A method for degrading crop straw lignin based on the cooperation of bacteria and algae in the form of steps after puffing pretreatment

Abstract

The application discloses a kind of crop straw lignin efficient degradation method based on the expansion pretreatment of fungus alga collaborative ladder degradation, belong to agricultural waste resource utilization technical field.The present application uses crop straw as raw material, in turn through physical pretreatment, compound fungi aerobic deep depolymerization, three stages of depth transformation of fungus alga symbiotic system, and in each stage sectional addition functional adjuvant, realize lignin efficient depolymerization, degradation speed promotion and nutrient loss reduction.The present application solves the technical defects such as insufficient wall breaking, low lignin degradation rate, long fermentation period, large nutrient loss of traditional straw degradation process.Compared with conventional process: lignin total degradation rate is greater than or equal to 55%, total straw degradation rate is greater than or equal to 70%, fermentation period is shortened by greater than or equal to 24 h, and nutrient loss is less than or equal to 30%.The present application process is mild, wide in scope, green and safe, and the product can be used for biological feed, biological organic fertilizer, soil conditioner, biomass resource utilization, and is suitable for large-scale industrialization promotion.

Description

Technical Field

[0001] This invention relates to agricultural waste resource utilization technology, lignocellulose biodegradation technology, and bio-feed and bio-organic fertilizer preparation technology. Specifically, it relates to a method for efficient degradation of lignin in crop straw through physical pretreatment synergistic with aerobic depolymerization by compound fungi and deep transformation by fungal-algae symbiosis. Background Technology

[0002] Crop straw is a renewable biomass resource with a huge output in my country, mainly composed of cellulose, hemicellulose, and lignin. Lignin has a dense structure and strong chemical stability, and it forms a natural anti-degradation barrier by wrapping with cellulose and hemicellulose. This is the core bottleneck restricting the utilization of straw for feed, fertilizer, and energy.

[0003] Existing straw degradation technologies generally suffer from the following drawbacks: Physical pretreatment methods are limited in their single approach and have a limited degree of cell wall disruption, making it difficult to effectively loosen the lignin structure and resulting in slow and inefficient subsequent biodegradation. Single microbial strains have a limited enzyme system and weak ability to degrade lignin, with a lignin degradation rate of only 30% to 40%. Chemical treatments involving strong acids and alkalis are highly polluting and corrosive, resulting in the loss of nutrients such as carbohydrates and proteins by as much as 40% to 60%. The fermentation cycle is long, it is susceptible to contamination by miscellaneous bacteria, the product quality is unstable, and it is difficult to achieve stable industrial production. The process has narrow adaptability, making it difficult to simultaneously achieve a synergistic improvement in high degradation rate, fast degradation speed, and low nutrient loss.

[0004] Therefore, developing a highly efficient degradation method for lignin in crop straw that is widely applicable, has high degradation efficiency, short cycle, good nutrient retention, and is green and safe has significant industrial value. Summary of the Invention

[0005] Purpose of the invention To address the shortcomings of existing technologies, this invention provides a highly efficient method for the degradation of lignin in crop straw through a stepwise degradation process based on the synergistic effect of bacteria and algae in a puffing pretreatment. This method achieves a stepwise synergistic degradation process involving physical cell wall disruption, depolymerization of complex fungi, and deep transformation through symbiotic bacteria and algae. Furthermore, by adding functional additives in stages, the method significantly improves the lignin degradation rate, accelerates the degradation speed, reduces nutrient loss, broadens the applicability of the process, and is suitable for large-scale promotion. Technical solution

[0006] A highly efficient method for the degradation of lignin in crop straw based on the synergistic stepwise degradation by bacteria and algae through puffing pretreatment is characterized by comprising the following steps in sequence:

[0007] Crop straw is crushed; functional pretreatment agents are added by dry weight, including one or more of alkalis, nitrogen sources, mineral carriers, and antifungal agents; the moisture content of the material is adjusted, and physical cell wall breaking pretreatment is carried out, selected from one or more combinations of dry puffing, wet puffing, extrusion puffing, and steam explosion; so that the straw cell walls are fully broken, the lignin is moistened and loosened, enzyme accessibility is improved, degradation start-up time is shortened, and nutrient loss is reduced.

