A strain of aspergillus chevalieri and its application in preparing liupao tea by solid state fermentation

Abstract

This invention discloses a strain of *Aspergillus cristatus* and its application in the solid-state fermentation of Liubao tea, belonging to the field of microbial fermentation and deep processing technology of tea. The strain, with preservation number CGMCC No. 42116, possesses characteristics of high flower and enzyme production, and a wide range of raw material adaptability. It can stably colonize and reproduce in various tea substrates, efficiently secreting multiple extracellular enzymes and directionally transforming the internal substances of tea. Based on this strain, this invention constructs a pure-strain solid-state fermentation process for Liubao tea, sequentially completing the entire process of strain activation and purification, spore suspension preparation, tea raw material moistening pretreatment, high-pressure steam sterilization, precise proportion inoculation and mixing, temperature and humidity controlled closed solid-state fermentation, and constant-temperature drying post-treatment. This process shortens the fermentation cycle, reduces batch quality fluctuations and the risk of contamination by other microorganisms, and produces Liubao tea with full golden flowers, harmonious flavor, and rich functional active ingredients, exhibiting excellent overall quality and meeting the needs of standardized, large-scale industrial production of Liubao tea.

Description

Technical Field

[0001] This invention belongs to the field of microbial fermentation and deep processing technology of tea, specifically involving a strain of Aspergillus cristatus and its application in the solid-state fermentation preparation of Liubao tea. Background Technology

[0002] Liubao tea, belonging to the dark tea category, is a geographical indication product of Wuzhou, Guangxi, and one of China's historical famous teas. It is renowned for its "red, strong, aged, and mellow" quality characteristics and unique "golden flower" fungal aroma. It also boasts significant health benefits such as lowering lipids and blood sugar, anti-oxidation, and regulating intestinal flora. In recent years, market demand has continued to grow, and the industry scale has been expanding. The core of Liubao tea's quality formation lies in the pile fermentation process, and the "golden flower" fungus is the absolutely dominant functional microorganism in the fermentation process. Its growth and metabolism directly determine the sensory quality, physicochemical properties, and functional value of Liubao tea. Traditional Liubao tea production uses a natural pile fermentation method, relying on naturally occurring microorganisms in the environment to complete the fermentation. This method suffers from problems such as a long fermentation cycle, poor process controllability, large batch-to-batch fluctuations in product quality, and a high risk of contamination by other microorganisms, failing to meet the demands of modern, standardized, and large-scale industrial development.

[0003] To address the shortcomings of traditional fermentation processes, the industry has gradually begun research on pure-strain inoculation fermentation technology. The core of this technology lies in screening high-performance "golden flower" strains to optimize the fermentation process and achieve precise control over the fermentation of Liubao tea. The mainstream classification of "golden flower" bacteria is *Eurotium cristatum* (also known as *Aspergillus cristatus*). Strains from different sources exhibit significant differences in flower-producing capacity, enzyme production characteristics, environmental adaptability, and raw material compatibility, directly determining the fermentation effect. Furthermore, the quality of Liubao tea is closely related to the variety of raw materials and the characteristics of different tea types. The inherent composition and structure of different tea raw materials differ fundamentally, directly affecting the growth, metabolism, and material conversion efficiency of the "golden flower" strains. Therefore, screening for the optimal combination of strains and raw materials is the core key to improving the quality of Liubao tea.

[0004] Currently, a series of studies have been conducted both domestically and internationally on the fermentation technology of Liubao tea, resulting in the accumulation of numerous patented technologies and academic research achievements. However, the existing technological system still has many unresolved technical defects. The specific existing research and existing problems are as follows:

[0005] Chinese patent application CN120360166A discloses a process for accelerating the aging of Liubao tea by inoculating with Aspergillus cristatus. It uses Aspergillus cristatus as the core functional strain, prepares a spore suspension and inoculates it onto sun-dried green tea. Through a two-stage process of pile fermentation and secondary inoculation combined with constant temperature and humidity aging fermentation, the aging cycle of Liubao tea is shortened and the basic quality is optimized. However, this process is only suitable for a single sun-dried green tea raw material, and the total fermentation cycle is more than 120 days. The production cycle is long and the process is relatively complicated.

[0006] Chinese patent application CN120584928A discloses a method for accelerating the aging of Liubao tea while ensuring its quality improvement. This method, also based on the study of *Gynostemma pentaphyllum*, accelerates the aging and quality improvement of Liubao tea. It uses sun-dried green tea as raw material and Liubao tea containing *Gynostemma pentaphyllum* as the inoculum. The process involves two inoculations combined with steaming and constant temperature and humidity aging to simplify the production process. While this technology can improve quality and optimize the production cycle, the use of naturally inoculated finished tea leaves presents challenges in controlling the types of bacteria and the content of live bacteria, easily leading to batch-to-batch variations in fermentation and making it difficult to achieve standardized and stable production.

[0007] In 2023, Wu Xinhui et al. published a paper titled "Identification of 'Golden Flower' Bacterium and Quality Changes in Liubao Tea After Inoculation and Fermentation" in *Food Science*. They isolated multiple strains of *Golden Flower* from Liubao tea pile samples and conducted solid-state fermentation experiments using Liubao tea from the Cangwu cultivar as raw material. They screened superior fermentation strains using sensory evaluation, biochemical detection, and principal component analysis. However, this study focused on screening non-*Aspergillus cristatus* strains such as *Penicillium mangosum* and *Aspergillus rubrum*, without conducting targeted in-depth research on the core beneficial microorganisms of Liubao tea. Furthermore, it was only suitable for a single tea raw material, limiting its applicability.

[0008] The 2024 paper by Wu Xinhui et al., published in *Food Science*, titled "Screening of Dominant Single Fungi for Solid-State Fermentation of Liubao Tea," isolated multiple fungal strains from Liubao tea samples. Using Liubao raw tea from the Cangwu cultivar as fermentation raw material, they screened several high-performance fermentation fungi through sensory and biochemical analyses combined with multivariate statistical methods. However, this study still falls under the category of broad-spectrum screening of multiple strains and does not focus on the targeted fermentation mechanism and quality improvement patterns of *Aspergillus cristatus*. Its specificity is weak, and it cannot establish a precise and standardized pure-strain fermentation process system.

