Aspergillus shiirii and application thereof in preparation of selenium-rich black tea by fermentation

Abstract

The application provides a strain of Aspergillus shivaramii and an application, and belongs to the technical field of microorganisms, wherein the strain is preserved in the China General Microbiological Culture Collection Center, and the preservation number is CGMCC No.42256; the strain is separated from the inside of tea pile in the process of selenium-rich Fuzhuan tea flower, and is determined as a new strain of Aspergillus shivaramii after isolation, purification, morphological identification and molecular biological identification, and can grow well in a PDA culture medium containing selenium or black tea raw materials and complete the process of flower production. When the strain is applied to the fermentation of selenium-rich black tea to prepare Fuzhuan tea, Fuzhuan tea products with different concentrations of aged woody aroma, floral aroma and fruity aroma can be obtained under different selenium concentrations, and different selenium-rich Fuzhuan tea products with different flavors can be prepared through the characteristics, so that different Fuzhuan tea flavors can be adjusted in time in the market. Compared with a traditional method for adjusting the flavor of Fuzhuan tea, the single-bacterium regulation has good stability and has a high market prospect.

Description

Technical Field

[0001] This invention belongs to the field of microbial technology, specifically relating to Aspergillus schavar and its application in the fermentation of selenium-enriched dark tea to prepare Fu brick tea. Background Technology

[0002] Aspergillus chevaleri ( Aspergillus chevalieri *Aspergillus chevalieri* is a filamentous fungus belonging to the genus *Aspergillus*, a non-type strain, native to China, and commonly found in fermentation substrates such as high-temperature daqu (a type of starter culture) and Fu brick tea. *Aspergillus chevalieri* imparts a unique "floral aroma" to tea, a complex fragrance that blends floral, woody, and minty notes, creating its signature aroma characteristics. *Aspergillus chevalieri* is one of the core fungal species responsible for the "golden flower" aroma in Fu brick tea. Fermentation is essentially a chemical process involving the oxidation, polymerization, and degradation of substances within tea leaves under both enzymatic and non-enzymatic conditions. During tea processing, aroma compounds are formed primarily through the following pathways: 1. Enzymatic oxidation: During withering and oxidation, tea cells are damaged, increasing the activity of endogenous enzymes and promoting the conversion of aroma precursors into volatile aroma compounds. 2. Thermochemical reactions: During fixation and baking, high temperatures promote the polymerization of polyphenols and Maillard reactions between amino acids and sugars, generating various aroma compounds. 3. Microbial metabolism: In the pile fermentation process of dark tea, microorganisms decompose macromolecules in the tea leaves through their secondary metabolism, generating unique aged aroma compounds. The dominance and degree of these pathways vary among teas with different fermentation levels, resulting in distinct aroma characteristics for each type.

[0003] Fu brick tea primarily relies on the metabolism of microorganisms such as *Aspergillus cristatus* or *Aspergillus chevallis* to directly produce a unique floral or aged aroma, which is the most significant characteristic distinguishing Fu brick tea from other dark teas (such as ripe Pu-erh tea and Liubao tea). *Aspergillus chevallis*, through the secretion of highly active esterases and ferulic acid esterases, directionally converts precursor substances in tea leaves into core floral and fruity aroma components such as linalool and 1-octen-3-ol, making it a key microorganism in the formation of the "floral aroma" in Fu brick tea. These key floral and fruity aroma substances significantly enhance the complex layers of sweet floral, fruity, and floral aromas in the tea soup.

[0004] Woody aromas typically manifest as a calm, restrained, and dry fragrance. Unlike floral aromas, they are not overpowering but rather serve as the "skeleton" or "base" of the dark tea's aroma, giving the tea soup a rich and stable texture. High-quality woody aromas smell clean and pure, without any musty or off-flavors, and upon tasting, one can experience a lingering sweetness similar to chewing dry twigs. Aged aroma is a complex and layered fragrance. It may manifest as medicinal, jujube, ginseng, honey, or a scent reminiscent of old paper from a vintage book. The core characteristics of aged aroma are "mellowness" and "purity." It smells comfortable and natural, without any harshness. In terms of taste, dark tea with an aged aroma usually has a smoother, more mellow mouthfeel, a long-lasting throat feel, and leaves one feeling refreshed and relaxed after drinking.

