Enterobacter hormaechei and application thereof

Abstract

The invention relates to the technical field of microorganisms, in particular to enterobacter hormaechei and application thereof. The strain is screened from rumen of cattle, cheap agricultural wastes such as corncobs and straws can be efficiently utilized as carbon sources for fermentation, the production cost of the xylanase is remarkably reduced, the yield of the xylanase is high, and the enzyme activity can reach 44.78 U / mL. Meanwhile, the xylanase produced by the strain has unique alkaline adaptability and still can keep more than 40% of activity in an alkaline environment with the pH value of 9.0, the catalytic activity of the xylanase can be effectively promoted by common additives such as Mn < 2 + > and Tween-80, the strain is suitable for production of the xylanase, and the application efficiency and economical efficiency of the strain are further improved.

Description

Technical Field

[0001] This invention relates to the field of microbial technology, and in particular to a strain of Enterobacter cholerae and its applications. Background Technology

[0002] Xylan is the main component of plant hemicellulose, a polysaccharide composed of xylose residues linked by β-1,4-glycosidic bonds. Its efficient hydrolysis depends on the action of xylanase. As an important industrial enzyme, xylanase is widely used in paper bleaching, feed processing, food brewing, and bioenergy, effectively reducing energy consumption and chemical pollution in production processes, aligning with the trend of green industry development.

[0003] Currently, xylanases used in industrial production are mainly derived from microorganisms. Reported xylanase-producing microorganisms primarily include those in the genera *Aspergillus* and *Trichoderma*. However, the developed strains are relatively limited in number and exhibit significant homogeneity, making it difficult to meet the diverse requirements for enzymatic properties (such as optimal pH, temperature stability, and substrate specificity) in different industrial settings. Furthermore, the fermentation media for many high-yield strains require the addition of expensive pure xylan as an inducing substrate, resulting in high production costs and hindering their large-scale industrial application.

[0004] The rumen of ruminants is a natural fermentation system rich in microbial resources, where the microbial community can efficiently degrade plant cellulose and hemicellulose. Rumen microorganisms, as a source of enzyme preparations with great development potential, are still underutilized. Therefore, screening new strains from the rumen's unique habitat that can efficiently utilize inexpensive agricultural waste to produce xylanase, and whose produced enzymes possess excellent characteristics, is of significant practical importance for reducing enzyme preparation production costs and broadening the application range of xylanase. Summary of the Invention

[0005] The purpose of this invention is to address the technical problems of existing xylanase-producing strains, such as homogeneity of resources, low utilization efficiency of inexpensive substrates, and difficulty in meeting specific industrial requirements for the performance of the produced enzyme preparations. This invention provides a novel *Enterobacter holmieae* strain (CGMCC No. 35272) screened from bovine rumen and its applications. It enables efficient production of xylanase using low-cost raw materials, with an enzyme activity reaching 44.78 U / mL. The produced xylanase exhibits good stability under alkaline conditions and good tolerance to specific metal ions and surfactants. The enzymes produced by this strain can be further used in the production of xylanase.

[0006] The first aspect of this invention provides a strain of Enterobacter holmieae, classified and named Enterobacter holmieae. Enterobacter hormaecheiIt was deposited on July 17, 2025 at the China General Microbiological Culture Collection Center (CGMCC), specifically at No. 3, Courtyard 1, Beichen West Road, Chaoyang District, Beijing, Institute of Microbiology, Chinese Academy of Sciences; accession number CGMCC No. 35272.

[0007] This invention provides a strain of *Enterobacter holmieae* screened from bovine rumen. This strain can efficiently utilize inexpensive agricultural waste such as corn cobs and straw as carbon sources for fermentation, significantly reducing the production cost of xylanase. It exhibits high xylanase yield, with an enzyme activity reaching 44.78 U / mL. Furthermore, the xylanase produced by this strain possesses unique alkalinity adaptability, maintaining over 40% activity even in an alkaline environment of pH 9.0. Moreover, the catalytic activity of this enzyme can be reduced by Mn... 2＋ Common additives such as Tween-80 effectively promote the production of xylanase by this strain, further improving its application efficiency and economy.

[0008] A second aspect of the present invention provides a microbial inoculant, the active ingredient of which is the aforementioned Enterobacter holmieae.

[0009] Furthermore, the bacterial agent is in liquid or solid form.

