Method for preparing xylobiose and xylotriose from agricultural and forestry waste bamboo sawdust

Abstract

The invention discloses a method for preparing xylobiose and xylotriose from agricultural and forestry waste bamboo sawdust, and belongs to the technical field of agricultural and forestry biomass degradation and conversion. The method comprises the following steps: firstly, adjusting the pH value of a lactic acid solution, then mixing the raw material bamboo sawdust with the lactic acid solution, hydrolyzing, and filtering to obtain a treatment solution containing xylooligosaccharide and filter residues; and then mixing the treating fluid with xylanase to carry out enzymolysis reaction, and further decomposing xylan and xylooligosaccharide with high polymerization degree in the aqueous solution into xylobiose and xylotriose. The xylobiose and the xylotriose are obtained by adjusting the pH value of the lactic acid solution in combination with an endo-xylanase hydrolysis method, so that the xylooligosaccharide with higher biological activity is prepared, and the xylooligosaccharide can be used as a functional feed additive and can also be used as a functional food additive through subsequent treatment.

Description

Technical Field

[0001] The invention belongs to the technical field of agricultural and forestry biomass degradation and conversion, and particularly relates to a method for preparing xylobiose and xylotriose by utilizing agricultural and forestry waste bamboo chips. Background Art

[0002] Xylooligosaccharides, also known as xylooligosaccharides, are oligosaccharides formed by connecting 2-10 xylose molecules with (β-1,4) glycosidic bonds. Xylooligosaccharides are a class of low-molecular polymers with multiple biological activities, among which xylose and xylose are widely used in food, health care and medical fields due to their unique prebiotic and antioxidant activities. Compared with other xylooligosaccharides, xylose and xylose have stronger biological activities, can effectively promote the growth of probiotics, inhibit the growth of harmful bacteria in the intestines, and help maintain the balance of intestinal flora. At the same time, they are both highly water-soluble, easily soluble in water, and easy to process and use. In addition, xylose and xylose also have strong antioxidant capacity, which helps to remove free radicals in the body and protect cells from oxidative damage, thereby delaying the aging process. Compared with other xylooligosaccharides with higher polymerization degree, the shorter chain length of xylobiose and xylotriose makes them more stable and not easily degraded by human or animal digestive enzymes. Therefore, they act in the intestines for a longer time, helping to better prevent constipation and regulate intestinal flora.

[0003] Xylo-oligosaccharides are widely distributed in nature and exist in milk, honey, fruits and vegetables, but the content is relatively low. Bamboo scraps contain a large amount of xylan-type hemicellulose and are one of the best raw materials for preparing xylo-oligosaccharides. At present, the preparation methods of xylo-oligosaccharides include enzymatic hydrolysis, acid hydrolysis and hydrothermal method. Enzymatic hydrolysis is to hydrolyze the separated xylan using xylanase secreted by microorganisms. Due to the barrier effect of lignin in biomass, alkaline method is required to extract xylan from agricultural and forestry biomass before enzymatic hydrolysis. Acid hydrolysis is to hydrolyze xylan in agricultural and forestry biomass with hydrochloric acid, sulfuric acid and the like to generate soluble xylo-oligosaccharides, but there are problems such as wide distribution of polymerization degree of xylo-oligosaccharides, many by-products, and high cost of subsequent separation and purification. Hydrothermal method is a method in which agricultural and forestry waste undergoes self-hydrolysis at high temperature and high pressure to obtain xylo-oligosaccharides. This method also has problems such as wide distribution of polymerization degree of xylo-oligosaccharides, many by-products and high energy consumption. Summary of the invention

[0004] The technical problem solved by the present invention is to provide a method for preparing xylobiose and xylotriose by using bamboo chips, which are agricultural and forestry wastes. By lactic acid hydrolysis and xylan enzymolysis, oligoxylose with higher biological activity is obtained, which can be used as a functional feed additive or as a functional food additive after subsequent treatment.

[0005] In order to solve the above technical problems, the technical solution adopted by the present invention is as follows:

[0006] A method for preparing xylobiose and xylotriose by using bamboo chips, which are agricultural and forestry waste, comprises a lactic acid hydrolysis step and a xylan enzymatic hydrolysis step, wherein the pH of the lactic acid used in the lactic acid hydrolysis step is 2.4-3.4, and the xylan enzymatic hydrolysis step uses xylan enzymatic lactic acid hydrolyzate.

[0007] The volume concentration of the lactic acid solution is 0.5% to 2%.

[0008] The chemical reagent used to adjust the pH of lactic acid is NaOH solution.

[0009] The hydrolysis temperature is 170-180°C.

[0010] The hydrolysis time is 30 to 80 minutes.

[0011] The mass volume ratio of the bamboo chips to the lactic acid solution is 1:10.

