Straw degrading bacterium and application thereof

Abstract

The invention discloses a straw degrading bacterium and application thereof, and belongs to the technical field of biotechnology and microbial degradation of agricultural wastes. The high-temperature straw degrading bacterium WLH-10 disclosed by the invention is classified and named as Delftia tsuurhinensis, and is preserved in the China General Microbiological Culture Collection Center on September 10, 2025, and the preservation number of the high-temperature straw degrading bacterium WLH-10 is CGMCC No. 35872. The microbial inoculum WLH-10 provided by the invention has the advantages of high degradation efficiency, clear action mechanism, adaptability to neutral conditions, environmental friendliness and the like, and an efficient and sustainable technical scheme is provided for biodegradation and resource utilization of lignocellulose wastes such as agricultural straws.

Description

Technical Field

[0001] This invention belongs to the field of biotechnology and microbial degradation technology of agricultural waste, specifically relating to a straw-degrading bacterium and its application. Background Technology

[0002] Straw is one of the most abundant byproducts of agricultural production, and its main chemical components are cellulose, hemicellulose, and lignin. These three components are cross-linked through complex covalent and non-covalent bonds, forming a highly dense and stable polymer network structure. This network constitutes a physical and chemical barrier against microbial degradation, leading to difficulties in natural degradation and low utilization rates. Therefore, developing efficient, environmentally friendly, and economically feasible technologies for the resource utilization of straw has become an urgent need to promote the green transformation of agriculture and the development of a circular economy.

[0003] Among various treatment methods, microbial degradation is widely recognized as one of the most promising technological pathways due to its advantages such as mild reaction conditions, low energy consumption, and no secondary pollution. The core of this strategy lies in utilizing functional microorganisms that can efficiently secrete cellulase, hemicellulase, and lignin-degrading enzymes (such as laccase and lignin peroxidase). Through the synergistic action of multiple enzymes, the complex structure of straw is destroyed, and it is degraded into soluble low-molecular-weight sugars and other usable substances.

[0004] Through the action of microorganisms, straw can be transformed into products with economic and agricultural value, such as biofuels, organic fertilizers, feed additives, or high-value-added chemicals. This transformation process not only realizes the fundamental change of straw from "agricultural waste" to "renewable biomass resource," but also aligns with the goal of resource recycling, providing key technological support for building a sustainable agricultural ecosystem.

[0005] Therefore, developing a microbial agent with efficient straw degradation capabilities has become one of the key directions for breaking through the bottleneck of straw resource utilization. Summary of the Invention

[0006] In view of this, the present invention provides a strain WLH-10 with highly efficient straw degradation capabilities and its application in straw biodegradation. By optimizing the culture conditions, the prepared microbial agent can significantly improve the weight loss rate and key enzyme activities (such as carboxymethyl cellulase and laccase) during straw degradation, thereby achieving effective decomposition and resource transformation of straw.

[0007] To achieve the above objectives, the present invention provides the following technical solution: This invention discloses a strain WLH-10 with highly efficient straw degradation ability. The strain was deposited on September 10, 2025 at the China General Microbiological Culture Collection Center (CGMCC) with accession number CGMCC No. 35872. The address of the depository is No. 3, No. 1 Beichen West Road, Chaoyang District, Beijing.

[0008] The present invention also discloses the application of the above-mentioned straw-degrading bacteria WLH-10 in the degradation of plant straw.

[0009] Preferably, the plant straw is selected from corn straw and / or rice straw.

[0010] The present invention also discloses a microbial agent containing the above-mentioned straw-degrading bacteria WLH-10.

[0011] The preparation method of the above-mentioned microbial agent containing straw-degrading bacteria WLH-10 is as follows: The WLH-10 agent is inoculated into sodium carboxymethyl cellulose liquid medium and cultured at 40℃ and 180 r / min for 24 h to activate it; the activated bacterial solution is transferred to straw seed medium at an inoculation rate of 2% (v / v) and cultured with shaking at 40℃ and 180 r / min for 15 days; the bacterial cells and impurities are removed by centrifugation and filtration to obtain the microbial agent. Preferably, the sodium carboxymethyl cellulose liquid culture medium is composed of the following components: 1.5g potassium dihydrogen phosphate, 5g peptone, 10g sodium carboxymethyl cellulose, 0.2g MgSO4, 5g NaCl, 1000mL distilled water, pH adjusted to 7.0, and sterilized at 121℃ for 20min.

