Method for cyclically preparing high-activity xylooligosaccharide from recoverable acid

Abstract

The invention discloses a method for cyclically preparing high-activity xylooligosaccharide from recoverable acid, and belongs to the technical field of xylooligosaccharide preparation. The method comprises the following steps: carrying out hydrolysis reaction on moso bamboo processing residues and a gallic acid solution, and carrying out solid-liquid separation to obtain a high-polymerization-degree xylooligosaccharide solution; then carrying out enzymolysis reaction on the xylooligosaccharide solution with high polymerization degree and xylanase to obtain a high-activity xylooligosaccharide solution, and carrying out concentration, refrigeration treatment and recrystallization on the obtained high-activity xylooligosaccharide solution to recover residual acid so as to obtain the high-concentration high-activity xylooligosaccharide solution. According to the method, the high-activity xylooligosaccharide is prepared through hydrolysis of the easily-recycled organic acid, and the method has the advantages of being high in xylooligosaccharide concentration, high in high-activity component content, simple in reagent recycling, easy to operate and the like and is suitable for preparing xylooligosaccharide through high-selectivity conversion of hemicellulose in bamboo processing residues.

Description

Technical Field

[0001] The invention belongs to the technical field of xylooligosaccharide preparation, and in particular relates to a method for preparing high-activity xylooligosaccharides by recycling recyclable acid. Background Art

[0002] As a functional polymer sugar, xylooligosaccharide is low in calories, selectively promotes the proliferation of beneficial intestinal bacteria, enhances immunity and protects the liver. It is widely used in food, health products, beverages, feed and other industries.

[0004] At present, the commercial production method of oligoxylose mainly uses endo-xylanase to hydrolyze alkaline-extracted xylan, but the alkaline extraction process involved in this method is complicated and the alkaline waste liquid will cause serious environmental pollution. The preparation of oligoxylose by organic acid hydrolysis does not require the separation of xylan by alkaline extraction, nor does it produce a large amount of wastewater due to alkaline neutralization. It has the advantages of simple process and environmental friendliness. It is one of the most promising methods for the commercial production of oligoxylose. However, there are technical bottlenecks such as high cost of acid recovery process, more by-products, and low content of highly active components.

[0005] Based on this, how to utilize agricultural and forestry wastes (such as bamboo processing residues) to prepare highly active oligoxylose and recover the acid used has become a problem that needs to be solved urgently. Summary of the invention

[0006] The purpose of the present invention is to propose a method for preparing highly active xylooligosaccharides by recycling recyclable acid, wherein the highly active xylooligosaccharides are prepared by hydrolysis using easily recyclable organic acids, the prepared xylooligosaccharides have high concentrations and high content of highly active components, and the reagent acid solution can be easily recovered, and the method is suitable for preparing xylooligosaccharides by highly selective conversion of hemicellulose in bamboo processing residues.

[0007] In order to solve the above problems, the technical solution adopted by the present invention is as follows:

[0008] A method for preparing high-activity oligoxylose by recycling acid with recoverable acid, comprising: hydrolyzing bamboo processing residues and gallic acid solution, and obtaining a high-polymerization oligoxylose solution after solid-liquid separation; adding xylanase to the obtained high-polymerization oligoxylose solution after pH adjustment, and concentrating and refrigerating the obtained high-activity oligoxylose solution, and recovering the remaining acid by recrystallization, thereby obtaining a high-concentration high-activity oligoxylose solution; wherein the acid recovery rate is 30% to 80%.

[0009] Furthermore, the bamboo processing residue is obtained by crushing and then sieving, and the sieving mesh number is not less than 60 meshes.

[0010] Furthermore, the concentration of the gallic acid solution is 30-100 mM.

[0011] Furthermore, the mass volume ratio of the bamboo processing residue to the gallic acid solution is 1g:10mL.

[0012] Furthermore, the temperature of the hydrolysis reaction is 150-170° C., and the time is 10-60 min.

[0013] Furthermore, the added amount of the xylanase is 1 U / mL.

[0014] Furthermore, the temperature of the enzymatic hydrolysis reaction is 50° C. and the time is 2 to 6 hours.