[0009] In summary, existing technologies generally suffer from the following technical bottlenecks: First, the standardization of inoculation systems is low. Some technologies use naturally occurring tea samples for inoculation, resulting in uncontrollable strain content and microbial structure, which can easily lead to batch-to-batch fermentation differences, contamination by other microorganisms, and difficulty in ensuring fermentation stability. Second, the depth of research on dominant strains is insufficient. Most studies focus on broad-spectrum screening of multiple strains, while research on the fermentation mechanism, metabolic patterns, and targeted quality improvement techniques of *Aspergillus cristatus*, a core quality-enhancing bacterium for Liubao tea, is weak, and the utilization of strains lacks specificity. Third, raw material compatibility is poor. Existing fermentation processes are mostly tested on single Liubao tea raw materials, without exploring the compatibility effects of strains with multiple types and varieties of tea raw materials, resulting in limited applicability and poor versatility. Fourth, production process efficiency is low. Some processes adopt a two-stage aging and fermentation model, which involves complex procedures, long production cycles, and high production costs, making it difficult to meet the needs of efficient industrial production.

[0010] To address the shortcomings of existing technologies, this invention selectively screens a strain of Aspergillus cristatus HZJH-10 with excellent fermentation performance from aged Liubao tea. The compatibility of this strain with different types of raw tea materials was systematically investigated, a multi-index comprehensive quality evaluation system was constructed, the optimal combination of fermentation raw materials was screened, and a precise and controllable pure-strain solid-state fermentation process was optimized and improved. This can comprehensively enhance the overall quality of Liubao tea and promote the modernization and upgrading of the Liubao tea industry. Summary of the Invention

[0011] The purpose of this invention is to address the shortcomings of existing technologies by providing a strain of Aspergillus cristatus that is high in flower production, high in enzyme production, and widely adaptable. Based on this strain, a method for solid-state fermentation to prepare Liubao tea is established, which enables precise and controllable fermentation of Liubao tea, improves the sensory quality, flavor harmony, and functional activity of the product, expands the raw material sources of Liubao tea, reduces production costs, adapts to the needs of industrialized and standardized production, and promotes the high-quality development of the Liubao tea industry.

[0012] To solve the above-mentioned technical problems, the present invention provides the following technical solution:

[0013] A strain of Aspergillus cristatus was deposited on June 30, 2025, at the China General Microbiological Culture Collection Center (CGMCC), located at No. 3, Courtyard 1, Beichen West Road, Chaoyang District, Beijing, China, with accession number CGMCCNo.42116, and named Aspergillus cristatus HZJH-10.

[0014] A method for preparing Liubao tea by solid-state fermentation, using Aspergillus cristatus HZJH-10 as the fermentation strain, includes the following steps:

[0015] Step 1: Activation and purification of the strain. The cryopreserved Aspergillus cristatus HZJH-10 strain was streaked onto Czapek's agar plates and incubated at 26-30°C in the dark for 7-10 days. Typical single colonies were picked and streaked three times to obtain the purified strain.

[0016] Step 2: Preparation of spore suspension. Pick mycelia and mature cleistothecia from the purified plate and place them in sterile physiological saline. Shake at 1500-2500 rpm for 10-20 minutes to disperse the spores. Filter with sterile absorbent cotton to remove residue, obtaining a spore concentration of 1×10⁻⁶. 6 ~1×10 8 A CFU / mL spore suspension, refrigerated at 4°C for use, should not be stored for more than 72 hours.

[0017] Step 3: Pretreatment of fermentation raw materials. Weigh 100g of raw tea leaves, add distilled water until the final moisture content of the raw materials is 25%, stir well, seal and let stand for 0.5~2 hours;

[0018] Step 4: Sterilization. After soaking and swelling, the tea leaves are divided into Erlenmeyer flasks, sealed with sterile, breathable sealing film, and placed in a high-pressure steam sterilizer. Sterilize at 121-130℃ and 0.1-0.3MPa for 15-30 minutes, then allow to cool naturally to room temperature.

[0019] Step 5: Inoculation and mixing. Inoculate the cooled tea raw materials with 1 mL of spore suspension for every 50 g of dry tea raw materials, stir thoroughly for at least 3 minutes, and gently compact.

[0020] Step 6: Constant temperature solid-state fermentation. Place the inoculated tea leaves in a constant temperature and humidity incubator at 25~30℃ and ferment in the dark, controlling the relative humidity at 60~70%, for 20~30 days;

[0021] Step 7: Drying and post-processing. After fermentation, spread the tea leaves evenly on a tray and dry them. Control the temperature in the drying oven to a stable 50-70℃ and dry until the moisture content is 8-12%. After naturally cooling to room temperature, the finished Liubao tea is obtained.

[0022] Further, in step 1, the Czapek's medium formula is as follows: 3g sodium nitrate, 1g dipotassium hydrogen phosphate, 0.5g magnesium sulfate, 0.5g potassium chloride, 0.01g ferrous sulfate, 30g sucrose, 20g agar, 1000mL distilled water, natural pH, autoclaved at 121℃ for 20 minutes for later use.

[0023] Furthermore, in step 2, the concentration of the spore suspension is 1×10⁻⁶. 7 CFU / mL.

[0024] Furthermore, in step 3, the raw tea material is selected from one of the following: Cangwu group spring tea raw tea, Cangwu group summer tea raw tea, green tea raw tea, yellow tea raw tea, and Yunpan tea raw tea.

[0025] Furthermore, in step 3, the mixture is stirred every 15 minutes during the settling period.

[0026] Furthermore, in step 4, the conditions for high-pressure steam sterilization are 121°C and 0.1 MPa for 20 minutes.

[0027] Furthermore, in step 6, the solid-state fermentation conditions are constant temperature fermentation at 28°C in the dark, relative humidity of the fermentation environment is 65%, and the fermentation time is 25 days.

[0028] Furthermore, in step 7, the drying temperature is 60°C, and the tea is dried until the moisture content of the finished tea product is 10%.

[0029] Compared with the prior art, the technical advantages of the present invention are as follows:

[0030] 1. The strain exhibits excellent performance, high yield and high viability, and wide adaptability to raw materials.

[0031] The *Aspergillus cristatus* strain HZJH-10 obtained in this invention was selected through multiple rounds of rigorous screening, including primary screening, secondary screening, targeted acclimatization, and comprehensive safety evaluation, demonstrating excellent overall performance. This strain exhibits strong flowering capacity, rapidly germinating and reproducing in tea substrates to form evenly distributed, plump, golden-yellow cleistothecia. It demonstrates good flowering stability, effectively solving the problems of sparse and uneven flowering in traditional strains, thus meeting the core requirement of Liubao tea for its golden flower quality. The strain can efficiently secrete various extracellular enzymes such as cellulase and polyphenol oxidase, synergistically decomposing the cell wall structure of tea leaves, fully releasing internal substances, and directionally catalyzing the transformation of macromolecules such as tea polyphenols and proteins, fundamentally promoting the formation of the distinctive quality of Liubao tea. Simultaneously, this strain has broad raw material adaptability, growing stably in various tea substrates, effectively expanding the raw material sources for Liubao tea production and reducing raw material procurement costs.

