Agricultural waste conversion and functional food base material preparation method based on compound enzyme synergistic effect

Abstract

The present invention discloses a compound enzyme synergistic effect-based agricultural waste conversion and functional food base material preparation method, and relates to the field of biotechnology and food science, and the method comprises the following steps: S1, compound enzyme preparation; s2, agricultural waste pretreatment; s3, carrying out enzymolysis reaction; s4, separating a product; s5, preparing a functional base material; through the synergistic effect of the compound enzyme, cellulose, hemicellulose and beta-glucan are specifically degraded, the oligosaccharide yield and diversity are remarkably improved, through the flexible combination of dilute acid treatment and steam explosion, the wood fiber structure is effectively destroyed, the accessibility of a substrate is enhanced, the enzymolysis time is shortened, residues are converted into slow-release feed or biogas through enzymolysis, and the quality of the feed is improved. Zero-waste cyclic utilization of agricultural wastes is realized, the environmental load is reduced, the obtained base material has prebiotic activity and an immune regulation function, and can be widely applied to the fields of functional foods, health care products and the like, and the added value of products is increased.

Description

Technical Field

[0001] The present invention relates to biotechnology and food science and technology, and in particular to a method for converting agricultural waste and preparing a functional food base material based on the synergistic action of a composite enzyme. Background Art

[0002] In the agricultural sector, large quantities of agricultural waste, such as straw, fruit shells, and sugarcane bagasse, are generated. These wastes are rich in renewable resources such as cellulose and hemicellulose. However, due to their complex wood fiber structure, the efficient conversion and utilization of these resources has become a major challenge. Traditional pretreatment methods, such as dilute acid treatment or steam explosion, often fail to fully destroy the lignin barrier, resulting in low efficiency in the subsequent enzymatic hydrolysis process and difficulty in achieving ideal conversion results.

[0003] At the same time, traditional enzymatic hydrolysis processes mostly use a single enzyme preparation, which is unable to synergistically degrade the different polysaccharide components in agricultural waste, resulting in low product yields and a single type of oligosaccharide. In addition, the existing process makes insufficient use of the residue after enzymatic hydrolysis, which not only causes a waste of resources, but also may cause secondary pollution. More importantly, due to process limitations, the resulting products often have high ash content and poor functionality, making it difficult to meet the high standards required for food-grade additives. Therefore, how to achieve efficient and safe utilization of agricultural waste and prepare a base material with high purity and good functionality has become a technical challenge that needs to be solved urgently. Summary of the Invention

[0004] The purpose of the present invention is to provide a method for converting agricultural waste and preparing a functional food base based on the synergistic action of a complex enzyme, so as to solve the problems raised in the above background technology.

[0005] In order to achieve the above-mentioned object, the present invention provides the following technical solution: a method for converting agricultural waste and preparing a functional food base based on the synergistic action of a complex enzyme, comprising the following steps:

[0006] S1. Complex enzyme configuration: The complex enzyme is composed of endomannanase, xylan / cellulase Cel5E, and β-1,3-glucanase in a mass ratio of 1:1.5:0.8 to 1.5:2:1;

[0007] S2. Agricultural waste pretreatment: Crush straw, fruit shells, or bagasse to 20-100 mesh and pretreat with dilute acid treatment and / or steam explosion, wherein the dilute acid pH is 4.0-5.5, the steam explosion pressure is 1.5-3.0 MPa, and the treatment time is 1-3 hours. The combination of dilute acid treatment and steam explosion can be adjusted according to the specific type and properties of the waste to achieve the best pretreatment effect. For example, for waste with a high lignin content, the steam explosion pressure and time can be appropriately increased;

[0008] S3, enzymatic hydrolysis reaction: the pretreated material is mixed with the complex enzyme, the amount of complex enzyme added is 0.5% to 2% of the dry weight of the substrate, and the reaction is carried out at 45 to 60 ° C and pH 5.0 to 6.5 for 6 to 24 hours;

[0009] S4. Product separation: remove the residue by centrifugation, and separate the supernatant through an ultrafiltration membrane with a molecular weight cutoff of 1 to 5 kDa to obtain an oligosaccharide mixture;

[0010] S5. Preparation of functional base materials: Concentrate and dry the oligosaccharide mixture to make it into powder or syrup, which can be used as food additives or raw materials for health products.