[0005] The market demands for fermented Fu brick tea with different flavors. Generally, different strains of Aspergillus cristatus, Aspergillus niger, or Aspergillus schafer are inoculated to adjust the flavor. In this invention, we found that the aroma of fermented Aspergillus schafer under different selenium concentrations is significantly different. The appropriate concentration of selenium can promote the growth and metabolic activity of Aspergillus schafer, causing it to show different results in the expression of aroma-related enzymes and the synthesis of aroma substances. Therefore, this characteristic can be used to ferment Fu brick tea products with different flavors. Summary of the Invention

[0006] The purpose of this invention is to provide a strain of Aspergillus chevalieri and its applications. This strain was deposited on October 27, 2025, at the China General Microbiological Culture Collection Center (CGMCC) under the name AKFX-003 and accession number CGMCC No. 42256.

[0007] The *Aspergillus schwanniferus* provided by this invention has the following characteristics: Taxonomic characteristics: This strain belongs to the kingdom Fungi, phylum Ascomycota, class Eurotiomycetes, order Eurotiales, family Aspergillaceae, and genus Aspergillus. Based on ITS sequence and β-tubulin gene sequence analysis, it was identified as *Aspergillus schevalieri*.

[0008] Morphological characteristics: On PDA medium, the initial colony is white and fluffy. As the culture time increases, a large number of brown to dark brown conidia are gradually produced. The overall colony is full and the mycelium grows densely. Under a microscope, septate hyphae can be seen, the conidiophores are smooth, the apical sac is typically hemispherical, and the sporulation structure is double-layered.

[0009] This invention also provides a method for preparing Fu brick tea with floral, fruity, woody, and aged aromas, characterized by comprising the following steps: (1) Add sodium selenite to the raw materials of black tea to adjust the total selenium content of the raw materials to 0.9-4.1 mg / kg, and sterilize; (2) The Aspergillus schwanniferus CGMCC No. 42256 was inoculated onto the raw material obtained in step (1) and fermented. (3) After fermentation, dry the tea to obtain a tea with floral, fruity, woody and aged aroma.

[0010] In step (1), the raw material for the black tea is Ziyang selenium-rich black tea.

[0011] Before adding sodium selenite, the moisture content of the raw materials should be adjusted to 25%–28%. Specifically, the sterilization process involves sterilizing at 121°C for 15–20 minutes.

[0012] In step (2), the inoculation specifically involves inoculating the Aspergillus serrata seed liquid into black tea at a volume-to-mass ratio of 5%, and then allowing it to ferment under conditions of 28±2℃ and 70%~75% relative humidity.

[0013] The fermentation time is 12 days, during which the compost is turned over every 3 days.

[0014] Among them, when the total selenium content of the raw materials is adjusted to 1.0±0.1 mg / kg in step (1), the selenium-enriched Fu tea is mainly characterized by floral and fruity aromas; when it is adjusted to 2.0±0.1 mg / kg, the selenium-enriched Fu tea has both aged and woody aromas, as well as floral and fruity aromas; when it is adjusted to 4.0±0.1 mg / kg, the selenium-enriched Fu tea is mainly characterized by aged and woody aromas. Beneficial effects

[0015] (1) The Aspergillus serrata CGMCC No.42256 obtained by screening in this invention is itself a dominant strain of "golden flower" selected from selenium-containing Fu brick tea. It can adapt to the fermentation environment of selenium-containing dark tea, grow and reproduce rapidly in a culture medium containing a certain amount of sodium selenite, and can stably exert its aroma-producing function. It realizes the directional regulation of the aroma of Fu tea under single strain fermentation. For the first time, a clear dose-response relationship was discovered between the aroma style and the total selenium content of the raw materials in the Fu brick tea system fermented with pure Aspergillus schwanniferum: when the total selenium content was 1.0 mg / kg, the product was rich in floral / fruity aroma compounds such as linalool oxide, benzaldehyde, and benzyl alcohol, presenting a fresh and pleasant floral and fruity aroma overall; when the total selenium content increased to 2.0 mg / kg, the proportion of woody / aged aroma compounds (such as 4-ethylphenol and 1,2,3-trimethoxybenzene) increased, while the proportion of floral / fruity aroma compounds remained significant, forming a harmonious intermediate aroma profile with floral, fruity, and aged notes; when the total selenium content reached 4.0 mg / kg, woody / aged aroma components increased significantly and became dominant, while the content of floral aroma compounds decreased significantly, and the product exhibited a rich woody and aged aroma characteristic. This pattern allows for the precise acquisition of a series of products covering "floral / fruity," "intermediate," and "woody / aged" aroma profiles under the same strain and process flow simply by changing the amount of selenium added to the raw materials, truly achieving on-demand flavor design.