[0032] 2. Construct a quantitative adaptation evaluation system to accurately select the optimal fermentation combination.

[0033] This invention constructs a standardized and quantifiable strain-raw material compatibility evaluation system, integrating national standard sensory evaluation with multi-index physicochemical analysis to avoid the subjective bias and one-sidedness of traditional experience-based judgment. At the sensory level, it strictly follows national tea evaluation standards, scoring from five dimensions: appearance, liquor color, aroma, taste, and infused leaf appearance, objectively reflecting the sensory quality and flavor characteristics of fermented products. At the physicochemical level, it screens core quality indicators covering three dimensions: taste, liquor color, and functional activity, accurately reflecting the material transformation laws during fermentation. Simultaneously, principal component analysis is used to reduce the dimensionality of multi-dimensional physicochemical data, calculating a comprehensive quality score to achieve precise quantitative evaluation of strain-raw material compatibility. This system can systematically screen optimal fermentation combinations, providing precise raw material selection basis for the standardized production of Liubao tea, and can also optimize and match fermentation processes, ensuring the stability and consistency of product quality, providing scientific and technical support for the standardized development of the industry.

[0034] 3. The fermentation process is precise and controllable, making it suitable for large-scale industrial production.

[0035] This invention addresses the bottlenecks of traditional Liubao tea fermentation, including poor controllability, long cycles, significant quality fluctuations, and cumbersome operations. It optimizes a pure-strain solid-state fermentation process suitable for industrialized, standardized, and large-scale production. The process employs a sterile, pure-strain inoculation fermentation model. From strain activation and bacterial solution preparation to raw material processing, inoculation fermentation, and post-processing, all parameters are clearly defined and standardized, effectively isolating environmental microorganisms and reducing the risks of mold and contamination found in traditional fermentation. By precisely controlling key parameters such as bacterial solution concentration, inoculation amount, raw material moisture content, temperature, humidity, and fermentation time, the metabolic rate of the strains can be effectively controlled, achieving targeted transformation of tea quality components. This effectively solves the problems of difficult-to-control fermentation levels and large batch-to-batch quality variations in traditional methods. This process significantly shortens the fermentation cycle, effectively reducing time, labor, and energy costs. Furthermore, it eliminates the need for complex operations such as turning the pile and repeated feeding; fermentation can be completed with a single inoculation, requiring less manual operation and facilitating the industry's transformation from traditional workshop-style production to modern industrial production.

[0036] 4. Targeted regulation of quality transformation enhances flavor harmony while preserving traditional characteristics.

[0037] To address the problems of excessively strong umami aroma, bland taste, lingering bitterness, and unbalanced flavor in existing fermented teas, this invention optimizes the product's flavor through strain adaptation and precise process control, preserving the traditional quality characteristics of Liubao tea. The complex extracellular enzymes secreted by the strains precisely regulate the transformation of tea substances, effectively degrading bitter substances such as ester-type catechins and tea polyphenols, thus reducing the astringency and bitterness of the tea soup. Simultaneously, it converts large-molecule flavor precursors into soluble small molecules, significantly enhancing the tea soup's richness, smoothness, and refreshing aftertaste, overcoming the shortcomings of traditional products with their single flavor and thin mouthfeel. In terms of flavor fusion, it balances the umami aroma with the natural tea aroma, ensuring full golden flowers and pure umami while preserving the tea's own aged and mellow fragrance, avoiding the problem of the umami aroma masking the original flavor. No exogenous nutrients or additives are added throughout the process, resulting in no off-flavors or impurities. It meets the standards for geographical indication products, and the finished product has a harmonious flavor and excellent quality, meeting the quality requirements of high-end Liubao tea and significantly enhancing its market competitiveness.

[0038] 5. Enriching functional active ingredients to enhance product health value and industry boundaries.

[0039] This invention utilizes targeted metabolic regulation by a bacterial strain to enrich the functional active ingredients of tea, enhancing the product's health value and expanding the application scenarios of Liubao tea. During fermentation, *Aspergillus cristatus* HZJH-10 can achieve targeted optimization and transformation of tea's active ingredients, converting low-bioavailability ester-type catechins into more stable and active non-ester-type catechins, thus improving the product's antioxidant capacity. Simultaneously, it can increase the content of phenolic acid active substances, balancing flavor optimization and health benefits. Furthermore, the strain can promote the targeted oxidation and polymerization of tea polyphenols, increasing the content of the core functional component theaflavins, thereby enhancing the health value of Liubao tea and optimizing the tea's color and mellow taste, achieving a simultaneous improvement in sensory quality and functional value. The improved Liubao tea can not only be used as a traditional tea beverage but also as a functional food ingredient in the health industry, helping to increase product added value and expand the boundaries of industrial development. Attached Figure Description

[0040] Figure 1 This image shows the growth morphology of Aspergillus cristatus HZJH-10 on Czapek's medium.

[0041] Figure 2 The images show the appearance of the dried Liubao tea samples prepared in Examples 1-5 (wherein, Figure 2 (a) is Example 1. Figure 2 (b) is Example 2. Figure 2 (c) is Example 3. Figure 2 (d) is Example 4. Figure 2 (e) is Example 5);

[0042] Figure 3The images show a comparison of the liquor color of Liubao tea samples prepared in Examples 1-5 and Comparative Examples 1-5 (wherein, Figure 3 (a) is Example 1. Figure 3 (b) is Comparative Example 1. Figure 3 (c) is Example 2. Figure 3 (d) is Comparative Example 2. Figure 3 (e) is Example 3. Figure 3 (f) is Comparative Example 3. Figure 3 (g) is Example 4. Figure 3 (h) is Comparative Example 4. Figure 3 (i) is Example 5. Figure 3 (j) is comparative example 5). Detailed Implementation

[0043] The present invention will be further described in detail below with reference to specific embodiments and comparative examples. The described embodiments are only used to explain the present invention and are not intended to limit the scope of protection of the present invention.