[0010] A third aspect of the present invention provides a fermentation medium for culturing Enterobacter hominis as described above to produce xylanase, the medium comprising corn cob as a carbon source and yeast extract powder as a nitrogen source.

[0011] Furthermore, it includes the following components: Corn cob 20.0-35.0 g / L, Na2HPO4 1.5-2.5 g / L, MgSO4·7H2O 0.2-0.4 g / L, CaCl2 0.2-0.4 g / L, (NH4)2SO4 1.0-1.8 g / L, yeast extract powder 1.0-2.0 g / L, tryptone 1.0-2.0 g / L, glucose 0.5-1.5 g / L, and trace nutrient solution 1-2 mL / L.

[0012] The trace nutrient solution includes: CoCl2 0.3-0.5 g / L, FeSO4 0.1-0.3 g / L, ZnCl2 0.2-0.5 g / L, and MnSO4 0.1-0.2 g / L.

[0013] A fourth aspect of the present invention provides a method for producing xylanase, comprising the following steps: The above-mentioned Enterobacter holmieae was inoculated into the above-mentioned fermentation medium for fermentation; The fermentation was carried out under the following conditions: culture temperature 35-37℃, initial pH of the culture medium 5.8-6.2, and culture time 24-26h.

[0014] This invention provides a fermentation culture medium and a method for producing xylanase using *Enterobacter holmieae*. The medium uses inexpensive corn cobs as the main carbon source and optimizes the ratio of nitrogen source and various inorganic salts, providing an excellent nutritional environment for efficient enzyme production by *Enterobacter holmieae*. When producing xylanase, the strain can achieve a xylanase activity as high as 44.78 U / mL by culturing at 35-37℃ and an initial pH of 5.8-6.2 for 24-26 hours. This significantly reduces the production cost of enzyme preparations, and the produced xylanase exhibits excellent alkalinity adaptability and catalytic efficiency, which is beneficial for industrial application and promotion.

[0015] The fifth aspect of the present invention provides a xylanase preparation obtained by the above method.

[0016] The sixth aspect of the present invention provides the application of the above-mentioned Enterobacter holmie in the preparation of xylanase.

[0017] The seventh aspect of the present invention provides the application of the above-mentioned Enterobacter holmie in the degradation of xylan.

[0018] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. This invention provides a strain of *Enterobacter holmieae* screened from bovine rumen. This strain can efficiently utilize inexpensive agricultural waste such as corn cobs as a carbon source for fermentation, significantly reducing the production cost of xylanase. It exhibits high xylanase yield, with an enzyme activity reaching 44.78 U / mL. Furthermore, the xylanase produced by this strain possesses unique alkalinity adaptability, maintaining over 40% activity even in an alkaline environment of pH 9.0. Moreover, the catalytic activity of this enzyme can be reduced by Mn... 2＋ Common additives such as Tween-80 effectively promote and further improve its application efficiency and economy.

[0019] 2. This invention provides a fermentation culture medium and a method for producing xylanase using *Enterobacter holmieae*. The culture medium uses inexpensive corn cobs as the main carbon source and optimizes the ratio of nitrogen source and various inorganic salts, providing an excellent nutritional environment for efficient enzyme production by *Enterobacter holmieae*. When producing xylanase, the strain can achieve a xylanase activity as high as 44.78 U / mL by culturing at 35-37℃ and an initial pH of 5.8-6.2 for 24-26 hours. This significantly reduces the production cost of enzyme preparations, and the produced xylanase exhibits excellent alkalinity adaptability and catalytic efficiency. This strain is suitable for xylanase production and is beneficial for industrial application and promotion.

[0020] 3. This invention provides the application of this Enterobacter hominis in the preparation of xylanase and the degradation of xylan. Attached Figure Description

[0021] Figure 1 This is a morphological identification diagram of Enterobacter holmie.

[0022] Figure 2 This is a phylogenetic evolutionary tree.

[0023] Figure 3 A graph showing the relationship between xylanase activity prepared from Enterobacter holmie strain F-4 under different temperature conditions.

[0024] Figure 4 The graph shows the relationship between xylanase activity prepared from Enterobacter holmie strain F-4 under different pH conditions.

[0025] Figure 5 The figure shows the effect of different metal conditions on xylanase activity of Enterobacter holmie strain F-4.

[0026] Figure 6 The graph shows the effect of different types of chemical reagents at a concentration of 10 mmol / L on xylanase activity.

