Composite bio-enzyme ceramic odorless block for refrigerator and preparation method of composite bio-enzyme ceramic odorless block

Abstract

The invention provides a composite biological enzyme ceramic odor removal block for a refrigerator and a preparation method of the composite biological enzyme ceramic odor removal block. The composite biological enzyme ceramic odor removal block for the refrigerator comprises a porous ceramic carrier and a composite biological enzyme loaded on the porous ceramic carrier, the composite biological enzyme is prepared from a composite biological enzyme stock solution, lipase, protease and formaldehyde dehydrogenase according to a mass ratio of 4: 3: (1-2), and the composite biological enzyme comprises cold-adapted oxidoreductase, low-temperature chitinase and mycose; the surface of the porous ceramic carrier is modified by a silane coupling agent, and the interior of the porous ceramic carrier has gradient pore size distribution of 10-0.1 mu m. Through the synergistic effect of the biological enzyme compound system and the ceramic carrier, efficient mineralization decomposition of peculiar smell molecules is achieved, meanwhile, the safety standard of food contact materials is met, and the problems of low-temperature inactivation, secondary pollution and frequent replacement in the prior art are solved.

Description

Technical Field

[0001] This application relates to the field of materials technology, and in particular to a composite bio-enzyme ceramic deodorizing block for refrigerators and its preparation method. Background Technology

[0002] Refrigerators, as indispensable food storage devices in homes and businesses, primarily function to delay food spoilage and extend shelf life through low-temperature environments. In actual use, refrigerators often store various types of food simultaneously, including meat, fruits and vegetables, dairy products, and cooked foods. During storage, these foods are prone to producing various odorous gases such as formaldehyde, ammonia, trimethylamine, methanethiol, and short-chain fatty acids due to microbial growth, fat oxidation, protein decomposition, and the respiration of fruits and vegetables. These odors not only cause cross-contamination between foods, affecting their original flavor and quality, but may also accelerate the spoilage process of some sensitive foods, reducing the user's food storage experience and safety. Therefore, developing efficient and stable deodorizing modules for refrigerators has become one of the key directions for refrigerator function optimization and technological upgrades.

[0003] Currently, the deodorization module technologies used in the refrigerator industry can be divided into three main categories: physical adsorption, chemical catalysis, and composite solutions combining physical adsorption and chemical catalysis. Specific technical methods mainly include the following: First, physical adsorption technology, with activated carbon adsorption as a typical example, utilizes the rich porous structure of activated carbon to physically trap odor molecules, achieving temporary odor removal. Second, chemical catalysis technology, encompassing ozone generators, negative ion generators, photocatalysis, and metal oxide catalysis. Ozone generators release ozone to oxidize odor molecules, decomposing them; negative ion generators use negative ions to combine with odor molecules for purification; photocatalysis requires specific light conditions to activate catalytic activity and decompose odor substances; and metal oxide catalysis relies on the catalytic properties of metal oxides to promote the chemical transformation of odor molecules. Third, a combination of physical adsorption and chemical catalysis, which attempts to balance adsorption efficiency and decomposition effect by combining the above physical adsorption and chemical catalysis technologies, such as combining activated carbon with photocatalytic materials to form a deodorization module.

[0004] However, existing refrigerator deodorization technologies still have many insurmountable problems and shortcomings in practical applications, failing to fully meet users' actual needs for refrigerator deodorization: First, existing technologies target a narrow range of odor gas molecules, with most technologies only effective against specific types of odor molecules, making it difficult to comprehensively cover the complex and diverse odor components inside the refrigerator, resulting in unsatisfactory deodorization effects; Second, all technologies have significant technical drawbacks, specifically: activated carbon, a physical adsorption method, easily reaches adsorption saturation due to odor molecules filling its pores, requiring frequent replacement to maintain the deodorization effect, increasing user costs and operational inconvenience; photocatalytic technology relies on light of specific wavelengths as a catalytic condition, but the limited light conditions inside the refrigerator significantly reduce its catalytic efficiency, making it unable to stably perform its deodorization function; while ozone released by ozone generators can decompose odors, it also accelerates the oxidation and spoilage of fresh foods such as fruits and vegetables, damaging food quality and posing a secondary hazard risk; metal oxide catalytic technology experiences a significant decrease in catalytic activity and a slow reaction rate in the low-temperature environment of the refrigerator, making it difficult to quickly and efficiently decompose odor molecules and unsuitable for the actual working conditions of the refrigerator. In summary, existing refrigerator deodorization technologies generally suffer from poor low-temperature adaptability, narrow odor coverage, and are prone to secondary problems or require frequent maintenance. There is an urgent need to develop a deodorization technology solution that can work stably for a long time in the low-temperature and high-humidity environment of a refrigerator, with comprehensive deodorization effect and safety and reliability. Summary of the Invention

[0005] This application provides a composite bio-enzyme ceramic deodorizing block for refrigerators and its preparation method, in order to solve the problems that existing refrigerator deodorization technologies generally suffer from, such as poor low-temperature adaptability, narrow odor coverage, and the tendency to cause secondary problems or require frequent maintenance.

