that the product meets the high standards of cosmetics for naturalness, safety, and traceability from the source. At the same time, by combining green and continuous production processes, it effectively avoids harmful impurities such as benzene compounds, polycyclic aromatic hydrocarbons, and synthetic preservatives that may be introduced during chemical synthesis, thus significantly improving the safety and purity of the product.

[0017] 2. This invention utilizes a multi-stage fine purification process, including continuous membrane integrated purification, ion exchange, and online neutralization, to efficiently remove impurities and pigments, obtaining natural sodium lactate with a relative content of ≥99.8%, optical purity of ≥99.9%, and extremely low content of heavy metals and harmful ions. The product exhibits a transmittance of ≥99.0% at a wavelength of 450nm, and shows minimal change in transmittance and no yellowing during accelerated stability testing, demonstrating excellent physicochemical stability and optical performance.

[0018] 3. This invention significantly improves production efficiency and product consistency through a fully continuous and automated production process, especially by using immobilized lactic acid bacteria for continuous fermentation, continuous membrane separation, continuous crystallization and drying, reducing human intervention and batch differences, ensuring stable and controllable product quality, and meeting the needs of large-scale, high-quality cosmetic raw material production.

[0019] 4. This invention integrates technologies such as mechanical vapor recompression (MVR) multi-effect evaporation, condensate recycling, and resource utilization of membrane electrolysis byproducts to achieve the recycling of energy and materials, significantly reducing water consumption, energy consumption, and waste emissions, embodying the environmental protection concept of green manufacturing, and meeting the requirements of sustainable development.

[0020] 5. By strictly controlling microbial indicators (such as total bacterial count ≤10 CFU / g) and adopting post-processing measures such as clean drying and nitrogen-filled packaging, this invention effectively ensures the microbial safety and chemical stability of the product during storage and use, extends the product's shelf life, and enhances its applicability and reliability in high-end cosmetic formulations. Attached Figure Description

[0021] Figure 1 is a process flow diagram of a natural sodium lactate for cosmetics and its green continuous production method proposed in this invention. Detailed Implementation

[0022] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0023] Please refer to Figure 1, which illustrates a natural sodium lactate for cosmetics and its green continuous production method. The raw material for preparing the natural sodium lactate is plant-derived carbohydrates that have been certified as non-GMO and organic. In the natural sodium lactate, the relative content of L-sodium lactate accounts for more than 99.8% of the total sodium lactate content, and the optical purity is ≥99.9%. Its impurity content meets the following limits: chloride content ≤50mg / kg, sulfate content ≤50mg / kg, total heavy metal content ≤5mg / kg, arsenic content ≤1mg / kg, and it does not contain detectable benzene compounds, polycyclic aromatic hydrocarbons, or synthetic preservatives. The transmittance of a 1.0g / mL aqueous solution of natural sodium lactate at a wavelength of 450nm is ≥99.0%, and after being stored for 90 days under accelerated stability test conditions of 40±2℃ and 75±5% relative humidity, the absolute value of the decrease in transmittance does not exceed 2.0%, and the solution color remains stable without obvious yellowing.

[0024] Furthermore, in the specific implementation process, the selected plant-derived carbohydrates must be certified by a third-party organic certification body to ensure their non-GMO status and organic cultivation origin, so as to meet the requirements of naturalness, safety and traceability of cosmetic raw materials.

[0025] The plant-derived carbohydrates are at least one of organic cane sugar, organic beet sugar, organic corn starch saccharification liquid, or organic cassava starch saccharification liquid. The natural sodium lactate crystals are regular prismatic or plate-like, with an angle of repose of 28°-35° and a tap density of 0.85-1.05 g / cm³. 3 .

[0026] Organic cane sugar is organic raw cane sugar or organic cane molasses with a sucrose content ≥99.5%; organic beet sugar is organic raw beet sugar or organic beet molasses with a beet sugar content ≥99.5%; organic corn starch saccharification liquid is organic corn starch enzymatic hydrolysate with a glucose equivalent value (DE) ≥95; organic cassava starch saccharification liquid is organic cassava starch enzymatic hydrolysate with a glucose equivalent value (DE) ≥95. These raw materials must undergo membrane filtration or activated carbon adsorption pretreatment before use to remove possible colloids, pigments, and trace impurities, ensuring the efficiency and purity of the fermentation process.