[0027] Figure 7 To cultivate time E. hormaechei The effect of F-4 on xylanase production.

[0028] Figure 8 The initial pH of the culture medium E. hormaechei The effect of F-4 on xylanase production.

[0029] Figure 9 To cultivate temperature E. hormaechei The effect of F-4 on xylanase production.

[0030] Figure 10 For carbon source and its concentration to E. hormaechei The effect of F-4 on enzyme production.

[0031] Figure 11 Using corn cob as a carbon source at different concentrations E. hormaechei The effect of F-4 on enzyme production.

[0032] Figure 12 For nitrogen source and its concentration E. hormaechei The effect of F-4 on xylanase production.

[0033] Figure 13 Yeast extract powder of different concentrations was used as a nitrogen source for culturing. E. hormaechei The effect of F-4 on enzyme production.

[0034] Figure 14 This is a response surface diagram. Detailed Implementation

[0035] The present invention will now be described in further detail with reference to specific embodiments. However, this should not be construed as limiting the scope of the present invention to the following embodiments; all technologies implemented based on the content of the present invention fall within the scope of the present invention.

[0036] The first aspect of this invention provides a strain classified and named Enterobacter holmieae. Enterobacter hormaechei It was deposited on July 17, 2025 at the China General Microbiological Culture Collection Center (CGMCC) with accession number CGMCC No. 35272.

[0037] The *Enterobacter holmieae* strain screened from bovine rumen can efficiently utilize inexpensive agricultural waste such as corn cobs and straw as carbon sources for fermentation, significantly reducing the production cost of xylanase. It exhibits high xylanase yield, with an enzyme activity reaching 44.78 U / mL, making this strain suitable for xylanase production. Furthermore, the xylanase produced by this strain possesses unique alkalinity adaptability, maintaining over 40% activity even in an alkaline environment of pH 9.0. Moreover, the catalytic activity of this enzyme can be inhibited by Mn... 2＋ Common additives such as Tween-80 effectively promote and further improve its application efficiency and economy.

[0038] A second aspect of the present invention provides a microbial inoculant, the active ingredient of which is the aforementioned Enterobacter holmieae.

[0039] In some embodiments, the microbial agent is a liquid or solid dosage form.

[0040] A third aspect of the present invention provides a fermentation medium for culturing Enterobacter hominis as described above to produce xylanase, the medium comprising corn cob as a carbon source and yeast extract powder as a nitrogen source.

[0041] In some embodiments, the following components are included: The formula consists of: corn cob 20.0-35.0 g / L, Na₂HPO₄ 1.5-2.5 g / L, MgSO₄·7H₂O 0.2-0.4 g / L, CaCl₂ 0.2-0.4 g / L, (NH₄)₂SO₄ 1.0-1.8 g / L, yeast extract powder 1.0-2.0 g / L, tryptone 1.0-2.0 g / L, glucose 0.5-1.5 g / L, and trace nutrient solution 1-2 mL / L. The trace nutrient solution includes: CoCl₂ 0.3-0.5 g / L, FeSO₄ 0.1-0.3 g / L, ZnCl₂ 0.2-0.5 g / L, and MnSO₄ 0.1-0.2 g / L.

[0042] For example, trace nutrient solutions include: CoCl2 0.4 g / L, FeSO4 0.2 g / L, ZnCl2 0.3 g / L, and MnSO4 0.15 g / L.

[0043] A fourth aspect of the present invention provides a method for producing xylanase, comprising the following steps: The above-mentioned Enterobacter holmieae was inoculated into the above-mentioned fermentation medium for fermentation; The fermentation was carried out under the following conditions: culture temperature 35-37℃, initial pH of the culture medium 5.8-6.2, and culture time 24-26h.

[0044] The xylanase produced achieved high activity when the culture temperature was 35℃, 36℃, or 37℃, the initial pH of the culture medium was 5.8, 5.9, 6.0, 6.1, or 6.2, and the culture time was 24h, 25h, or 26h.

[0045] This culture medium uses inexpensive corn cobs as the main carbon source and optimizes the ratio of nitrogen source and various inorganic salts, providing an excellent nutritional environment for the efficient enzyme production of *Enterobacter holmieae*. When producing xylanase, the strain can achieve a xylanase activity as high as 44.78 U / mL after culturing at 35-37℃ and an initial pH of 5.8-6.2 for 24-26 hours. This significantly reduces the production cost of enzyme preparations, and the produced xylanase exhibits excellent alkalinity adaptability and catalytic efficiency. This strain is suitable for xylanase production and is conducive to its industrial application and promotion.

