CN105463040A - Method for raising yield of xylooligosaccharide - Google Patents

Abstract

The invention discloses a method for increasing the yield of xylooligosaccharides, which belongs to the fields of chemical industry and food. The method uses corn stalks as raw materials, first air-dried, pulverized, and soaked in water and ethanol to remove water-soluble and fat-soluble impurities in the raw materials, and then use sodium chlorite method for delignification treatment; secondly, through alkali extraction method Obtain the xylan extract, adjust the pH to neutral, concentrate and desalt; finally use enzymatic hydrolysis and acid hydrolysis to depolymerize xylan, and then freeze-dry after centrifugation and activated carbon treatment to obtain oligomeric xylan sugar products. The present invention has the following advantages: (1) the hydrolysis reaction of the xylan liquid prepared by the present invention saves the complicated separation and drying steps in the preparation process; The sugar yield can be improved without too much impact on the acidity and alkalinity of the product; (3) the use of straw as raw material has good economic benefits and ecological significance.

Description

A method for improving xylo-oligosaccharide yield

technical field

The invention relates to a method for increasing the yield of xylooligosaccharides, which belongs to the technical fields of chemical industry and food.

Background technique

At present, the hydrolysis methods for degrading hemicellulose into xylooligosaccharides are mainly divided into four types: enzymatic hydrolysis, acid hydrolysis, self-hydrolysis, and chemical enzymatic hydrolysis. Among them, enzymatic hydrolysis relies on its mild reaction conditions and low pollution. , has become the mainstream method for the preparation of xylooligosaccharides. However, at present, the yield of xylo-oligosaccharides produced by single enzymatic or acid hydrolysis is generally not high. Insufficient binding sites for enzymes and sugars, etc. Acid degradation is more thorough, but there is no specificity of bond breaking. Therefore, if a method of organically combining enzymatic hydrolysis and acid hydrolysis to achieve a higher yield of xylo-oligosaccharides can be found, it will have substantial significance for industrial production. In addition, in the traditional extraction process, alcohol precipitation method is used to separate and obtain xylan. Although this method can reduce the content of residual lignin in xylan, but because ethanol has obvious inhibitory effect on subsequent enzymatic hydrolysis, so on the basis of separation Ethanol still needs to be removed by drying and other methods, and the subsequent hydrolysis process is carried out in a liquid state, so this process is too cumbersome. If the lignin is removed in the pretreatment stage, alcohol precipitation method is not used, and each process step is completed in a liquid state, it will not only make it easier for xylanase to contact xylan during the enzymolysis process, but also significantly improve Manipulability of the entire process.

China Agricultural University disclosed the "preparation method of xylooligosaccharides" (application number 01131171.1), using various corn cobs as raw materials, after pretreatment with alkali metal hydroxides, direct pyrolysis under the action of a weak acid catalyst, and then using Enzymatic preparation of xylooligosaccharides, and finally refined to obtain high-purity xylooligosaccharide products, but the yield of this invention is low, and there is no further treatment of the hydrolysis residue, resulting in the waste of some hemicellulose components. Li Xiufang and others disclosed "the method of using biological straw to prepare xylo-oligosaccharides, dissolving pulp and bio-fuel". The residual enzymolysis slag after enzymolysis was pulped, washed and screened, delignified, pretreated, and bleached. Preparation of dissolving pulp and a series of treatments, so as to utilize the enzymolysis slag, the technological process of this invention is complicated and the energy consumption is relatively large. If the enzymatic slag is further degraded to produce sugar, the process is not only simple, but also compatible with the overall process flow, which can directly increase the xylo-oligosaccharide yield by about 6%-10%.

Contents of the invention

The invention provides a kind of method that improves xylo-oligosaccharide productive rate, adopts following technical scheme:

a Raw material preparation: After the straw is air-dried, use a pulverizer to crush it until the particle size is below 2mm;

b Raw material treatment: put the above corn stalk powder into a heat-resistant container, soak in boiling water for 1-3h, separate the solid and liquid to take the filter residue, and soak in 75-95% (v/v) ethanol for 1-3h again to remove the corn stalk For water-soluble and fat-soluble impurities in the raw materials, the treated mixture is separated from solid and liquid, and the filter residue is taken, dried at 40-80°C until the solid content is greater than 90%, and then the solid-liquid ratio is 1:10-15 (w/v) Add 6% (w/v) sodium chlorite, and use 8%-12% (w/v) acetic acid to adjust the pH to 3.6-3.8, then treat at 75°C for 2-4h;