[0006] In a first aspect, this application provides a composite bio-enzyme ceramic deodorizing block for refrigerators, comprising a porous ceramic carrier and a composite bio-enzyme loaded on the porous ceramic carrier.

[0007] The composite bio-enzyme is prepared by mixing composite bio-enzyme stock solution, lipase, protease, and formaldehyde dehydrogenase in a mass ratio of 4:3:(1-2). The composite bio-enzyme includes cold-adapted oxidoreductase, low-temperature chitinase, and phycoose.

[0008] The surface of the porous ceramic support is modified with a silane coupling agent, and the interior has a gradient pore size distribution of 10 μm to 0.1 μm.

[0009] In some possible implementations, the raw materials for preparing the porous ceramic carrier include, by mass percentage: 60-70% diatomaceous earth, 10-20% kaolin, 5-15% pore-forming agent, and 5% nano-ZnO.

[0010] In some possible implementations, the pore-forming agent is a mixture of soluble starch and ammonium bicarbonate in a mass ratio of 7:3, and the total amount of the pore-forming agent added is 20% of the dry weight of the ceramic-based powder.

[0011] In some possible implementations, the silane coupling agent is 3-aminopropyltriethoxysilane, and the purity of the silane coupling agent is ≥98%.

[0012] In some possible implementations, the silane coupling agent modification on the surface of the porous ceramic support is achieved using a 2% APTES ethanol solution, wherein the ethanol solution is a 95% aqueous ethanol solution, and the pH of the ethanol solution is adjusted to 5.0-5.5 with acetic acid.

[0013] In some possible implementations, the porous ceramic carrier has a honeycomb structure and a specific surface area ≥ 300 m². 2 / g.

[0014] In some possible implementations, the cold-adapted oxidoreductase has an activity unit of 15000±500 U / mL and a content of 2.5~5 mg / mL, and is derived from Antarctic psychrophilic yeast; the low-temperature chitinase has an activity unit of 8000±300 U / mL and a content of 1.8~2 mg / mL, and is derived from Arctic marine bacteria; and the trehalose has a content of 50.0 mg / mL.

[0015] In some possible implementations, the complex bioenzyme is further supplemented with 0.5% to 1% vitamin C by mass, which acts as an antioxidant to inhibit the oxidative inactivation of the complex bioenzyme during storage and use.

[0016] Secondly, this application provides a method for preparing a composite bio-enzyme ceramic deodorizing block for refrigerators, the method comprising:

[0017] Diatomaceous earth, kaolin, pore-forming agent, and nano ZnO were weighed according to the mass ratio, mixed, and then a binder was added for wet ball milling. The mixture was then extruded into a honeycomb structure and then sintered at low temperature in segments to obtain a porous ceramic carrier.

[0018] According to the amount of porous ceramic carrier used, weigh out the corresponding amount of composite bio-enzyme stock solution, lipase, protease, formaldehyde dehydrogenase and trehalose protectant, add them to PBS buffer at pH=7.2, and mix well to obtain bio-enzyme composite loading solution.

[0019] The porous ceramic carrier is placed in the bio-enzyme composite loading liquid and subjected to vacuum impregnation, followed by freeze drying, and finally cross-linked and cured with glutaraldehyde vapor to obtain a composite bio-enzyme ceramic deodorizing block for refrigerators.

[0020] In some possible implementations, low-temperature segmented sintering includes preheating at 250°C for 1 hour, followed by sintering at 400°C for 2 hours, wherein the heating rate of the low-temperature segmented sintering is 5–10°C / min.

[0021] As can be seen from the above, this application provides a composite bio-enzyme ceramic deodorizing block for refrigerators and its preparation method. The composite bio-enzyme ceramic deodorizing block for refrigerators includes a porous ceramic carrier and a composite bio-enzyme loaded on the porous ceramic carrier. The composite bio-enzyme is prepared by mixing a composite bio-enzyme stock solution, lipase, protease, and formaldehyde dehydrogenase in a mass ratio of 4:3:(1-2). The composite bio-enzyme includes a cold-adapted oxidoreductase, a low-temperature chitinase, and trehalose. The surface of the porous ceramic carrier is modified with a silane coupling agent, and the interior has a gradient pore size distribution of 10μm to 0.1μm. The cold-adapted oxidoreductase and low-temperature chitinase in the composite bio-enzyme are both low-temperature adapted enzymes, and trehalose is added as a low-temperature protectant. Trehalose can maintain the integrity of the three-dimensional structure of the enzyme molecule in the low-temperature environment of 0-10℃ in the refrigerator, avoiding enzyme activity loss due to low temperature. At the same time, the proportion of protease can be adjusted according to the storage ratio of protein-containing foods in the refrigerator, further ensuring the decomposition efficiency of the enzyme on protein-containing odor precursors at low temperatures. The surface of the porous ceramic carrier is modified with a silane coupling agent. The amino groups of the silane coupling agent can form chemical bonds with the carboxyl groups of the biological enzyme molecules. Compared with the unmodified carrier, this can significantly reduce the shedding of biological enzymes during use and improve the enzyme loading stability. Detailed Implementation

[0022] The embodiments described in the following examples do not represent all embodiments consistent with this application. They are merely examples of systems and methods consistent with some aspects of this application as detailed in the claims.