[0027] The viscosity of a 1.0 g / mL aqueous solution of natural sodium lactate at 25℃ is 1.8-2.5 mPa·s, and the pH value is 6.5-7.0. The microbiological indicators of natural sodium lactate meet the following requirements: total bacterial count ≤10 CFU / g, total mold and yeast count ≤10 CFU / g, and pathogenic bacteria such as Staphylococcus aureus, Pseudomonas aeruginosa, and Escherichia coli must not be detected.

[0028] To achieve the aforementioned microbiological indicators, during the drying process in step S6, the hot air entering the vibrating fluidized bed dryer must be sterilized by a high-efficiency particulate air (HEPA) filter to ensure that the air cleanliness meets the Class A (ISO 5) standard. After drying, the product is cooled in the cooling section by sterilized filtered room-temperature air and undergoes ultraviolet surface sterilization treatment before packaging, ensuring that the packaging environment cleanliness is not lower than ISO Class 8.

[0029] A green, continuous production method for natural sodium lactate for cosmetics includes the following steps: S1, continuous fermentation: A sterile culture medium prepared from plant-derived carbohydrates that has passed non-GMO and organic certification is continuously pumped at a constant flow rate into a series of bioreactors containing immobilized lactic acid bacteria for fermentation. The pH of the fermentation broth is monitored and adjusted in real time to 5.5-6.0, and the temperature is maintained at 37-40℃. Fermentation broth containing natural L-lactic acid is continuously collected. Specifically, the concentration of the sterile culture medium is 100-200 g / L (based on reducing sugar), and organic nitrogen sources (such as organic soybean peptone, organic yeast extract) and inorganic salts (such as phosphates, magnesium salts) are added. All excipients must meet organic certification standards. During fermentation, the process is monitored in real time by online pH electrodes and temperature sensors, and an automatic alkali addition system (such as food-grade sodium hydroxide or ammonia) is used to maintain pH stability. The alkali flow rate is automatically adjusted according to the pH feedback signal. The continuous fermentation system can be set up with 2-4 bioreactors in series, with the immobilized lactic acid bacteria filling rate of 40%-60% in each reactor to ensure lactic acid conversion rate ≥95%.

[0030] S2. Continuous Membrane Integrated Purification: The fermentation broth collected in step S1 is first passed through a continuous ceramic membrane microfiltration system. Under cross-flow velocity of 3-6 m / s and operating pressure of 0.2-0.6 MPa, bacterial cells and insoluble impurities are removed. The resulting microfiltration permeate then enters a spiral wound nanofiltration membrane system for continuous decolorization and removal of small molecule impurities under operating pressure of 2.0-3.0 MPa and temperature of 25-40℃, obtaining high-purity lactic acid solution. The ceramic membrane microfiltration system uses tubular or multi-channel ceramic membrane elements, with alumina or zirconium oxide as the membrane material. The membrane surface is hydrophilically modified to reduce membrane fouling. The microfiltration process employs periodic backwashing (every 30-60 minutes, backwash pressure 0.8-1.2 MPa) and online chemical cleaning (using food-grade citric acid or sodium hydroxide solution) to maintain stable membrane flux. The nanofiltration system uses a polyamide composite membrane that is resistant to organic solvents and acids and alkalis. It has a lactic acid rejection rate of ≤5% and a pigment and divalent or higher ion rejection rate of ≥95%, thereby achieving efficient separation of lactic acid and impurities.