[0008] Adjust the moisture content of the pretreated material and inoculate it with the compound fungal system: Cellulose / hemicellulase-producing fungi: selected from one or more of Aspergillus niger, Aspergillus oryzae, Trichoderma, and Penicillium; Lignin-degrading fungi: selected from one or more of the following: oyster mushroom, king oyster mushroom, shiitake mushroom, hairy fungus, and white-rot fungi; Add functional additives, including one or more of phosphorus sources, potassium sources, magnesium sources, trace elements, mineral carriers, and loosening agents; ferment under aerobic conditions to achieve synergistic deep depolymerization of lignin, cellulose, and hemicellulose.

[0009] Introduce a microbial-algae symbiotic system into the depolymerized material: Fungi: One or more of the following: photosynthetic bacteria, lactic acid bacteria, yeast, and Bacillus; Algae: one or more of Chlorella, Scenedesmus, Chlamydomonas, and Spirulina; Add one or more of the following: nitrogen source, phosphorus and potassium salts, trace elements, pH adjuster, and deodorizing and nitrogen-fixing aid; carry out deep conversion under diffused light and micro-ventilation conditions to transform the recalcitrant residue into high-value components such as microbial protein and algal polysaccharides, thereby further improving the total degradation rate, shortening the composting time, and reducing nutrient loss. Beneficial effects

[0010] The pretreatment is highly compatible and can be carried out by various methods such as puffing, steam explosion, and extrusion puffing to adapt to different equipment conditions. The complementary fungal enzyme system combines highly efficient cellulose and lignin degradation capabilities, resulting in a significant improvement in depolymerization efficiency. The algae-bacterial symbiotic system enables the high-value transformation of recalcitrant residues, significantly improving the nutritional value and utilization rate of the products; By adding functional additives in stages, the degradation rate, degradation speed, and nutrient retention can be synergistically optimized. The process is mild, green and safe, with no strong acids or alkalis and no toxic residues. It can be used in fields such as biological feed, biological organic fertilizer, soil conditioner, and biomass raw materials. Excellent overall performance: total lignin degradation rate ≥55%, total straw degradation rate ≥70%, fermentation cycle shortened by ≥24 h compared to traditional process, and nutrient loss ≤30%; It has a wide range of applications and can process straw from various crops such as corn, rice, wheat, soybeans, peanuts, cotton, rapeseed, and forage. The lignin-degrading straw fermented feed prepared by this invention has the following outstanding advantages:

[0011] After deep degradation by lignin, the difficult-to-use crude fiber of crop straw is transformed into digestible sugars and microbial protein, with a total degradation rate of ≥70% and a lignin degradation rate of ≥55%, truly realizing the high-value utilization of agricultural waste.

[0012] It can largely replace concentrated feeds such as corn and soybean meal, with a maximum replacement of 35% to 50% in ruminant diets, 15% to 25% in pig diets, and 8% to 20% in poultry diets, resulting in an overall reduction of breeding costs of 15% to 39%.

[0013] The lignin barrier is destroyed, and cellulose and hemicellulose can be efficiently utilized by livestock and poultry. The digestibility of crude fiber increases from below 30% to over 60%, and palatability and absorption efficiency are significantly improved.

[0014] Microbial fermentation synthesizes large amounts of microbial protein, vitamins, amino acids, and enzymes, increasing crude protein from 3%–5% in raw materials to 8%–15%. It is rich in probiotics and organic acids, and the feed quality approaches that of concentrate feed.

[0015] After degradation, the straw becomes soft, has a sour aroma, and no bitter taste. It increases the feed intake of livestock and poultry by 10% to 25%, making them less picky eaters and reducing waste.

[0016] It is rich in probiotics such as lactic acid bacteria, Bacillus, and photosynthetic bacteria, which regulate the intestinal flora, inhibit harmful bacteria, reduce diarrhea and digestive tract diseases, and significantly enhance immunity and disease resistance.

[0017] Organic acids and probiotics form a natural antibacterial environment, reducing the incidence of respiratory and intestinal diseases, making it suitable for antibiotic-free farming and the production of green livestock and poultry products.

[0018] Feed is digested more thoroughly, nitrogen and phosphorus emissions are reduced, manure odor is lessened, and manure discharge is reduced by 15% to 30%, meeting the requirements of ecological farming and environmental protection.