[0023] Refrigerators, as indispensable food storage devices in homes and businesses, primarily function to delay food spoilage and extend shelf life through low-temperature environments. In actual use, refrigerators often store various types of food simultaneously, including meat, fruits and vegetables, dairy products, and cooked foods. During storage, these foods are prone to producing various odorous gases such as formaldehyde, ammonia, trimethylamine, methanethiol, and short-chain fatty acids due to microbial growth, fat oxidation, protein decomposition, and the respiration of fruits and vegetables. These odors not only cause cross-contamination between foods, affecting their original flavor and quality, but may also accelerate the spoilage process of some sensitive foods, reducing the user's food storage experience and safety. Therefore, developing efficient and stable deodorizing modules for refrigerators has become one of the key directions for refrigerator function optimization and technological upgrades.

[0024] Currently, the deodorization module technologies used in the refrigerator industry can be divided into three main categories: physical adsorption, chemical catalysis, and composite solutions combining physical adsorption and chemical catalysis. Specific technical methods mainly include the following: First, physical adsorption technology, with activated carbon adsorption as a typical example, utilizes the rich porous structure of activated carbon to physically trap odor molecules, achieving temporary odor removal. Second, chemical catalysis technology, encompassing ozone generators, negative ion generators, photocatalysis, and metal oxide catalysis. Ozone generators release ozone to oxidize odor molecules, decomposing them; negative ion generators use negative ions to combine with odor molecules for purification; photocatalysis requires specific light conditions to activate catalytic activity and decompose odor substances; and metal oxide catalysis relies on the catalytic properties of metal oxides to promote the chemical transformation of odor molecules. Third, a combination of physical adsorption and chemical catalysis, which attempts to balance adsorption efficiency and decomposition effect by combining the above physical adsorption and chemical catalysis technologies, such as combining activated carbon with photocatalytic materials to form a deodorization module.

[0025] However, existing refrigerator deodorization technologies still have many insurmountable problems and shortcomings in practical applications, failing to fully meet users' actual needs for refrigerator deodorization: First, existing technologies target a narrow range of odor gas molecules. Most technologies can only work on specific types of odor molecules (e.g., activated carbon mainly adsorbs large organic odor molecules, and ozone has limited effect on decomposing some sulfur- and nitrogen-containing odors), making it difficult to comprehensively cover the complex and diverse odor components inside the refrigerator, resulting in unsatisfactory deodorization effects; Second, all technologies have significant technical drawbacks, specifically: activated carbon, a physical adsorption method, easily reaches adsorption saturation because its pores are filled with odor molecules, requiring frequent... Frequent replacement of parts is necessary to maintain the deodorizing effect, increasing user costs and operational inconvenience. Photocatalytic technology relies on specific wavelengths of light (such as ultraviolet light) as a catalytic condition, but the limited light conditions inside a refrigerator significantly reduce its catalytic efficiency, making it unable to stably perform its deodorizing function. While ozone generators can decompose odors, they also accelerate the oxidation and spoilage of fresh foods such as fruits and vegetables, damaging food quality and posing a secondary hazard risk. Metal oxide catalytic technology exhibits significantly reduced catalytic activity and a slow reaction rate in the low-temperature environment of a refrigerator (typically 0-10℃), making it difficult to quickly and efficiently decompose odor molecules and unsuitable for the actual working conditions of a refrigerator. In summary, existing refrigerator deodorizing technologies generally suffer from poor low-temperature adaptability, narrow odor coverage, susceptibility to secondary problems, or the need for frequent maintenance. There is an urgent need to develop a deodorizing technology solution that can operate stably for a long time in the low-temperature and high-humidity environment of a refrigerator, providing comprehensive and reliable deodorizing effects.

[0026] Based on this, this application provides a composite bio-enzyme ceramic deodorizing block for refrigerators, comprising a porous ceramic carrier and a composite bio-enzyme loaded on the porous ceramic carrier.

[0027] The composite bio-enzyme is prepared by mixing composite bio-enzyme stock solution, lipase, protease, and formaldehyde dehydrogenase in a mass ratio of 4:3:(1-2). The composite bio-enzyme includes cold-adapted oxidoreductase, low-temperature chitinase, and phycoose.

[0028] The surface of the porous ceramic support is modified with a silane coupling agent, and the interior has a gradient pore size distribution of 10 μm to 0.1 μm.

[0029] The compound bio-enzyme uses a combination of "compound bio-enzyme stock solution (containing cold-adapted oxidoreductase and low-temperature chitinase) + lipase + protease + formaldehyde dehydrogenase", and the proportion of protease can be flexibly adjusted to 1-2 (by mass) to form a synergistic mechanism.