[0016] (2) This invention greatly simplifies the process of flavor control in Fu brick tea, making it suitable for large-scale industrial production. Traditional Fu brick tea production often requires screening and compounding different microbial communities (such as adjusting the proportions of *Aspergillus cristatus*, yeast, and bacteria) to adjust the aroma style, or using complex methods such as changing temperature and humidity, turning frequency, and fermentation cycle to influence microbial metabolism. This process is cumbersome and results in large batch-to-batch fluctuations. This invention uses only one strain of *Aspergillus sieboldii*, with selenium content as the single control variable. It eliminates the need for frequent changes or domestication of the strain, while keeping the remaining fermentation steps unchanged. This provides a wide process window and simple operation. By simply adding the selenium source at the target concentration during the pretreatment stage of the raw black tea material, the product aroma can be quickly switched on the same production line, greatly reducing the technical threshold and switching costs for flavor control. This makes it very suitable for continuous, standardized, and large-scale industrial production.

[0017] (3) Significantly shortens aging time and reduces storage costs. The rich aged aroma and woody fragrance of traditional Fu brick tea rely on a post-fermentation and aging process that lasts for months or even years, which not only occupies a lot of storage space but also causes slow capital turnover. Under the condition of high total selenium content (e.g., 4.0 mg / kg), the present invention can accumulate a large amount of aged / woody fragrance characteristic substances such as 4-ethylphenol and 1,2,3-trimethoxybenzene during the fermentation stage, so that the product exhibits aroma characteristics similar to long-term aging after fermentation. It can be put on the market without long storage and aging, which greatly shortens the production cycle, reduces inventory pressure and storage costs, and significantly improves production efficiency and economic benefits.

[0018] (4) Good batch-to-batch consistency in flavor and stable product quality. Due to the use of a single strain of pure culture for fermentation, the metabolic background is clear, eliminating the aroma uncertainty caused by the drift of microbial community structure during multi-strain co-fermentation. Under the condition of a fixed total selenium content, the aroma profile of Fu tea prepared by the same process has high reproducibility and small batch-to-batch differences, which is conducive to the brand to establish a standardized flavor profile and quality control system. This characteristic of "total selenium content determines aroma type, and single strain ensures stability" allows the product to highlight its distinctive aroma type while maintaining the basic style of Fu tea, ensuring the consistency of consumer experience.

[0019] (5) Flexibly meet diverse consumer demands and expand market space. By simply adjusting the selenium content, various selenium-enriched Fu brick tea products can be produced, such as floral and fruity aromas, aged and woody aromas, and a combination of both. Floral and fruity aromas are suitable for young people and female consumers who prefer a fresh and fragrant taste; aged and woody aromas are more favored by traditional tea drinkers and middle-aged and elderly consumers. Enterprises can flexibly schedule production according to market feedback, and use the same set of fermentation equipment to achieve flexible manufacturing of multiple varieties, small batches, and rapid production changes, enriching the product matrix and enhancing market competitiveness with almost no increase in hardware investment.

[0020] (6) While achieving flavor control, the product is endowed with a scientifically reasonable selenium content. The total selenium content is controlled within the range of 1.0 to 4.0 mg / kg, which not only meets the nutritional fortification needs of selenium-enriched tea, but also falls within the safe intake range. The product organically combines selenium supplementation function with a pleasant sensory experience, overcoming the problems of some selenium-enriched teas on the market having a single aroma, strong fermentation odor, or substandard selenium content. The concept of "selenium-enriched Fu brick tea with selectable flavors" further enhances the added value of the product.

