Straw solid state fermentation trichoderma longibrachiatum and fermentation process thereof

Abstract

The invention relates to the field of microorganism and biomass treatment, and particularly discloses a straw solid state fermentation trichoderma longibrachiatum and a fermentation process thereof. Trichoderma longibrachiatum is subjected to mutagenesis improvement by adopting a normal-temperature and normal-pressure plasma mutagenesis technology, and efficient lignocellulose degradation mutant bacteria are obtained by screening through a hierarchical screening system. Compared with an original strain, the mutant strain is remarkably improved in the aspects of lignocellulose degrading enzyme activity and protein accumulation. Experiments show that by means of the fermentation technology, the true protein content of the corn straw can reach 17.57%, and the degradation rate of cellulose, the degradation rate of hemicellulose and the degradation rate of lignin can reach 24.89%, 23.54% and 22.28% respectively. According to the invention, efficient bioconversion of corn straws is realized, and a solution is provided for resource utilization of agricultural wastes.

Description

Technical Field

[0001] The present invention relates to the field of microbial and biomass treatment, and specifically discloses a Trichoderma longibrachiatum for solid-state fermentation of corn straw and its fermentation process. Background Art

[0002] Corn straw is mainly composed of cellulose, hemicellulose and lignin. This complex lignocellulose structure significantly restricts its degradation and conversion efficiency. At present, the treatment and utilization of corn straw mainly include physical methods, chemical methods and biological methods. Among them, although physical and chemical treatment methods are relatively efficient, they have high energy consumption and serious environmental pollution. The biological method is considered to be the most sustainable technical path due to its environmental friendliness and low energy consumption.

[0003] In biological treatment methods, the microbial solid-state fermentation technology has been widely used for the conversion of lignocellulosic biomass due to its advantages such as simple process, low environmental load and diverse products. However, conventional solid-state fermentation has problems such as low lignocellulose degradation efficiency, long fermentation cycle and unstable product quality. This is mainly limited by: (1) the insufficient lignocellulose degradation ability of existing strains; (2) the lack of systematic optimization of fermentation process parameters; (3) the lack of in-depth understanding of the law of substrate structure evolution during the fermentation process.

[0004] In recent years, as a new mutagenesis technology, ARTP (atmospheric and room temperature plasma) has shown great potential in microbial breeding due to its high efficiency, broad spectrum and environmental safety. This technology can induce high-frequency and broad-spectrum gene mutations by generating highly active free radicals and charged particles, and is expected to obtain strains with significantly enhanced lignocellulose degradation ability.

[0005] In previous studies, through the systematic evaluation of four filamentous fungi, namely Aspergillus niger Aspergillus niger Trichoderma longibrachiatum Trichoderma longibrachiatum Aspergillus oryzae Aspergillus oryzae Trichoderma reesei Trichoderma reesei T. longibrachiatum it was found that Trichoderma longibrachiatum

[0006] showed the best comprehensive performance in the solid-state fermentation of corn straw, but there is still much room for improvement in terms of its degradation efficiency, protein synthesis ability and fermentation cycle. T. longibrachiatum In view of this, the present invention aims to use ARTP technology to carry out directional mutagenesis and improvement on Trichoderma longibrachiatum Summary of the Invention

[0007] The purpose of the present invention is to provide a highly efficient lignocellulose-degrading long-branch Trichoderma mutant strain bred by ARTP mutagenesis technology and a preparation method thereof, as well as a corn straw solid-state fermentation optimization process based on the mutant strain, so as to achieve efficient bioconversion of corn straw.

[0008] To achieve the above objectives, the present invention provides the following technical solutions.

[0009] A long-branched Trichoderma Trichoderma longibrachiatum ), and its deposit number is CGMCC No. 41915. Its deposit date is April 15, 2025, and the deposit date is the General Microbiology Center of China Microbiological Culture Collection Administration (CGMCC).

[0010] The application of the long-branched Trichoderma in the solid-state fermentation of biomass straw.

[0011] Specifically, the biomass straw is one or more of corn straw, sorghum straw, wheat straw, rice straw, and oat straw.

[0012] The present invention further provides a method for solid-state fermentation of biomass straw, comprising the following steps: (1) crushing the biomass straw, sterilizing it at high temperature and cooling it to room temperature; (2) mixing the fermentation nutrient solution with the biomass straw treated in (1), inoculating the long-branched Trichoderma, and fermenting it.