[0012] Preferably, the straw seed culture medium consists of the following components: 10g straw, 5g peptone, 3g yeast extract, 2.0g CaCO3, 5g NaCl, 1000 mL distilled water, natural pH, sterilized at 121℃ for 20min.

[0013] Preferably, the straw seed culture medium consists of the following components: 10g corn straw, 8g yeast extract, 2g CaCO3, 5g NaCl, 1000mL distilled water, pH 7, sterilized at 121℃ for 20min.

[0014] Compared with the prior art, the present invention has the following beneficial effects: This invention provides a highly efficient straw-degrading bacterium—*Delftiatsuruhatensis* WLH-10. Compared with the prior art, this application has the following outstanding advantages: The inoculum formed clear and transparent hydrolysis zones in the Congo red staining screening method, with a D / d value as high as 3.42, exhibiting excellent cellulase activity. After 5 days of fermentation, the inoculum WLH-10 showed the best degradation effect at 40℃, with a weight loss rate of 20.35 ± 0.71% (see...). Figure 4 Scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR) confirmed that after treatment with this fungus, obvious cracks and holes appeared on the surface of the straw, and the fiber structure became loose and broken, especially at 1230-1250 cm⁻¹. -1 and 1420-1430 cm -1 The significant decrease in characteristic absorption peaks indicates that the structure of key components such as cellulose and lignin in its cell wall has been effectively disrupted (see...). Figure 11 and Figure 12 ).

[0015] The microbial agent provided by this invention has the advantages of high degradation efficiency, clear mechanism of action, adaptability to neutral conditions, and environmental friendliness. It provides an efficient and sustainable technical solution for the biodegradation and resource utilization of lignocellulosic wastes such as agricultural straw, and has good application prospects and promotion value. Attached Figure Description

[0016] Figure 1 The colony morphology of strain WLH-10 of this invention on solid culture medium; Figure 2 This is an electron micrograph of the strain WLH-10 of the present invention. Figure 3 This is the phylogenetic tree of strain WLH-10 of the present invention; Figure 4 Temperature gradient experiment for strain WLH-10 of this invention; Figure 5 The growth curve of strain WLH-10 of this invention at 40℃ is shown. Figure 6 This study analyzes the degradation performance of the microbial agent WLH-10 of the present invention on straw under different carbon source (a), nitrogen source (b) and pH (c) conditions; Figure 7 The effect of the inoculant WLH-10 of the present invention on the activity of carboxymethyl cellulase (CMCase) under different carbon source (a), nitrogen source (b) and pH (c) conditions; Figure 8 The effect of the bacterial agent WLH-10 of the present invention on the activity of filter paper enzyme (FPase) under different carbon source (a), nitrogen source (b) and pH (c) conditions; Figure 9 The effect of the inoculant WLH-10 of the present invention on laccase activity under different carbon source (a), nitrogen source (b) and pH (c) conditions; Figure 10 The effect of the microbial agent WLH-10 of the present invention on the activity of lignin peroxidase (LiP) under different carbon source (a), nitrogen source (b) and pH (c) conditions.

[0017] Figure 11 SEM images of corn stalks before (a) and after (b) degradation by the microbial agent WLH-10. Figure 12 FTIR results of corn stalks before (a) and after (b) degradation by the microbial agent WLH-10. Detailed Implementation

[0018] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0019] Unless otherwise specified, the experimental methods used in the following examples are conventional methods.

[0020] Unless otherwise specified, all materials and reagents used in the following examples are commercially available.

[0021] This invention discloses a strain WLH-10 with highly efficient straw degradation ability. The strain was deposited on September 10, 2025 at the China General Microbiological Culture Collection Center (CGMCC) with accession number CGMCC No. 35872. The address of the depository is No. 3, No. 1 Beichen West Road, Chaoyang District, Beijing.

[0022] This invention also discloses the application of the aforementioned straw-degrading bacteria WLH-10 in the degradation of plant straw. The plant straw is preferably corn straw, rice straw, or a mixture of both.