[0011] Furthermore, the oligosaccharide mixture contains manno-oligosaccharide (MOS), xylooligosaccharide (XOS) and β-1,3-glucooligosaccharide (GOS), the polymerization degree of the three oligosaccharides is 2-6, and the mass ratio is 1:0.8-1.2:0.5-1.0.

[0012] Furthermore, the uses of functional base materials include:

[0013] a) As a prebiotic additive in food, the addition amount is 0.1% to 5% of the total weight of the food;

[0014] b) As an immunomodulator in health products, made into capsules or oral solutions.

[0015] Furthermore, surfactants or metal ions are added to the enzymatic hydrolysis reaction at a concentration of 0.05% to 0.2% w / v. Adding surfactants or metal ions to the enzymatic hydrolysis reaction can significantly improve the enzymatic hydrolysis efficiency and promote the effective binding of the enzyme and the substrate and the reaction by changing the surface properties or catalytic environment of the enzyme molecules.

[0016] Furthermore, in the pretreatment step, the dilute acid is sulfuric acid or hydrochloric acid with a concentration of 0.5% to 2% v / v, and the pretreated material is washed with water to neutrality.

[0017] Furthermore, after separation by ultrafiltration membrane, the residue is anaerobic fermented to generate biogas, or dried and used as an animal feed additive to achieve zero-waste recycling of agricultural waste, reducing environmental pollution and resource waste.

[0018] Furthermore, the pretreatment step includes: treating with dilute acid at pH 4.5-5.0 for 1 hour, washing with water, and then steam explosion at a pressure of 2.5-3.0 MPa for 8-12 minutes.

[0019] Furthermore, in the complex enzyme, the enzyme activity of endomannanase is ≥500 U / mg, the enzyme activity of xylanase Cel5E is ≥800 U / mg, and the enzyme activity of β-1,3-glucanase is ≥400 U / mg.

[0020] Furthermore, the oligosaccharide mixture separated by ultrafiltration membrane is desalted by nanofiltration membrane with a molecular weight cutoff of 200-500Da, with a desalination rate of ≥90%, and then prepared into powder by spray drying. The inlet air temperature of the spray drying is 180°C and the outlet air temperature is 80°C.

[0021] A functional food base material is made from an oligosaccharide mixture prepared by any of the above methods, wherein the total oligosaccharide content is ≥85%, the ash content is ≤3%, and the moisture content is ≤5%, so as to ensure the quality and safety of the functional base material.

[0022] Compared with the existing technology, the agricultural waste conversion and functional food base preparation method based on the synergistic action of complex enzymes provided by the present invention can specifically degrade cellulose, hemicellulose and β-glucan through the synergistic action of complex enzymes, significantly improving the yield and diversity of oligosaccharides.

[0023] Through the flexible combination of dilute acid treatment and steam explosion, the wood fiber structure is effectively destroyed, the substrate accessibility is enhanced, and the enzymatic hydrolysis time is shortened;

[0024] Ultrafiltration and nanofiltration fractionation processes are used to remove macromolecular residues and inorganic salts, ensuring the high purity and low ash content of the oligosaccharide mixture, meeting food additive standards;

[0025] By converting enzymatic residues into slow-release feed or biogas, we can achieve zero-waste recycling of agricultural waste and reduce environmental load;

[0026] The obtained base material has both prebiotic activity and immune regulation function, and can be widely used in functional foods, health products and other fields to enhance product added value. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments described in the present invention. For ordinary technicians in this field, other drawings can also be obtained based on these drawings.

[0028] Figure 1 A process flow chart provided for an embodiment of the present invention. DETAILED DESCRIPTION

[0029] In order to enable those skilled in the art to better understand the technical solution of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings.