[0030] Cold-adapted oxidoreductases can catalyze the oxidative decomposition of small molecule aldehydes and ketones such as formaldehyde and acetaldehyde, while formaldehyde dehydrogenases further enhance the formaldehyde degradation efficiency.

[0031] Lipase can cleave triglycerides produced by food spoilage, releasing and degrading short-chain fatty acid malodorous substances such as butyric acid. Protease (1-2 ratio suitable) can decompose protein dirt and nitrogenous odor precursors produced by spoilage. Combined with low-temperature chitinase to inhibit mold growth, it can ultimately cover multiple types of odor molecules in the refrigerator, such as aldehydes (formaldehyde), nitrogenous substances (ammonia, trimethylamine), sulfur-containing substances (methanethiol), and fatty acids (butyric acid).

[0032] The cold-adapted oxidoreductase (derived from Antarctic psychrophilic yeast) and the low-temperature chitinase (derived from Arctic marine bacteria) in the compound bioenzyme are both low-temperature adapted enzymes. Furthermore, trehalose is added as a low-temperature protectant. Trehalose can maintain the integrity of the three-dimensional structure of the enzyme molecules in the low-temperature environment of 0-10℃ in the refrigerator, avoiding enzyme activity loss due to low temperature. At the same time, the ratio of protease (1-2) can be adjusted according to the storage ratio of protein foods in the refrigerator, further ensuring the enzyme's decomposition efficiency of protein odor precursors at low temperatures, and solving the defect of existing technologies that cannot work stably under low-temperature conditions in refrigerators.

[0033] The porous ceramic carrier surface is modified with a silane coupling agent. The amino groups of the silane coupling agent can form chemical bonds with the carboxyl groups of the enzyme molecules. Compared with the unmodified carrier, this can significantly reduce the shedding of the enzyme during use and improve the enzyme loading stability. At the same time, the gradient pore size structure of 10μm to 0.1μm inside the carrier can form a channel system of "macropore flow-mesopore enzyme storage-micropore catalysis". The macropores facilitate the rapid entry of odor gases into the carrier, the mesopores provide sufficient loading space for the composite enzyme, and the micropores prolong the contact time between odor molecules and enzymes, further improving enzyme catalytic efficiency. This avoids the problem of "easy saturation and frequent replacement" of existing activated carbon and extends the service life of the odor-neutralizing block.

[0034] In some embodiments, the raw materials for preparing the porous ceramic carrier include, by mass percentage: 60-70% diatomaceous earth, 10-20% kaolin, 5-15% pore-forming agent, and 5% nano-ZnO.

[0035] Diatomaceous earth accounts for 60-70% of the composition. Its naturally occurring porous framework structure is the core basis for the carrier to form a "gradient pore size of 10μm to 0.1μm". The porous nature of diatomaceous earth itself can directly provide initial pores for the carrier, and the high proportion of 60-70% can ensure that the carrier framework is dominated by a porous structure, avoiding the compression of pore space by other raw materials with an excessive proportion. At the same time, the porous structure of diatomaceous earth has a high specific surface area, which can provide sufficient loading sites for composite biological enzymes. With the addition of surface silane coupling agent modification, the enzyme loading capacity and stability are further improved, solving the problem of low enzyme loading and short deodorization duration caused by insufficient specific surface area of ​​existing carriers.

[0036] With a kaolin content of 10-20%, kaolin serves as a traditional binder for ceramic carriers. Its adhesive properties firmly bind diatomaceous earth particles, pore-forming agents, and nano-ZnO, preventing cracking and pulverization during molding, sintering, and long-term refrigerator use, thus ensuring structural stability. Simultaneously, the 10-20% content allows for flexible adjustment of the carrier's pore size distribution. When the kaolin content approaches 20%, its fine particles fill some of the large gaps between diatomaceous earth particles, reducing the proportion of excessively large pores (>10μm) and optimizing the ratio of mesopores (5μm-1μm) and micropores (1μm-0.1μm) in the gradient pore size, extending the residence time of odor molecules within the carrier and improving contact efficiency with biological enzymes. When the kaolin content approaches 10%, more natural macropores of diatomaceous earth are retained, enhancing the rapid conduction of odor gases and adapting to different odor concentration scenarios within the refrigerator.

[0037] In some embodiments, the pore-forming agent is a mixture of soluble starch and ammonium bicarbonate in a mass ratio of 7:3, and the total amount of the pore-forming agent added is 20% of the dry weight of the ceramic-based powder.

[0038] Soluble starch gradually burns, carbonizes, and completely volatilizes during sintering, leaving behind macropores with sizes concentrated between 5μm and 10μm. The 70% starch content ensures that sufficient macroporous channels are formed inside the carrier, serving as "drainage channels" for odor gases to quickly enter the carrier. At the same time, it provides sufficient loading space for complex bio-enzymes, avoiding the blockage of pores by enzyme molecules due to single small pores. Furthermore, the starch combustion process is gentle and does not produce violent gas impacts, ensuring that the carrier skeleton maintains its structural integrity after pore formation, preventing cracking or pore collapse.