[0021] (7) The single strain is safe and controllable, avoiding the risks of contaminating bacteria and harmful metabolites. The entire fermentation process uses pure Aspergillus chevaleris strain, which has a simple and stable fermentation microecology and is not prone to the growth of toxin-producing fungi such as Aspergillus flavus, significantly reducing the possibility of the production of harmful secondary metabolites and ensuring food safety. At the same time, the preparation, preservation and use of the single-strain fermentation agent are simple, reducing the risk of strain degradation or contamination caused by dependence on traditional "golden flower" bacteria, and making operation and management more convenient.

[0022] (8) This invention provides a novel approach to regulating the aroma of fermented tea based on trace elements. It reveals the crucial role of selenium in influencing the secondary metabolism of Aspergillus chevaleris, particularly in the synthesis of volatile aroma components, and confirms that the directional design of the main aroma profile of fermented tea can be achieved through the differentiated addition of trace elements. This regulatory strategy not only has direct guiding significance for the production of selenium-enriched Fu brick tea, but also provides a novel and easily engineerable methodological reference for the flavor modification of other post-fermented teas such as Pu'er tea and black tea, and even a wider range of fermented foods, demonstrating significant pioneering potential and promising prospects for widespread application. Attached Figure Description

[0023] Figure 1 Colony morphology of Aspergillus schwannii CGMCC No. 42256 at different stages on PDA medium.

[0024] Figure 2 Hyphae and conidial structures of Aspergillus chevaleri CGMCC No. 42256 under an optical microscope.

[0025] Figure 3 Metabolite diagram of Aspergillus chevaleri CGMCC No. 42256.

[0026] Figure 4 Growth curves of Aspergillus schwanniferus CGMCC No. 42256 at different selenium concentrations.

[0027] Figure 5 Aroma data of black tea fermented with Aspergillus schwanniferus CGMCC No. 42256 and containing 1.0 mg / kg selenium.

[0028] Figure 6 Extraction ion chromatogram and total ion chromatogram of black tea fermented with Aspergillus schwannii CGMCC No. 42256 and containing 1.0 mg / kg selenium.

[0029] Figure 7 Aroma data of black tea fermented with Aspergillus schwanniferus CGMCC No. 42256 with a selenium content of 2.0 mg / kg.

[0030] Figure 8 Extraction ion chromatogram and total ion chromatogram of black tea fermented with Aspergillus chevalericus CGMCC No. 42256 and containing 2.0 mg / kg selenium.

[0031] Figure 9 Aroma data of black tea fermented with Aspergillus schwanniferus CGMCC No. 42256 with a selenium content of 4.0 mg / kg.

[0032] Figure 10 Extraction ion chromatogram and total ion chromatogram of black tea fermented with Aspergillus schwannii CGMCC No. 42256 with a selenium content of 4.0 mg / kg. Detailed Implementation

[0033] The present invention will be further described below with reference to specific embodiments.

[0034] In this embodiment, all fermentation substrates were Ziyang selenium-rich black tea, specifically made from fresh leaves harvested in late spring and early summer in Ziyang County, processed through steps such as fixation, rolling, piling, and sun-drying. Ziyang County has high selenium content in its soil, with some areas exceeding 10 mg / kg. The selenium-rich black tea used in this study contained between 0.631 and 4.906 mg / kg of selenium, exceeding the national standard of 0.22 mg / kg for selenium enrichment. Example 1

[0035] This embodiment provides a method for the isolation, identification, and preservation of the strain *Aspergillus sieversi* of the present invention, as detailed below.

[0036] Sample collection: Fermented Fu brick tea samples were collected from Ziyang County, Ankang City, Shaanxi Province.

[0037] Separation and purification: Take 10 g of a sample of fermented Fu brick tea from Ziyang County with good aroma, add 90 mL of sterile water, and shake to mix. After serial dilution of the supernatant, spread it onto Martin's agar plates containing 2% glucose (with 0.5% K₂Cr₂O₇ added to inhibit bacteria), and incubate at 28℃ for 5–7 days. Look for well-grown, yellowish-brown typical mold colonies on the plates. Pick the target colonies with an inoculation needle and perform repeated streak plating on CYA agar plates until multiple morphologically identical pure colonies are obtained.