[0015] Furthermore, after the high-activity xylooligosaccharide solution is concentrated, the volume is reduced to 1 / 2 to 1 / 3; and the temperature of the refrigeration treatment is 4°C.

[0016] Furthermore, any of the above-mentioned methods for preparing highly active xylo-oligosaccharides by recycling recyclable acid comprises the following steps:

[0017] (1) Weighing the bamboo processing residue, adding a gallic acid solution with a molar concentration of 30 to 100 mM according to a solid-liquid ratio of 1:10, hydrolyzing the mixture at a temperature of 150 to 170° C. for 10 to 60 minutes, cooling the mixture to room temperature, performing solid-liquid separation using a vacuum filter, collecting the supernatant, and obtaining a hydrolyzate rich in high-polymerization-degree xylo-oligosaccharides;

[0018] (2) taking the hydrolyzate rich in high-polymerization degree xylooligosaccharides obtained in step (1), adjusting the pH with sodium hydroxide solution, adding 1 U / mL xylanase to the hydrolyzate, reacting in a constant temperature shaking water bath at 50° C. for 2 to 6 hours, boiling in a boiling water bath for 10 minutes to inactivate the enzyme, and cooling to room temperature to obtain a high-activity xylooligosaccharide solution;

[0019] (3) The high-activity xylooligosaccharide solution is concentrated to 1 / 2 of the original volume of the xylooligosaccharide solution using a rotary evaporator, refrigerated in a 4° C. refrigerator overnight, and solid-liquid separation is performed using a vacuum filter. The solid portion is a recrystallized organic acid, and the liquid portion is a high-concentration high-activity xylooligosaccharide solution.

[0020] Furthermore, in any of the above-mentioned methods for preparing highly active xylo-oligosaccharides by recycling recyclable acid, the yield of the prepared xylo-oligosaccharides is 69.7%, the yield of highly active components xylobiose and xylotriose is 54.0%, and the proportion of gallic acid recovered by recrystallization is 72.8%.

[0021] Compared with the prior art, the advantages of the present invention are as follows:

[0022] 1) The present invention adopts a two-step method of organic acid hydrolysis and enzyme hydrolysis to prepare xylooligosaccharides, and can directly produce xylooligosaccharides using agricultural and forestry wastes such as bamboo processing residues as raw materials, thereby simplifying the production process; the gallic acid used can be recovered and reused by recrystallization, with low recovery energy consumption and high recovery rate.

[0023] 2) In the preparation method disclosed in the present invention, by changing the concentration of gallic acid, the hydrolysis temperature and the hydrolysis time, the yields of the products xylooligosaccharides, xylobiose and xylotriose and xylose can be increased, and the recovery rate of gallic acid can also be increased.

[0024] 3) After gallic acid is used to hydrolyze the bamboo processing residue, the invention controls the enzymatic hydrolysis time to achieve the regulation of the yield of xylooligosaccharides, the yield of xylobiose and xylotriose and the recovery rate of gallic acid.

[0025] 4) Under the conditions of gallic acid concentration of 30 mM, hydrolysis temperature of 170°C, hydrolysis time of 60 min and enzymatic hydrolysis time of 4 h, the yield of oligoxylose prepared by the present invention is as high as 69.7%, and the yield of highly active components xylobiose and xylotriose is 54.0%. At the same time, the gallic acid that can be recovered by recrystallization can reach 72.8%.

[0026] 5) In the preparation method disclosed by the present invention, after gallic acid is recycled and reused once, the yield of xylo-oligosaccharides is 67.2%, the yield of xylobiose and xylotriose is 51.9%, the yield of xylose is 7.2%, and the recovery rate of gallic acid is 53.1%; after gallic acid is recycled and reused 5 times, the yield of xylo-oligosaccharides is 58.6%, the yield of xylobiose and xylotriose is 42.7%, the yield of xylose is 3.7%, and the recovery rate of gallic acid is 32.6%. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 This is a production process flow chart of Example 1 of the present invention. DETAILED DESCRIPTION

[0028] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the specific implementation methods of the present invention are described in detail below in conjunction with specific embodiments.