[0044] The application of a strain of *Aspergillus cristatus* in the solid-state fermentation preparation of Liubao tea includes the following steps:

[0045] Step 1: Activation and purification of the strain. The cryopreserved *Aspergillus cristatus* strain HZJH-10 was inoculated onto freshly prepared Czapek's agar plates using the streak plating method in a clean bench. After inoculation, the plates were inverted and placed in a constant temperature incubator at 26-30℃ for activation in the dark. After 7-10 days of incubation, uniform and vigorous single colonies grew on the plates. Typical single colonies were then picked and subjected to streak plating again for purification. This purification process was repeated three times to obtain the purified target strain. The Czapek's agar medium formula was: 3g sodium nitrate, 1g dipotassium hydrogen phosphate, 0.5g magnesium sulfate, 0.5g potassium chloride, 0.01g ferrous sulfate, 30g sucrose, 20g agar, and 1000mL distilled water, with a natural pH. After preparation, the medium was autoclaved at 121℃ for 20 minutes before use.

[0046] Step 2: Preparation of spore suspension. In a clean bench, use a sterile inoculation loop to pick up the mycelium and mature golden-yellow cleistothecia from the purified plate and transfer them to a 250 mL sterile centrifuge tube containing 100 mL of sterile physiological saline. Add 10 sterile glass beads to the centrifuge tube, tighten the cap, and place it on a vortex mixer. Shake thoroughly at 1500-2500 rpm for 10-20 minutes to ensure that the spores in the cleistothecia are completely dispersed in the physiological saline. After shaking, filter the bacterial solution with sterile absorbent cotton to remove mycelium and cleistothecia residue, obtaining a pure spore suspension. Count the spore concentration under a microscope using a hemocytometer. Adjust the concentration of the spore suspension to 1 × 10⁻⁶ using sterile physiological saline. 6~1×10 8 CFU / mL, store in a refrigerator at 4°C for up to 72 hours.

[0047] Step 3: Pretreatment of Fermentation Raw Materials. Weigh 100g of raw tea leaves and place them in a clean stainless steel container. Add distilled water until the final moisture content of the raw materials is 25%. Stir continuously and evenly with a clean glass rod to fully mix the distilled water and tea leaves. After stirring, seal the raw materials and let them stand for 0.5 to 2 hours to allow the tea leaves to fully absorb water and swell. Stir every 15 minutes during this period to ensure that the overall moisture content of the raw materials is uniform.

[0048] Step 4: Sterilization. Distribute the soaked and swollen tea leaves evenly into 500mL high-temperature resistant conical flasks, 50g of raw material per flask (based on dry tea weight). Seal the flasks tightly with sterile, breathable sealing film, ensuring good air permeability. Place the flasks in a high-pressure steam sterilizer and sterilize at 121-130℃ and 0.1-0.3MPa for 15-30 minutes. After sterilization, turn off the power to the sterilizer and allow the pressure inside to drop naturally to atmospheric pressure. Then, open the sterilizer, remove the flasks, and immediately place them in a clean bench to cool naturally to room temperature for later use.

[0049] Step 5: Inoculation and Mixing. In a clean bench, add 1 mL of spore suspension to each 50 g of tea raw material after cooling, according to the inoculation ratio of 1 mL of spore suspension per 50 g of tea raw material. After adding, use a sterile glass rod to thoroughly stir the tea raw material for at least 3 minutes to ensure that the spore suspension and tea raw material are completely and evenly mixed. Gently compact the tea raw material to ensure that the looseness of the raw material is uniform.

[0050] Step 6: Constant Temperature Solid-State Fermentation. After inoculation, reseal the mouth of the conical flask with sterile, breathable sealing film to ensure a secure seal. Then, place the conical flask neatly in a constant temperature and humidity incubator at 25-30℃ for light-protected, constant temperature solid-state fermentation. During the fermentation process, maintain the relative humidity in the incubator at 60-70%. The total fermentation time is 20-30 days.

[0051] Step 7: Drying and Post-processing. After fermentation, open the incubator, remove the conical flask, and pour out the fermented tea leaves. Spread them evenly on a clean stainless steel tray, with a thickness not exceeding 2 cm. Then place the tray in a constant temperature forced-air drying oven at 50-70℃, turning it over every 2 hours to ensure even drying. Dry until the moisture content of the tea leaves is 8-12%. Close the drying oven, remove the tray, and allow the tea leaves to cool naturally to room temperature in a clean environment. The final product is fermented Liubao tea. The cooled tea sample is pulverized using a high-speed pulverizer, passed through a 2mm standard sieve, and the sieved powder is collected, sealed in a clean sample bottle, and stored in a cool, dry, and dark place.

[0052] The preparation principle of this invention:

[0053] 1. Growth, metabolism and enzyme production mechanism of Aspergillus cristatus HZJH-10

[0054] Aspergillus cristatus HZJH-10 is an important functional microorganism involved in the quality formation of Liubao tea during fermentation. Suitable temperature, humidity, and nutrient environment can promote the germination of spores and the formation of vegetative mycelium. The mycelium can spread and grow on the surface and in the pores of the tea matrix and penetrate into the interior of tea cells. It metabolizes and produces a variety of extracellular enzymes such as cellulase, polyphenol oxidase, protease, pectinase, and glycosidase. Through a series of enzymatic reactions, it improves the structure of the tea matrix and transforms its internal substances.

[0055] The various extracellular enzymes secreted by the strain play a dual role. Cellulase and pectinase, among other cell wall-degrading enzymes, can disrupt the dense structure of tea leaves, loosen the texture, and promote the dissolution of flavor substances such as tea polyphenols, amino acids, and catechins from within the cells, thereby increasing the extraction efficiency of tea components. Simultaneously, they provide ample attachment space and aeration for mycelial growth, supporting the continuous metabolic reproduction of the strain. Polyphenol oxidase, protease, and glycosidase can participate in the transformation and metabolism of key flavor substances in tea, promoting the oxidative degradation of tea polyphenols and the hydrolysis of proteins, and facilitating the decomposition and transformation of aroma precursors.

[0056] 2. The directional transformation mechanism of core quality components in tea

[0057] The metabolic and enzymatic reactions of *Aspergillus cristatus* HZJH-10 guide the orderly transformation of substances within tea leaves, gradually forming the unique flavor and quality of Liubao tea. Tea polyphenols and catechins are key substances determining the taste of tea and are the main sources of bitterness. During fermentation, tea polyphenols undergo oxidative degradation and polymerization, resulting in an overall decrease in content, effectively weakening the astringency and bitterness of the tea. Ester-type catechins, as the main bitter substances, undergo hydrolytic degradation, leading to a continuous decrease in content. The increased EC content enhances the smooth texture of the tea, improves its blandness, and promotes a shift towards a mellow and mellow flavor.