[0023] This invention also discloses a microbial agent containing the above-mentioned straw-degrading bacteria WLH-10. The preparation method is as follows: the bacterial agent WLH-10 is inoculated into sodium carboxymethyl cellulose liquid culture medium and cultured at 40℃ and 180 r / min for 24 h to activate it; the activated bacterial solution is transferred to straw seed culture medium at an inoculation amount of 2% (v / v) and cultured with shaking at 40℃ and 180 r / min for 15 days; the bacterial cells and impurities are removed by centrifugation and filtration to obtain the bacterial agent.

[0024] The above-mentioned sodium carboxymethyl cellulose liquid culture medium consists of the following components: 1.5g potassium dihydrogen phosphate, 5g peptone, 10g sodium carboxymethyl cellulose, 0.2g MgSO4, 5g NaCl, 1000mL distilled water, pH adjusted to 7.0, and sterilized at 121℃ for 20min.

[0025] The straw seed culture medium consists of the following components: 10g straw, 5g peptone, 3g yeast extract, 2.0g CaCO3, 5g NaCl, 1000 mL distilled water, natural pH, sterilized at 121℃ for 20min.

[0026] The above-mentioned straw seed culture medium is preferably composed of the following components: 10g corn straw, 8g yeast extract, 2g CaCO3, 5g NaCl, 1000mL distilled water, pH 7, sterilized at 121℃ for 20min.

[0027] The technical solution of the present invention will be further described below with reference to the accompanying drawings and specific embodiments: The culture medium in the following examples: Sodium carboxymethyl cellulose liquid culture medium: 1.5g potassium dihydrogen phosphate, 5g peptone, 10g sodium carboxymethyl cellulose, 0.2g MgSO4, 5g NaCl, 1000mL distilled water, adjust pH to 7.0, sterilize at 121℃ for 20min.

[0028] Initial straw seed culture medium: 10g straw, 5g peptone, 3g yeast extract, 2.0g CaCO3, 5g NaCl, 1000 mL distilled water, natural pH, sterilized at 121℃ for 20min.

[0029] Example 1 1. Isolation, purification and identification of bacterial agents 1.1 Soil sample preparation and inoculant isolation Take 1.0 g of surface soil sample from Gaofeng Forest Farm in Nanning City, Guangxi Province, and place it in an Erlenmeyer flask containing 90 mL of sterile water and 4-5 glass beads with a diameter of 6 mm. Place the Erlenmeyer flask in a constant temperature shaker at 25℃ and shake at 170 r / min for 30 min to fully disperse the soil particles and obtain the original soil suspension.

[0030] Using aseptic technique, transfer 1 mL of the above suspension to a test tube containing 9 mL of sterile water, vortex for 10-15 seconds to mix, and obtain 10 -1 Prepare 10-fold dilutions sequentially using the 10-fold serial dilution method. -2 10 -3 10 -4 10 -5 and 10 -6 Soil dilution suspension with equal concentration gradient.

[0031] The sterile carboxymethyl cellulose sodium (CMC-Na) solid culture medium plates were labeled as 10. -4 10 -5 and 10 -6 Three dilution gradients were used, with three replicates for each gradient. 0.1 mL of the corresponding dilution of soil suspension was inoculated onto the corresponding agar plate and spread evenly using a sterile spreader.

[0032] After inoculation, invert the plate for 5-10 minutes until the bacterial suspension is completely absorbed, then incubate at 40℃ for 1-2 days. After incubation, remove the plate for colony observation and purification. Select single colonies with obvious clear zones or significant morphological differences and transfer them to fresh CMC-Na solid medium plates, incubating upside down at 40℃. Obtain morphologically uniform and purified single colonies, such as... Figure 1 As shown, its surface is flat and smooth, with regular and rounded edges, indicating a uniform growth state.

[0033] The purified bacterial agent was observed using a scanning electron microscope, such as... Figure 2 As shown, the results indicate that the cells are straight rods or slightly curved rods.

[0034] 1.2 Initial screening of cellulose degradation ability (Congo red staining method) The purified bacterial agents were inoculated onto CMC-Na solid culture plates using a spot inoculation method, with 3 spots per plate and 3 replicates for each agent. After incubation at 40℃ for 24-48 h, 1 mg / mL Congo red solution was added for staining for 30 min. After discarding the stain, the plates were destained with 1 mol / L NaCl solution for 30 min, and the formation of the hydrolysis zone was observed. The colony diameter (d, cm) and the diameter of the clear zone (D, cm) were measured, and the D / d ratio was calculated.