[0039] Ammonium bicarbonate supplements the formation of small and medium-sized interconnected pores: Ammonium bicarbonate decomposes and releases NH3 and CO2 gases above 60℃. This decomposition is rapidly completed during the sintering preheating stage (250℃). The escaped gases create small and medium-sized interconnected pores (0.1μm–5μm) between the macropores formed by starch. A 30% ammonium bicarbonate content precisely supplements the "mesopores (1μm–5μm) + micropores (0.1μm–1μm)" ratio in the gradient pore size structure, constructing a "macropore drainage-mesopore enzyme storage-micropore catalysis" system. The continuous pore system: The small and medium interconnected pores can prolong the residence time of odor molecules (such as formaldehyde, methanethiol and other small molecules) inside the carrier, improve the contact efficiency with complex biological enzymes (such as cold-adapted oxidoreductase and formaldehyde dehydrogenase), and avoid the problem of "too many macropores and too few small and medium pores" caused by single starch pore formation, which in turn affects the sufficiency of enzyme catalytic reaction; In addition, the decomposition products of ammonium bicarbonate are gaseous and have no solid residue, so they will not contaminate the carrier or block the formed pores, ensuring the cleanliness and conductivity of the pores.

[0040] In some embodiments, the silane coupling agent is 3-aminopropyltriethoxysilane, and the purity of the silane coupling agent is ≥98%.

[0041] In some embodiments, the silane coupling agent modification on the surface of the porous ceramic carrier is performed using a 2% APTES ethanol solution, wherein the ethanol solution is a 95% aqueous ethanol solution, and the pH value of the ethanol solution is adjusted to 5.0-5.5 with acetic acid.

[0042] The hydrolysis of APTES is an acid-catalyzed reaction, with acetic acid, as a weak acid, providing a suitable amount of H₂. + It catalyzes the ethoxylation of APTES to generate silanol groups, within the pH range of 5.0-5.5, H + The concentration can optimize the hydrolysis rate of APTES: it avoids excessive acidity at pH < 4.0, which leads to excessively rapid hydrolysis and rapid polymerization of APTES in solution to form a precipitate (which cannot be grafted onto the carrier surface); it also avoids excessively weak acidity at pH > 6.0, which leads to a slow hydrolysis rate and a significant increase in modification reaction time (e.g., from 3 hours to more than 6 hours), thus reducing production efficiency.

[0043] In some embodiments, the porous ceramic carrier has a honeycomb structure and a specific surface area ≥300m². 2 / g.

[0044] The honeycomb structure has regular hexagonal or square channels that are interconnected. When air flows through the deodorizing block inside the refrigerator, the airflow can pass smoothly along the honeycomb channels. The resistance is only 1 / 3 to 1 / 2 of that of a granular carrier of the same volume, avoiding the accumulation of local odors due to the obstruction of the carrier structure. At the same time, the interconnected channels allow odor gases (such as formaldehyde, ammonia, and trimethylamine) to quickly penetrate into the interior of the carrier, rather than just staying on the surface of the carrier. This significantly shortens the contact time between odor molecules and the complex bio-enzymes, increasing the deodorizing response speed by 40% to 50%.

[0045] The high humidity environment inside a refrigerator can easily cause traditional porous carriers (such as block ceramics with irregular pores) to become clogged due to water vapor condensation and enzyme molecule aggregation. However, the honeycomb structure has uniform and regular pore sizes, so even if a small amount of water vapor or enzyme molecules adhere, it will not completely block the airflow channels. At the same time, the open structure of the honeycomb pores facilitates air circulation and flushing inside the refrigerator, reducing the deposition of impurities in the pores and ensuring that the odor-eliminating block maintains good gas flow during long-term use (such as more than 5 months), avoiding a sharp drop in odor-eliminating efficiency due to pore blockage.

[0046] In some embodiments, the cold-adapted oxidoreductase has an activity unit of 15000±500 U / mL and a content of 2.5~5 mg / mL, and is derived from Antarctic psychrophilic yeast; the low-temperature chitinase has an activity unit of 8000±300 U / mL and a content of 1.8~2 mg / mL, and is derived from Arctic marine bacteria; the trehalose has a content of 50.0 mg / mL.

[0047] In some embodiments, the compound bioenzyme is further supplemented with 0.5% to 1% vitamin C by mass, which acts as an antioxidant to inhibit the oxidative inactivation of the compound bioenzyme during storage and use.

[0048] Adding 0.5% to 1% by mass of vitamin C (ascorbic acid) allows it to exert a protective effect through a "preferential oxidation" mechanism: the enediol structure in the molecule of vitamin C has strong reducing properties, which can preemptively react with oxidizing substances (oxygen, peroxides) in the environment and be oxidized to dehydroascorbic acid, thereby preventing oxidizing substances from attacking the active groups of enzyme molecules; at the same time, this concentration range can ensure that vitamin C is evenly dispersed in the complex bioenzyme system, forming a stable antioxidant microenvironment.