[0030] Example 1:

[0031] See also Figure 1 The method for converting agricultural waste and preparing functional food base materials based on the synergistic action of complex enzymes comprises the following steps:

[0032] S1. Compound enzyme preparation: endomannanase, xylan / cellulase Cel5E, and β-1,3-glucanase were mixed in a mass ratio of 1:1.8:1 to prepare the compound enzyme;

[0033] S2. Agricultural waste pretreatment: Sugarcane bagasse was crushed to 60 mesh, treated with 1.5% v / v sulfuric acid (pH 4.5) for 2 hours, washed with water until neutral, and then neutralized with 2% w / w sodium carbonate;

[0034] S3, enzymatic hydrolysis reaction: the pretreated material was mixed with the complex enzyme, the amount of complex enzyme added was 1.5% w / w (based on the dry weight of the substrate), the conditions were 50°C, pH 6.0, and the reaction was carried out for 12 hours; the synergist was added with 0.1% w / v Tween-80 + 0.05% w / v Ca 2+ ;

[0035] S4. Product separation: centrifugation (4000 rpm, 15 minutes) to remove the residue, the supernatant was passed through an ultrafiltration membrane with a molecular weight cutoff of 3 kDa, and the ultrafiltrate was desalted through a nanofiltration membrane with a molecular weight cutoff of 300 Da (desalination rate 92%) to obtain an oligosaccharide mixture;

[0036] S5. Preparation of base material: The oligosaccharide mixture was concentrated under reduced pressure at 60°C to a solid content of 30%, and spray-dried (inlet air 180°C / outlet air 80°C) to obtain a powder with a fluidity of 85%.

[0037] The oligosaccharide content in the ultrafiltrate was analyzed by high performance liquid chromatography (HPLC), and the yield was calculated based on the initial total sugar content of the substrate. Yield = oligosaccharide mass in the ultrafiltrate / initial total sugar mass of the substrate × 100%. The base material index was quantitatively analyzed by HPLC for total oligosaccharides. The ash content was determined by the muffle furnace burning method (550°C, 4 hours) according to GB 5009.4-2016 Determination of ash in food; the moisture content was measured by oven drying method (105°C constant weight). 1 g of base material powder was weighed and dissolved in 100 mL of distilled water (25°C). After centrifugation, the solid content of the supernatant was determined to obtain water solubility data. Bifidobacterium was inoculated in MRS medium containing 1% oligosaccharide base and cultured at 37°C for 48 hours. The colony count increase was calculated by the plate count method, and the probiotic proliferation rate was measured. The results are as follows:

[0038] Oligosaccharide yield: 88% (MOS:XOS:GOS=1:1.0:0.7, degree of polymerization 2-6);

[0039] Base material indicators: total oligosaccharides 87%, ash 2.5%, moisture 4%, water solubility 96%;

[0040] Probiotic proliferation rate (48 hours): Bifidobacterium proliferation 320%.

[0041] According to the above content, through the synergistic effect of 1.5% dilute sulfuric acid pretreatment and complex enzyme (1:1.8:1), the oligosaccharide yield reached 88%, and the base material water solubility (96%) and prebiotic activity (Bifidobacterium proliferation 320%) were significantly better than the conventional process.

[0042] Example 2:

[0043] The method for converting agricultural waste and preparing functional food base materials based on the synergistic action of complex enzymes comprises the following steps:

[0044] S1. Composite enzyme configuration: Same as in Example 1, except that the mass ratio of endomannanase, xylan / cellulase Cel5E, and β-1,3-glucanase is adjusted to 1.2:2:1;

[0045] S2. Preprocessing:

[0046] Raw materials: wheat straw crushed to 80 mesh;

[0047] Steam explosion: pressure 2.8MPa, time 10 minutes;

[0048] S3, enzymatic hydrolysis reaction: enzyme addition amount: 2% w / w; conditions: 55°C, pH 5.5, reaction time: 18 hours;

[0049] S4. Product separation: centrifugation (same as in Example 1); ultrafiltration membrane with a cutoff of 5 kDa to collect the oligosaccharide mixture; residue treatment: drying and mixing with 4% bentonite to granulate the particles to a particle size of 2-4 mm;

[0050] S5. Preparation of base material: Concentration and drying: same as in Example 1.

