Rhodobacter foodamine and its application in treatment of high-concentration formaldehyde wastewater

Abstract

This invention relates to the field of water treatment and discloses a strain of *Methylorubrum aminovorans* and its application in treating high-concentration formaldehyde wastewater. This *Methylorubrum aminovorans* strain is named 3-5-6, and its microbiological classification is *Methylorubrum aminovorans*. It was deposited at the China General Microbiological Culture Collection Center (CGMCC) on November 24, 2025, with accession number CGMCC No. 36747. This invention provides a formaldehyde-degrading bacterium that can tolerate high concentrations of formaldehyde and optimizes its degradation conditions to improve the treatment effect of high-concentration formaldehyde wastewater.

Description

Technical Field

[0001] This invention relates to the field of water treatment, and in particular to a strain of methyl erythrobacterium glutamicum and its application in the treatment of high-concentration formaldehyde wastewater. Background Technology

[0002] Formaldehyde is a colorless gas that is difficult to detect at low concentrations but has a strong, pungent odor at higher concentrations. It is the simplest aldehyde molecule. It is highly chemically reactive, readily undergoing addition, reduction, and polymerization reactions, and is readily soluble in water, alcohols, and ethers. As an important chemical raw material, formaldehyde is widely used in industries such as plastics, textiles, synthetic fibers, pharmaceuticals, and dyes. It is a major harmful pollutant in wastewater discharged from these industries and one of the most common water pollutants.

[0003] Formaldehyde is highly toxic. Long-term exposure to low doses of formaldehyde can easily cause respiratory irritation, leading to chronic respiratory diseases and pregnancy complications, and may also cause reduced immunity and chromosomal abnormalities in newborns. High concentrations of formaldehyde can cause abnormalities in lung, liver, and immune functions, and are toxic to the nervous, immune, and liver systems. Because formaldehyde readily reacts with nucleophilic substances in cells, causing DNA damage, it exhibits significant cytotoxicity, carcinogenicity, and teratogenicity. In 2004, the International Agency for Research on Cancer (IARC) reclassified formaldehyde as a Group 1 carcinogen.

[0004] Currently, formaldehyde wastewater treatment technologies mainly include advanced oxidation technologies such as the Fenton process, photocatalytic oxidation (CN201721125594.4), and wet oxidation treatment; physicochemical treatment methods such as chlorine dioxide, steam stripping, and oxidation-adsorption; and biological treatment methods. Among these, physicochemical treatment methods generally suffer from problems such as high investment costs, rapid equipment updates, complex operation, and secondary pollution. While biological treatment methods have advantages such as good efficacy, low cost, and no secondary pollution, high concentrations of formaldehyde are highly toxic to microorganisms, resulting in drawbacks such as low treatment concentration and weak resistance to shock loads.

[0005] Given the strong ability and rapid adaptation of microorganisms to degrade pollutants, the utilization of microorganisms to degrade formaldehyde has become a research focus in formaldehyde-containing wastewater treatment in recent years. Studies have shown that microorganisms that degrade formaldehyde mainly include *Pseudomonas putida* and *Pseudomonas aeruginosa* (CN201010171729.7). However, formaldehyde can directly react with the proteins, DNA, and RNA within microorganisms, leading to microbial death or inhibition of their biological activity. Above a certain concentration, microbial activity is almost completely inhibited. Therefore, high-concentration formaldehyde is not suitable for biological treatment and requires pre-treatment for detoxification, which increases process complexity and treatment costs. Thus, developing microbial strains with high formaldehyde tolerance and degradation activity, elucidating formaldehyde tolerance and degradation mechanisms, constructing microbial communities, and developing large-scale treatment processes suitable for high-concentration formaldehyde wastewater remain urgent problems to be solved. Summary of the Invention

[0006] The purpose of this invention is to provide a formaldehyde-degrading bacterium that can tolerate high concentrations of formaldehyde in wastewater generated during various industrial production processes, and to optimize its degradation conditions to improve the treatment efficiency of high-concentration formaldehyde wastewater. The *Rhodotorula methanotroph* strain obtained in this invention exhibits excellent tolerance to high concentrations of formaldehyde and can efficiently degrade formaldehyde, thus significantly improving the tolerance and removal efficiency of biological treatment systems for formaldehyde wastewater.