[0031] S3. Continuous Ion Exchange and Online Neutralization: The high-purity lactic acid solution obtained in step S2 is continuously passed into a continuous ion exchange device consisting of at least three ion exchange columns. Food-grade hydrogen-form cation exchange resin adsorbs lactic acid and displaces hydrogen ions, yielding a purified lactic acid solution. This purified lactic acid solution is then continuously neutralized with a food-grade sodium hydroxide solution from a membrane electrolysis device through an online precision metering and dynamic mixing system. Real-time feedback is used to adjust the acid and alkali flow rates to control the final pH value at 6.8-7.2, generating a sodium lactate solution. The ion exchange resin is a strongly acidic styrene-based cation exchange resin with a crosslinking degree of 8%-10% and an exchange capacity ≥4.2 mmol / g. The continuous ion exchange system employs simulated moving bed (SMB) technology or a multi-column series adsorption-regeneration cycle mode to ensure a lactic acid adsorption rate ≥99%. The membrane electrolysis device uses a perfluorosulfonic acid proton exchange membrane, with refined salt solution as raw material. The sodium hydroxide produced by electrolysis has a concentration of 20%-30%, high purity, and is free of heavy metals and organic impurities. The neutralization reaction is completed instantaneously in a static mixer or an online dynamic mixer, with the neutralization temperature controlled at 30-40℃ to prevent local overheating that could lead to the decomposition or discoloration of sodium lactate.

[0032] S4. Continuous Energy-Saving Concentration: The sodium lactate solution generated in step S3 is introduced into a multi-effect evaporation system employing mechanical vapor recompression technology for continuous concentration at a vacuum degree of -0.08. A concentrated solution with a sodium lactate mass fraction of 70%-80% is obtained by applying a pressure of -0.095 MPa and maintaining a final evaporation temperature not exceeding 60℃. The multi-effect evaporation system employs a triple- or quadruple-effect falling film evaporator with a reasonable temperature distribution between effects. The final evaporation temperature is strictly controlled below 60℃ to reduce degradation of heat-sensitive components and changes in product color. The mechanical vapor recompression (MVR) system uses the secondary steam, after being heated and pressurized by a compressor, as a heat source for reuse, significantly reducing steam consumption. The condensate generated during the concentration process has a conductivity ≤10 μS / cm and is entirely recycled for culture medium preparation or equipment cleaning, achieving water resource recycling.

[0033] S5. Continuous Crystallization and Separation: The concentrated solution obtained in step S4 is pumped into a continuous cooling crystallizer. Following a preset program, the solution is gradually cooled at a rate of 0.5-1.5℃ / min to induce the nucleation and growth of sodium lactate crystals. The slurry containing the crystals is continuously fed into a piston-driven centrifuge for solid-liquid separation to obtain wet sodium lactate crystals. The mother liquor is returned to step S4. The continuous cooling crystallizer is an Oslo-type or DTB-type crystallizer, equipped with a flow guide and stirring device to ensure uniform cooling of the solution and suspension of the crystals. The gradient cooling program is automatically controlled by a PLC, specifically: cooling from 60℃ to 40℃ at a rate of 1.0℃ / min, maintaining a constant temperature at 40℃ for 45 minutes to grow crystals, and then cooling to 22℃ at a rate of 0.8℃ / min for discharge. During the crystal growth stage, an ultrasonic seed generator (frequency 20-40kHz) is activated to promote uniform crystal nucleus generation, thereby obtaining regular crystals with a concentrated particle size distribution (D50 of 200-400μm). The moisture content of the wet crystals after centrifugation is controlled at 5%-10%.

[0034] S6. Continuous drying and processing: The wet sodium lactate crystals obtained in step S5 are fed into a continuous vibrating fluidized bed dryer. A segmented temperature control method is adopted. The temperature of the drying section is 60-75℃, and the cooling section is cooled to below 35℃ by passing sterilized and filtered room temperature air through it. Finally, natural sodium lactate crystals with a moisture content of ≤0.5% are obtained.

[0035] The vibrating fluidized bed dryer consists of three sections: a pre-drying section (60-65℃), a main drying section (70-75℃), and a cooling section. Hot air is supplied by a steam heat exchanger, with an inlet air temperature of 80-90℃, and the air volume is automatically adjusted according to the material's moisture content. After drying, the product passes through a built-in cyclone separator and bag filter to recover fine powder, which can be returned to the crystallization system as seed crystals. After cooling, the product immediately enters an online metal detector (sensitivity Fe≥1.5mm, SUS≥2.0mm), and is packaged using an automatic metering-nitrogen filling-sealing integrated packaging machine. The packaging material is aluminum-plastic composite film or aluminized film, with nitrogen purity ≥99.9% and residual oxygen content ≤1%.