[0038] The fermented *Aspergillus chevaleri* exhibits woody, camphorate, and light floral aromas, along with coumarin-like notes and a slight musky undertone, blending with the woody notes to create a mellow, aged aroma base. Its colony morphology at different stages on PDA medium is shown in [Figure / image / description]. Figure 1 The hyphae and conidia structures under an optical microscope are shown below. Figure 2 .

[0039] Depend on Figure 1 and Figure 2 It can be seen that the strain initially forms white, fluffy colonies on PDA medium. As the culture time increases, it gradually produces a large number of brown to dark brown conidia. The overall colony morphology is full and the mycelium grows densely. Under the microscope, septate hyphae, smooth conidiophores, and typical hemispherical vesicles are visible. The sporulation structure is double-layered, which is consistent with the morphological characteristics of Aspergillus chevaleri.

[0040] Molecular biological identification: Genomic DNA was extracted, and the ITS region and β-tubulin gene were amplified.

[0041] Sequencing yields the sequence (as shown in the provided sequence fragments; the full-length sequence is assembled).

[0042] BLAST comparison in the NCBI database showed that it had more than 99% homology with Aspergillus chevalieri.

[0043] The genome sequence of *Aspergillus schwanniferus* was _TSS20251021-022-01559-BSND . Preservation: The purified strain was inoculated onto a PDA slant and sent to the China General Microbiological Culture Collection Center (CGMCC). The preservation date was October 27, 2025, and the preservation number was CGMCC No. 42256. Example 2

[0044] This embodiment uses black tea culture medium as a basis to provide growth curves of Aspergillus chevaleri at different selenium concentrations. The specific method is as follows.

[0045] Preserved *Aspergillus chevaleri* was inoculated onto fresh PDA plates and incubated at 28°C for 7 days until colonies matured and spores formed in large quantities. The colony surface was rinsed with sterile water, and the spore suspension was collected. Mycelial fragments were removed by filtration through gauze, and the spore concentration was adjusted to 1×10⁻⁶ using a hemocytometer. 6 The concentration of Aspergillus schwanniferus spores was increased to 1 / mL to obtain the Aspergillus schwanniferus spore solution.

[0046] Black tea was steeped in 95℃ hot water for 1 hour, and 3% glucose was added. The final concentration of sodium selenite in the culture medium was adjusted to 0, 10, 20, 40, and 80 μg / mL according to different gradients. Then, the medium was sterilized at 121℃ to obtain black tea culture medium with different selenium concentrations. Aspergillus spores were inoculated into the medium at a rate of 5% and cultured on a shaker.

[0047] Set up 3 parallel culture flasks, and terminate the culture and take samples at each time point (0, 0.5, 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, 5, 5.5, 6, 6.5, 7 days).

[0048] The culture medium was filtered through a glass fiber filter of known constant weight. The mycelium was washed 2-3 times with a small amount of sterile water or physiological saline to remove residual culture medium components. The filter paper containing the mycelium was placed in an oven and dried at 80-105℃ until constant weight. After cooling, it was weighed, and the dry weight of the mycelium was calculated. Mycelial dry weight (g / 100mL) = Mycelium / Culture medium volume (100mL) A growth curve was plotted with culture time on the x-axis and mycelial dry weight on the y-axis, as shown in the figure. Figure 4 .

[0049] Depend on Figure 4 It can be seen that within the sodium selenite concentration range of 0~20μg / mL, the addition of sodium selenite has little effect on the growth rate of Aspergillus chevaleris. Overall, the mycelial dry weight during the stable period of the selenium-containing fermentation broth is lower than that of the unselenium-added fermentation broth. When the sodium selenite concentration increases to 40μg / mL, the growth rate of the strain slows down, but can still maintain a relatively normal level. When the selenium content is 80μg / mL, the growth of the strain is significantly inhibited, and the mycelial dry weight is only about 30% of that of the control group. This indicates that this strain can tolerate a sodium selenite concentration of no more than 80μg / mL. Within this concentration range, the strain can still survive and grow, meeting the requirements of selenium-enriched Fu brick tea fermentation. Example 3

[0050] This embodiment provides a method for fermenting Ziyang selenium-rich black tea using Aspergillus schwanniferus, as detailed below.