[0058] The dynamic transformation of tea pigments is key to the formation of the color of Liubao tea liquor. During fermentation, tea polyphenols gradually oxidize to produce theaflavins and thearubigins. These two light-colored pigments further polymerize to transform into theabrownins, resulting in an overall decrease in the content of theaflavins and thearubigins, while theabrownins continuously accumulate. Theabrownins are important active substances that contribute to the rich, bright red color and mellow taste of Liubao tea. Through synergistic regulation of bacterial strains and processing techniques, the enrichment of theabrownins can be effectively promoted, optimizing the overall quality of the finished product.

[0059] Fermentation metabolism can also optimize the functionality and aroma quality of tea. During fermentation, substances such as lactone-type catechins and phenolic esters in tea leaves hydrolyze to produce gallic acid, which can optimize the freshness of the tea soup and enhance the physiological activity and health benefits of the finished tea. Tea proteins are hydrolyzed by proteases to produce free amino acids, which can not only enhance the freshness of the tea soup, but also act as aroma precursors, undergoing Maillard reactions with reducing sugars to generate aroma components unique to Liubao tea, such as fungal aroma, aged aroma, and mellow aroma, enriching the aroma layers of the finished product. Caffeine can form complexes with the oxidation products of tea polyphenols, weakening its own irritant properties, harmonizing the overall flavor of the tea soup, and improving palatability.

[0060] 3. The adaptation mechanism between bacterial strains and tea raw materials

[0061] The physicochemical properties and tissue structure of different tea raw materials vary significantly, which directly affects the growth and reproduction efficiency and enzyme production capacity of Aspergillus cristatus HZJH-10, thus leading to differences in the quality of fermented products. The effectiveness of raw material matching mainly depends on two dimensions: nutrient supply capacity and physical structural characteristics.

[0062] Different types of tea have varying ratios of carbon and nitrogen nutrients, minerals, and other internal substances. Raw materials with nutritional compositions that better match the growth needs of the bacterial strains are more conducive to the colonization, growth, and enzyme production of the strains, significantly improving the efficiency of substance conversion in tea. At the same time, the physical properties of tea leaves, such as their looseness and porosity, directly affect mycelial attachment, oxygen transport, and water retention. A loosely structured tea substrate with suitable porosity is more suitable for the spread and growth of the bacterial strains, while a densely structured tea leaf will inhibit the metabolic activity of the strains to some extent.

[0063] This invention systematically explores the compatibility patterns between different tea raw materials and strains, and combines the differences in strain growth status, enzyme production characteristics, and sensory and physicochemical quality of the finished product to screen out fermentation raw materials with better compatibility. This can give full play to the metabolic and quality-improving advantages of strains and effectively optimize the overall quality of Liubao tea fermentation products.

[0064] The present invention will be further illustrated below through specific embodiments and comparative examples.

[0065] All the following examples and comparative examples share the same experimental materials and culture conditions:

[0066] The fermentation raw materials used, including spring tea, summer tea, green tea, yellow tea, and Yunpan tea from the Cangwu Qunti variety, were all purchased from a regular tea factory in Wuzhou, Guangxi. All tea raw materials meet the requirements for raw tea raw materials in DB45 / T 1114-2014 "Geographical Indication Product Liubao Tea", and are free from mold, off-odors, and impurities.

[0067] The formula of Czapek's medium used in the experiment was as follows: 3g sodium nitrate, 1g dipotassium hydrogen phosphate, 0.5g magnesium sulfate, 0.5g potassium chloride, 0.01g ferrous sulfate, 30g sucrose, 20g agar, and 1000mL distilled water. The pH was natural. After the medium was prepared, it was sterilized by autoclaving at 121℃ for 20 minutes before use.

[0068] Example 1

[0069] The application of a strain of *Aspergillus cristatus* in the solid-state fermentation preparation of Liubao tea, using spring tea leaves from the Cangwu cultivar as the fermentation raw material, specifically includes the following steps:

[0070] Step 1: Activation and purification of the strain. The cryopreserved *Aspergillus cristatus* strain HZJH-10 was inoculated onto freshly prepared Czapek's agar plates using the streak plating method in a clean bench. After inoculation, the plates were inverted and placed in a 28°C incubator for activation in the dark. After 7 days of incubation, uniform and vigorous single colonies grew on the plates. Typical single colonies were then picked and subjected to streak plating again for purification. This purification process was repeated three times to obtain the purified target strain. The growth morphology of *Aspergillus cristatus* HZJH-10 on Czapek's agar is shown in the image below. Figure 1 As shown. The *Aspergillus cristatus* HZJH-10 was deposited on June 30, 2025, at the China General Microbiological Culture Collection Center (CGMCC), located at No. 3, Courtyard 1, Beichen West Road, Chaoyang District, Beijing, China, with accession number CGMCC No. 42116.

[0071] Step 2: Preparation of spore suspension. In a clean bench, use a sterile inoculation loop to pick up the mycelium and mature golden-yellow cleistothecia from the purified plate and transfer them to a 250 mL sterile centrifuge tube containing 100 mL of sterile physiological saline. Add 10 sterile glass beads to the centrifuge tube, tighten the cap, and place it on a vortex mixer. Shake thoroughly at 2000 rpm for 15 minutes to ensure that the spores in the cleistothecia are completely dispersed in the physiological saline. After shaking, filter the bacterial solution with sterile absorbent cotton to remove mycelium and cleistothecia residue, obtaining a pure spore suspension. Count the spore concentration under a microscope using a hemocytometer. Adjust the concentration of the spore suspension to 1 × 10⁻⁶ using sterile physiological saline. 7 CFU / mL, store in a refrigerator at 4°C for up to 72 hours.

[0072] Step 3: Pretreatment of Fermentation Raw Materials. Weigh 100g of Cangwu Quntizhong spring tea raw material and place it in a clean stainless steel container. Add distilled water until the final moisture content of the raw material is 25%. Stir continuously and evenly with a clean glass rod to fully mix the distilled water and tea raw material. After stirring, seal the raw material and let it stand for 1 hour to allow the tea raw material to fully absorb water and swell. Stir once every 15 minutes during this period to ensure that the overall moisture content of the raw material is uniform.

[0073] Step 4: Sterilization. Distribute the soaked and swollen tea leaves evenly into 500mL high-temperature resistant conical flasks, 50g of raw material per flask (based on dry tea weight). Seal the flasks tightly with sterile, breathable sealing film, ensuring a tight seal and good air permeability. Place the conical flasks in a high-pressure steam sterilizer and sterilize at 121℃ and 0.1MPa for 20 minutes. After sterilization, turn off the power to the sterilizer and allow the pressure inside to drop naturally to atmospheric pressure. Then, open the sterilizer, remove the conical flasks, and immediately place them in a clean bench to cool naturally to room temperature for later use.