[0013] Specifically, the fermentation nutrient solution contains ammonium sulfate, bran and Mg² + .

[0014] More specifically, the fermentation nutrient solution is based on the dry weight of the fermentation substrate, calculated by the dry weight of the straw, and the amount of ammonium sulfate is 3.91% (w / w), the amount of bran is 22.06% (w / w), the pH is adjusted to 5.5, and 3 mmol / L of Mg² is added. + It should be noted that this addition method based on substrate dry weight is more suitable for solid-state fermentation and helps to maintain the consistency of component ratios in different batches of fermentation. Other inorganic salts in the nutrient solution are calculated according to the solution volume concentration (g / L), and the amount of solution added is added according to the specified liquid-solid ratio.

[0015] In a specific embodiment, the fermentation nutrient solution also contains: KH2PO4 2.0 (g / L), NaCl 0.5 (g / L), CaCl2 0.3 (g / L), FeSO4•7H2O 0.005 (g / L), MnSO4•H2O 0.0016 (g / L), ZnSO4•7H2O0.0014 (g / L), and CoCl2 0.002 (g / L).

[0016] In the specific implementation, the spore suspension of Trichoderma longibrachiatum cultured using a PDA plate (for example, cultured for 4 days) is used as the fermentation strain; the spore concentration in the spore suspension is 10 5 -10 7 spores / g of substrate.

[0017] Specifically, the fermentation nutrient solution and biomass straw are mixed at a liquid-solid ratio of 1-3:1; The fermentation temperature is 26-37°C, and the fermentation is carried out for 3 to 7 days to obtain the fermentation product. The treatment of the fermented product depends on the final application purpose.

[0018] The present invention also provides the fermentation product obtained by the method described above.

[0019] In the present invention, the entire fermented material (including the solid-liquid mixture) can be directly collected after fermentation; if used as feed, it is dried at an appropriate temperature to an appropriate moisture content (usually ≤12%); if used for extracting bioactive substances, it can be extracted with a buffer solution and then centrifuged. The post-treatment methods under different application scenarios can be carried out according to the product requirements.

[0020] Compared with the prior art, the present invention has the following beneficial effects: The present invention has successfully selected and bred a mutant strain TL_MU07 of Trichoderma longibrachiatum with significantly enhanced lignocellulose degradation ability by using the ARTP mutagenesis technology. Compared with the original strain, the filter paper enzyme activity FPase, endo-enzyme CMCase and xylanase Xylanase activities of this mutant strain are increased by 22.1%, 10.1% and 16.1% respectively; the degradation rates of cellulose and hemicellulose are increased by 14.6% and 12.9% respectively; the true protein content is increased by 14.7%.

[0021] The present invention has established a solid-state fermentation process highly matched with the TL_MU07 strain by systematically optimizing the process parameters. The optimized process enables the true protein content of corn straw to reach 17.57%, which is increased by 53.45% compared with the single-factor optimization stage; the degradation rates of cellulose, hemicellulose and lignin reach 24.89%, 23.54% and 22.28% respectively, which are increased by 25.64%, 20.97% and 30.37% respectively compared with the single-factor optimization stage; the filter paper enzyme activity FPase is increased by 30.44%, and the peptide content is increased by 67.61%.

[0022] The combination of the strain selected and bred by ARTP mutagenesis and the optimized solid-state fermentation process in the present invention significantly shortens the fermentation cycle (only 4.10 days are required), improves the substrate conversion efficiency, and has important application value for the resource utilization of agricultural waste.

[0023] In summary, the Trichoderma longibrachiatum mutant strain TL_MU07 provided by the present invention and its solid-state fermentation process can achieve efficient biological conversion of corn straw. It can be used for the production of high-protein feed: the true protein content in the fermentation product reaches 17.57%, and the peptide content reaches 2.38%, which can be used as a protein feed resource to alleviate the shortage of feed protein resources. The process is simple and easy to implement with low cost: the fermentation period is short (only 4.10 days), no complex equipment is required, and it is suitable for large-scale production. Environmentally friendly: it realizes the biological resource utilization of agricultural waste, reduces environmental pollution, and meets the requirements of sustainable development. It can be popularized and applied to the biological conversion of other agricultural wastes and has broad market prospects.