[0051] Results: Oligosaccharide yield: 82%;

[0052] Feed additive performance: granule hardness 18N, sustained release rate (24 hours) 80% (granule compressive strength was measured using a texture analyzer (TA.XT Plus); oligosaccharide residue was measured after immersion in simulated gastric fluid (pH 2.0) for 24 hours);

[0053] Base material ash content: 2.8%, moisture 5%.

[0054] According to the above content, steam explosion (2.8MPa) destroyed the lignin-cellulose structure, and the enzymatic hydrolysis yield was 82%. After the residue was granulated with bentonite, the particle hardness increased to 18N, the sustained release rate was 80%, and the full utilization of waste was achieved.

[0055] Example 3:

[0056] The method for converting agricultural waste and preparing functional food base materials based on the synergistic action of complex enzymes comprises the following steps:

[0057] S1, compound enzyme configuration: same as Example 1;

[0058] S2. Pretreatment: Raw materials: walnut shells crushed to 40 mesh; dilute acid treatment: soaking in 0.8% v / v hydrochloric acid (pH 4.8) for 1 hour, washing with water until neutral; steam explosion: pressure 3.0 MPa, explosion for 12 minutes;

[0059] S3, enzymatic hydrolysis reaction: enzyme addition amount: 1% w / w; conditions: 60°C, pH 6.5, reaction time: 6 hours;

[0060] S4, product separation: ultrafiltration membrane cut-off 1kDa; nanofiltration desalination (cut-off 200Da), desalination rate 95%;

[0061] S5. Preparation of base material: Syrup form: Concentrate to syrup (solid content 50%) and fill aseptically.

[0062] result:

[0063] Lignin removal rate: 88% (single pretreatment ≤ 70%);

[0064] Enzymatic hydrolysis efficiency: The oligosaccharide production per unit time is 25% higher than that in Example 1;

[0065] Syrup properties: total oligosaccharides 85%, viscosity 350 cP (25°C);

[0066] The lignin removal rate refers to the acid-insoluble lignin determination method of TAPPI T222 om-02, where removal rate = (lignin mass before pretreatment - lignin mass after pretreatment) / lignin mass before pretreatment × 100%.

[0067] According to the above content, the combined pretreatment increased the lignin removal rate to 88% (single method ≤ 70%), the enzymatic hydrolysis efficiency was 25% higher than that in Example 1, and the syrup base viscosity was 350 cP, which can be directly used in liquid health products.

[0068] Example 4:

[0069] The method for converting agricultural waste and preparing functional food base materials based on the synergistic action of complex enzymes comprises the following steps:

[0070] S1, complex enzyme configuration: endomannanase (enzyme activity 400 U / mg), xylanase Cel5E (enzyme activity 600 U / mg), β-1,3-glucanase (enzyme activity 300 U / mg), mass ratio 1:1.5:0.8;

[0071] S2-S5: Same as Example 1.

[0072] Results: Oligosaccharide yield: 58% (incomplete degradation due to insufficient enzyme activity); the amount of reducing sugar released was measured by regular sampling, and the time required to reach 80% degradation rate was determined. It was found that the reaction time needed to be extended to 24 hours to achieve 80% degradation rate.

[0073] According to the above content, when the enzyme activity is lower than the threshold (400 U / mg for mannanase and 600 U / mg for Cel5E), the oligosaccharide yield drops sharply to 58%, and the reaction time is extended to 24 hours, highlighting the irreplaceable role of high enzyme activity in process efficiency.

[0074] Example 5:

[0075] The method for converting agricultural waste and preparing functional food base materials based on the synergistic action of complex enzymes comprises the following steps:

[0076] S1-S4: Same as Example 1, but omitting the nanofiltration desalination step in S4;

[0077] S5. Base material preparation: directly spray-drying the undesalted oligosaccharide solution.

[0078] result:

[0079] Ash content: 8.0% (far exceeding the ≤3% in claim 10);

[0080] Water solubility: 78% (salt causes oligosaccharide aggregation).