[0029] Unless otherwise specified, the raw materials or reagents used in the following examples are commercially available products or products obtained by conventional technical means.

[0030] The detection method of the xylooligosaccharide content in the hydrolyzate in the following embodiments is as follows:

[0031] The contents of xylose, xylose, xylose, xylopentaose and xylohexose in the hydrolyzate 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 retaining 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.

[0032] The formulas for calculating the yield of xylo-oligosaccharides and the yield of xylobiose and xylotriose in the xylo-oligosaccharide solution in the following examples are as follows:

[0033] The yield of oligoxylose in the hydrolyzate (%) = the mass of oligoxylose produced by hydrolysis (g) / the mass of xylan in the untreated bamboo processing residue (g) × 100%;

[0034] Yield of xylobiose and xylotriose in xylooligosaccharide solution (%) = mass of xylobiose and xylotriose in hydrolyzate

[0035] (g) / the mass of xylan in the untreated bamboo processing residue (g) × 100%;

[0036] The xylan content in the raw materials in the above formula is determined according to the method of the National Renewable Energy Laboratory of the United States.

[0037] Example 1

[0038] A method for preparing highly active xylo-oligosaccharides by recycling recyclable acid, comprising the following steps:

[0039] (1) Gallic acid hydrolysis

[0040] Weigh 10 g of the bamboo processing residue with a dry weight, add a gallic acid solution with a molar concentration of 30 mM according to a solid-liquid ratio of 1:10, pre-hydrolyze at 170°C for 60 min, cool to room temperature, separate the solid and liquid using a vacuum filter, collect the supernatant, and obtain a hydrolyzate rich in high-polymerization degree xylooligosaccharides.

[0041] (2) Xylanase hydrolysis

[0042] Take 100 mL of the hydrolyzate rich in high-polymerization degree xylooligosaccharides prepared above, adjust the pH to 5.0 with a 5% mass fraction of sodium hydroxide solution, add 1 U / mL of xylanase in the hydrolyzate, react in a constant temperature shaking water bath at 50°C for 4 hours, boil in a boiling water bath for 10 minutes to inactivate the enzyme, and cool to room temperature to obtain a high-activity xylooligosaccharide solution.

[0043] (3) Acid recovery

[0044] The high-activity xylooligosaccharide solution was concentrated to 1 / 2 the volume of the original xylooligosaccharide solution using a rotary evaporator, refrigerated in a 4°C refrigerator overnight, and solid-liquid separation was performed using a vacuum filter. The solid portion was the recrystallized organic acid, and the liquid portion was a high-concentration high-activity xylooligosaccharide solution.

[0045] After determination and calculation, the yields of xylobiose, xylotriose, xylotetraose, xylopentose and xylohexaose in the hydrolysate hydrolyzed by gallic acid were 7.6%, 9.1%, 4.9%, 6.0% and 3.4% respectively, the yield of oligoxylose was 31.0%, the yield of high-polymerized oligoxylose was 41.3%, and the yield of xylose was 7.5%; the yields of xylobiose, xylotriose, xylotetraose, xylopentose and xylohexaose in the hydrolysate hydrolyzed by endoxylanase were 26.8%, 27.2%, 12.4%, 3.1% and 0.2% respectively, the yield of oligoxylose was 69.7%, the yield of xylobiose and xylotriose was 54.0%, and the yield of xylose was 8.4%. After the oligoxylose solution was concentrated to 1 / 2 volume, the recovery rate of gallic acid was 72.8%.

[0046] The final yield of xylo-oligosaccharides obtained in this example was 69.7%, of which the yields of xylobiose and xylotriose were 54.0%, the yield of xylose was 8.4%, and the recovery rate of gallic acid was 72.8%.

[0047] Example 2

[0048] In the method of Example 1 above, the gallic acid concentration, hydrolysis temperature, hydrolysis time and enzymatic hydrolysis time were changed respectively. By measuring and calculating the components in the final hydrolyzate, the yields of different products were compared with the changes in reaction conditions, as shown in Table 1 below.