[0074] Step 5: Inoculation and Mixing. In a clean bench, add 1 mL of spore suspension to each 50 g of tea raw material after cooling, according to the inoculation ratio of 1 mL of spore suspension per 50 g of tea raw material. After adding, use a sterile glass rod to thoroughly stir the tea raw material for at least 3 minutes to ensure that the spore suspension and tea raw material are completely and evenly mixed. Gently compact the tea raw material to ensure that the looseness of the raw material is uniform.

[0075] Step 6: Constant temperature solid-state fermentation. After inoculation, reseal the mouth of the conical flask with sterile, breathable sealing film to ensure a secure seal. Then, place the conical flask neatly in a constant temperature and humidity incubator at 28°C for light-proof, constant temperature solid-state fermentation. During the fermentation process, maintain the relative humidity in the incubator at 65%. The total fermentation time is 25 days.

[0076] Step 7: Drying and Post-processing. After fermentation, open the incubator, remove the conical flask, and pour out the fermented tea leaves. Spread them evenly on a clean stainless steel tray, with a thickness not exceeding 2 cm. Place the tray in a 60℃ constant-temperature forced-air drying oven, turning it every 2 hours to ensure even drying. Dry until the moisture content of the finished tea reaches 10%. Then, close the drying oven, remove the tray, and allow the tea leaves to cool naturally to room temperature in a clean environment. The final product is fermented Cangwu group spring tea. The cooled tea sample is pulverized using a high-speed grinder, passed through a 2mm standard sieve, and the sieved powder is collected, sealed in a clean sample bottle, and stored in a cool, dry, and dark place for subsequent quality testing.

[0077] Example 2

[0078] The application of a strain of Aspergillus cristatus in the solid-state fermentation preparation of Liubao tea was carried out. The raw material was Cangwu group summer tea. The specific preparation steps and process parameters were completely consistent with those in Example 1. Only the raw material in step 3 was replaced with Cangwu group summer tea. All other operations remained unchanged. Finally, the fermented Cangwu group summer tea was obtained and sealed for later use.

[0079] Example 3

[0080] The application of a strain of Aspergillus cristatus in the solid-state fermentation preparation of Liubao tea was carried out. Green tea leaves were used as the fermentation raw material. The specific preparation steps and process parameters were completely consistent with those in Example 1. Only the fermentation raw material in step 3 was replaced with green tea leaves. All other operations remained unchanged. Finally, the fermented green tea product was obtained and sealed for storage.

[0081] Example 4

[0082] The application of a strain of Aspergillus cristatus in the solid-state fermentation preparation of Liubao tea was carried out. Yellow tea leaves were used as the fermentation raw material. The specific preparation steps and process parameters were completely consistent with those in Example 1. Only the fermentation raw material in step 3 was replaced with yellow tea leaves. All other operations remained unchanged. Finally, the fermented yellow tea product was obtained and sealed for storage.

[0083] Example 5

[0084] The application of a strain of Aspergillus cristatus in the solid-state fermentation preparation of Liubao tea was carried out. Yunpan tea was used as the fermentation raw material. The specific preparation steps and process parameters were completely consistent with those in Example 1. Only the fermentation raw material in step 3 was replaced with Yunpan tea. All other operations remained unchanged. Finally, fermented Yunpan tea was obtained and sealed for storage.

[0085] Comparative Example 1

[0086] This comparative example serves as the blank control group for Example 1. It uses spring tea leaves from the Cangwu cultivar as raw material, without inoculating any bacterial strains. The remaining preparation steps and process parameters are consistent with those of Example 1.

[0087] Comparative Example 2

[0088] This comparative example serves as the blank control group for Example 2. It uses summer tea leaves from the Cangwu cultivar as raw material, without inoculating any bacterial strains. The remaining preparation steps and process parameters are consistent with those of Example 1.

[0089] Comparative Example 3

[0090] This comparative example serves as the blank control group for Example 3. It uses raw green tea leaves as raw material, without inoculating any bacterial strains, and the remaining preparation steps and process parameters are consistent with those of Example 1.

[0091] Comparative Example 4

[0092] This comparative example serves as the blank control group for Example 4. Yellow tea leaves are used as raw material, and no bacterial strains are inoculated. The remaining preparation steps and process parameters are consistent with those of Example 1.

[0093] Comparative Example 5

[0094] This comparative example serves as the blank control group for Example 5. It uses Yunpan tea leaves as raw material, without inoculating any bacterial strains, and the remaining preparation steps and process parameters are consistent with those of Example 1.

[0095] Performance testing and results analysis

[0096] All testing indicators were conducted using currently valid national standard methods, as detailed below:

[0097] 1. Sensory quality evaluation: The evaluation shall be conducted in accordance with DB45 / T 1114-2014 "Geographical Indication Product Liubao Tea" and GB / T 23776-2018 "Sensory Evaluation Method of Tea", and shall be scored from five dimensions: appearance, liquor color, aroma, taste and infused leaves.

[0098] 2. Tea polyphenol content: determined according to the Folin-Ciocalteu colorimetric method in GB / T 8313-2018 "Determination of tea polyphenol and catechin content in tea".

[0099] 3. Total free amino acids: determined by the ninhydrin colorimetric method in GB / T 8314-2013 "Determination of total free amino acids in tea".

[0100] 4. Water extract content: determined according to the total amount method in GB / T 8305-2013 "Determination of Water Extract Content in Tea".

[0101] 5. Soluble sugar content: The total soluble sugar content of tea leaves was determined by the anthrone colorimetric method.

[0102] 6. Theaflavins: Performed according to GB / T 30483-2013 "Determination of Theaflavins in Tea by High Performance Liquid Chromatography".

[0103] 7. The content of thearubigin and theabrownin: determined by systematic analysis, referring to the systematic analysis method of tea pigments in "Tea Biochemistry" (3rd edition, edited by Wan Xiaochun).

[0104] 8. Gallic acid and catechin components (EGC, C, EC, EGCG, ECG, GCG) content: determined by high performance liquid chromatography in GB / T 8313-2018 "Determination of tea polyphenols and catechins in tea".

[0105] 9. Caffeine content: determined by high performance liquid chromatography according to GB / T 8312-2013 "Determination of Caffeine in Tea".

[0106] 10. Principal Component Analysis: Using IBM SPSS Statistics 18.0 statistical analysis software, principal component analysis was performed on the 15 core physicochemical quality indicators obtained from the test. Principal components with eigenvalues ​​greater than 1 were extracted, and the variance contribution rate and comprehensive score of each principal component were calculated. The comprehensive score was calculated as follows: F = Σ (Fi × variance contribution rate), where Fi is the score of each principal component. The higher the comprehensive score, the better the overall quality of the sample.