[0081] According to the above content, the failure to desalinate leads to excessive ash content and decreased water solubility, which proves that the nanofiltration process is a necessary step to meet food grade standards.

[0082] Application Experimental Example (Application of the Base Material Prepared in Example 1 in Food):

[0083] 1. Experimental Materials and Methods

[0084] (1) Materials:

[0085] Oligosaccharide base: powder prepared in Example 1 (total oligosaccharides 87%, MOS:XOS:GOS=1:1.0:0.7);

[0086] Yogurt ingredients: fresh milk (3.2% protein), Lactobacillus bulgaricus, Streptococcus thermophilus;

[0087] Control group: commercially available fructooligosaccharide (FOS, purity 95%);

[0088] (2) Experimental design:

[0089] Group:

[0090] Experimental group: 1% oligosaccharide base (w / w) was added to milk;

[0091] Control group: 1% FOS (w / w) was added to milk;

[0092] Blank group: no prebiotics were added.

[0093] Yogurt preparation: preheat milk to 45°C, add prebiotics and homogenize; inoculate with bacteria (L.bulgaricus:S.thermophilus=1:1), ferment at 42°C for 6 hours; cool to 4°C and ripen for 24 hours.

[0094] (3) Detection indicators: Number of viable probiotic bacteria: measured at 0 days, 7 days, and 14 days after fermentation (CFU / g); Bifidobacterium proliferation rate: in vitro simulated intestinal environment (pH 6.8, 37°C), 1% yogurt sample was added, and the number of bacteria was detected after culturing for 24 hours; Sensory evaluation: 20 subjects scored the taste and flavor (out of 10 points).

[0095] 2. Experimental results:

[0096]

[0097]

[0098] 3. Conclusion

[0099] Prebiotic effect: The viable bacteria preservation rate in the experimental group yogurt (70.8% at 14 days) was significantly higher than that in the control group (54.5%) and the blank group (32%), demonstrating that the oligosaccharide-based prebiotics have superior stability.

[0100] The bifidobacterium proliferation rate (320%) was 28% higher than that of commercially available FOS (250%);

[0101] Sensory advantages: The oligosaccharide base gives yogurt a softer sweetness (MOS / XOS is sweeter than FOS), and the sensory score is improved by 10%.

[0102] Technical value: It was verified that the base prepared in the above embodiment can be directly applied to food and has commercial potential (such as low-sugar and high-fiber yogurt).

[0103] In summary, the present application uses the synergistic action of a composite enzyme (endomannanase, xylan / cellulase Cel5E, β-1,3-glucanase) to specifically degrade cellulose, hemicellulose, and β-glucan in agricultural waste, significantly improving the yield and diversity of oligosaccharides. Compared with traditional single enzyme preparations, it can produce more types of oligosaccharides with higher activity, such as mannan oligosaccharides (MOS), xylooligosaccharides (XOS), and β-1,3-glucooligosaccharides (GOS), providing a richer selection of raw materials for functional foods and health products.

[0104] The present invention uses dilute acid treatment and / or steam explosion to pretreat agricultural waste, effectively destroying the wood fiber structure and enhancing the accessibility of the substrate. This pretreatment method not only improves the efficiency of enzymatic hydrolysis, but also significantly shortens the enzymatic hydrolysis time and reduces production costs. By flexibly combining dilute acid treatment and steam explosion, it is possible to optimize the treatment according to the characteristics of different wastes to achieve the best pretreatment effect.

[0105] The residue after separation by ultrafiltration membrane is anaerobic fermented to generate biogas or dried and used as animal feed additive, achieving zero-waste recycling of agricultural waste. This not only reduces environmental pollution but also improves resource utilization, with significant environmental and economic benefits.

[0106] The functional base prepared by the present invention possesses both prebiotic activity and immunomodulatory functions and can be widely used in functional foods, health supplements, and other fields. As a food additive, it can significantly enhance the health value and market competitiveness of products. As a raw material for health supplements, it can be formulated into capsules, oral liquids, and other forms to meet consumer demand for healthy products. This helps increase the added value of agricultural waste and promotes its resource utilization and industrial development.