[0049] Table 1 Comparison of the effects of changing the preparation conditions in Example 1 on the product yield

[0050]

[0051] From the comparison of the treatment conditions of each group and the final product yield in Table 1, it can be seen that with the increase of gallic acid concentration, the yield of xylooligosaccharides, xylobiose and xylotriose, and xylose all increased; when the hydrolysis temperature increased from 150°C to 170°C, not only the yield of xylooligosaccharides, xylobiose and xylotriose, and xylose all increased, but the recovery rate of gallic acid also increased; when the enzymatic hydrolysis time increased, the yield of xylooligosaccharides, xylobiose and xylotriose increased, but the recovery rate of gallic acid decreased.

[0052] Example 3

[0053] In this embodiment, the gallic acid recovered in Example 1 is used to prepare acid solution, which is used again to hydrolyze the bamboo processing residue. The specific steps are the same as in Example 1, the only difference being that the acid solution uses the recovered gallic acid. The yields of xylobiose, xylotriose, xylotetrose, xylopentose and xylohexaose in the final obtained xylo-oligosaccharide solution are 26.9%, 25.2%, 11.4%, 4.5% and 0.6%, respectively, the yield of xylo-oligosaccharides is 68.6%, the yields of xylobiose and xylotriose are 52.1%, and the yield of xylose is 7.5%. After the xylo-oligosaccharide solution is concentrated to 1 / 2 volume, the recovery rate of gallic acid is 66.1% (calculated based on the amount of gallic acid used in Example 1).

[0054] Example 4

[0055] In this embodiment, the gallic acid recovered in Example 3 is used to prepare acid solution, which is used again to hydrolyze the bamboo processing residue. The specific steps are the same as those in Example 1, with the only difference being that the gallic acid recovered for the first time is used in the acid solution. The yields of xylobiose, xylotriose, xylotetraose, xylopentaose and xylohexaose in the final obtained xylo-oligosaccharide solution are 26.0%, 25.9%, 10.4%, 3.9% and 1.0%, respectively, the yield of xylo-oligosaccharides is 67.2%, the yields of xylobiose and xylotriose are 51.9%, and the yield of xylose is 7.2%. After the xylo-oligosaccharide solution is concentrated to 1 / 2 volume, the recovery rate of gallic acid is 53.1% (calculated based on the amount of gallic acid used in Example 1).

[0056] Example 5

[0057] In this embodiment, the gallic acid recovered in Example 4 is used to prepare acid solution, which is used again to hydrolyze the bamboo processing residue. The specific steps are the same as those in Example 1, with the only difference being that the gallic acid recovered for the second time is used in the acid solution. The yields of xylobiose, xylotriose, xylotetraose, xylopentaose and xylohexaose in the final obtained xylo-oligosaccharide solution are 23.0%, 23.9%, 13.4%, 4.9% and 1.6%, respectively, the yield of xylo-oligosaccharides is 66.8%, the yields of xylobiose and xylotriose are 46.9%, and the yield of xylose is 6.3%. After the xylo-oligosaccharide solution is concentrated to 1 / 2 volume, the recovery rate of gallic acid is 42.1% (calculated based on the amount of gallic acid used in Example 1).

[0058] Example 6

[0059] In this embodiment, the gallic acid recovered in Example 5 is used to prepare acid solution, which is used again to hydrolyze the bamboo processing residue. The specific steps are the same as those in Example 1, with the only difference being that the gallic acid recovered for the third time is used in the acid solution. The yields of xylobiose, xylotriose, xylotetraose, xylopentaose and xylohexaose in the final obtained xylo-oligosaccharide solution are 25.7%, 22.9%, 10.4%, 3.9% and 1.8% respectively, the yield of xylo-oligosaccharides is 64.7%, the yields of xylobiose and xylotriose are 48.6%, and the yield of xylose is 3.9%. After the xylo-oligosaccharide solution is concentrated to 1 / 2 volume, the recovery rate of gallic acid is 35.6% (calculated based on the amount of gallic acid used in Example 1).