[0024] In conclusion, the mutant strain and fermentation process provided by the present invention provide a new technical solution for the resource utilization of agricultural waste, and have significant economic, social and ecological benefits.

[0025] Biological material preservation information: The strain TL_MU07 of the present invention was preserved on April 15, 2025 at the General Microbiological Center of the China Committee for Culture Collection of Microorganisms (abbreviation: CGMCC, address: No. 3, Courtyard 1, Beichen West Road, Chaoyang District, Beijing, China), and the preservation number is CGMCC No. 41915. The taxonomic name is Trichoderma longibrachiatum Trichoderma longibrachiatum 。 Description of the Drawings

[0026] Figure 1 Growth results of TL_MU07 under different temperature conditions a~h: 15°C, 20°C, 25°C, 30°C, 33°C, 37°C, 40°C, 43°C).

[0027] Figure 2 Comparison of growth results of TL_MU07 under different pH value conditions a~h: pH = 3, 4, 5, 6, 7, 8, 9, 10.

[0028] Figure 3 Shows the effects of inoculum amount on the true protein and dry matter loss rate in solid-state fermentation.

[0029] Figure 4 Shows the effects of fermentation time on the true protein and dry matter loss rate in solid-state fermentation.

[0030] Figure 5Effects of different nitrogen sources on the yields of lignocellulose hydrolases and proteins. Among them, (a) effects of different nitrogen sources on the filter paper enzyme activity; (b) effects of different nitrogen sources on the endo-enzyme activity; (c) effects of different nitrogen sources on the β-glucosidase activity; (d) effects of different nitrogen sources on the xylanase activity; (e) effects of different nitrogen sources on the β-xylosidase activity; (f) effects of different nitrogen sources on the laccase activity; (g) effects of different nitrogen sources on the manganese peroxidase activity; (h) effects of different nitrogen sources on the lignin peroxidase activity; (i) effects of different nitrogen sources on the true protein content; (j) effects of different nitrogen sources on the peptide content.

[0031] Figure 6 Effects of different metal ions on the biomass and enzyme system activities. Among them, (a) effects of different metal ions on the spore yield; (b) effects of different metal ions on the dry matter loss rate; (c) effects of different metal ions on the filter paper enzyme activity; (d) effects of different metal ions on the endo-enzyme activity; (e) effects of different metal ions on the xylanase activity; (f) effects of different metal ions on the laccase activity.

[0032] Figure 7 Three-dimensional response surface plots of the effects of ammonium sulfate, fermentation time, and bran addition amount on the true protein content. Among them, (a) effects of fermentation time and ammonium sulfate content on the true protein content; (b) effects of bran inoculum amount and ammonium sulfate content on the true protein content; (c) effects of fermentation time and bran inoculum amount on the true protein content. Detailed implementation manners

[0033] The present invention will be further described in detail below with reference to specific embodiments. Those skilled in the art should understand that these embodiments are only used to illustrate the present invention and not to limit the scope of the present invention.

[0034] Example 1: Screening of ARTP-mutagenized strains of Trichoderma longibrachiatum 1.1 Test strains and materials In this example, Trichoderma longibrachiatum ([[]] Trichoderma longibrachiatum Trichoderma longibrachiatum ) isolated from farmland soil was used as the starting strain and stored on a PDA slant. The substrate was corn straw collected in Nanning, Guangxi. After natural ventilation and drying, it was dried to a constant weight at 65 °C and crushed through a 10-mesh sieve for standby. The main components of corn straw were: cellulose 30.30 ± 0.86%, hemicellulose 24.91 ± 0.72%, lignin 19.45 ± 0.53%, and nitrogen content 10.22 ± 0.31 g / kg (based on dry matter).

[0035] 1.2 Preparation of culture media (1) PDA medium (g / L): 200 g of potato juice, 20 g of glucose, 20 g of agar, pH 6.5.

[0036] (2) Initial screening plate medium of CMC-Na (g / L): (NH4)2SO4 1.0, Na2HPO4 1.2, KH2PO4 0.9, MgSO4•7H2O 0.5, KCl 0.5, yeast extract powder 0.5, acid-hydrolyzed casein 0.5, congo red 0.2, cellulose powder 5.0, agar 15.0, pH 4.8.