[0012] The enzyme dosage for xylan enzymolysis is 1 U / mL; and then the mixture is placed in a 50° C. water bath shaker.

[0013] The xylan enzymatic hydrolysis was carried out in a shaker at a shaking speed of 150 r / min for 6 hours.

[0014] Any of the above methods for preparing xylobiose and xylotriose using bamboo scraps from agricultural and forestry wastes comprises the following steps:

[0015] The first step is to adjust the pH value of the lactic acid solution to 2.4-3.4 using a NaOH solution, then mix the raw bamboo chips with the lactic acid solution at a volume concentration of 0.5%-2%, perform lactic acid catalytic hydrolysis at a temperature of 170-180° C. for 30-80 minutes, and filter after cooling to obtain a hydrolyzate;

[0016] In the second step, the hydrolyzate obtained in the first step was mixed with 1 U / mL of xylanase, and reacted at a shaking speed of 150 r / min in a 50° C. water bath shaker for 6 h to obtain an enzymatic hydrolyzate containing xylo-oligosaccharides.

[0017] Compared with the prior art, the present invention has the following advantages:

[0018] The present invention uses waste bamboo chips as raw materials, and can efficiently hydrolyze and dissolve xylan in the raw materials through lactic acid catalytic hydrolysis with adjusted pH; the treated liquid obtained after suction filtration is hydrolyzed by xylanase, and the xylan and high-polymerization oligoxylose therein can be converted into xylobiose and xylotriose, thereby preparing oligoxylose with higher biological activity, which can be used as a functional feed additive, and can also be used as a functional food additive after subsequent treatment; the solid residue after suction filtration can be subsequently separated into cellulose and lignin, which can be used in the production of pulp, bioethanol, adhesives, bio-based materials and other fields. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is a process roadmap for preparing xylobiose and xylotriose from bamboo chips. DETAILED DESCRIPTION

[0020] The present invention is further illustrated below in conjunction with specific examples. The examples are implemented based on the technical solutions of the present invention. It should be understood that these examples are only used to illustrate the present invention and are not used to limit the scope of the present invention.

[0021] The calculation formula for the yield of xylo-oligosaccharides in the following examples is as follows:

[0022]

[0023] The detection method of the xylooligosaccharide content in the hydrolyzate in the following embodiments is as follows:

[0024] The contents of xylose, xylose, xylotetraose, xylopentaose and xylohexose in the hydrolysate were determined by high performance liquid ion chromatography. Chromatographic conditions: American Dionex ICS-3000 ion chromatography system, equipped with CarboPacM PA200 (3mm×250mm) chromatographic column and guard column (3×50mm), ED electrochemical detector, column temperature 30℃, injection volume 10μL; binary gradient elution was performed with 500mmol / L sodium acetate solution (A) and 100mmol / L sodium hydroxide solution (B) as eluents, and the flow rate was 0.3mL / min (elution program: 0min, 100% A; 30min, 75% A, 25% B; 38-45min, 100% A). The detection mode of the electrochemical detector was a gold working electrode and a pH-Ag / AgCl composite reference electrode, and the content of the sugar components was determined by the integrated pulse amperometric detection method and the chromatographic peak area integration method.

[0025] Example 1

[0026] A method for preparing xylobiose and xylotriose using bamboo scraps from agricultural and forestry waste, the specific steps are as follows:

[0027] Preparation of lactic acid solution: Take 0.5 mL of lactic acid solution in a 100 mL beaker, add 60 mL of deionized water to dilute, transfer to a 100 mL volumetric flask to make up to volume, and adjust the pH to 3.0 with NaOH solution.

[0028] In the first step, 5g of bamboo powder was mixed with 50mL of a prepared aqueous solution of lactic acid solution (concentration of 0.5%, v / v), with a solid-liquid ratio of 1:10 and a pH of 3.0; the mixture was placed in a high-pressure reactor, heated to 170°C for 60 minutes, and after the reaction, the treated liquid was separated by a vacuum filtration device. The results were as follows: the yield of xylobiose and xylotriose was 12.6%, the yield of xylotetrose to xylohexaose was 16.3%, and the yield of xylose was 15.1%.

[0029] In the second step, 5 mL of the treated solution was placed in a 50 mL conical flask, 9.5 mL of sodium citrate buffer was added, 0.5 mL of xylanase was added to make its enzyme activity 1 U / mL, and the mixture was placed in a 50°C water bath shaker and oscillated at 150 r / min for 6 hours. The results were as follows: the yields of xylobiose and xylotriose increased to 42.5%, the yields of xylotetrose to xylohexaose were 12.3%, and the yield of xylose was 17.9%.