[0049] In some embodiments, this application provides a method for preparing a composite bio-enzyme ceramic deodorizing block for refrigerators, the method comprising:

[0050] Diatomaceous earth, kaolin, pore-forming agent, and nano ZnO were weighed according to the mass ratio, mixed, and then a binder was added for wet ball milling. The mixture was then extruded into a honeycomb structure and then sintered at low temperature in segments to obtain a porous ceramic carrier.

[0051] According to the amount of porous ceramic carrier used, weigh out the corresponding amount of composite bio-enzyme stock solution, lipase, protease, formaldehyde dehydrogenase and trehalose protectant, add them to PBS buffer at pH=7.2, and mix well to obtain bio-enzyme composite loading solution.

[0052] The porous ceramic carrier is placed in the bio-enzyme composite loading liquid and subjected to vacuum impregnation, followed by freeze drying, and finally cross-linked and cured with glutaraldehyde vapor to obtain a composite bio-enzyme ceramic deodorizing block for refrigerators.

[0053] In some embodiments, low-temperature segmented sintering includes preheating at 250°C for 1 hour, followed by sintering at 400°C for 2 hours, wherein the heating rate of the low-temperature segmented sintering is 5–10°C / min.

[0054] Example

[0055] This embodiment provides a composite bio-enzyme ceramic deodorizing block for refrigerators, comprising a porous ceramic carrier and a loaded composite bio-enzyme. The composite bio-enzyme is prepared by combining composite bio-enzyme stock solution, lipase, protease, and formaldehyde dehydrogenase in a mass ratio of 4:3:2:1. It is a composite low-temperature enzyme preparation specially developed by this invention for refrigerator environments. It is not a single enzyme, but a basic enzyme group. The main active ingredients and their contents are shown in Table 1 below:

[0056] Table 1

[0057]

[0058]

[0059] Definition of active unit:

[0060] Oxidoreductase unit (U): The amount of enzyme required to catalyze the production of 1 μmol NADH per minute at pH 7.0 and a temperature of 4°C.

[0061] Chitinase unit (U): The amount of enzyme required to release 1 μmol of N-acetylglucosamine per minute from colloidal chitin at pH 6.5 and a temperature of 4°C.

[0062] The following is a method for preparing the composite bio-enzyme ceramic deodorizing block for refrigerators provided in this embodiment.

[0063] 1. Preparation of ceramic matrix

[0064] Raw materials: 60% diatomaceous earth, 20% kaolin, 15% pore-forming agent (starch), 5% nano ZnO;

[0065] Molding: Extruded into a honeycomb structure (specific surface area ≥ 300m²) 2 / g);

[0066] Sintering: Preheat at 250℃ for 1 hour → Sinter at 400℃ for 2 hours (heating rate 5℃ / min).

[0067] 2. Bioenzyme composite loading

[0068] Enzyme solution formulation (dosage per 100g carrier);

[0069]

[0070] 3. Loading process

[0071] Vacuum impregnation (-0.08MPa, 30min, 5℃) → freeze drying (-40℃, 24h) → cross-linking curing (0.5% glutaraldehyde vapor treatment for 10min);

[0072] 4. Technical effect data are shown in Table 2:

[0073] Table 2

[0074] Inspection items Experimental conditions result Formaldehyde removal rate <![CDATA[1m 3 Sealed chamber, 24 hours 93.3％ Ammonia decomposition rate <![CDATA[1m 3 Sealed chamber, 24 hours 88.4％ Trimethylamine decomposition rate <![CDATA[1m 3 Sealed chamber, 24 hours 94.2％ Methanethiol decomposition rate <![CDATA[1m 3 Sealed chamber, 24 hours 81.2％

[0075] 5. To determine the optimal compounding ratio, an orthogonal experiment was conducted to test the 24-hour removal rates (per 1m³) of formaldehyde and ammonia at different ratios. 3 The experiment was conducted in a sealed chamber with an initial concentration of 1.0 ± 0.1 ppm, a temperature of 4°C, and a humidity of 70% RH. The experimental group design (compound enzyme: lipase: protease: formaldehyde dehydrogenase = A:B:C:D) is shown in Table 3.

[0076] Table 3

[0077]

[0078] Conclusion: The ratio in Experiment 3 (20000:15000:10000:5000) showed the best overall purification efficiency and was determined as the final ratio. At this ratio, the synergistic effect of each enzyme was strongest, rather than a simple additive effect.

[0079] 6. The specific mechanism of synergistic action of the four enzymes

[0080] Using butyric acid (a short-chain fatty acid and source of odor) produced from the degradation of spoiled butter as an example, a four-stage synergistic degradation process is demonstrated:

[0081] ① Lipase performs the initial cleavage:

[0082] Lipase first attacks triglycerides, releasing free butyric acid.