[0037] (3) Shake flask fermentation seed medium (g / L): glucose 10.0, peptone 5.0, Tween-80 2 mL, (NH4)2SO4 1.4, CaCl2 0.3, urea 0.3, MgSO4•7H2O 0.3, FeSO4•7H2O 0.005, MnSO4•H2O 0.0016, ZnSO4•7H2O 0.0014, CoCl2 0.002, pH 4.8.

[0038] (4) Shake flask fermentation enzyme-producing medium (g / L): microcrystalline cellulose 20.0, wheat bran 10.0, corn steep liquor 17.0, K2HPO4 2.0, (NH4)2SO4 1.4, MgSO4•7H2O 0.3, urea 0.3, CaCl2 0.3, Tween-80 2 mL, FeSO4•7H2O 0.005, MnSO4•H2O 0.0016, ZnSO4•7H2O 0.0014, CoCl2 0.002, pH 4.8.

[0039] The above media need to be autoclaved at 121 °C for 20 min before use.

[0040] 1.3 ARTP mutagenesis treatment (1) Cultivate Trichoderma longibrachiatum in PDA medium for 4 days, scrape the spores with 10 mL of 0.9% normal saline, transfer them to a 150 mL conical flask, add 50 glass beads with a diameter of 4 mm, shake at 250 rpm / min for 15 min to fully disperse the spores, and adjust the spore concentration to 10^6 - 10^8 / mL.

[0041] (2) Take 10 μL of the spore suspension and spread it evenly on a sterilized metal slide. The ARTP mutagenesis conditions are: radio frequency input power 120 W, irradiation distance 2 mm, plasma temperature < 35 °C, gas flow rate 10 SLM, and set 11 gradients for the mutagenesis time from 0 s to 400 s.

[0042] (3) After the mutagenesis treatment, place the metal slide in a 5 mL centrifuge tube containing 1 mL of 0.9% normal saline, shake and mix well, let it stand for 2 - 3 h, dilute it by an appropriate multiple, take 100 μL and spread it on a PDA plate. Each group has three parallels, count after culturing at 30 °C for 72 h, and calculate the survival rate.

[0043] (4) Based on the survival rate curve analysis, 320 s (about 85% lethality) was determined as the optimal mutagenic exposure time for subsequent large-scale mutagenic treatments.

[0044] 1.4 Screening of mutant strains (1) Primary screening on plates: After appropriately diluting the spore suspension treated by mutagenesis for 320 s, it was spread on the CMC-Na plates and cultured at 30 °C for 4 days. It was stained with 0.1% congo red solution for 15 min and decolorized with 1 mol / L NaCl solution for 30 min. The ratio of the diameter of the hydrolysis zone (D) to the diameter of the colony (d) (HC = D / d) was measured. With the HC value (2.081 ± 0.262) of the original strain as a reference, strains with HC values higher than 35% (HC > 2.800) were screened, and 19 mutant strains were obtained.

[0045] (2) Secondary screening in shake flasks: Spore suspensions (10 6 cells / mL) of the 19 mutant strains obtained by screening were prepared. 2.0 mL of the spore suspension was inoculated into the liquid seed medium and cultured at 30 °C and 200 rpm for 24 h to form an active bacterial solution. It was transferred to the enzyme-producing fermentation medium at a ratio of 5% (v / v) and continued to ferment for 96 h under the same conditions. The FPase, water-soluble protein concentration, and peptide concentration in the culture broth were measured, and three mutant strains TL_MU06, TL_MU07, and TL_MU15 with the best comprehensive performance were screened.

[0046] (3) Tertiary screening by solid-state fermentation: Corn straw was used as the substrate for solid-state fermentation to evaluate the performance of the three candidate mutant strains. 10 g of corn straw was weighed into a 250 mL conical flask, sterilized at 121 °C for 20 min, and then cooled to room temperature. The spore suspension of the strain was inoculated at 10 6 spores / g of the substrate, and the inorganic salt nutrient solution was added at a water-to-substrate ratio of 2:1, and cultured at a constant temperature of 30 °C for 5 days. The activities of FPase, CMCase, and xylanase, the degradation rates of cellulose, hemicellulose, and lignin, the true protein content, and the peptide content were measured.