[0046] The present invention provides a xylanase preparation obtained by the above method in its fifth aspect.

[0047] The sixth aspect of the present invention provides the application of the above-mentioned Enterobacter holmie in the preparation of xylanase.

[0048] The seventh aspect of the present invention provides the application of the above-mentioned Enterobacter holmie in the degradation of xylan.

[0049] To better understand the technical solutions of the above embodiments, the following more detailed implementation methods are provided for further explanation.

[0050] Example The screening and identification method for Enterobacter hopnea euri includes the following steps: S1. Strain screening: A high-xylanase-producing strain was isolated and purified from rumen fluid using a screening method with corn cob powder as the sole carbon source, obtained from the rumen of ruminants.

[0051] S2, Strain identification: Enterobacter holmie ( Enterobacter hormaecheiThe F-4 strain was identified by the following method.

[0052] S21. Identification by morphology; like Figure 1 As shown, the strain presents as white, well-defined, raised, opaque, round colonies on solid plates. Gram staining of the cells under a microscope reveals a pale red color, indicating that it belongs to the Gram-negative short bacillus group.

[0053] S22. Physiological and biochemical identification, as shown in Table 1; Table 1. Physiological and Biochemical Identification Results

[0054] Note: +: positive; -: negative As shown in the table, the strain is responsive to various sugar fermentations and other biochemical tests.

[0055] S23. Molecular biological identification, as shown in Table 2.

[0056] Table 2 Molecular biological identification results

[0057] As shown in the table, the 16S rDNA sequence of the strain has a similarity of over 99% with that of Enterobacteriaceae, including Enterobacter cloacae (Enterobacter). Enterobacter cloacae ), Enterobacter carcinogens ( Enterobacter cancerogenus ) and Enterobacter hopterii ( Enterobacter hormaechei These are three highly similar bacterial species. Therefore, it is speculated that the strain may belong to one of these three strains.

[0058] Fasta sequences of the 16S rDNA from the target strain and the reference strain were imported into molecular biology software, and a phylogenetic tree was constructed using genetic analysis procedures. Figure 2 It can be seen that strain F-4 is related to Enterobacter cholerae (C. cholerae). Enterobacter hormaechei Based on the fact that SitB416 is on the same branch, and ensuring the accuracy of the phylogenetic tree, combined with other previous identification experiments, the strain can be identified as *Enterobacter holmieae*, and named... Enterobacter hormaechei F-4.

[0059] Furthermore, the biological agent is a liquid agent.

[0060] The application of the above-mentioned biological agents in xylanase production.

[0061] A method for producing xylanase specifically includes the following steps: A1. Prepare enrichment culture medium; 20.0 g corn cob powder, 2.0 g Na2HPO4, 0.3 g MgSO4·7H2O, 0.3 g CaCl2, 1.4 g (NH4)2SO4, 1 mL trace nutrient solution (trace nutrient solution includes: CoCl2 0.4 g / L, FeSO4 0.2 g / L, ZnCl2 0.3 g / L, MnSO4 0.15 g / L), 1.0 g glucose, 1.5 g yeast extract powder, 1.5 g tryptone, add distilled water to 1 L.

[0062] A2. Enterobacter holmie strain F-4 was inoculated into a culture medium containing corn cob powder as the sole carbon source and cultured at 37°C and 180 r / min for 36-48 h. The activity of xylanase could then be measured by the DNS method.

[0063] The beneficial effects of the technical solution provided by the present invention are as follows: The present invention provides a strain of Enterobacter holmie, F-4, which significantly improves xylanase activity through optimization of enzyme production conditions.

[0064] The enzyme's enzymatic properties and enzyme production conditions were analyzed and optimized using the following methods: B1. Optimal reaction temperature: 50℃. The enzyme has good stability under conditions of 35-50℃. The results of enzymatic reactions between enzymes and substrates at different temperatures are as follows: Figure 3 As shown, the temperature effect of the enzyme changes significantly when the temperature of the enzymatic reaction is below 45℃ or above 55℃. E. hormaechei The optimal reaction temperature for F-4 xylanase is 50℃. B11. Optimal reaction pH: 8.0, and it can maintain good stability under pH 6.0-7.0 conditions; The results of enzymatic reactions between enzymes and substrates at different pH values ​​are as follows: Figure 4 As shown, the optimal reaction pH for this xylanase is 8.0, and it can still exert about 40% of its enzyme activity at pH 9.0, which means that the enzyme is suitable for functioning in a slightly alkaline environment.