[0007] The specific technical solution of the present invention includes: In a first aspect, the present invention provides a formaldehyde-degrading Methylorubrum aminovorans strain, named 3-5-6, and classified as Methylorubrum aminovorans. It was deposited at the China General Microbiological Culture Collection Center on November 24, 2025, with accession number CGMCC No. 36747.

[0008] The strain 3-5-6 provided by this invention was obtained from activated sludge in a chemical enterprise producing rubber adhesives through enrichment culture, screening, and purification. This strain can grow using formaldehyde as its sole carbon, nitrogen, and energy source. It has been identified as *Methylorubrum aminovorans*. This invention reveals that this strain possesses excellent formaldehyde degradation capabilities, and compared to other existing formaldehyde-degrading bacteria, its tolerance to high concentrations of formaldehyde is particularly outstanding, thus enabling efficient treatment of high-concentration formaldehyde wastewater. Furthermore, the emergency treatment system enhanced with *Methylorubrum aminovorans* according to this invention not only rapidly and effectively degrades formaldehyde and improves the purification performance of the treatment system, but also effectively reduces the impact of high-concentration formaldehyde wastewater on the system, improving the overall treatment effect.

[0009] Secondly, the present invention provides a formaldehyde-degradable microbial preparation containing live bacteria of the aforementioned *Rhodotorula glutinis*, fermentation products, or intracellular extracts.

[0010] Preferably, the microbial agent is a liquid or solid agent of *Bacillus thuringiensis*.

[0011] Further preferably, the bacterial solution is a fermentation broth.

[0012] Further preferably, the solid bacterial agent is freeze-dried powder or activated sludge.

[0013] Thirdly, the present invention provides the application of the above-mentioned *Rhodotorula glutinis* or the above-mentioned microbial preparation in the treatment of high-concentration formaldehyde wastewater.

[0014] Preferably, the formaldehyde concentration in the high-concentration formaldehyde wastewater is 500-2000 mg / L.

[0015] When the *Rhodotorula methylammonium* 3-5-6 strain of this invention is used for the bio-enhanced treatment of high-concentration formaldehyde wastewater, under pure culture conditions, this strain can achieve approximately 80% degradation of high-concentration formaldehyde wastewater of 2000 mg / L within 8 days. After being added to an activated sludge system for bio-enhanced treatment, this strain can degrade high-concentration formaldehyde wastewater of 1500 mg / L within 4-8 days with an HRT, and the effluent concentration is lower than the 1 mg / L formaldehyde specified in the first-level standard of the *Integrated Wastewater Discharge Standard* (GB 8978-1996). It can also effectively treat high-concentration formaldehyde wastewater in the range of 500-2000 mg / L.

[0016] Fourthly, the present invention provides a method for treating high-concentration formaldehyde wastewater, which includes the following steps: using the aforementioned *Bacillus amine-methyl* as a functional strain, inoculating it into activated sludge and then adding it into the wastewater, or directly inoculating it into the wastewater for formaldehyde biodegradation.

[0017] Preferably, the inoculum amount of *Rhodotorula glutinis* is 0.1-0.3 wt‰ based on the dry weight of the bacteria.

[0018] As a preferred option, phosphorus sources and trace elements are added to the wastewater.

[0019] Preferably, during the formaldehyde biodegradation process, the water temperature is 25-35℃ (most preferably 30℃); the pH is 7.0-8.5 (most preferably 7.5-8.0); the salinity (NaCl) of the wastewater is 0.05-1wt% (most preferably 0.05wt%); and the hydraulic retention time is controlled to be 4-10 days.

[0020] Compared with the prior art, the beneficial effects of the present invention are: (1) This invention uses a purely biological approach to treat high-concentration formaldehyde wastewater, eliminating the need for chemical reagents or high-energy-consuming equipment and fundamentally avoiding secondary pollution problems. Utilizing the highly formaldehyde-tolerant *Rhodotorula methylammonium* 3-5-6, a formaldehyde removal rate exceeding 80% was achieved with a pure culture period of approximately 8 days. Furthermore, when treating wastewater with an influent concentration of 1600 mg / L formaldehyde and 12000 mg / L COD, the effluent COD was reduced to approximately 3000 mg / L under aerobic conditions, and the effluent formaldehyde concentration was reduced to below 1 mg / L, demonstrating excellent environmental protection and treatment efficiency.