[0030] Example 2

[0031] A method for preparing xylobiose and xylotriose using bamboo scraps from agricultural and forestry waste, the specific steps are as follows:

[0032] Preparation of emulsion solution: Take 2 mL of lactic acid solution in a 100 mL beaker, add 60 mL of deionized water to dilute, transfer to a 100 mL volumetric flask to make up to volume, and adjust the pH to 3.0 with NaOH solution.

[0033] In the first step, 5g of bamboo powder was mixed with 50mL of a prepared aqueous solution of lactic acid solution (concentration of 2%, v / v), with a solid-liquid ratio of 1:10 and a pH of 3.0; the mixture was placed in a high-pressure reactor, heated to 170°C for 60 minutes, and after the reaction, the treated liquid was separated by a vacuum filtration device. The results were as follows: the yield of xylobiose and xylotriose was 20.5%, the yield of xylotetrose to xylohexaose was 14.2%, and the yield of xylose was 18.4%.

[0034] In the second step, 5 mL of the treated solution was placed in a 50 mL conical flask, 9.5 mL of sodium citrate buffer was added, 0.5 mL of xylanase was added to make its enzyme activity 1 U / mL, and the mixture was placed in a 50°C water bath shaker and oscillated at 150 r / min for 6 hours. The results were as follows: the yield of xylobiose and xylotriose increased to 30.6%, the yield of xylotetrose to xylohexaose was 4.3%, and the yield of xylose was 27.8%.

[0035] Example 3

[0036] A method for preparing xylobiose and xylotriose using bamboo scraps from agricultural and forestry waste, the specific steps are as follows:

[0037] The difference from Example 1 is that the reaction time of the first step is 80 minutes. The results obtained by the reaction are: the yield of xylobiose and xylotriose is 17.2%, the yield of xylotetrose to xylohexaose is 15.5%, and the yield of xylose is 23.5%. The results of the second step are: the yield of xylobiose and xylotriose is increased to 35.9%, the yield of xylotetrose to xylohexaose is 6.8%, and the yield of xylose is 27.6%.

[0038] Example 4

[0039] A method for preparing xylobiose and xylotriose using bamboo scraps from agricultural and forestry waste, the specific steps are as follows:

[0040] The difference from Example 2 is that the pH of the lactic acid solution is adjusted to 3.2, and the pH of the mixed solution is 3.2. The results obtained by the reaction are: the yield of xylobiose and xylotriose is 17.3%, the yield of xylotetrose to xylohexaose is 15.8%, and the yield of xylose is 17.6%. Step 2: The results are: the yield of xylobiose and xylotriose is increased to 58.4%, the yield of xylotetrose to xylohexaose is 5.7%, and the yield of xylose is 21.8%.

[0041] Example 5

[0042] A method for preparing xylobiose and xylotriose using bamboo scraps from agricultural and forestry waste, the specific steps are as follows:

[0043] The difference from Example 2 is that the pH of the lactic acid solution is adjusted to 3.4, and the pH of the mixed solution is 3.4. The results obtained by the reaction are: the yield of xylobiose and xylotriose is 17.4%, the yield of xylotetraose to xylohexaose is 18.2%, and the yield of xylose is 15.4%. In the second step, the results are: the yield of xylobiose and xylotriose is increased to 35.0%, the yield of xylotetraose to xylohexaose is 6.5%, and the yield of xylose is 23.5%.

[0044] Example 6

[0045] A method for preparing xylobiose and xylotriose using bamboo scraps from agricultural and forestry waste, the specific steps are as follows:

[0046] The difference from Example 2 is that the reaction time is adjusted to 40 min. The results obtained by the reaction are: the yield of xylobiose and xylotriose is 5.6%, the yield of xylotetrose to xylohexaose is 7.7%, and the yield of xylose is 11.3%. The results of the second step are: the yield of xylobiose and xylotriose is increased to 17.5%, the yield of xylotetrose to xylohexaose is 3.3%, and the yield of xylose is 14.6%.

[0047] Example 7

[0048] A method for preparing xylobiose and xylotriose using bamboo scraps from agricultural and forestry waste, the specific steps are as follows:

[0049] The difference from Example 2 is that the reaction temperature is adjusted to 180°C. The results obtained by the reaction are: the yield of xylobiose and xylotriose is 16.8%, the yield of xylotetrose to xylohexaose is 7.9%, and the yield of xylose is 28.7%. In the second step, the results are: the yield of xylobiose and xylotriose is increased to 27.4%, the yield of xylotetrose to xylohexaose is 4.0%, and the yield of xylose is 32.4%.