[0036] In step S1, the immobilized lactic acid bacteria are prepared by embedding and immobilizing Lactobacillus plantarum or Lactobacillus acidophilus using calcium alginate, κ-carrageenan or polyvinyl alcohol as carriers. The series of bioreactors are connected in series or parallel, and the total average hydraulic retention time is 18-36 hours.

[0037] The immobilized carrier was prepared as follows: An activated lactic acid bacteria suspension was mixed with a 2%-4% sodium alginate solution at a volume ratio of 1:3. This mixture was then added dropwise to a 0.1M calcium chloride solution using a dropping device to form immobilized gel beads with a diameter of 1-3 mm. After hardening, the beads were washed with physiological saline for later use. The immobilized particles were packed to 2 / 3 of the effective height of the reactor, and slight fluidization was maintained by bottom aeration or mechanical stirring to prevent bacterial hypoxia and blockage.

[0038] In step S2, the membrane pore size of the continuous ceramic membrane microfiltration system is 0.05-0.2 micrometers; the membrane molecular weight cutoff of the spiral wound nanofiltration membrane system is 200-300 Da, and its rejection rate of pigments and divalent or higher metal ions in lactic acid solution is ≥95%.

[0039] The ceramic membrane microfiltration system can be configured with multiple membrane modules operating in parallel, enabling non-stop switching and cleaning to ensure continuous production. The nanofiltration system uses spiral wound membrane elements, with 3-6 membrane elements packed in each pressure vessel, achieving a system recovery rate of ≥85%. The nanofiltration concentrate mainly contains pigments, proteins, and multivalent ions, and can be used as a raw material for organic fertilizer or further processed to realize the resource utilization of waste.

[0040] In step S3, the continuous ion exchange device operates in a simulated moving bed or multi-column alternating adsorption / regeneration cycle mode; the membrane electrolysis device uses refined brine as raw material, and the resulting food-grade sodium hydroxide solution is used for neutralization in step S3, while the by-product hydrochloric acid and chlorine are used for the regeneration of the cation exchange resin and system disinfection, respectively.

[0041] The ion exchange resin is regenerated using a 4%-6% hydrochloric acid solution at a regeneration flow rate of 2-4 BV / h. After regeneration, it is washed with deionized water until neutral. The chlorine gas produced as a byproduct of membrane electrolysis is converted into sodium hypochlorite disinfectant via an absorption tower. This disinfectant is used for periodic disinfection of system pipelines and equipment (e.g., once a week) at a concentration of 100-200 ppm, with a contact time of at least 30 minutes, followed by thorough rinsing.

[0042] In step S4, the high-purity condensate produced by the multi-effect evaporation system of mechanical vapor recompression technology is completely recycled and used as water for culture medium preparation or system cleaning in step S1.

[0043] The recovered condensate is stored in a stainless steel insulated tank (≥80℃) and sterilized by an ultraviolet sterilizer before use to ensure that its microbiological indicators meet the requirements for process water (total bacterial count ≤10CFU / mL).

[0044] In step S5, the continuous cooling crystallizer has a built-in ultrasonic seed generator or a multi-point seed injection device. The gradient cooling procedure is as follows: cool down from 60°C to 40°C at a constant rate, then maintain the temperature at 40°C for 30-60 minutes to grow crystals, and then continue to cool down at a constant rate to 20-25°C to discharge the material.

[0045] The ultrasonic seed generator operates at a frequency of 28kHz and has adjustable power. It is intermittently turned on during the crystal growth stage (e.g., on for 10 seconds, then off for 20 seconds) to prevent crystal breakage. Alternatively, the seed crystals can be fine powder recovered from the drying process (passing through a 200-mesh sieve), continuously injected into the crystallizer via a metering screw at a rate of 0.5%-1.0% of the feed rate.

[0046] In step S6, the product exiting the continuous vibrating fluidized bed dryer immediately enters the online metal detection and rejection system, and is sealed and packaged using an automatic metering and packaging system with nitrogen protection.