[0083] R-COO-R' (ester) + H2O → R-COOH (butyric acid) + R'-OH;

[0084] ② Oxidation is dominated by oxidoreductases in complex bioenzymes:

[0085] Oxidoreductases catalyze the oxidation of butyric acid to produce butyraldehyde and water.

[0086] R-COOH (butyric acid) → R-CHO (butyraldehyde) + [O];

[0087] ③ Continue oxidation to generate the final product:

[0088] The same oxidoreductase continues to catalyze butyraldehyde, eventually producing odorless carbon dioxide and water.

[0089] R-CHO (butyraldehyde) + [O] → CO2 + H2O;

[0090] ④ Proteases and chitinases control the source:

[0091] Throughout the process, proteases break down any protein contaminants that may adhere to the surface, while chitinases inhibit mold growth and prevent the formation of new odor molecules. The entire process forms a highly efficient biocatalytic cycle, thoroughly mineralizing large molecules and highly odorous organic matter.

[0092] 7. Complete parameters of silane coupling agent modification process

[0093] ① Silane coupling agent type and purity:

[0094] Model: 3-Aminopropyltriethoxysilane (APTES, CAS No.: 919-30-2);

[0095] Purity: ≥98% (Sigma-Aldrich or equivalent reagent-grade products are recommended);

[0096] ② Preparation of the modification solution:

[0097] Concentration: 2% (v / v) APTES ethanol solution.

[0098] Solvent: 95% aqueous ethanol solution (requires deionized water for preparation).

[0099] pH value: Adjust to 5.0-5.5 with acetic acid (at this pH, APTES hydrolysis and carrier binding efficiency are optimal).

[0100] ③ Modification process parameters:

[0101] Temperature: 60±2℃;

[0102] Time: 3 hours (with continuous gentle stirring);

[0103] Solid-liquid ratio: 1g ceramic carrier: 10mL modification solution;

[0104] Post-treatment: After the reaction is complete, wash three times with anhydrous ethanol to remove the physically adsorbed coupling agent, and then vacuum dry at 80°C for 2 hours to ensure that the coupling agent is firmly bonded to the surface of the support.

[0105] 8. Gradient aperture preparation scheme

[0106] Gradient pore size is achieved through dual control of raw material particle size distribution and pore-forming agent.

[0107] ① Raw material gradation scheme:

[0108] Macropore-forming component: coarse-grained diatomaceous earth (200 mesh, particle size approximately 75 μm), accounting for 60%.

[0109] Mesopore-forming component: fine-grained kaolin (800 mesh, particle size approximately 18 μm), accounting for 25%.

[0110] Microporous and binder components: Nanoscale fumed silica (particle size 10-20nm), accounting for 15%.

[0111] Principle: When particles of different sizes are packed together, a pore size gradient is naturally formed. Large particles form the framework, creating macropores, while small particles fill the gaps, forming mesopores.

[0112] ② Method of adding pore-forming agent:

[0113] Pore-forming agent selection: soluble starch (200 mesh) and ammonium bicarbonate (NH4HCO3) are mixed in a mass ratio of 7:3.

[0114] Starch: Burns during sintering, leaving large pores.

[0115] Ammonium bicarbonate decomposes at low temperatures (above 60°C) to release NH3 and CO2 gases, creating interconnected pores.

[0116] How to add:

[0117] Mix the pore-forming agent with ceramic-based powders (diatomaceous earth, kaolin, etc.) thoroughly.

[0118] Then add the binder (such as 5% PVA solution) and wet ball mill for 4 hours to ensure uniform dispersion of the pore-forming agent.

[0119] The total amount of pore-forming agent added is 20% of the dry weight of the ceramic-based powder.

[0120] Molding and Sintering: After extrusion molding, the material is sintered at 350°C. At this temperature, the starch and ammonium bicarbonate completely decompose and volatilize, leaving abundant interconnected channels without disrupting the pre-designed particle size distribution.

[0121] As can be seen from the above embodiments, this application provides a composite bio-enzyme ceramic deodorizing block for refrigerators and its preparation method. The composite bio-enzyme ceramic deodorizing block for refrigerators includes a porous ceramic carrier and a composite bio-enzyme loaded on the porous ceramic carrier. The composite bio-enzyme is prepared by mixing a composite bio-enzyme stock solution, lipase, protease, and formaldehyde dehydrogenase in a mass ratio of 4:3:(1-2). The composite bio-enzyme includes a cold-adapted oxidoreductase, a low-temperature chitinase, and trehalose. The surface of the porous ceramic carrier is modified with a silane coupling agent, and the interior has a gradient pore size distribution of 10μm to 0.1μm. The cold-adapted oxidoreductase and low-temperature chitinase in the composite bio-enzyme are both low-temperature adapted enzymes, and trehalose is added as a low-temperature protectant. Trehalose can maintain the integrity of the three-dimensional structure of the enzyme molecule in the low-temperature environment of 0-10℃ in the refrigerator, avoiding enzyme activity loss due to low temperature. At the same time, the proportion of protease can be adjusted according to the storage ratio of protein-based foods in the refrigerator, further ensuring the decomposition efficiency of the enzyme on protein-based odor precursors at low temperatures. The surface of the porous ceramic carrier is modified with a silane coupling agent. The amino groups of the silane coupling agent can form chemical bonds with the carboxyl groups of the biological enzyme molecules. Compared with the unmodified carrier, this can significantly reduce the shedding of biological enzymes during use and improve the enzyme loading stability.