[0035] The results showed that a clear and transparent hydrolysis zone formed around the bacterial agent, with a D / d value of 3.42, significantly higher than other isolated bacterial agents, indicating that it has a strong cellulose degradation ability. After screening, a highly efficient cellulose-degrading bacterium was obtained and named WLH-10.

[0036] 1.3 Molecular biological identification Genomic DNA was extracted from the bacterial agent WLH-10 and used as a template for PCR amplification of the bacterial 16S rRNA gene using universal primers 27F and 1492R. The amplified products were sequenced by BGI Genomics Co., Ltd. (China). The obtained sequences were BLAST-aligned in the NCBi GenBank database, and a phylogenetic tree was constructed based on the alignment results using the neighbor-joining method. Figure 3The fungal agent WLH-10 and Delftia tsuruhatensis belong to the same evolutionary branch and have high genetic homology.

[0037] Based on the combined analysis of colony morphology, cell morphology, cellulose degradation activity, and 16S rRNA gene sequence, the bacterial agent was identified as *Delftia tsuruhatensis*.

[0038] 1.4 Preservation of microbial strains The identified microbial agent WLH-10 was deposited on September 10, 2025, at the China General Microbiological Culture Collection Center (CGMCC), located at No. 3, Courtyard 1, Beichen West Road, Chaoyang District, Beijing, with accession number CGMCC No. 35872.

[0039] Example 2 This example illustrates the effect of the microbial agent WLH-10 on the degradation performance of straw at different temperatures.

[0040] The *Delftia tsuruhatensis* WLH-10 strain obtained from the initial screening was inoculated into sodium carboxymethyl cellulose liquid medium and cultured at 40℃ and 180 r / min for 24 h for activation. The activated bacterial solution was then transferred to the initial straw seed medium at a 2% (v / v) inoculation rate. The culture was carried out at 30℃, 35℃, 40℃, 45℃, and 50℃ in a constant temperature shaking incubator at 180 r / min. On day 5, samples were collected, and straw residue was washed three times repeatedly with sterile water to remove bacteria and soluble metabolites. The residue was then dried in a 60℃ oven to constant weight, weighed, and the relative degradation rate of the straw was calculated. The degradation rate (%) was calculated using the following formula: Degradation rate (%) = (M1-M2) / M1×100%; Where M1 is the initial straw mass and M2 is the straw mass after degradation.

[0041] The results are as follows Figure 4 As shown, after 5 days of fermentation, the straw weight loss rate of the microbial agent WLH-10 showed significant differences at different temperatures. The degradation effect was best at 40℃, with a weight loss rate of 20.35 ± 0.71%, which was significantly higher than that of other temperature groups.

[0042] The growth curve of the bacterial agent WLH-10 at the optimum temperature (40℃) was further determined, and the results are as follows: Figure 5 As shown, the bacterial agent WLH-10 exhibited a typical S-shaped growth curve when cultured at 40℃, with its logarithmic growth phase concentrated between days 2.5 and 6.5, and OD... 600The nanometer value can reach 1.6813±0.10, indicating that the bacterial agent has excellent growth performance and metabolic activity at this temperature.

[0043] Example 3 This embodiment analyzes the straw degradation efficiency and enzyme activity of the microbial agent WLH-10 under different culture conditions. To systematically optimize the degradation performance of the microbial agent WLH-10, the following multi-factor experiments were conducted to evaluate the effects of different carbon sources, nitrogen sources, and initial pH values ​​on straw degradation efficiency and key enzyme activities.

[0044] (1) Influence of carbon source type Rice straw or corn straw were used as the sole carbon source in the initial straw seed culture medium, with all other components kept constant, and the carbon source concentration was controlled at 10 g / L. The optimal carbon source was determined by comparing the degradation efficiency of the inoculum and the activity of key enzymes under the two carbon sources.

[0045] (2) Influence of nitrogen source type Using corn straw as the carbon source, NH4Cl, (NH4)2SO4, peptone, and yeast extract were used as the sole nitrogen source to replace the initial composite nitrogen source (peptone + yeast extract) in the straw-seed culture medium, respectively, with the nitrogen source concentration in the culture medium controlled at 8 g / L. The optimal nitrogen source was screened by measuring the straw degradation rate and enzyme activity of each treatment group.