[0050] Example 8

[0051] A method for preparing xylobiose and xylotriose using bamboo scraps from agricultural and forestry waste, the specific steps are as follows:

[0052] The difference from Example 1 is that the pH is adjusted to 2.4, the pH of the mixed solution is 2.4, and the reaction time is adjusted to 30 minutes. The results obtained by the reaction are: the yield of xylobiose and xylotriose is 4.8%, the yield of xylotetrose to xylohexaose is 12.1%, and the yield of xylose is 3.7%. The second step, the result is: the yield of xylobiose and xylotriose is increased to 15.1%, the yield of xylotetrose to xylohexaose is 2.8%, and the yield of xylose is only 5.2%.

[0053] Example 9

[0054] A method for preparing xylobiose and xylotriose using bamboo scraps from agricultural and forestry waste, the specific steps are as follows:

[0055] The difference from Example 1 is that the raw material is corn cob. The results obtained by the reaction are: the yield of xylobiose and xylotriose is 21.2%, the yield of xylotetrose to xylohexaose is 25.6%, and the yield of xylose is 17.1%. In the second step, the results are: the yield of xylobiose and xylotriose is increased to 41.7%, the yield of xylotetrose to xylohexaose is 8.1%, and the yield of xylose is 20.2%.

[0056] Example 10

[0057] The difference from Example 9 is that the pH is adjusted to 2.8, and the pH of the mixed solution is 2.8. The results obtained by the reaction are: the yield of xylobiose and xylotriose is 24.7%, the yield of xylotetrose to xylohexaose is 22.5%, and the yield of xylose is 19.3%. The results of the second step are: the yield of xylobiose and xylotriose is increased to 37.2%, the yield of xylotetrose to xylohexaose is 6.2%, and the yield of xylose is 22.8%.

[0058] According to the results of the above specific implementation cases, xylanase hydrolysis can effectively increase the yield of xylobiose and xylotriose, and a good yield of xylo-oligosaccharides can be obtained by xylanase hydrolysis at 170°C with a 2% lactic acid solution adjusted to a pH of 3.2 as a catalyst. Under the optimal conditions, i.e., a reaction temperature of 170°C, a reaction time of 60 min, a catalyst concentration of 2% (v / v), and a pH of 3.2, the yield of xylobiose and xylotriose is 58.4%.

[0059] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for preparing xylobiose and xylotriose using bamboo scraps from agricultural and forestry waste, comprising a lactic acid hydrolysis step and a xylan enzymatic hydrolysis step, characterized in that: The pH of the lactic acid used in the lactic acid hydrolysis step is 2.4-3.4, and the xylan enzymatic hydrolysis step uses xylan enzymatic lactic acid hydrolyzate.

2. The method for preparing xylobiose and xylotriose by using bamboo chips from agricultural and forestry waste according to claim 1, characterized in that: The volume concentration of the lactic acid solution is 0.5% to 2%.

3. The method for preparing xylobiose and xylotriose by using bamboo chips from agricultural and forestry waste according to claim 1, characterized in that: The chemical reagent used to adjust the pH of lactic acid is NaOH solution.

4. The method for preparing xylobiose and xylotriose by using bamboo chips from agricultural and forestry waste according to claim 1, characterized in that: The hydrolysis temperature is 170-180°C.

5. The method for preparing xylobiose and xylotriose by using bamboo chips from agricultural and forestry waste according to claim 1, characterized in that: The hydrolysis time is 30 to 80 minutes.

6. The method for preparing xylobiose and xylotriose by using bamboo chips from agricultural and forestry waste according to claim 1, characterized in that: The mass volume ratio of the bamboo chips to the lactic acid solution is 1:

10.

7. The method for preparing xylobiose and xylotriose by using bamboo chips from agricultural and forestry waste according to claim 1, characterized in that: The enzyme dosage for xylan enzymolysis is 1 U / mL; and then the mixture is placed in a 50° C. water bath shaker.

8. The method for preparing xylobiose and xylotriose by using bamboo chips from agricultural and forestry waste according to claim 1, characterized in that: The xylan enzymatic hydrolysis was carried out in a shaker at a shaking speed of 150 r / min for 6 hours.

9. The method for preparing xylobiose and xylotriose by using bamboo chips from agricultural and forestry waste according to any one of claims 1 to 8, characterized in that: Here are the steps: The first step is to adjust the pH value of the lactic acid solution to 2.4-3.4 using a NaOH solution, then mix the raw bamboo chips with the lactic acid solution at a volume concentration of 0.5%-2%, perform lactic acid catalytic hydrolysis at a temperature of 170-180° C. for 30-80 minutes, and filter after cooling to obtain a hydrolyzate; In the second step, the hydrolyzate obtained in the first step was mixed with 1 U / mL of xylanase, and reacted at a shaking speed of 150 r / min in a 50° C. water bath shaker for 6 h to obtain an enzymatic hydrolyzate containing xylo-oligosaccharides.

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