[0047] The results showed that the TL_MU07 strain exhibited comprehensively enhanced hydrolase activities: the FPase was 6.382 U / g d.s., a 22.1% increase compared to the original strain; the CMCase reached 11.076 U / g d.s., with an increase of 10.1%; the xylanase activity increased by 16.1% to reach 2.874 U / g d.s. The analysis of lignocellulose component degradation showed that the cellulose degradation rate of the TL_MU07 strain increased by 14.6% compared to the original strain, and the hemicellulose degradation rate increased by 12.9%. In terms of biomass and protein synthesis, the true protein content in the fermentation group of the TL_MU07 strain reached 8.621%, a 14.7% increase compared to the original strain, and the peptide content also showed a significant increase. In addition, the spore yield of TL_MU07 was significantly higher than that of the original strain and other mutant strains, indicating that this strain had stronger substrate adaptability and reproduction potential under solid-state fermentation conditions.

[0048] Therefore, TL_MU07 was determined as the best mutant strain. After continuous subculture for 5 generations to measure stability, the results showed that the excellent enzyme-producing performance of this strain had good genetic stability.

[0049] Example 2: Optimization of the solid-state fermentation process of the mutant strain TL_MU07 2.1 Single-factor optimization experiment (1) Temperature optimization: Inoculate the TL_MU07 strain on a PDA plate and culture it at 15, 20, 25, 30, 33, 37, 40, and 43 °C for 4 days. Observe the colony morphology, measure the colony diameter, and calculate the spore yield ( Figure 1 ). The results showed that the spore yield reached a peak (8.69×10 8 cells / mL) at 33 °C, and the colony diameter reached the maximum value (8.90 cm) at 37 °C. Considering comprehensively, the optimal culture temperature was determined to be 33 °C.

[0050] (2) pH value optimization: Inoculate the TL_MU07 strain on a PDA plate and adjust the pH value of the medium to 3, 4, 5, 6, 7, 8, 9, and 10, and culture it at 33 °C for 4 days. The results showed that the colony diameter reached the maximum value (8.54 cm) at pH 7, and the spore formation reached the highest level (1.94×10 8 cells / mL) at pH 6. Considering that the cellulase activity has a higher catalytic efficiency in a weak acid environment during solid-state fermentation, the optimal pH was determined to be 5.5 ( Figure 2 ).

[0051] (3) Inoculum size optimization: Set 5 inoculum size gradients: 10 4 、10 5 、10 6 、10 7 、10 8Spores / g d.s. The corn straw and the inorganic salt nutrient solution were mixed at a solid-liquid ratio of 1:2 and cultured at 33 °C for 4 days, and the true protein content and the dry matter loss rate were measured. The results showed that when the spore content was 10 6 spores / g d.s., the true protein content reached the highest value (8.75%). The optimal inoculation amount was determined to be 10 6 spores / g d.s. ( Figure 3 ).

[0052] (4) Optimization of fermentation time: Inoculation was carried out with the optimal inoculation amount, and samples were taken on the 2nd, 3rd, 4th, 5th, 6th, and 7th days to measure the true protein content and the dry matter loss rate. The results showed that the true protein content reached a peak (8.80%) on the 5th day and then tended to be stable and decreased slightly. The dry matter loss rate showed a continuous growth pattern, but the growth rate gradually slowed down. The optimal fermentation time was determined to be 4 - 5 days ( Figure 4 ).

[0053] (5) Optimization of nitrogen source: The effects of different inorganic nitrogen sources (ammonium sulfate, ammonium chloride, urea, ammonium dihydrogen phosphate, diammonium hydrogen phosphate, sodium nitrate) and organic nitrogen sources (peptone, yeast extract) on the fermentation effect were investigated. The nitrogen source addition amount was adjusted according to the same nitrogen content provided (0.5% of the substrate dry weight). The results showed that the enzyme activities (FPase, CMCase, BGL, xylanase, β-xylosidase, Lac, MnP, LiP) in the ammonium sulfate treatment group all reached or were close to the highest level, and the true protein (11.45%) and peptide (1.42%) contents were also significantly higher than those in other nitrogen source treatment groups. Ammonium sulfate was determined to be the optimal nitrogen source ( Figure 5 ).