[0051] Raw material pretreatment: Take Ziyang selenium-rich black tea, adjust the moisture content to 25%~28%, calculate the amount of each type of black tea according to the measured selenium content in each batch of black tea, mix the black teas in proportion, and finally make the total selenium content of the black tea 1.0±0.1mg / kg, 2.0±0.1mg / kg and 4.0±0.1mg / kg respectively. After mixing, pack into a tea box with breathable cotton paper packaging, sterilize with high pressure steam at 121℃ for 20 minutes, and cool to room temperature for later use.

[0052] Inoculation and fermentation: The activated Aspergillus schwanniferus CGMCC No.42256 was inoculated into PDA liquid seed medium and cultured in shake flasks at 28℃ and 180rpm for 48 hours to obtain seed liquid; the seed liquid was evenly sprayed onto the sterilized black tea at an inoculation rate of 5% and placed in a constant temperature and humidity incubation room at 28±2℃ and 70%~75% relative humidity for fermentation. The fermentation time was 12 days, and the pile was turned over every 3 days to ensure uniform fermentation.

[0053] Drying the finished product: After the fermentation process is completed, place the Fu tea in a 60℃ forced-air drying oven and dry it until the moisture content is below 12% to obtain the finished selenium-enriched fermented Fu tea.

[0054] The selenium-enriched fermented Fu brick tea was brewed with 95℃ hot water and steeped for 10 minutes. The aroma components in the tea soup were then measured. The specific method is as follows: The aroma components in Fu brick tea liquor were determined using a headspace solid-phase microextraction (HS-SPME) coupled with gas chromatography-mass spectrometry (GC-MS). The specific method is as follows.

[0055] ①Headspace Extraction Fiber selection: 50 / 30 µm DVB / CAR / PDMS or 65 µm PDMS / DVB fibers are recommended (they have good adsorption properties for phenols, alcohols, and esters). Insertion: Insert the fiber needle into the rubber stopper of the bottle cap. Extraction conditions: Extract at 50°C-70°C for 30-60 minutes.

[0056] ②GC-MS Analysis (Instrumental Analysis) Thermal desorption: Immediately insert the fiber into the GC inlet (250°C) and desorb for 5-10 minutes.

[0057] Chromatographic column: Commonly used columns are DB-5ms (30m × 0.25mm × 0.25µm) or DB-Wax (60m × 0.25mm × 0.25µm). Polar / non-polar columns are selected according to the target components.

[0058] Temperature program: Example (DB-5ms): 35°C (keep warm for 5 minutes) Increase temperature by 3°C / min to 150°C (hold for 5 min). Increase temperature at 10°C / min to 250°C (hold for 10 min). ③Mass spectrometry conditions: Electron impact (EI) 70 eV, scan range 33-475 m / z.

[0059] Injection mode: Splitless Injection time: 2 min ⑤ Carrier gas: Pressure: 112.4 MPa, Total flow rate: 30.3 ml / min, Column flow rate: 1.40 ml / min, Purge flow rate: 3.0 ml / min, Split ratio: -1.0.

[0060] The data results for a total selenium content of 1.0 mg / kg are as follows: Figure 5 As shown, the extracted ion chromatogram and total ion chromatogram are shown below. Figure 6 As shown.

[0061] The data results for a total selenium content of 2.0 mg / kg are as follows: Figure 7 As shown, the extracted ion chromatogram and total ion chromatogram are shown below. Figure 8 As shown.

[0062] The data result for a total selenium content of 4.0 mg / kg is as follows: Figure 9 As shown, the extracted ion chromatogram and total ion chromatogram are shown below. Figure 10 As shown.

[0063] The aroma composition of fermented Fu brick tea with different selenium contents clearly shows that when the total selenium content is 1.0 mg / kg, the content of floral / fruity aroma substances (linalool oxide, benzaldehyde, benzyl alcohol, etc.) is relatively high, while the proportion of woody / aged aroma substances (4-ethylphenol, 1,2,3-trimethoxybenzene, etc.) is relatively low, and the overall aroma is dominated by floral and fruity flavors. When the total selenium content increases to 2.0 mg / kg, the proportion of woody / aged aroma substances increases, while the proportion of floral / fruity aroma substances decreases slightly. When the total selenium content reaches 4.0 mg / kg, the content of floral aroma substances decreases significantly, while the content of aged and woody aroma substances increases significantly. This indicates that the aroma components obtained by this strain in the fermentation of black tea with different selenium concentrations are different. Fu brick tea with floral and fruity flavors is obtained at lower selenium addition levels, while Fu brick tea with more woody / aged aroma substances is obtained under higher selenium addition levels.