[0107] The sequences of the endomannanase, xylanase Cel5E, and β-1,3-glucanase (enzyme activity 300 U / mg) in the above examples are as follows:

[0108] Protein name: Endo-1,4-β-mannanases gmuG endomannanase (pectinase);

[0109] Source: Bacillus sp.MK-2;

[0110] Expression vector: pET30a(+);

[0111] Shake flask expression conditions: 0.5 mM IPTG, 16°C for 12 h (OD600 = 0.6);

[0112] Amino acid sequence: Note: NdeI and XhoⅠ are restriction endonuclease sites;

[0113] NdeI-HTVSPVNPNAQQTTKTVMNWLAHLPNRTENRVLSGAFGGYS HDTFSMAEADRIRSATGQSPAIYGCDYARGWLETANIEDSIDVSCNGDLMSYWKNGGIPQISLHLANPAFQSGHFKTPITNDQYKKILDSSTVEGKRLNAMLSKIADGLQELENQGVPVLFRPLHEMNGEWFWWGLTSYNQKDNERISLYKQLYK KIYHYMTDTRGLDHLIWVYSPDANRDFKTDFYPGASYVDIVGLDAYFQDAYSINGYDQLTALNKPFAFTEVGPQTANGSFDYSLFINAIKQKYPKTIYFLAWNDEWSAAVNKGASALYHDSWTLNKGEIWNGDSLTPIVE-XhoI-6×His-stop condon.

[0114] Protein name: cellulase Cel5E xylan / cellulase;

[0115] Source: Clostridium thermocellum;

[0116] Expression vector: pET26b(+);

[0117] Shake flask expression conditions: 0.4 mM IPTG, 30°C, 12 h (OD600 = 0.6);

[0118] Amino acid sequence: Note: NcoI and XhoⅠ are restriction endonuclease sites;

[0119] NcoI-2 protective bases GC-

[0120] KAVDPFEMVRKMGMGTNLGNTLEAPYEGSWSKSAMEYYFDDFKAAGYKNVRIPVRWDNHTMRTYPYTIDKAFLDRVEQVVDWSLSRGFVTIINSHHDDWIKEDYNGNIERFEKIWEQIAERFKNKSENLLFEIMNEPFGNITDEQIDDMNSRILKIIRKTN PTRIVIIGGGYWNSYNTLVNIKIPDDPYLIGTFHYYDPYEFTHKWRGTWGTQEDMDTVVRVFDFVKSWSDRNNIPVYFGEFAVMAYADRTSRVKWYDFISDAALERGFACSVWDNGVFGSLDNDMAIYNRDTRTFDTEILNALFN-XhoI-6×His-stop condon.

[0121] Protein name: β-1,3-glucanasesβ-1,3-glucanase;

[0122] Expression vector: pET28a(+);

[0123] Shake flask expression conditions: 0.4 mM IPTG, 30°C, 12 h (OD600 = 0.6);

[0124] Amino acid sequence: Note: NdeI and XhoⅠ are restriction endonuclease sites;

[0125] NdeI-KVLDGINLGHNPNNCPTVEELEKRLTVLKPYTDTVRIFALSVC NIAEKTLKACKKLGMKVILGMWIDSRESYEKELEALKKILENEDVSNVEGLSVGNETLYRGYFSPEEYAEYVKEVKELVKPYGIKVSTREAYDKYPEVVVEELDFIEINYFP FWEGVSVEDATDELLKKYEIAKSRSLGKPVYIGETGWPSGGENIGNAVASTENQQKFLQDFLAAAEERNIKTTYFQAFDEPYRGGYESHYGLFDANEKVKEGITIESGK-Xho I-WSHPQFEK-stopcondon.

[0126] The above description is merely illustrative of certain exemplary embodiments of the present invention. It goes without saying that those skilled in the art will be able to modify the described embodiments in various ways without departing from the spirit and scope of the present invention. Therefore, the above drawings and description are illustrative in nature and should not be construed as limiting the scope of protection of the claims.