[0046] (3) Effect of initial pH Corn straw was used as the sole carbon source in the initial straw seed culture medium, with all other components kept constant. The carbon source concentration was controlled at 10 g / L to prepare the fermentation medium. The initial pH of the medium was adjusted to 6.0, 6.5, 7.0, 7.5, and 8.0 using dilute hydrochloric acid and NaOH solution, with three replicates for each pH gradient. The effect of the initial pH value on the degradation performance of the inoculant WLH-10 was further investigated.

[0047] (4) Culture conditions and detection methods The *Delftia tsuruhatensis* WLH-10 strain obtained from the initial screening was inoculated into sodium carboxymethyl cellulose liquid medium and cultured at 40℃ and 180 r / min for 24 h to activate it. The activated bacterial suspension was then inoculated into straw seed culture medium from the above treatment groups at a 2% (v / v) inoculation rate and cultured with shaking at 40℃ and 180 r / min for 15 days. Samples were taken every 5 days from the start of cultivation to determine the straw degradation rate and to detect the activities of key enzymes (carboxymethyl cellulase, filter paper enzyme, laccase, and lignin peroxidase). Enzyme activity unit is defined as the amount of enzyme required to catalyze the production of 1 μmol of reducing sugar or oxidation product per hour.

[0048] Figure 6 The degradation performance of *Delftia tsuruhatensis* WLH-10 on straw under different carbon sources, nitrogen sources, and pH conditions was analyzed; among which, Figure 6 (a) The effect of different carbon sources (rice straw vs. corn straw) on straw degradation rate. Figure 6 (b) The effect of different nitrogen sources (NH4Cl, (NH4)2SO4, peptone, yeast extract) on the degradation rate of straw. Figure 6 (c) shows the effect of initial pH value on straw degradation rate.

[0049] The results showed that: (1) During the same culture period, when corn straw was used as the carbon source, the degradation rate reached 19.75±1.16% on the 15th day, which was significantly higher than that of the rice straw group (15.17±0.36%), indicating that the microbial agent had a stronger adaptability to corn straw; (2) Among the four nitrogen sources, the degradation rate of the yeast extract treatment group was the highest, reaching 21.51±0.99% on the 15th day, which was significantly better than other nitrogen sources, indicating that it could effectively promote the growth of the microbial agent and the expression of enzymes; (3) When the initial pH was 7.0, the straw degradation rate reached its peak on the 15th day (23.75±0.37%), and remained at a high level for 15 days, indicating that the microbial agent performed best in a neutral environment.

[0050] Figure 7 The study investigated the changes in carboxymethyl cellulase (CMCase) activity of *Delftia tsuruhatensis* WLH-10 under different carbon sources, nitrogen sources, and pH conditions. Figure 7 (a) Effects of different carbon sources (rice straw vs. corn straw) on CMCase activity; Figure 7 (b) Effects of different nitrogen sources (NH4Cl, (NH4)2SO4, peptone, yeast extract) on CMCase activity; Figure 7 (c) Effect of initial pH on CMCase activity.

[0051] The results showed that: (1) When corn straw was used as a carbon source, the CMCase activity was significantly higher than that of rice straw (e.g., 16.16±0.24 U / mL on day 5 vs. 12.44±0.22 U / mL in the rice straw group), indicating that the microbial agent had a stronger inducing effect on corn straw; (2) Among the four nitrogen sources, the yeast extract treatment group had the highest CMCase activity, reaching 22.28±0.09 U / mL on day 5, which was significantly better than that of inorganic nitrogen sources, indicating that it could effectively promote the synthesis of cellulase; (3) When the initial pH was 7.0, the CMCase activity reached its peak on day 5 (21.19±0.71 U / mL), and remained at a high level for 10-15 days; while under acidic or alkaline conditions, the enzyme activity decreased significantly, indicating that the enzyme system of the microbial agent was most active in a neutral environment.

[0052] Figure 8 The study investigated the changes in filter paper enzyme (FPase) activity of *Delftia tsuruhatensis* WLH-10 under different carbon sources, nitrogen sources, and pH conditions. Figure 8 (a) Effects of different carbon sources (rice straw vs. corn straw) on FPase activity; Figure 8 (b) Effects of different nitrogen sources (NH4Cl, (NH4)2SO4, peptone, yeast extract) on FPase activity; Figure 8 (c) Effect of initial pH on FPase activity.