[0064] In other words, the preparation of Fu brick tea can achieve targeted production of selenium-enriched Fu brick tea with different flavors by adjusting the selenium content of the raw materials. When a woody / aged aroma Fu brick tea is needed, only black tea with a high selenium content needs to be added to participate in fermentation to increase the aged and woody aromas. Unlike traditional Fu brick tea, there is no need to constantly adjust the microorganisms to achieve the purpose of flavor adjustment. After this adjustment, the overall flavor of the fermented Fu brick tea is relatively stable. The flavor can be targeted and controlled simply by adjusting the selenium content of the raw materials. The process is simple and controllable, can adapt to the flavor needs of different consumers, reduces the difficulty of flavor control, and is more suitable for large-scale industrial production.

Claims

1. A strain of Aspergillus chevaleri, characterized by: The *Aspergillus schwannii* strain is named AKFX-003, and its Latin name is: Aspergillus chevalieri It is deposited in the China General Microbiological Culture Collection Center, with accession number CGMCC No. 42256.

2. The use of Aspergillus chevaleri as described in claim 1, characterized in that: The *Aspergillus serrata* strain is used to ferment selenium-enriched tea. During liquid fermentation, the sodium selenite content is less than or equal to 80 μg / mL, and during solid fermentation, the total selenium content is less than or equal to 4.1 mg / kg.

3. The use of Aspergillus chevaleri according to claim 2, characterized in that: The Aspergillus spp. fermentation is used to prepare Fu tea that simultaneously possesses floral, fruity, woody, and aged aromas.

4. A method for preparing Fu brick tea with floral, fruity, woody, and aged aromas, characterized in that, Includes the following steps: (1) Add sodium selenite to the raw materials of black tea to adjust the total selenium content of the raw materials to 0.9-4.1 mg / kg, and sterilize; (2) Inoculate the Aspergillus schwanniferum as described in claim 1 or 2 onto the raw material obtained in step (1) and carry out fermentation; (3) After fermentation, the tea is dried to obtain Fu tea with floral, fruity, woody and aged aromas.

5. The preparation method of Fu brick tea with floral, fruity, woody, and aged aromas according to claim 4, characterized in that, In step (1), the raw material for the black tea is Ziyang selenium-rich black tea.

6. The method for preparing Fu brick tea with floral, fruity, woody, and aged aromas according to claim 4, characterized in that, Before adding sodium selenite, adjust the moisture content of the raw materials to 25%–28%.

7. The method for preparing Fu brick tea with floral, fruity, woody, and aged aromas according to claim 4, characterized in that, The sterilization process specifically involves sterilizing at 121°C for 15–20 minutes.

8. The method for preparing Fu brick tea with floral, fruity, woody, and aged aromas according to claim 4, characterized in that, In step (2), the inoculation specifically involves inoculating the Aspergillus serrata seed liquid into black tea at a volume-to-mass ratio of 5%, and carrying out fermentation under conditions of a temperature of 28±2℃ and a relative humidity of 70%~75%.

9. The method for preparing Fu brick tea with floral, fruity, woody, and aged aromas according to claim 8, characterized in that, The fermentation time is 12 days, during which the compost is turned over every 3 days.

10. The method for preparing Fu brick tea with floral, fruity, woody, and aged aromas according to any one of claims 4 to 9, characterized in that, When the total selenium content of the raw materials is adjusted to 1.0±0.1 mg / kg in step (1), the resulting selenium-enriched Fu tea is mainly characterized by floral and fruity aromas; when adjusted to 2.0±0.1 mg / kg, the resulting selenium-enriched Fu tea has both aged and woody aromas, as well as floral and fruity aromas; when adjusted to 4.0±0.1 mg / kg, the resulting selenium-enriched Fu tea is mainly characterized by aged and woody aromas.

Images