[0047] The online metal detection system is linked to a pneumatic rejection valve, automatically rejecting the batch of products when a metallic foreign object is detected. The nitrogen-filled packaging system is equipped with a residual oxygen analyzer to monitor the residual oxygen level inside the packaging in real time and adjust the nitrogen filling flow accordingly. Packaging specifications can be set to 1kg, 5kg, 25kg, etc., according to customer needs. The packaging bags are printed with batch numbers, production dates, and organic certification marks for easy traceability.

[0048] The working principle of this invention is as follows: Employing a fully continuous, closed-loop green production process, starting with organic plant-derived carbohydrates, the process involves continuous fermentation using immobilized cells, membrane-integrated purification, continuous ion exchange and neutralization, energy-saving MVR concentration, program-controlled crystallization, and clean drying and packaging to ultimately obtain a high-purity, high-optical-purity, low-impurity, and highly stable natural sodium lactate crystal product. The entire process achieves organic traceability of raw materials, continuous and efficient production, resource recycling, and near-zero emissions of waste, meeting the requirements for natural, safe, environmentally friendly, and high-quality cosmetic raw materials.

[0049] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely preferred examples and are not intended to limit the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed. The scope of protection of the present invention is defined by the appended claims and their equivalents.

Claims

1. A natural sodium lactate for use in cosmetics, characterized in that, The raw material for preparing natural sodium lactate is plant-derived carbohydrates that have been certified as non-GMO and organic. In the natural sodium lactate, the relative content of L-sodium lactate accounts for more than 99.8% of the total sodium lactate content, and the optical purity is ≥99.9%. Its impurity content meets the following limits: chloride content ≤50mg / kg, sulfate content ≤50mg / kg, total heavy metal content ≤5mg / kg, arsenic content ≤1mg / kg, and it does not contain detectable benzene compounds, polycyclic aromatic hydrocarbons, or synthetic preservatives. A 1.0g / mL aqueous solution of the natural sodium lactate has a transmittance of ≥99.0% at a wavelength of 450nm, and after being stored for 90 days under accelerated stability testing conditions of 40±2℃ and 75±5% relative humidity, the absolute decrease in transmittance does not exceed 2.0%, and the solution color remains stable without obvious yellowing.

2. The natural sodium lactate for cosmetics according to claim 1, characterized in that, The plant-derived carbohydrate is at least one of organic cane sugar, organic beet sugar, organic corn starch saccharification solution, or organic cassava starch saccharification solution. The natural sodium lactate crystals are regular prismatic or plate-like in shape, with an angle of repose of 28°-35° and a tap density of 0.85-1.05 g / cm³. 3 .

3. The natural sodium lactate for cosmetics according to claim 2, characterized in that, The 1.0 g / mL aqueous solution of the natural sodium lactate has a viscosity of 1.8-2.5 mPa·s at 25°C and a pH value of 6.5-7.

0. The microbiological indicators of the natural sodium lactate meet the following requirements: total bacterial count ≤10 CFU / g, total mold and yeast count ≤10 CFU / g, and pathogenic bacteria such as Staphylococcus aureus, Pseudomonas aeruginosa, and Escherichia coli must not be detected.