[0060] Example 7

[0061] In this embodiment, the gallic acid recovered in Example 6 is used to prepare acid solution, which is used again to hydrolyze the bamboo processing residue. The specific steps are the same as those in Example 1, with the only difference being that the gallic acid recovered for the fourth time is used in the acid solution. The yields of xylobiose, xylotriose, xylotetraose, xylopentose and xylohexaose in the final obtained xylo-oligosaccharide solution are 21.9%, 20.8%, 9.9%, 3.9% and 2.1% respectively, the yield of xylo-oligosaccharides is 58.6%, the yields of xylobiose and xylotriose are 42.7%, and the yield of xylose is 3.7%. After the xylo-oligosaccharide solution is concentrated to 1 / 2 volume, the recovery rate of gallic acid is 32.6% (calculated based on the amount of gallic acid used in Example 1).

[0062] By comparing the results of the above-mentioned embodiments of the present invention, it can be seen that the method provided by the present invention controls the degradation of a large amount of hemicellulose in bamboo scraps into oligoxylose, and the yield of the prepared oligoxylose is up to 69.7%, and the yield of highly active components xylobiose and xylotriose is 54.0%, and 72.8% of gallic acid can be recovered by recrystallization. The recovered gallic acid is reused again. In the 5-cycle process, the yield of oligoxylose is 58.6% to 68.6%, and the yield of xylobiose and xylotriose is 42.7% to 52.1%. After 5 cycles, the recovery rate of gallic acid is 32.6% (calculated based on the gallic acid dosage of Example 1).

[0063] Comparative Example 1

[0064] In this comparative example, hydrochloric acid was used instead of gallic acid to hydrolyze the bamboo processing residue. The experimental conditions were the same as those in Example 1, except that a 50 mM hydrochloric acid solution was used to hydrolyze the bamboo processing residue. The yields of xylobiose, xylotriose, xylotetose, xylopentose and xylohexaose in the final obtained xylo-oligosaccharide solution were 3.9%, 2.8%, 0.2%, 0.0% and 0.0%, respectively, the yield of xylo-oligosaccharides was 6.9%, the yields of xylobiose and xylotriose were 6.7%, and the yield of xylose was 58.7%.

[0065] Comparative Example 2

[0066] In this comparative example, sulfuric acid was used instead of gallic acid to hydrolyze the bamboo processing residue. The experimental conditions were the same as those in Example 1, except that a 50 mM hydrochloric acid solution was used to hydrolyze the bamboo processing residue. The yields of xylobiose, xylotriose, xylotetose, xylopentose and xylohexaose in the resulting xylo-oligosaccharide solution were 4.2%, 2.9%, 0.8%, 0.1% and 0.0%, respectively, the yield of xylo-oligosaccharides was 8.0%, the yields of xylobiose and xylotriose were 7.1%, and the yield of xylose was 60.1%.

[0067] Comparative Example 3

[0068] In this comparative example, acetic acid was used instead of gallic acid to hydrolyze the bamboo processing residue. The experimental conditions were the same as those in Example 1, except that an acetic acid solution with a concentration of 50 mM was used to hydrolyze the bamboo processing residue. The yields of xylobiose, xylotriose, xylotetose, xylopentose and xylohexaose in the final obtained xylo-oligosaccharide solution were 23.2%, 19.1%, 6.8%, 3.1% and 1.0%, respectively, the yield of xylo-oligosaccharides was 53.2%, the yields of xylobiose and xylotriose were 42.3%, and the yield of xylose was 21.1%.

[0069] The use of gallic acid for xylan hydrolysis has obvious advantages over traditional inorganic acids (such as hydrochloric acid, sulfuric acid) and acetic acid. Gallic acid provides a mild acidic environment, can effectively control the selectivity of xylan hydrolysis reaction, reduce excessive degradation, significantly improve the yield and purity of oligoxylose, and significantly increase the yield of oligoxylose and the yield of xylobiose and xylotriose. However, inorganic acid, due to its strong acidity, easily leads to excessive degradation of xylan, generates more xylose, causes the yield and purity of oligoxylose to decrease, and the recovery difficulty of inorganic acid and acetic acid is large. The recovery rate of gallic acid is high, and it can be recycled for many times, increases the utilization efficiency of acid, and reduces production costs. In addition, the use of low-concentration gallic acid has less impact on the environment and equipment, and is more environmentally friendly. Therefore, the present invention adopts gallic acid to hydrolyze bamboo processing residues to prepare high-activity oligoxylose, which not only improves the yield and purity of oligoxylose, but also helps to improve the economy and sustainability of the reaction, which is significantly better than the traditional acid hydrolysis method.