Claims

1. A method for converting agricultural waste and preparing a functional food base based on the synergistic action of a complex enzyme, characterized in that: The following steps are involved: S1. Complex enzyme configuration: The complex enzyme is composed of endomannanase, xylan / cellulase Cel5E, and β-1,3-glucanase in a mass ratio of 1:1.5:0.8 to 1.5:2:1; S2. Agricultural waste pretreatment: crush straw, fruit shell or bagasse to 20-100 mesh, and pretreat with dilute acid treatment and / or steam explosion, wherein the dilute acid pH is 4.0-5.5, the steam explosion pressure is 1.5-3.0 MPa, and the treatment time is 1-3 hours; S3, enzymatic hydrolysis reaction: the pretreated material is mixed with the complex enzyme, the amount of complex enzyme added is 0.5% to 2% of the dry weight of the substrate, and the reaction is carried out at 45 to 60 ° C and pH 5.0 to 6.5 for 6 to 24 hours; S4. Product separation: remove the residue by centrifugation, and separate the supernatant through an ultrafiltration membrane with a molecular weight cutoff of 1 to 5 kDa to obtain an oligosaccharide mixture; S5. Preparation of functional base materials: Concentrate and dry the oligosaccharide mixture to make it into powder or syrup, which can be used as food additives or raw materials for health products.

2. The method for converting agricultural waste and preparing functional food base materials based on the synergistic action of complex enzymes according to claim 1, characterized in that: The oligosaccharide mixture contains manno-oligosaccharide, xylo-oligosaccharide and beta-1,3-glucose oligosaccharide, the polymerization degrees of the three oligosaccharides are 2-6, and the mass ratio is 1:0.8-1.2:0.5-1.

0.

3. The method for converting agricultural waste and preparing functional food base materials based on the synergistic action of complex enzymes according to claim 1, characterized in that: Functional binders are used for: a) As a prebiotic additive in food, the addition amount is 0.1% to 5% of the total weight of the food; b) As an immunomodulator in health products, made into capsules or oral solutions.

4. The method for converting agricultural waste and preparing functional food base materials based on the synergistic action of complex enzymes according to claim 1, characterized in that: During the enzymatic hydrolysis reaction, a surfactant or metal ion is added at a concentration of 0.05% to 0.2% w / v.

5. The method for converting agricultural waste and preparing functional food base materials based on the synergistic action of complex enzymes according to claim 1, characterized in that: In the pretreatment step, the dilute acid is sulfuric acid or hydrochloric acid with a concentration of 0.5% to 2% v / v. After the pretreatment, the material is washed with water to neutrality.

6. The method for converting agricultural waste and preparing functional food base materials based on the synergistic action of complex enzymes according to claim 1, characterized in that: After separation by ultrafiltration membrane, the residue is anaerobically fermented to produce biogas, or dried and used as an animal feed additive.

7. The method for converting agricultural waste and preparing functional food base materials based on the synergistic action of complex enzymes according to claim 1, characterized in that: The pretreatment steps include: treating with dilute acid of pH 4.5-5.0 for 1 hour, washing with water and then steam explosion at a pressure of 2.5-3.0 MPa for 8-12 minutes.

8. The method for converting agricultural waste and preparing functional food base materials based on the synergistic action of complex enzymes according to claim 1, characterized in that: In the complex enzyme, the enzymatic activity of endomannanase is ≥500U / mg, the enzymatic activity of xylanase Cel5E is ≥800U / mg, and the enzymatic activity of β-1,3-glucanase is ≥400U / mg.

9. The method for converting agricultural waste and preparing functional food base materials based on the synergistic action of complex enzymes according to claim 1, characterized in that: The oligosaccharide mixture separated by ultrafiltration membrane is desalted by nanofiltration membrane with a molecular weight cutoff of 200-500Da, with a desalination rate of ≥90%, and then prepared into powder by spray drying. The inlet air temperature of the spray drying is 180℃ and the outlet air temperature is 80℃.

10. A functional food base, characterized by: The oligosaccharide mixed liquid is prepared by the method of any one of claims 1 to 9, wherein the total oligosaccharide content is ≥85%, the ash content is ≤3%, and the moisture content is ≤5%.

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