[0053] The results showed that: (1) When corn straw was used as a carbon source, the FPase activity was significantly higher than that of rice straw (e.g., 19.04±0.05 U / mL on day 5 vs. 15.36±0.03 U / mL), indicating that the microbial agent had a stronger inducing effect on corn straw; (2) Among the four nitrogen sources, the yeast extract treatment group had the highest FPase activity, reaching 23.18±0.04 U / mL on day 5, which was significantly better than that of inorganic nitrogen sources, indicating that it could effectively promote the expression of cellulase system; (3) When the initial pH was 7.0, the FPase activity reached its peak on day 5 (22.43±0.02 U / mL), and remained at a high level for 10-15 days; while under acidic or alkaline conditions, the enzyme activity decreased significantly, indicating that the enzyme system of this microbial agent was most active in a neutral environment.

[0054] Figure 9 The changes in laccase activity of Delftia tsuruhatensis WLH-10 under different carbon sources, nitrogen sources and pH conditions. Figure 9 (a) Effects of different carbon sources (rice straw vs. corn straw) on laccase activity; Figure 9(b) Effects of different nitrogen sources (NH4Cl, (NH4)2SO4, peptone, yeast extract) on laccase activity; Figure 9 (c) Effect of initial pH on laccase activity.

[0055] The results showed that: (1) when corn straw was used as a carbon source, the laccase activity was significantly higher than that of rice straw (e.g., 13.81±0.17 U / mL on day 5 vs. 11.16±0.33 U / mL), indicating that the microbial agent showed a stronger response in degrading lignin-like substances; (2) among the four nitrogen sources, the yeast extract treatment group had the highest laccase activity, reaching 16.56±0.48 U / mL on day 5, which was significantly better than that of inorganic nitrogen sources, indicating that it could effectively promote the synthesis of laccase; (3) when the initial pH was 7.0, the laccase activity reached its peak on day 5 (17.43±0.04 U / mL), and remained at a high level for 10-15 days; while under acidic or alkaline conditions, the enzyme activity decreased significantly, indicating that the enzyme system of the microbial agent was most active in a neutral environment.

[0056] Figure 10 The changes in lignin peroxidase (LiP) activity of Delftia tsuruhatensis WLH-10 under different carbon sources, nitrogen sources, and pH conditions were investigated. Figure 10 (a) The effect of different carbon sources (rice straw vs. corn straw) on LiP activity; Figure 10 (b) Effects of different nitrogen sources (NH4Cl, (NH4)2SO4, peptone, yeast extract) on LiP activity; Figure 10 (c) Effect of initial pH on LiP activity.

[0057] The results showed that: (1) When corn straw was used as a carbon source, the LiP activity was significantly higher than that of rice straw (e.g., 12.49±0.47 U / mL on day 5 vs. 7.44±0.33 U / mL), indicating that the microbial agent had a stronger response to corn straw rich in lignin; (2) Among the four nitrogen sources, the yeast extract treatment group had the highest LiP activity, reaching 15.82±0.47 U / mL on day 5, which was significantly better than that of inorganic nitrogen sources, indicating that it could effectively promote the synthesis of lignin-degrading enzymes; (3) When the initial pH was 7.0, the LiP activity reached its peak on day 5 (16.17±0.35 U / mL) and remained at a high level for 10-15 days; while under acidic or alkaline conditions, the enzyme activity decreased significantly, indicating that the microbial agent had a strong lignin degradation potential in a neutral environment.

[0058] comprehensive Figures 6 to 10It can be seen that under 40℃ conditions, the straw degradation rate and key enzyme activity of the microbial agent WLH-10 reached the highest level when corn straw was used as the carbon source (10 g / L), yeast extract powder was used as the nitrogen source (8 g / L), and the initial pH was 7.0, which is the optimal culture condition.

[0059] Example 4 Based on the optimal culture conditions in Example 3 above, the *Delfordia tsurugi* (*Delfordia tsurugi*) was cultured. Delftia tsuruhatensis Straw degradation tests were conducted using WLH-10.