[0122] Similar parts between the embodiments provided in this application can be referred to mutually. The specific implementation methods provided above are only a few examples under the overall concept of this application and do not constitute a limitation on the scope of protection of this application. For those skilled in the art, any other implementation methods extended from the solution of this application without creative effort shall fall within the scope of protection of this application.

Claims

1. A composite bio-enzyme ceramic deodorizing block for refrigerators, characterized in that, It includes a porous ceramic support and a composite biological enzyme loaded on the porous ceramic support; The composite bio-enzyme is prepared by mixing composite bio-enzyme stock solution, lipase, protease, and formaldehyde dehydrogenase in a mass ratio of 4:3:(1-2). The composite bio-enzyme includes cold-adapted oxidoreductase, low-temperature chitinase, and phycoose. The surface of the porous ceramic support is modified with a silane coupling agent, and the interior has a gradient pore size distribution of 10 μm to 0.1 μm.

2. The composite bio-enzyme ceramic deodorizing block for refrigerators according to claim 1, characterized in that, The raw materials for preparing the porous ceramic carrier include, by mass percentage: 60-70% diatomaceous earth, 10-20% kaolin, 5-15% pore-forming agent, and 5% nano-ZnO.

3. The composite bio-enzyme ceramic deodorizing block for refrigerators according to claim 2, characterized in that, The pore-forming agent is a mixture of soluble starch and ammonium bicarbonate in a mass ratio of 7:3, and the total amount of the pore-forming agent added is 20% of the dry weight of the ceramic-based powder.

4. The composite bio-enzyme ceramic deodorizing block for refrigerators according to claim 1, characterized in that, The silane coupling agent is 3-aminopropyltriethoxysilane, and the purity of the silane coupling agent is ≥98%.

5. The composite bio-enzyme ceramic deodorizing block for refrigerators according to claim 1, characterized in that, The silane coupling agent modification on the surface of the porous ceramic carrier is performed using a 2% APTES ethanol solution, wherein the ethanol solution is a 95% aqueous ethanol solution, and the pH value of the ethanol solution is adjusted to 5.0-5.5 with acetic acid.

6. The composite bio-enzyme ceramic deodorizing block for refrigerators according to claim 1, characterized in that, The porous ceramic carrier has a honeycomb structure and a specific surface area ≥300m². 2 / g.

7. The composite bio-enzyme ceramic deodorizing block for refrigerators according to claim 1, characterized in that, The cold-adapted oxidoreductase has an activity unit of 15000±500 U / mL and a content of 2.5~5 mg / mL, and is derived from Antarctic psychrophilic yeast; the low-temperature chitinase has an activity unit of 8000±300 U / mL and a content of 1.8~2 mg / mL, and is derived from Arctic marine bacteria; the trehalose has a content of 50.0 mg / mL.

8. The composite bio-enzyme ceramic deodorizing block for refrigerators according to claim 2, characterized in that, The compound bio-enzyme also contains 0.5% to 1% vitamin C by mass. The vitamin C acts as an antioxidant to inhibit the oxidative inactivation of the compound bio-enzyme during storage and use.

9. A method for preparing a composite bio-enzyme ceramic deodorizing block for refrigerators according to any one of claims 1-8, characterized in that, The method includes: Diatomaceous earth, kaolin, pore-forming agent, and nano ZnO were weighed according to the mass ratio, mixed, and then a binder was added for wet ball milling. The mixture was then extruded into a honeycomb structure and then sintered at low temperature in segments to obtain a porous ceramic carrier. According to the amount of porous ceramic carrier used, weigh out the corresponding amount of composite bio-enzyme stock solution, lipase, protease, formaldehyde dehydrogenase and trehalose protectant, add them to PBS buffer at pH=7.2, and mix well to obtain bio-enzyme composite loading solution. The porous ceramic carrier is placed in the bio-enzyme composite loading liquid and subjected to vacuum impregnation, followed by freeze drying, and finally cross-linked and cured with glutaraldehyde vapor to obtain a composite bio-enzyme ceramic deodorizing block for refrigerators.

10. The preparation method of the composite bio-enzyme ceramic deodorizing block for refrigerators according to claim 9, characterized in that, The low-temperature segmented sintering process includes preheating at 250°C for 1 hour, followed by sintering at 400°C for 2 hours. The heating rate of the low-temperature segmented sintering is 5–10°C / min.

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