[0107] I. Sensory Quality Evaluation Results and Analysis

[0108] To investigate the effects of Aspergillus cristatus HZJH-10 on the solid-state fermentation quality of different tea raw materials, fermented tea products were prepared using spring tea, summer tea, green tea, yellow tea, and Yunpan tea as fermentation raw materials. A comprehensive sensory evaluation was conducted on each group of samples, considering appearance, liquor color, aroma, taste, and infused leaf appearance. Figure 2 Appearance images of dried Liubao tea samples obtained in Examples 1-5 Figure 3 The comparison charts of the liquor color of Liubao tea samples prepared in Examples 1-5 and Comparative Examples 1-5, and Table 1 show the sensory quality evaluation results of the samples in Examples 1-5, so as to comprehensively analyze the quality of the fermented finished product.

[0109]

[0110] Depend on Figure 2 The appearance of the dried tea leaves clearly shows significant differences in the growth and reproduction of *Aspergillus cristatus* HZJH-10 in different tea raw materials, indicating varying adaptability of the strain to different tea substrates. Specifically, this strain exhibited the most vigorous growth in summer tea, green tea, and Yunpan tea from the Cangwu group, resulting in abundant and plump golden flowers on the finished dried tea leaves. In yellow tea, the strain's growth was second strongest, with good golden flower coverage. However, in spring tea from the Cangwu group, the strain's growth was generally weaker compared to summer tea, green tea, Yunpan tea, and yellow tea from the same group. Overall, all groups of fermented tea leaves showed widespread golden flowers, with no contamination from other microorganisms or mold.

[0111] Combination Figure 3 The comparison results of the soup color of each group of samples show that the soup color of all fermented tea samples in Examples 1 to 5 is yellowish-brown and bright. The clarity and color uniformity of the soup color of each group are basically the same, and there are no adverse phenomena such as turbidity, dullness, or blackening.

[0112] Based on the sensory quality scoring results in Table 1 and the analysis of various sensory indicators, it can be concluded that the sensory quality of the finished products obtained from the fermentation of different tea raw materials is highly matched with the growth status of the bacterial strains, and the overall quality performance is excellent with significant differences. Example 2 (Summer tea from the Cangwu cultivar) and Example 3 (Green tea) showed vigorous bacterial growth, resulting in a rich aroma, a mellow and smooth tea soup, and excellent quality. Example 5 (Yunpan tea) showed the best performance, with abundant golden flowers, a dark and lustrous color, and outstanding rich, mellow, and sweet aftertaste, exhibiting a significant smoothness and the best overall taste. Example 4 (Yellow tea) showed moderate bacterial growth, resulting in a relatively abundant golden flower in the finished product. Example 1 (Spring tea from the Cangwu cultivar) showed relatively weak bacterial growth, with only a strong aroma and a slightly astringent taste in the tea soup, placing it at a medium level among the groups.

[0113] II. Results and Analysis of Core Physicochemical Quality Tests

[0114] The core physicochemical quality indicators of the samples from Examples 1-5 and Comparative Examples 1-5 were tested, and the test results are shown in Table 2.

[0115]

[0116] 1. Changes in tea polyphenols, free amino acids, and water extracts

[0117] Tea polyphenols are the core substances that constitute the bitter and astringent flavor of tea infusion, and their content directly affects the overall quality of tea. As shown in Table 2, after fermentation and metabolism by the strain, the tea polyphenol content in Examples 1-5 was significantly lower than that in the uninoculated control group (Examples 1-5). Among them, Example 4 showed the most significant decrease in tea polyphenol content, indicating that the strain can effectively degrade bitter and astringent substances in tea and improve the astringency of the tea infusion.

[0118] Free amino acids are important precursors for the formation of aroma and fresh taste in tea. Microbial growth and metabolism utilize amino acids as a nitrogen source and promote the transformation of flavor substances. The free amino acid content in Examples 1-5 was significantly lower than that in the corresponding blank control groups.

[0119] Water extract can comprehensively reflect the accumulation level of soluble flavor substances in tea. Compared with the corresponding blank control groups (Comparative Examples 1-5), the water extract of Examples 1, 2, 3 and 5 decreased to varying degrees, while only the water extract of Example 4 showed a slight increase. Overall, the water extract content of each tea raw material remained at a high level, ensuring the mellow texture of the fermented tea soup. At the same time, the metabolic consumption of some soluble substances by the bacterial strain also promoted the benign transformation of the substances contained in the tea.

[0120] 2. Changes in gallic acid and catechins

[0121] Gallic acid possesses excellent anti-inflammatory and antioxidant physiological activities and is an important functional product of the hydrolysis and degradation of tea polyphenols. As shown in Table 2, the changes in gallic acid content after fermentation by different tea raw materials by various strains are significant. The gallic acid content in Examples 1, 2, 3, and 5 is significantly higher than that in the corresponding blank control groups (Comparative Examples 1, 2, 3, and 5). Only the gallic acid content in Example 4 is lower. This indicates that Aspergillus cristatus can promote the decomposition of macromolecular tea polyphenols and enrich functional gallic acid in most tea matrices, thereby enhancing the health benefits of fermented tea.

[0122] Catechins are the most abundant component of tea polyphenols and the main source of bitterness and astringency in tea. After fermentation, all groups of ester-type catechins showed a significant degradation trend. The contents of EGC, EGCG, ECG, and GCG were significantly lower than those of the corresponding blank control groups (comparative examples 1-5). The large-scale decomposition of various ester-type catechins effectively weakened the bitterness and astringency of the tea soup and promoted the transformation of the tea flavor towards mellowness and smoothness.

[0123] The content of non-ester catechins (EC) in all samples increased significantly. The increase in EC content can improve the smoothness of the tea soup, avoid bland taste, and optimize the overall palatability.

[0124] The changes in the content of simple catechin C varied depending on the tea raw material matrix. The C content in Examples 1, 2, and 3 showed a decreasing trend, while the C content in Examples 4 and 5 showed an increasing trend, further demonstrating the differences in metabolic compatibility between different tea raw materials and strains.

[0125] 3. Changes in caffeine, thearubigin, theabrownin, and theaflavins

[0126] Caffeine is an important flavor substance and functional component of tea. Its content changes have a certain impact on the bitterness and flavor balance of tea soup. The caffeine content in Example 1 was 16.8% lower than that in the blank control Example 1, while the caffeine content in Examples 2 to 5 all increased slightly. The overall fluctuation range was small and would not have an adverse effect on the overall flavor of the tea soup.