[0060] The specific process was as follows: *Delftia tsuruhatensis* WLH-10, obtained from the initial screening, was inoculated into sodium carboxymethyl cellulose liquid medium and cultured at 40℃ and 180 r / min for 24 h for activation. The activated bacterial solution was then inoculated at a rate of 2% (v / v) into a straw seed culture medium with corn straw as the sole carbon source (10 g / L), yeast extract as the sole nitrogen source (8 g / L), and an initial pH of 7.0. The medium was then cultured for 15 days in a constant temperature shaking incubator at 40℃ and 180 r / min. After the culture period, the relative degradation rate of straw was measured, and on day 15, the fermentation broth was collected to determine the activities of key enzymes, including carboxymethyl cellulase (CMCase), filter paper enzyme (FPase), laccase (Lac), and lignin peroxidase (LiP). The enzyme activity unit was defined as the amount of enzyme required to catalyze the production of 1 μmol of reducing sugar or oxidation product per hour, which is 1 U. The results are shown in Table 1.

[0061] Table 1

[0062] As shown in the table, under these optimal conditions, after 15 days of cultivation, strain WLH-10 achieved a degradation rate of 29.75 ± 0.35% for corn straw, significantly higher than the single-factor treatment groups in Example 3. Simultaneously, the activities of its key enzymes all reached high levels: CMCase activity was 24.60 ± 0.13 U / mL, FPase activity was 26.14 ± 0.02 U / mL, Lac activity was 18.67 ± 0.48 U / mL, and LiP activity was 19.70 ± 0.36 U / mL. These results fully validate the effectiveness of the optimal cultivation conditions determined in Example 3, further demonstrating that strain WLH-10 possesses efficient and stable straw degradation performance under suitable conditions and has good application potential.

[0063] Example 5 This embodiment uses scanning electron microscopy (SEM) to analyze changes in straw structure. SEM was used to observe the surface morphology of untreated corn straw and the residue after degradation by the inoculant WLH-10 under optimal culture conditions to assess its destructive effect on the straw's microstructure.

[0064] Control group: Untreated dried corn stalk powder (passed through a 40-mesh sieve).

[0065] Experimental group: Strain WLH-10 was activated by inoculating sodium carboxymethyl cellulose liquid medium and then transferred at a 2% (v / v) inoculation rate to a seed fermentation medium with corn straw as the carbon source (wherein, the straw seed medium consisted of 10g corn straw, 8g yeast extract, 2g CaCO3, 5g NaCl, 1000mL distilled water, pH 7, and sterilized at 121℃ for 20min). After shaking culture at 40℃ and 180 r / min for 15 days, the residual straw was collected, repeatedly washed with deionized water to remove bacterial cells and soluble metabolites, dried at 60℃, and passed through a 40-mesh sieve to obtain the degradation residue sample.

[0066] The corn stalk residues from both the control and experimental groups, after 15 days of degradation, were washed, dried, and sprayed with gold. SEM observation was then performed at an accelerating voltage of 5 kV. Figure 11 As shown, where Figure 11 (a) is the undegraded control group. Figure 11 (b) is the experimental group.

[0067] The results showed that: (1) Undegraded corn stalks had tightly packed fiber bundles, smooth and intact surfaces, and a dense and orderly structure; (2) After degradation by WLH-10, the surface of the stalks showed obvious erosion, cracks and holes, the fiber structure was loose and broken, and some areas showed honeycomb-like collapse. These results directly demonstrate that the microbial agent WLH-10 can effectively destroy the cell wall structure of corn stalks, promote the exposure and further degradation of its internal components.

[0068] Example 6 To further verify the degradation effect of the microbial agent WLH-10 on the main components of straw, Fourier transform infrared spectroscopy (FTIR) was used to analyze the chemical structure of the corn straw residue after degradation in the control group and the experimental group in Example 5.

[0069] Spectroscopic determination method: FTIR detection was performed using the tablet compression method. 1.5 mg of each of the above-mentioned straw powders were accurately weighed and mixed with 150 mg of dry potassium bromide (KBr) powder. After thorough grinding and homogenization, the mixture was placed in a tableting mold and vacuum-pressed under a tableting machine to form transparent sheets.

[0070] The scan was performed using a Fourier transform infrared spectrometer with the following parameters set: Scan range: 4000 -1 up to 400 cm -1 Resolution: 2 cm -1 Number of scans: 32; Background correction: using pure KBr pellets as the blank background, the infrared spectra of (a) undegraded corn stalks (control group) and (b) degraded corn stalks (experimental group) were obtained as follows: Figure 12 As shown.