[0070] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for preparing highly active xylo-oligosaccharides by recycling recyclable acid, characterized in that: The bamboo processing residue and gallic acid solution are hydrolyzed, and after solid-liquid separation, a high-polymerization degree xylooligosaccharide solution is obtained; after adjusting the pH, xylanase is added to the obtained high-polymerization degree xylooligosaccharide solution to obtain a high-activity xylooligosaccharide solution, which is concentrated and refrigerated, and the remaining acid is recovered by recrystallization to obtain a high-concentration high-activity xylooligosaccharide solution; wherein the acid recovery rate is 30% to 80%.

2. The method for preparing highly active xylo-oligosaccharides by recycling recyclable acid according to claim 1, characterized in that: The bamboo processing residue is obtained by crushing and then sieving, and the sieving mesh number is not less than 60 meshes.

3. The method for preparing highly active xylo-oligosaccharides by recycling recyclable acid according to claim 1, characterized in that: The concentration of the gallic acid solution is 30-100 mM.

4. The method for preparing highly active xylo-oligosaccharides by recycling recyclable acid according to claim 1, characterized in that: The mass volume ratio of the bamboo processing residue to the gallic acid solution is 1g:10mL.

5. The method for preparing highly active xylo-oligosaccharides by recycling recyclable acid according to claim 1, characterized in that: The temperature of the hydrolysis reaction is 150-170° C., and the time is 10-60 minutes.

6. The method for preparing highly active xylo-oligosaccharides by recycling recyclable acid according to claim 1, characterized in that: The added amount of the xylanase is 1 U / mL.

7. The method for preparing highly active xylo-oligosaccharides by recycling recyclable acid according to claim 1, characterized in that: The temperature of the enzymatic hydrolysis reaction is 50° C. and the time is 2 to 6 hours.

8. The method for preparing highly active xylo-oligosaccharides by recycling recyclable acid according to claim 1, characterized in that: After the high-activity xylooligosaccharide solution is concentrated, the volume is reduced to 1 / 2 to 1 / 3; the temperature of the refrigeration treatment is 4°C.

9. The method for preparing highly active xylo-oligosaccharides by recycling recyclable acid according to any one of claims 1 to 8, characterized in that: Here are the steps: (1) Weighing the bamboo processing residue, adding a gallic acid solution with a molar concentration of 30 to 100 mM according to a solid-liquid ratio of 1:10, hydrolyzing the mixture at a temperature of 150 to 170° C. for 10 to 60 minutes, cooling the mixture to room temperature, performing solid-liquid separation using a vacuum filter, collecting the supernatant, and obtaining a hydrolyzate rich in high-polymerization-degree xylo-oligosaccharides; (2) taking the hydrolyzate rich in high-polymerization degree xylooligosaccharides obtained in step (1), adjusting the pH with sodium hydroxide solution, adding 1 U / mL xylanase to the hydrolyzate, reacting in a constant temperature shaking water bath at 50° C. for 2 to 6 hours, boiling in a boiling water bath for 10 minutes to inactivate the enzyme, and cooling to room temperature to obtain a high-activity xylooligosaccharide solution; (3) The high-activity xylooligosaccharide solution is concentrated to 1 / 2 of the original volume of the xylooligosaccharide solution using a rotary evaporator, refrigerated in a 4° C. refrigerator overnight, and solid-liquid separation is performed using a vacuum filter. The solid portion is a recrystallized organic acid, and the liquid portion is a high-concentration high-activity xylooligosaccharide solution.

10. The method for preparing highly active xylo-oligosaccharides by recycling recyclable acid according to any one of claims 1 to 9, characterized in that: The yield of the prepared xylooligosaccharides was 69.7%, the yield of the highly active components xylobiose and xylotriose was 54.0%, and the proportion of gallic acid recovered by recrystallization was 72.8%.

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