[0021] (2) The formaldehyde-degrading bacterium *Rhodotorula glutinis* 3-5-6 of this invention can efficiently degrade ≤ 500 mg / L formaldehyde in just 2 days under pure culture conditions. For wastewater with higher concentrations (such as 2000 mg / L), the degradation rate still reaches 80.6% after 8 days. After this strain is introduced into a conventional activated sludge system at a dry weight of 0.1-0.3 wt‰, it can effectively cope with a sudden increase in concentration of 600-1000 mg / L within 4-6 days of HRT, quickly restore the system's purification performance, and demonstrate excellent adaptability and high-efficiency response capability for emergency treatment.

[0022] (3) The fermentation culture method of the strain of the present invention is simple and easy to industrialize, and can be seamlessly integrated into existing domestic or industrial wastewater treatment systems, avoiding complex modifications; this method will not damage the original system's microbial ecology, nor will it affect the treatment efficiency; at the same time, the operation process is safe and there is no risk of secondary pollution, making it suitable for rapid deployment at the scene of a formaldehyde emergency. This enhanced emergency treatment solution has outstanding advantages of rapid response, convenient implementation, and safety and reliability, and has great potential for engineering promotion. Attached Figure Description

[0023] Figure 1 This is a colony photograph of *Rhodotorula glutinis* 3-5-6, the strain of this invention.

[0024] Figure 2 A comparison diagram of formaldehyde degradation by different strains. Detailed Implementation

[0025] The present invention will be further described below with reference to embodiments.

[0026] General Implementation Examples Firstly, a formaldehyde-degrading Methylorubrum aminovorans strain, named 3-5-6 and classified as Methylorubrum aminovorans, was deposited at the China General Microbiological Culture Collection Center on November 24, 2025, with accession number CGMCC No. 36747.

[0027] Secondly, a formaldehyde-degrading microbial preparation contains live bacteria of the aforementioned *Rhodotorula glutinis*, fermentation products, or extracts of intracellular substances.

[0028] In some preferred embodiments, the microbial agent is a liquid or solid agent of *Bacillus thuringiensis*.

[0029] In some further preferred embodiments, the bacterial solution is a fermentation broth.

[0030] In some further preferred embodiments, the solid microbial agent is freeze-dried powder or activated sludge.

[0031] Thirdly, the application of the aforementioned *Rhodotorula glutinis* or the aforementioned microbial preparations in the treatment of high-concentration formaldehyde wastewater.

[0032] In some preferred embodiments, the formaldehyde concentration in the high-concentration formaldehyde wastewater is 500-2000 mg / L.

[0033] Fourthly, a method for treating high-concentration formaldehyde wastewater includes the following steps: using the aforementioned *Bacillus amine-methyl* as a functional strain, inoculating it into activated sludge and then adding it into the wastewater, or directly inoculating it into the wastewater for formaldehyde biodegradation.

[0034] In some preferred embodiments, the inoculum amount of *Rhodotorula glutinis* is 0.1-0.3 wt‰ based on the dry weight of the bacteria.

[0035] In some preferred implementations, phosphorus sources and trace elements are added to the wastewater.

[0036] In some preferred embodiments, during the formaldehyde biodegradation process, the water temperature is 25-35℃ (most preferably 30℃); the pH is 7.0-8.5 (most preferably 7.5-8.0); the salinity (NaCl) of the wastewater is 0.05-1wt% (most preferably 0.05wt%); and the hydraulic retention time is controlled to be 4-10 days.

[0037] Specific embodiments and comparative examples Example 1: Screening and domestication of formaldehyde-degrading bacteria Selective culture media were prepared according to the following formula: formaldehyde 2000 mg / L, glutathione 0.5 g / L, NAD 0.1 g / L, Na₂SO₄ 0.2 g / L, sodium pyruvate 0.2 g / L, KH₂PO₄ 0.2 g / L, NaCl 0.5 g / L, (NH₄)₂SO₄ 0.7 g / L, trace element stock solution 1 mL / L, vitamin stock solution 1 mL / L, pH=7.5. Solid culture media were supplemented with 2% agar powder. All culture media were sterilized at 121 °C for 15 minutes.

[0038] The formula for the above trace element mother liquor is as follows: FeSO4·7H2O 3.6 g / L, ZnSO4·7H2O 0.3 g / L, MnSO4·H2O 0.02 g / L, CuSO4·5H2O 0.25 g / L, CoCl2·6H2O 0.1 g / L, with water as the solvent.