[0071] Comparative analysis revealed that after 15 days of treatment with the microbial agent WLH-10, the infrared spectrum of corn stalk residue showed significant changes at several characteristic absorption peaks, specifically as follows: the infrared spectrum of corn stalks changed significantly between 1230 and 1250 cm⁻¹. -1 1420-1430 cm -1 2300 - 2400 cm -1 There is a clear peak variation at 1250-1230 cm. -1 The wavelength variation at 1430–1420 cm⁻¹ corresponds to the characteristic absorption of C–O stretching vibrations in phenols and cellulose esters. -1 The wavelength changes at this point are due to the deformation vibrations of -CH2 groups attached to double bonds or carbonyl groups in lignin and aliphatic compounds, as well as the absorption of inorganic ammonium ions, nitrate ions, and organic carbohydrates, in the wavelength range of 2400-2300 cm⁻¹. -1 The wavelength changes at that point represent multiple composite bands of proteins, amino acids, and ammonium ions from ammonium salt compounds in corn stalks.

[0072] Depend on Figure 12 It is evident that after degradation by the microbial agent WLH-10, the absorption peak intensities of corn stalks in multiple characteristic functional group regions related to cellulose, hemicellulose, and lignin significantly decreased, indicating that these macromolecular structures had been effectively decomposed by microorganisms. This was particularly evident in the 1230-1250 cm⁻¹ region. -1 and 1420-1430 cm -1 The weakening of the absorption peak directly proves the destruction of the lignin and cellulose network structure, indicating that WLH-10 has cellulose degradation ability. This result confirms the high efficiency of WLH-10 in degrading corn stalks at the molecular structure level, providing strong support for its application in the resource utilization of agricultural waste.

[0073] The foregoing has provided a detailed description of a straw-degrading bacterium disclosed in this invention and its applications. Specific examples have been used to illustrate the principles and implementation methods of this invention. The descriptions of the embodiments above are merely for the purpose of helping to understand the method and core ideas of this invention. It should be noted that those skilled in the art can make various improvements and modifications to this invention without departing from its principles, and these improvements and modifications also fall within the protection scope of the claims of this invention.

Claims

1. A strain with highly efficient straw degradation ability, WLH-10, is classified and named *Dalfordia tsurugi*. Delftia tsuruhatensis It was deposited on September 10, 2025, at the China General Microbiological Culture Collection Center (CGMCC), with accession number CGMCC No. 35872.

2. The application of the straw-degrading bacteria WLH-10 as described in claim 1 in the degradation of plant straw.

3. The application according to claim 2, characterized in that, The plant straw is selected from corn straw and / or rice straw.

4. A microbial agent containing the straw-degrading bacteria WLH-10 as described in claim 1.

5. The method for preparing the microbial inoculant according to claim 4, characterized in that, The steps are as follows: Inoculate strain WLH-10 into sodium carboxymethyl cellulose liquid medium and culture it at 40℃ and 180 r / min for 24 h to activate it; transfer the activated bacterial solution to straw seed medium at an inoculation rate of 2% (v / v) and culture it with shaking at 40℃ and 180 r / min for 15 days; centrifuge and filter to remove bacterial cells and impurities to obtain the bacterial agent.

6. The preparation method according to claim 5, characterized in that, The sodium carboxymethyl cellulose liquid culture medium consists of the following components: 1.5g potassium dihydrogen phosphate, 5g peptone, 10g sodium carboxymethyl cellulose, 0.2g MgSO4, 5g NaCl, and 1000mL distilled water. The pH is adjusted to 7.0, and the medium is sterilized at 121℃ for 20min.

7. The preparation method according to claim 5, characterized in that, The straw seed culture medium consists of the following components: 10g straw, 5g peptone, 3g yeast extract, 2.0g CaCO3, 5g NaCl, 1000mL distilled water, natural pH, sterilized at 121℃ for 20min.

8. The preparation method according to claim 7, characterized in that, The straw seed culture medium consists of the following components: 10g corn straw, 8g yeast extract, 2g CaCO3, 5g NaCl, 1000mL distilled water, pH 7, sterilized at 121℃ for 20min.

Images