[0054] (6) Optimization of metal ions: The effects of five metal ions (1.0 mmol / L), namely Cu² + , Mn² + , Mg² + , Zn² + , and Ca² + , on the fermentation effect were investigated. The results showed that Mg² + showed comprehensive advantages in promoting spore production, substrate degradation, and lignocellulase activity. Mg² + was determined to be the optimal metal ion additive ( Figure 6 ).

[0055] 2.2 Response surface optimization experiment (1) Screening of significant factors by Plackett-Burman design: Ten factors that might affect the fermentation process were selected, including: (A) Ammonium sulfate addition amount, (B) Initial pH value, (C) Mg² +Dosage, (D) Inoculum size, (E) Fermentation time, (F) Liquid-solid ratio, (G) Temperature, (H) Tween-80 dosage, (I) Wheat bran dosage, (J) PEG 6000 dosage. Two levels, high (+1) and low (-1), were set for each factor, with the true protein content as the response value. The results of variance analysis showed that fermentation time (E), ammonium sulfate dosage (A), and wheat bran dosage (I) had significant effects on the true protein yield ( P <0.05), and the cumulative contribution rate reached 86.86%.

[0056] (2) Determination of the optimal region by the steepest ascent method: According to the standardized effects of each factor, the steepest ascent test was designed. By observing the change trend of the true protein yield, it was determined that the highest true protein yield of 15.73 ± 0.91% was achieved when the ammonium sulfate concentration was 4%, the fermentation time was 4 days, and the wheat bran dosage was 23%.

[0057] (3) Box-Behnken design and response surface analysis: Using ammonium sulfate concentration (X1), fermentation time (X2), and wheat bran dosage (X3) as independent variables and true protein yield (Y) as the response value, 17 groups of experiments (including 5 central points) were designed. Through response surface analysis, the optimal process parameter combination was determined as: ammonium sulfate concentration 3.91%, fermentation time 4.10 days, and wheat bran dosage 22.06%. Under these conditions, the model predicted that the true protein content was 16.77% ( Figure 7 ).

[0058] (4) Process verification: Six parallel verification experiments were carried out under the optimized conditions. The measured true protein content was 17.57%, and the relative error compared with the model prediction value was 4.55%( P >0.05), and the relative standard deviation (RSD) of the 6 groups of parallel experiments was only 3.8%, which confirmed the accuracy of the model and the stability of the process.

[0059] 2.3 Evaluation of the fermentation effect of the optimized process Compared with the single-factor optimization stage, the final optimized process significantly improved the fermentation effect, and the results are as follows: (1) The true protein content increased from 11.45% to 17.57%, with an increase of 53.45%; (2) FPase increased from 8.41 U / g to 10.97 U / g, with an increase of 30.44%; (3) The cellulose degradation rate increased to 24.89% (an increase of 25.64%), the hemicellulose degradation rate increased to 23.54% (an increase of 20.97%), and the lignin degradation rate reached 22.28% (an increase of 30.37%); (4) The peptide content increased from 1.42% to 2.38%, with an increase of 67.61%.

[0060] Example 3: Structural Characterization Analysis of Solid-State Fermentation Products 3.1 Observation by Scanning Electron Microscope (SEM) The corn straw samples before and after solid-state fermentation were observed by SEM, and the results showed that: (1) The surface structure of the unfermented corn straw was dense and smooth, the fiber bundles were closely arranged, and the cell wall was intact.

[0061] (2) The corn straw after fermentation with the optimized process showed significant structural damage characteristics: the surface became rough and porous, with a large number of cracks and micropores; the fiber bundles were dissociated, forming a loose network structure; a large number of mycelia could be observed adhering to the surface of the substrate and penetrating into the tissue interior.

[0062] These microscopic structural changes indicate that the extracellular enzyme system of the TL_MU07 strain effectively decomposed the complex structure of corn straw, destroyed the integrity of the cell wall, and improved the bioaccessibility of the substrate.