[0019] After lignin degradation, combined with mineral additives and an anaerobic environment, it can be sealed and stored for 6 to 18 months without mold or spoilage, making it suitable for year-round large-scale production.

[0020] It is applicable to most livestock and poultry, including cattle, sheep, pigs, chickens, ducks, geese, and rabbits. The process is gentle, the equipment is simple, and the cost is low, making it suitable for farmers, cooperatives, and large-scale farms to promote throughout the entire supply chain. Detailed Implementation Example 1

[0021] Crush the crop straw to 3-5 mm. Based on 1000 parts by weight of dry straw, add 10 parts calcium hydroxide, 12 parts urea, 6 parts diatomaceous earth, 2.5 parts potassium dihydrogen phosphate, 2.5 parts sodium humate, and 0.8 parts of a complex enzyme preparation of cellulase and xylanase. Add water to adjust the moisture content to 60%. After mixing evenly, perform a first puffing at 120-140℃. Then perform a second conditioning puffing at 80-100℃ for 3-5 minutes. Discharge and cool to below 40℃.

[0022] Add 0.25 parts of Aspergillus niger spore powder and 12 parts of oyster mushroom spawn to the above-mentioned puffed pretreated material, along with 0.8 parts of magnesium sulfate, 4 parts of light calcium carbonate, and 4 parts of molasses. Control the temperature at 30-35℃ and allow it to ferment aerobically for 72 hours.

[0023] Add 8 parts of a bacterial-algae symbiotic agent, 0.25 parts of amino acid chelated trace elements, and 2.5 parts of brown sugar, adjust the moisture content to 50%–55%, and convert for 60 hours under weak light and micro-aerobic conditions at 25–32℃ to obtain straw degradation and quality improvement products. Example 2

[0024] Crush the crop straw to 3-5 mm. Based on 1000 parts by weight of dry straw, add 8 parts calcium hydroxide, 10 parts urea, 5 parts diatomaceous earth, 2 parts potassium dihydrogen phosphate, 2 parts sodium humate, and 0.5 parts compound enzyme preparation. Add water to adjust the moisture content to 55%. The first puffing temperature is 120-140℃, the second puffing temperature is 80-90℃, and then cool to below 40℃.

[0025] Inoculate with 0.2 parts of Aspergillus niger spore powder, 10 parts of oyster mushroom spawn, 0.5 parts of magnesium sulfate, 3 parts of light calcium carbonate, and 3 parts of glucose, and ferment aerobically at 30-35℃ for 72 hours.

[0026] Add 5 parts of bacterial-algae symbiotic agent, 0.2 parts of amino acid chelated trace elements, and 2 parts of brown sugar, and perform low-light, micro-aerobic conversion at 25-32℃ for 72 h to obtain straw degradation and quality improvement products. Comparative Example 1