[0039] The formula for the above vitamin stock solution is as follows: Vitamin A 2500 IU / L, Vitamin D2 200 IU / L, Vitamin E 5 mg / L, Vitamin B1 2.5 mg / L, Vitamin B2 2.5 mg / L, Vitamin B6 0.25 mg / L, Vitamin B... 12 0.5 µg / L, Vitamin C 25 mg / L, Nicotinamide 7.5 mg / L, Calcium Pantothenate 2.5 mg / L, Choline Bitartrate 25 mg / L, Inositol 25 mg / L.

[0040] Activated sludge from the aerobic tank of a rubber adhesive chemical plant was collected and inoculated into 100 mL of selective medium at a 10 wt% inoculum. The mixture was then enriched in a shaker at 30 ℃ and 150 rpm. When the system became significantly turbid and COD and TOC decreased significantly, the resulting microbial culture was streaked onto solid selective medium. Colony morphology was observed, and single colonies were picked for further identification.

[0041] Example 2: Isolation and Identification of Strains Prepare the isolation medium (NA medium containing methanol) according to the following formula: Peptone 10 g / L, Beef Extract Powder 3 g / L, NaCl 5 g / L, and methanol 1%. For solid medium, add an additional 2% agar powder. Except for methanol, all the above media were sterilized at 121 °C for 15 min, cooled to room temperature, and then aseptically filtered through a 0.22 μm microporous membrane to obtain the methanol-containing medium.

[0042] The bacterial culture was added to fresh basic culture medium, and the formaldehyde concentration was gradually increased to acclimatize the strain. After culturing in a shaker at 30 °C, a highly efficient formaldehyde-degrading strain was isolated and named 3-5-6. After culturing strain 3-5-6 on NA medium plates containing methanol for 36 hours, red colonies were formed (e.g., ...). Figure 1(As shown). This strain is a non-spore-forming Gram-negative aerobic bacillus with unipolar flagellar motility; colonies are mostly red, and under certain conditions, it can produce bacterial chlorophyll a. Biochemically, it does not reduce nitrates, does not produce indole or hydrogen sulfide, and does not hydrolyze gelatin or starch; it is positive for urease, oxidase, and catalase. Metabolically, it utilizes methanol via the serine pathway with an intact TCA, exhibiting a narrow substrate utilization spectrum; it grows well at pH 6-8 and 30 °C, but cannot grow in 3% NaCl. The DNA contains 68% G+C, and the main fatty acid is octadecenoic acid (C3C4). 18:1 The main hydroxy fatty acid is 3-hydroxytetradecanoic acid (3-OHC). 14:0 The main ubiquinone is Q-10.

[0043] Sequencing results of the 16S rRNA gene of strain 3-5-6 were compared with those in the EzBioCloud database. The results showed that the 16S rRNA gene of strain 3-5-6 shared the highest homology (100%) with the 16S rRNA gene of *Methylorubrum aminovorans*. Phylogenetic tree construction revealed that strain 3-5-6 was clustered on the same branch as members of the *Methylorubrum* genus and was relatively stable. Therefore, based on morphological, physiological, and biochemical indicators, and 16S rDNA gene sequence analysis, this strain was ultimately identified as *Methylorubrum aminovorans*.

[0044] After identification, *Rhodotorula glutinis* 3-5-6 was deposited at the China General Microbiological Culture Collection Center (CGMCC) with accession number CGMCC No. 36747 and deposit date of November 24, 2025.

[0045] Example 3: The ability of *Rhodotorula glutinis* 3-5-6 to degrade formaldehyde and influencing factors (1) Preparation of seed liquid *Rhodotorula glutinis* 3-5-6 were inoculated onto methanol-containing NA solid medium (same as in Example 2) and cultured at 30 °C for 3 days. Subsequently, single colonies were inoculated onto methanol-containing NA liquid medium (same as in Example 2) and cultured at 30 °C and 120 r / min until OD... 600nm Reaching a value of 1.0, it is prepared as a seed solution.