[0065] B12. Influence of metal ions: 1 mmol / L Mg 2+ Mn 2+ and 10 mmol / L Zn 2+ It has a promoting effect on this enzyme, while Co 2+ Fe 3+ Ca 2+ Cu 2+ It has an inhibitory effect on the activity of this enzyme; The effects of different types and concentrations of metal ions on enzyme activity are as follows: Figure 5 As shown, 1 mmol / L Mg2+ Mn 2+ and 10 mmol / L Zn 2+ It promoted xylanase activity, increasing it by 5%, 20%, and 4%, respectively; while Co 2+ Fe 3+ Ca 2+ Cu 2+ It has a significant inhibitory effect on xylanase activity, of which Co 2+ Fe 3+ It has the strongest inhibitory effect on xylanase.

[0066] B13. Substrate specificity: The enzyme activity is the highest when using corn cob xylan as a substrate, which is superior to beech xylan.

[0067] Table 3. Effects of different substrate types on xylanase activity.

[0068] The effects of different substrates on xylanase activity are shown in Table 3. No xylanase activity was detected when soluble starch, 2×1 filter paper, or sodium carboxymethyl cellulose were used as substrates. However, the highest enzyme activity was observed when corn cob xylan and beech xylan were used as substrates. E. hormaechei The xylanase secreted by F-4 is highly specific, catalyzing only xylan substrates; at the same time, the activity of xylanase varies significantly with xylan substrates from different sources, with corn cob xylan showing higher enzyme activity than beech xylan when used as a substrate.

[0069] B14. Effects of chemical reagents: 10 mmol / L Tween-80 and Tris have a certain promoting effect on the enzyme activity, while SDS, EDTA and urea have an inhibitory effect on the enzyme activity.

[0070] The effects of different types of chemical reagents at a concentration of 10 mmol / L on xylanase activity are as follows: Figure 6 As shown, SDS, EDTA, and urea have a certain inhibitory effect on xylanase activity, Triton X-100 has no significant effect on the enzymatic reaction, while Tween-80 and Tris have a certain promoting effect on xylanase activity. Among them, Tween-80 has the most significant promoting effect on xylanase, which can increase xylanase activity by about 15%.

[0071] C2. Single-factor experiment: C21. The optimal enzyme production condition is a culture time of 24 h. Enzyme-producing culture medium: 30.0 g corn cob powder, 5.0 g Na2HPO4, 6.0 g yeast extract powder, 0.5 g MgSO4•7H2O, 0.5 g CaCl2, add distilled water to 1 L.

[0072] Incubation time E. hormaechei The effect of F-4 xylanase production, such as Figure 7 As shown, the xylanase activity produced by strain F-4 showed an increasing trend with the extension of culture time from 6 to 24 h, reaching a maximum value of 35.76 U / mL at 24 h. Thereafter, the xylanase activity produced by strain F-4 gradually decreased with the extension of culture time.

[0073] C22, initial pH of the culture medium 6.0; Initial pH of the culture medium E. hormaechei The effect of F-4 xylanase production, such as Figure 8 As shown, when the initial pH of the culture medium is below 6.0 or above 7.0, the activity of xylanase is greatly affected and the enzyme activity is very low. However, when the initial pH of the culture medium is 6.0, the xylanase activity can reach a maximum of 42.25 U / mL.

[0074] C23, culture temperature 37℃; Incubation temperature E. hormaechei The effect of F-4 xylanase production, such as Figure 9 As shown, when the culture temperature is between 25-37℃, the xylanase activity of the strain shows an increasing trend with the increase of culture temperature. At the culture temperature of 37℃, the xylanase activity reaches a maximum of 43.53 U / mL. After that, the enzyme activity decreases rapidly with the increase of culture temperature.

[0075] C24, carbon source and corn cob with a carbon source concentration of 3%; The effect of carbon source and its concentration on E. hormaechei The effect of F-4 enzyme production, such as Figure 10 As shown, when corn cobs in the enzyme-producing medium were replaced by 3% (by mass) of corn stalks, wheat bran, oat straw, corn husks, glucose, and xylan, respectively, under the aforementioned optimal conditions, the strain exhibited the best enzyme production effect when corn cobs were used as the carbon source, followed by wheat bran and corn stalks. However, when xylan was used as the carbon source, the enzyme production activity of the strain was significantly lower than when corn cobs were used.