[0063] 3.2 Fourier Transform Infrared Spectroscopy (FTIR) Analysis The FTIR analysis results showed that significant changes occurred in the characteristic peak positions and relative intensities of the samples after fermentation: (1) The intensity of the -OH stretching vibration peak at 3400 cm -1 decreased, indicating that the cellulose hydrogen bond network was damaged; (2) The relative intensity of the lignin skeleton vibration peak at 1510 cm -1 decreased, indicating that the lignin structure was partially degraded; (3) The lateral order index (LOI, α1437 cm -1 / α899 cm -1 ) decreased from 1.48 to 1.24, indicating that the regular arrangement of cellulose molecular chains was damaged; (4) The total crystallinity index of infrared (TCI, α1378 cm -1 / α2900 cm -1 ) decreased from 1.31 to 1.03, indicating that the crystallinity of cellulose decreased; (5) The cellulose / lignin ratio (α3400 cm -1 / α1510 cm -1 ) decreased from 1.60 to 1.30, indicating that the relative stability of the lignin structure is higher than that of cellulose.

[0064] These spectral changes confirm that the solid-state fermentation process of the TL_MU07 strain has a profound impact on the chemical structure of corn straw, especially reducing the cellulose crystallinity and destroying the organizational structure of lignocellulose.

[0065] 3.3 X-ray Diffraction (XRD) Analysis The results of XRD analysis showed that fermentation treatment led to significant changes in the crystalline structure of corn straw: (1) The diffraction peak intensity of the sample after fermentation at 2θ = 22° (002 crystal plane) decreased significantly, indicating a reduction in the crystalline region; (2) The scattering intensity at 2θ = 18° (amorphous region) increased relatively, indicating an increase in the proportion of the amorphous region; (3) The relative crystallinity of cellulose (CrI) decreased from the initial 43.89% to 36.37% after fermentation with the optimized process, indicating the transformation of crystalline cellulose to the amorphous region during fermentation.

[0066] The decrease in crystallinity is beneficial to enzymatic hydrolysis because enzyme molecules are more easily accessible to and can catalyze cellulose molecules in the amorphous region, thus improving the bioaccessibility and degradation efficiency of the substrate.

[0067] The above results of structural characterization confirmed at the microscopic and molecular levels that solid-state fermentation by strain TL_MU07 could effectively destroy the physical structure and chemical composition of corn straw and reduce the cellulose crystallinity, which was consistent with the high degradation rate and bioconversion efficiency observed macroscopically.

Claims

1. A Trichoderma longibrachiatum ( Trichoderma longibrachiatum ), characterized in that Its deposit number is CGMCC No.41915.

2. Use of the long-branch Trichoderma as claimed in claim 1 in solid-state fermentation of biomass straw.

3. The application according to claim 2, wherein The biomass straw is one or more of corn straw, sorghum straw, wheat straw, rice straw and oat straw.

4. A method for solid-state fermentation of biomass straw, characterized in that, The following steps are involved: (1) crushing the biomass straw, sterilizing it at high temperature and cooling it to room temperature; (2) Mixing the fermentation nutrient solution with the biomass straw treated in (1), inoculating the long-branched Trichoderma as described in claim 1, and fermenting.

5. The method according to claim 4, characterized in that, The fermentation nutrient solution contains ammonium sulfate, wheat bran and Mg² + .

6. The method according to claim 5, wherein Based on the dry weight of the fermentation substrate in the fermentation nutrient solution, calculated by the dry weight of straw, the dosage of ammonium sulfate is 3.91% (w / w), the dosage of wheat bran is 22.06% (w / w), the pH is adjusted to 5.5, and 3 mmol / L of Mg² + .

7. The method according to claim 5, characterized in that, The fermentation nutrient solution also contains: KH2PO4 2.0 (g / L), NaCl 0.5 (g / L), CaCl2 0.3 (g / L), FeSO4•7H2O 0.005 (g / L), MnSO4•H2O 0.0016 (g / L), ZnSO4•7H2O 0.0014 (g / L), and CoCl2 0.002 (g / L).

8. The method according to claim 5, wherein Using a PDA plate to culture the spore suspension of Trichoderma longibrachiatum as described in claim 1 as the fermentation strain; the spore concentration in the spore suspension is 10 5 -10 7 spores / g of substrate.

9. The method according to claim 8, wherein The fermentation nutrient solution and the biomass straw are mixed in a liquid-to-solid ratio of 1-3:1; the fermentation temperature is 26-37°C, and the fermentation culture is carried out for 3 to 7 days to obtain a fermentation product.

10. A fermentation product obtained by the method according to any one of claims 4 to 9.

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