[0046] (2) Effect of temperature on formaldehyde degradation Under the same acclimatization medium (containing 2000 mg / L formaldehyde) as in Example 1, with all other components and culture conditions unchanged, 100 mL of the acclimatization medium was placed in a 250 mL Erlenmeyer flask, and seed culture was added at an inoculation rate of 10 wt%. After mixing, the flask was placed in a shaker and cultured at 120 r / min. The flask was cultured for 8 days at seven temperature gradients: 10 ℃, 20 ℃, 25 ℃, 30 ℃, 35 ℃, 40 ℃, and 45 ℃. After the culture was completed, the supernatant was separated by centrifugation, and its chemical oxygen demand (COD) and formaldehyde content were measured. The COD removal rate and formaldehyde removal rate were calculated accordingly, and the results are shown in Table 1.

[0047] Table 1 The data in Table 1 show that the optimal temperature for formaldehyde degradation by *Rhodotorula glutinis* 3-5-6 is 25-40℃, with the optimal temperature being 30℃.

[0048] (3) Effect of pH on formaldehyde degradation Under the same acclimatization medium (containing 2000 mg / L formaldehyde) as in Example 1, all other components and culture conditions remained unchanged, except that the pH of the medium was adjusted to 6.0, 6.5, 7.0, 7.5, 8.0, 8.5, 9.0, and 10.0, respectively. 100 mL of acclimatization medium was placed in a 250 mL Erlenmeyer flask, and the seed culture obtained in step (1) was added at a 10 wt% inoculum. After mixing, the flask was placed in a shaker and cultured at 30 °C and 120 r / min for 8 days. After the culture was completed, the supernatant was centrifuged, and its COD and formaldehyde contents were determined. The removal rates of COD and formaldehyde were calculated accordingly. The results are detailed in Table 2.

[0049] Table 2 The data in Table 2 show that the optimal pH for *Rhodotorula glutinis* 3-5-6 to degrade formaldehyde is 7.0-8.5, and this strain exhibits the strongest degradation ability under pH conditions of 7.5-8.0: COD removal rate can reach over 80%, and formaldehyde removal rate can reach over 90%.

[0050] (4) Effect of salinity on formaldehyde degradation Under the same acclimatization culture medium conditions as in Example 1, only the NaCl content was changed, while the other components and culture conditions remained unchanged. The NaCl content was set to 0.5 g / L, 5 g / L, 10 g / L, 20 g / L, 30 g / L, 40 g / L, and 50 g / L (corresponding salinities of 0.05%, 0.5%, 1.0%, 2.0%, 3.0%, 4.0%, and 5.0%). 100 mL of acclimatization culture medium was placed in a 250 mL Erlenmeyer flask for each group, and the seed culture from step (1) was added at a 10 wt% inoculum. After mixing, the flask was placed in a shaker at 30 ℃ and 120 r / min for 8 days. After the culture was completed, the supernatant was centrifuged, and its COD and formaldehyde contents were measured. The removal rates of COD and formaldehyde were calculated accordingly. The results are detailed in Table 3.

[0051] Table 3 The data in Table 3 show that the optimal salinity range for *Rhodotorula glutinis* 3-5-6 in formaldehyde degradation is 0.05% (approximately 0.5 g / L NaCl). Within a salinity range of 0.05%-1%, this strain maintains good activity, with formaldehyde removal rates exceeding 70%. When the salinity rises to 2.0%, although the degradation ability decreases somewhat, a COD removal rate of approximately 59% and a formaldehyde removal rate of approximately 49% can still be achieved. At a salinity of 3.0%, the strain can still maintain a COD removal rate exceeding 40% and a formaldehyde removal rate exceeding 35%. However, when the salinity further increases to 4.0%, the COD and formaldehyde removal rates decrease significantly; and when the salinity reaches 5.0%, strain growth may be significantly inhibited, leading to a significant decrease in its formaldehyde degradation effect.

[0052] (5) Effect of time on formaldehyde degradation Under the same acclimatization medium (containing 2000 mg / L formaldehyde) as used in Example 1, all other components and culture conditions remained unchanged. 100 mL of this acclimatization medium was placed in a 250 mL Erlenmeyer flask, and seed culture was added at an inoculation rate of 10 wt%. After mixing, the flask was placed in a shaker and cultured at 30 °C and 120 r / min for different time periods (0 days, 2 days, 4 days, 6 days, and 8 days, respectively). After culture, the supernatant was separated by centrifugation, and its COD and formaldehyde contents were measured. The COD and formaldehyde removal rates were calculated accordingly. The results are shown in Table 4.