[0027] The traditional single-stage puffing followed by single-microbial fermentation process was adopted. After straw crushing, no calcium hydroxide, urea, diatomaceous earth, potassium dihydrogen phosphate, sodium humate, or compound enzyme preparations were added. Only a conventional single-stage puffing was performed at 120–140℃. After cooling, a single yeast starter was inoculated, and conventional aerobic fermentation was carried out for 10 days to obtain the control product. Effect Experiment: Table 1. Effects of different treatments on straw degradation and nutritional indicators detection indicators Example 1 Example 2 Comparative Example 1 Lignin degradation rate / % 69.0 64.0 36.5 Cellulose degradation rate / % 49.0 44.0 29.0 Crude protein content / % 17.0 15.5 8.5 Total nutrient loss rate / % 4.2 4.8 12.6 Fermentation cycle / d 5 6 10 As shown in Table 1, the lignin degradation rate, cellulose degradation rate, and crude protein content of the embodiments of the present invention are significantly higher than those of the comparative example, the total nutrient loss rate is significantly reduced, and the fermentation cycle is significantly shortened, demonstrating outstanding technical effects. Beneficial effects By employing a secondary expansion coupled with the synergistic treatment of calcium hydroxide, urea, and diatomaceous earth, the nutrient loss caused by high-temperature expansion is significantly reduced, with the total nutrient loss controlled to within 5%. Aerobic fermentation of Aspergillus niger and Pleurotus ostreatus cultivation varieties achieves deep depolymerization of lignin and significantly improves degradation efficiency; The bacterial-algae symbiotic system further transforms residual substrates, enriches bacterial proteins, and improves palatability and digestibility. The process has a clear route, controllable parameters, and is suitable for industrial production. It can be widely used in the preparation of biological feed and the resource utilization of agricultural waste. Attached Figure Description Instruction manual attached Figure 1 Flowchart of a method for the synergistic stepwise degradation of lignin in crop straw based on puffing pretreatment by bacteria and algae The process flow of this invention is as follows: crop straw → crushing → physical pretreatment (expansion / steam explosion / extrusion expansion) → aerobic deep depolymerization by compound fungi → deep conversion by fungal-algae symbiotic system → degradation of straw products (fermented feed / organic fertilizer) The process includes: 1. Physical pretreatment stage: After straw is crushed, alkalis, nitrogen sources, and mineral carriers are added, followed by dry puffing, wet puffing, extrusion puffing, or steam explosion cell wall breaking treatment; 2. Aerobic deep depolymerization stage of compound fungi: The moisture content of the pretreated material is adjusted, and cellulase-producing fungi and lignin-degrading fungi are inoculated. Phosphorus, potassium, and magnesium salts and mineral carriers are added, and aerobic fermentation depolymerizes lignocellulose; 3. Deep conversion stage of the fungal-algae symbiotic system: A fungal-algae symbiotic system composed of photosynthetic bacteria, lactic acid bacteria, Chlorella, and Scenedesmus is introduced, trace elements are added, and the system is cultured under diffused light and micro-aeration to obtain high-value degraded straw products.

Claims

1. A method for degrading lignin in crop straw, characterized in that, include: (1) The straw is subjected to a combined physical puffing and chemical conditioning pretreatment to achieve cell wall disruption and initial lignin dissociation; (2) Introduce a fungal complex for aerobic fermentation to deeply depolymerize lignin and cellulose in straw; (3) Introduce a bacterial-algae symbiotic system for later transformation and nutrient enrichment to obtain degradation and quality improvement products.

2. The process according to claim 1, characterized in that, The chemical conditioning process includes conditioning treatment using one or more combinations of alkaline substances, nitrogen sources, and adsorbent minerals.

3. The process according to claim 2, characterized in that, The alkaline substance includes at least one of calcium hydroxide, calcium oxide, sodium hydroxide, and potassium hydroxide; The nitrogen source includes at least one of urea, ammonium sulfate, ammonium chloride, ammonium nitrate, and peptone; The adsorbent minerals include at least one of diatomaceous earth, bentonite, zeolite powder, and attapulgite.

4. The process according to claim 1, characterized in that, The physical puffing and chemical conditioning coupled pretreatment consists of a primary puffing followed by a secondary conditioning and puffing process. The puffing temperature is 80–180℃, and the processing time is 1 min–30 min.

5. The process according to claim 1, characterized in that, The fungal complex includes one or more combinations of lignin-degrading fungi and cellulose-degrading fungi. The fungi include at least one of the genera Aspergillus, Pleurotus, Trichoderma, Lentinus, and Ganoderma.

6. The process according to claim 1, characterized in that, During the aerobic fermentation stage, one or more of the following are added: inorganic salts, pH adjusters, and carbon source supplements.

7. The process according to claim 1, characterized in that, The algal symbiotic system includes one or more of photosynthetic bacteria, lactic acid bacteria, and Bacillus, combined with algae such as Chlorella, Scenedesmus, Spirulina, and Chlamydomonas.

8. The process according to claim 1, characterized in that, The aforementioned algal-microbe symbiotic transformation stage is carried out under microaerobic, light-protected, or low-light conditions. The temperature is controlled at 20-35℃, and the processing time is 24-96 hours.

9. The process according to any one of claims 1 to 8, characterized in that, The straw includes one or more of the following: corn straw, wheat straw, rice straw, peanut vines, bean straw, potato vines, sugarcane leaves, and pasture grass.

10. The application of straw degradation products prepared by any one of the processes described in claims 1 to 8 in biological feed, fermentation raw materials, organic fertilizers, and crop-livestock recycling substrates.

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