[0076] Different concentrations of corn cob as carbon source E. hormaechei The effect of F-4 enzyme production, such as Figure 11As shown, when the corn cob concentration is between 0.5% and 3.0%, the xylanase activity increases with increasing concentration. When the concentration is 3.0%, the enzyme activity reaches its maximum value of 43.76 U / mL. When the concentration is higher than 3.0%, the enzyme activity decreases sharply.

[0077] C25, nitrogen source, and yeast extract powder with a nitrogen source concentration of 0.8%.

[0078] Nitrogen source and its concentration on E. hormaechei The effect of F-4 xylanase production, such as Figure 12 As shown, yeast extract powder is the best nitrogen source for enzyme production culture medium, followed by beef extract. At the same time, organic nitrogen sources are more conducive to the secretion of xylanase by the strain than inorganic nitrogen sources.

[0079] Yeast extract powder of different concentrations as nitrogen source for culture E. hormaechei The effect of F-4 enzyme production, such as Figure 13 As shown, when the concentration is 0.2% to 0.8%, the xylanase activity of the strain increases with the increase of concentration. When the concentration is 0.8%, the enzyme activity reaches the maximum value of 45.03 U / mL. After that, as the concentration of yeast extract powder continues to increase, the enzyme activity of the strain gradually decreases.

[0080] S3. Response surface methodology, with conditions shown in Table 4: Table 4 Response Surface Experiment Conditions

[0081] The optimized enzyme production conditions were: 25 h culture time, 36 °C culture temperature, and initial pH of the culture medium of 6.0.

[0082] From response surface Figure 14 It can be seen that all response surface plots have steep surface changes and large slope changes, while the shape of the contour plots is close to an ellipse. This indicates that the interaction between factors such as A and B, A and C, and B and C is obvious and has a significant impact on xylanase activity.

[0083] This invention provides a method for culturing *Enterobacter holmieae* through single-factor experiments and response surface methodology, comprising the following steps: determining the optimal culture conditions as follows: culture time 25 hours, culture temperature 36℃, initial pH of the culture medium 6.0, carbon source and corn cob with a carbon source concentration of 3%, nitrogen source and yeast extract powder with a nitrogen source concentration of 0.8%. Under these culture conditions, xylanase activity can reach 44.78 U / mL.

[0084] The 16S rDNA sequence of strain F-4 is SEQ ID NO.1:

[0085] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A strain of Enterobacter hopterii, characterized in that, The strain was classified as Enterobacter holmium. Enterobacter hormaechei It was deposited on July 17, 2025 at the China General Microbiological Culture Collection Center (CGMCC) with accession number CGMCC No. 35272.

2. A microbial inoculant, characterized in that, Its active ingredient is Enterobacter holmie as described in claim 1.

3. The microbial agent as described in claim 2, characterized in that, The bacterial agent can be in liquid or solid form.

4. A fermentation medium for culturing *Enterobacter holmieae* as described in claim 1 to produce xylanase, characterized in that, The culture medium contains corn cobs as a carbon source and yeast extract powder as a nitrogen source.

5. The fermentation medium as described in claim 4, characterized in that, It includes the following components: Corn cob 20.0-35.0 g / L, Na2HPO4 1.5-2.5 g / L, MgSO4·7H2O 0.2-0.4 g / L, CaCl2 0.2-0.4 g / L, (NH4)2SO4 1.0-1.8 g / L, yeast extract powder 1.0-2.0 g / L, tryptone 1.0-2.0 g / L, glucose 0.5-1.5 g / L, and trace nutrient solution 1-2 mL / L.

6. A method for producing xylanase, characterized in that, Includes the following steps: The Enterobacter holmie described in claim 1 is inoculated into the fermentation medium described in claim 4 or 5 for fermentation; The fermentation was carried out under the following conditions: culture temperature 35-37℃, initial pH of the culture medium 5.8-6.2, and culture time 24-26h.

7. A xylanase preparation prepared by the method of claim 6.

8. The use of the Enterobacter holmieum of claim 1 in the preparation of xylanase.

9. The application of *Enterobacter holmieae* as described in claim 1 in the degradation of xylan.

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