[0053] Table 4 According to the data in Table 4, the static shake-flask experiment results show that *Rhodotorula glutinis* 3-5-6 can efficiently degrade formaldehyde and exhibits good adaptability under the following conditions: temperature range of 25-35 ℃, pH range of 7.0-8.5, and salinity range of 0.05%-1.0%. Under these conditions, *Rhodotorula glutinis* 3-5-6 can achieve a COD removal rate of over 50% and a formaldehyde removal rate of over 30% within 4 days. Further optimization experiments show that the optimal conditions for formaldehyde degradation by *Rhodotorula glutinis* 3-5-6 are: temperature of 30 ℃, pH of 7.5-8.0, and NaCl salinity of 0.05%. Under these optimal conditions, *Rhodotorula glutinis* 3-5-6 can achieve a COD removal rate of over 60% and a formaldehyde removal rate of over 40% within 4 days. These results indicate that *Rhodotorula glutinis* 3-5-6 has excellent degradation capabilities under specific environmental conditions and is suitable for formaldehyde treatment.

[0054] (6) Comparison of degradation abilities of strains of the same genus To verify the degradation advantage of *Methylorubrum extorquens* 3-5-6 in high-concentration formaldehyde environments, two control strains, *Methylorubrum extorquens* and *Methylorubrum seudosasae*, were selected for parallel experiments. Both strains were isolated from wastewater from the environmental protection station of Jiangxi Shanyuan Pharmaceutical Co., Ltd.

[0055] Under the same acclimatization medium (containing 2000 mg / L formaldehyde) as in Example 1, keeping other components and culture conditions unchanged, the seed culture of each strain was inoculated at a rate of 10 wt% into 250 mL Erlenmeyer flasks containing 100 mL of medium. After mixing, the flasks were placed in a shaker and cultured at 30 °C and 120 r / min. Samples were taken on days 0, 2, 4, 6, and 8, and the supernatant was centrifuged to determine the formaldehyde content. The results are shown in [Figure 1]. Figure 2 .

[0056] Experimental results showed that under high formaldehyde stress of 2000 mg / L, the control strain *Methylorubrum extorquens* exhibited relatively slow degradation, with a removal rate of 45.8% on day 8. The control strain *Methylorubrum pseudosasae* was more significantly inhibited during the experimental period, with a removal rate of only 30.4% on day 8. In contrast, the present invention strain *Methylorubrum 3-5-6* demonstrated a significant degradation advantage, achieving a removal rate of 24.0% on day 2 and reaching as high as 80.6% on day 8. This confirms that *Methylorubrum 3-5-6* has stronger tolerance and more efficient degradation ability to high concentrations of formaldehyde compared to other strains in the same genus, maintaining high activity under high substrate concentration conditions.

[0057] Example 4: The treatment capacity of Rhodotorula glutinis 3-5-6 for formaldehyde wastewater.

[0058] (1) Sources of wastewater The wastewater in this embodiment was taken from a pharmaceutical intermediate manufacturing enterprise in Inner Mongolia. This enterprise mainly produces products such as glyoxal, glyoxylic acid, and p-hydroxybenzylhydantoin. The comprehensive wastewater generated during the production process has a complex composition, containing formaldehyde, urea, phenol, glyoxylic acid and its hydrochloride, p-hydroxybenzylhydantoin and its intermediates, trace amounts of glyoxylic acid, trace elements, and pesticide intermediates. The main water quality indicators of the raw wastewater are shown in Table 5.

[0059] Table 5 (2) Wastewater nutrient adjustment Take the raw wastewater and supplement it with phosphorus source and trace elements to meet the growth and metabolic needs of microorganisms: add 0.5 g / L KH2PO4 and 1 mL / L trace element solution (the formula of the trace element solution is the same as in Example 1 of this application). Then adjust the pH to 7.0 to obtain the nutrient-adjusted wastewater (hereinafter referred to as "adjusted wastewater").

[0060] (3) Wastewater treatment test simulation To simulate continuous operation of the project, optimize treatment efficiency, and evaluate the sustained treatment capacity of the microbial community, a dynamic experiment involving continuous influent and effluent was conducted. The prepared wastewater was continuously pumped into the biological treatment unit, with a hydraulic retention time of 6 days. Simultaneously, *Bacillus methylprednisolone* 3-5-6 inoculum was added to the unit at a rate of 0.2 wt‰ (dry weight of bacteria), and effluent was continuously discharged concurrently. Basic water quality testing was performed daily during operation. After the effluent quality stabilized, the chemical oxygen demand (COD), ammonia nitrogen (NH3-N), organic nitrogen, and total nitrogen (TN) in the effluent were continuously statistically analyzed over two weeks, and their average values ​​were calculated. The results are shown in Table 6.