4. A green and continuous production method for natural sodium lactate for cosmetics, characterized in that, Includes the following steps: S1. Continuous Fermentation: Sterilized culture medium prepared from plant-derived carbohydrates that have passed non-GMO and organic certification is continuously pumped into a series of bioreactors containing immobilized lactic acid bacteria at a constant flow rate for fermentation. The pH of the fermentation broth is monitored and adjusted in real time to 5.5-6.0 and the temperature to 37-40℃, and the fermentation broth containing natural L-lactic acid is continuously collected. S2. Continuous Membrane Integrated Purification: The fermentation broth collected in step S1 is first passed through a continuous ceramic membrane microfiltration system. Under cross-flow velocity of 3-6 m / s and operating pressure of 0.2-0.6 MPa, bacterial cells and insoluble impurities are removed. The resulting microfiltration permeate then enters a spiral wound nanofiltration membrane system for continuous decolorization and removal of small molecules under operating pressure of 2.0-3.0 MPa and temperature of 25-40℃. S2. Continuous Ion Exchange and Online Neutralization: The high-purity lactic acid solution obtained in step S2 is continuously passed into a continuous ion exchange device consisting of at least three ion exchange columns. Food-grade hydrogen-form cation exchange resin adsorbs lactic acid and replaces hydrogen ions, yielding a purified lactic acid solution. This purified lactic acid solution is then continuously neutralized with a food-grade sodium hydroxide solution from a membrane electrolysis device using an online precision metering and dynamic mixing system. Real-time feedback is used to adjust the acid and alkali flow rates to control the final pH value at 6.8-7.2, generating a sodium lactate solution. S3. Continuous Energy-Saving Concentration: The sodium lactate solution generated in step S3 is continuously concentrated using a multi-effect evaporation system employing mechanical vapor recompression technology, maintaining a vacuum of -0.08... -0.095MPa, final evaporation temperature not exceeding 60℃, to obtain a concentrated solution with a sodium lactate mass fraction of 70%-80%; S5, continuous crystallization and separation: the concentrated solution obtained in step S4 is pumped into a continuous cooling crystallizer, and the temperature is gradually reduced at a rate of 0.5-1.5℃ / min according to a preset program to induce the nucleation and growth of sodium lactate crystals. The slurry containing crystals is continuously fed into a piston pusher centrifuge for solid-liquid separation to obtain wet sodium lactate crystals. The mother liquor is returned to step S4; S6, continuous drying and processing: the wet sodium lactate crystals obtained in step S5 are fed into a continuous vibrating fluidized bed dryer. A segmented temperature control method is adopted. The temperature of the drying section is 60-75℃, and the cooling section is circulated with sterilized and filtered room temperature air to cool the product to below 35℃, finally obtaining natural sodium lactate crystals with a moisture content ≤0.5%.

5. A green and continuous production method for natural sodium lactate for cosmetics according to claim 4, characterized in that, In step S1, the immobilized lactic acid bacteria are prepared by embedding and immobilizing Lactobacillus plantarum or Lactobacillus acidophilus using calcium alginate, κ-carrageenan or polyvinyl alcohol as carriers. The series of bioreactors are connected in series or in parallel, and the total average hydraulic retention time is 18-36 hours.

6. A green and continuous production method for natural sodium lactate for cosmetics according to claim 4, characterized in that, In step S2, the membrane pore size of the continuous ceramic membrane microfiltration system is 0.05-0.2 micrometers; the membrane molecular weight cutoff of the spiral wound nanofiltration membrane system is 200-300 Da, and its rejection rate for pigments and divalent or higher metal ions in lactic acid solution is ≥95%.

7. A green and continuous production method for natural sodium lactate for cosmetics according to claim 4, characterized in that, In step S3, the continuous ion exchange device operates in a simulated moving bed or multi-column alternating adsorption / regeneration cycle mode; the membrane electrolysis device uses refined brine as raw material, and the resulting food-grade sodium hydroxide solution is used for neutralization in step S3, while the byproduct hydrochloric acid and chlorine are used for the regeneration of the cation exchange resin and system disinfection, respectively.

8. A green and continuous production method for natural sodium lactate for cosmetics according to claim 4, characterized in that, In step S4, the high-purity condensate produced by the multi-effect evaporation system of the mechanical vapor recompression technology is completely recycled and used as water for culture medium preparation or system cleaning in step S1.

9. A green and continuous production method for natural sodium lactate for cosmetics according to claim 4, characterized in that, In step S5, the continuous cooling crystallizer is equipped with an ultrasonic seed generator or a multi-point seed injection device. The gradient cooling procedure is as follows: the temperature is uniformly reduced from 60°C to 40°C, then kept at 40°C for 30-60 minutes to grow crystals, and then the temperature is uniformly reduced to 20-25°C for discharge.

10. A green and continuous production method for natural sodium lactate for cosmetics according to claim 4, characterized in that, In step S6, the product exiting the continuous vibrating fluidized bed dryer immediately enters the online metal detection and rejection system, and is sealed and packaged using an automatic metering and packaging system with nitrogen protection.

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