[0127] Theaflavins and thearubigins are light-colored pigments in tea leaves, which together determine the bright color of the tea soup. Theabrownins are typical deep oxidation and polymerization products of post-fermented tea, with a stable and mellow color. According to the data in Table 2, after fermentation by the bacterial strain, the content of theaflavins and thearubigins in each example group was lower than that in the corresponding blank control group. At the same time, the content of theabrownins in each group showed a significant upward trend. This indicates that bacterial fermentation can promote the directional conversion of theaflavins and thearubigins to theabrownins, which is consistent with the color evolution characteristics of Liubao tea after post-fermentation. This promotes the stable yellow-brown and bright color of the fermented tea soup, forming the unique mellow flavor foundation of black tea.

[0128] III. Principal Component Analysis and Overall Quality Evaluation Results

[0129] Principal component analysis was performed on the fermented tea samples from Examples 1-5 using SPSS 18.0 software. Based on the screening criterion of eigenvalues ​​greater than 1, three effective principal component factors were extracted. The eigenvalues ​​and variance contribution rates of the principal components from Examples 1-5 are shown in Table 3, the principal component loading matrices of the core quality components from Examples 1-5 are shown in Table 4, and the comprehensive scores and rankings of the principal components from Examples 1-5 are shown in Table 5.

[0130]

[0131] As can be seen from Table 3, the cumulative variance contribution rate of the three extracted principal components reached 92.585%, which is highly representative and can be used for comprehensive quality evaluation.

[0132]

[0133]

[0134] As can be seen from the comprehensive scores in Table 5, the overall quality ranking of the fermented samples from Examples 1 to 5 is: Example 5 > Example 2 > Example 3 > Example 1 > Example 4. Among them, the comprehensive scores of Examples 5 and 2 are significantly higher than those of other raw materials, making them the optimal raw materials for Aspergillus cristatus HZJH-10, which can yield Liubao tea products with the best overall quality.

[0135] The above content should not be construed as limiting the specific embodiments of the present invention to the above description. For those skilled in the art, several simple deductions or substitutions can be made without departing from the concept of the present invention, and all such deductions or substitutions should be considered as falling within the scope of patent protection defined by the claims submitted by the present invention.

Claims

1. A strain of *Aspergillus cristatus*, characterized in that, This strain was deposited on June 30, 2025, at the China General Microbiological Culture Collection Center (CGMCC), located at No. 3, Courtyard 1, Beichen West Road, Chaoyang District, Beijing, China, with accession number CGMCC No. 42116, and named *Aspergillus cristatus* HZJH-10.

2. A method for preparing Liubao tea by solid-state fermentation, characterized in that, Using Aspergillus cristatus HZJH-10 as the fermentation strain according to claim 1, the fermentation process includes the following steps: Step 1: Activation and purification of the strain. The cryopreserved Aspergillus cristatus HZJH-10 strain was streaked onto Czapek's agar plates and incubated at 26-30°C in the dark for 7-10 days. Typical single colonies were picked and streaked three times to obtain the purified strain. Step 2: Preparation of spore suspension. Pick mycelia and mature cleistothecia from the purified plate and place them in sterile physiological saline. Shake at 1500-2500 rpm for 10-20 minutes to disperse the spores. Filter with sterile absorbent cotton to remove residue, obtaining a spore concentration of 1×10⁻⁶. 6 ~1×10 8 A CFU / mL spore suspension, refrigerated at 4°C for use, should not be stored for more than 72 hours. Step 3: Pretreatment of fermentation raw materials. Weigh 100g of raw tea leaves, add distilled water until the final moisture content of the raw materials is 25%, stir well, seal and let stand for 0.5~2 hours; Step 4: Sterilization. After soaking and swelling, the tea leaves are divided into Erlenmeyer flasks, sealed with sterile, breathable sealing film, and placed in a high-pressure steam sterilizer. Sterilize at 121-130℃ and 0.1-0.3MPa for 15-30 minutes, then allow to cool naturally to room temperature. Step 5: Inoculation and mixing. Inoculate the cooled tea raw materials with 1 mL of spore suspension for every 50 g of dry tea raw materials, stir thoroughly for at least 3 minutes, and gently compact. Step 6: Constant temperature solid-state fermentation. Place the inoculated tea leaves in a constant temperature and humidity incubator at 25~30℃ and ferment in the dark, controlling the relative humidity at 60~70%, for 20~30 days; Step 7: Drying and post-processing. After fermentation, spread the tea leaves evenly on a tray and dry them. Control the temperature in the drying oven to a stable 50-70℃ and dry until the moisture content is 8-12%. After naturally cooling to room temperature, the finished Liubao tea is obtained.

3. The method for preparing Liubao tea by solid-state fermentation according to claim 2, characterized in that, In step 1, the Czapek's medium formula is as follows: 3g sodium nitrate, 1g dipotassium hydrogen phosphate, 0.5g magnesium sulfate, 0.5g potassium chloride, 0.01g ferrous sulfate, 30g sucrose, 20g agar, 1000mL distilled water, natural pH, autoclaved at 121℃ for 20 minutes for later use.

4. The method for preparing Liubao tea by solid-state fermentation according to claim 2, characterized in that, In step 2, the concentration of the spore suspension is 1×10⁻⁶. 7 CFU / mL.

5. The method for preparing Liubao tea by solid-state fermentation according to claim 2, characterized in that, In step 3, the raw tea material is selected from one of the following: Cangwu group spring tea raw tea, Cangwu group summer tea raw tea, green tea raw tea, yellow tea raw tea, and Yunpan tea raw tea.

6. The method for preparing Liubao tea by solid-state fermentation according to claim 2, characterized in that, In step 3, stir once every 15 minutes during the settling period.

7. The method for preparing Liubao tea by solid-state fermentation according to claim 2, characterized in that, In step 4, the high-pressure steam sterilization conditions are 121°C and 0.1 MPa for 20 minutes.

8. The method for preparing Liubao tea by solid-state fermentation according to claim 2, characterized in that, In step 6, the solid-state fermentation conditions are constant temperature fermentation at 28℃ in the dark, relative humidity of the fermentation environment is 65%, and the fermentation time is 25 days.

9. The method for preparing Liubao tea by solid-state fermentation according to claim 2, characterized in that, In step 7, the drying temperature is 60°C, and the tea leaves are dried until the moisture content of the finished product is 10%.

10. The application of the Aspergillus cristatus strain according to claim 1 in the solid-state fermentation of Liubao tea.

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