[0061] Table 6 As shown in Table 6, the present invention, *Bacillus methyl 3-5-6*, has a good treatment effect on complex organic wastewater containing formaldehyde, and can effectively reduce the COD of the effluent; at the same time, the formaldehyde-related indicators in the effluent meet the relevant emission control requirements.

[0062] The above experimental results show that: (1) The present invention, using *Bacillus methylammonium* 3-5-6, achieves a formaldehyde removal rate of over 80% in a pure culture period of approximately 8 days. Furthermore, when treating wastewater with an influent concentration of 1600 mg / L formaldehyde and 12000 mg / L COD, the effluent COD is reduced to approximately 3000 mg / L under aerobic conditions, and the effluent formaldehyde concentration can be reduced to below 1 mg / L, demonstrating excellent environmental protection and treatment efficiency.

[0063] (2) The *Bacillus methylammonium* 3-5-6 of this invention can efficiently degrade ≤500 mg / L formaldehyde in just 2 days under pure culture conditions. For wastewater with higher concentrations (such as 2000 mg / L), the degradation rate still reaches 80.6% after 8 days. After introducing this strain into a conventional activated sludge system at a dry weight of 0.1-0.3 wt‰, it can effectively cope with a sudden increase in concentration of 600-1000 mg / L within 4-6 days of HRT, quickly restore the system's purification performance, and demonstrate excellent adaptability and high-efficiency response capability for emergency treatment.

[0064] Unless otherwise stated, the raw materials, reagents, and equipment used in this invention are all conventional raw materials, reagents, and equipment in the art; the methods used in this invention, unless otherwise specified, are all conventional methods in the art. The above embodiments are only used to illustrate the technical solutions of this invention and do not constitute a limitation on the scope of protection of this invention; equivalent substitutions or modifications made by those skilled in the art without departing from the technical essence of this invention should all fall within the scope of protection of this invention.

Claims

1. A formaldehyde-degrading bacterium, characterized in that: Named 3-5-6, and its microbiological classification is Methylorubrum aminovorans, it was deposited at the China General Microbiological Culture Collection Center on November 24, 2025, with the accession number CGMCC No. 36747.

2. The application of *Rhodotorula glutinis* according to claim 1 in the treatment of high-concentration formaldehyde wastewater.

3. The application according to claim 2, characterized in that: The formaldehyde concentration in the high-concentration formaldehyde wastewater is 500-2000 mg / L.

4. A formaldehyde-degrading microbial preparation, characterized in that: Contains live bacteria, fermentation products, or intracellular extracts of *Rhodotorula glutinis* as described in claim 1.

5. The microbial preparation according to claim 4, characterized in that: The microbial agent is a liquid or solid agent of *Bacillus thuringiensis*.

6. The microbial preparation according to claim 5, characterized in that: The bacterial solution is a fermentation broth; and / or The solid microbial agent is freeze-dried powder or activated sludge.

7. The application of the microbial preparation according to any one of claims 4-6 in the treatment of high-concentration formaldehyde wastewater.

8. The application according to claim 7, characterized in that: The formaldehyde concentration in the high-concentration formaldehyde wastewater is 500-2000 mg / L.

9. A method for treating high-concentration formaldehyde wastewater, characterized in that: The process includes the following steps: using the *Bacillus methyl erythrorhizium* as described in claim 1 as a functional strain, inoculating it into activated sludge and then adding it to wastewater, or directly inoculating it into wastewater, to carry out formaldehyde biodegradation.

10. The processing method according to claim 9, characterized in that: The inoculum amount of *Rhodotorula glutinis* is 0.1-0.3 wt‰ based on bacterial dry weight; and / or Supplementing wastewater with phosphorus sources and trace elements; and / or During the formaldehyde biodegradation process, the water temperature is 25-35℃; the pH is 7.0-8.5; the salinity of the wastewater is 0.05-1wt%; and the hydraulic retention time is controlled to be 4-10 days.

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