c xylan preparation: use 8-15% (w/v) NaOH solution to treat the above-mentioned treated stalks at 90-160°C for 0.5- 2h, take the filtrate after solid-liquid separation;

d Adjust the pH of the filtrate to 6-8 with concentrated HCl, desalt after concentration, and obtain the xylan extract;

e enzyme hydrolysis: the above-mentioned xylan solid is dissolved in deionized water with 1.5-2.5% (w/v) substrate concentration, and 1% (w/w) commercial xylanase preparation is added by substrate weight, and the enzyme The hydrolysis temperature is 45-55°C, and the enzymatic hydrolysis is 4-24h under stirring conditions;

f Acid treatment: separate the liquid from the solid of the enzymolysis liquid, prepare the enzymolysis residue as a 1-2% (w/v) mixture as the acid treatment substrate, use 0.8-1.2% (v/v) acetic acid at 140-160°C Under the reaction 60-120min;

g Purification: Combine the enzymatic hydrolysis solution of step e and the acid hydrolysis solution of step f, adjust the pH to 4.0, use 4% (w/v) activated carbon to adsorb, and then use 15%, 30%, and 60% of 1 volume ethanol for eluting and concentrating under reduced pressure to obtain a xylooligosaccharide liquid, which is then freeze-dried to obtain a xylooligosaccharide product.

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

1. The hydrolysis reaction of the xylan liquid prepared by the present invention saves the cumbersome separation and drying steps in the preparation process, and is more conducive to the uniformity of the preparation process;

2. Treating the enzymatic residue with acetic acid at high temperature can increase the yield of xylo-oligosaccharides without too much impact on the acidity and alkalinity of the product, and the reduction of the molecular weight of the product is conducive to its solubility and reduces the residue of solid residue during the hydrolysis process ;

3. In the pretreatment stage, the removal of water-soluble and fat-soluble impurities in straw raw materials, as well as the removal of lignin to a certain extent, reduces the influence of factors that are not conducive to subsequent hydrolysis experiments, and reduces the color value of xylan. Facilitate subsequent product purification;

4. Using agricultural waste straw as raw material has good economic benefits and ecological significance;

detailed description

The enzyme used in the present invention is an endo-xylanase; the xylo-oligosaccharide (xylobiose-xylose) content is measured by high-performance liquid chromatography (HPLC); The hemicellulose content is calculated based on the benchmark.

The present invention will be further described below by way of examples, but its content is not limited thereto.

Example 1

Raw material preparation: After the corn stalks are air-dried, use a high-speed mill to pulverize them until the particle size is below 2mm; Raw material processing: Put the above corn stalk powder into a heat-resistant container, soak in boiling water for 2 hours, separate the solid-liquid to take the filter residue, and use it again for 80 Soak in % ethanol for 2 hours to remove water-soluble and fat-soluble impurities in the corn stalk raw material, separate the solid-liquid from the treated mixture and take the filter residue, dry at 60°C until the solid content is greater than 90%, and then mix with 1:10 (w/ v) Solid-to-liquid ratio Add 6% (w/v) sodium chlorite, and use 10% (w/v) HAc to adjust the pH to 3.6-3.8, then treat at 75°C for 4h; xylan preparation: the above Treat corn stalks with 10% (w/v) NaOH solution, set the solid-to-liquid ratio of 1:10 (w/v), treat at 105°C for 2 hours, and take the filtrate after solid-liquid separation; adjust the filtrate with concentrated HCl After the pH reaches 6-8, concentrate and desalt to obtain the xylan extract; enzymatic hydrolysis: dissolve the above xylan solid in deionized water at a substrate concentration of 2% (w/v), Add 1% (w/w) commercial xylanase preparation, enzymolysis temperature 50 ℃, enzymolysis 18h under stirring conditions; acid treatment: after solid-liquid separation of enzymolysis liquid, prepare enzymolysis residue to 1% (w/w v) The mixture is used as an acid treatment substrate, using 1% (v/v) acetic acid to react at 160°C for 60 minutes; Activated carbon adsorption, followed by elution with 1 volume of 15%, 30%, and 60% ethanol, and concentration under reduced pressure to obtain a xylooligosaccharide liquid, which was freeze-dried to obtain a xylooligosaccharide product.

After each step of hydrolysis is completed, samples are taken, centrifuged, passed through a membrane, and the concentration of oligosaccharides and monosaccharides in the hydrolyzed solution is analyzed by high performance liquid chromatography. It is determined that the yield of xylooligosaccharides in the enzymatic hydrolysis process is 42.6%, the yield of xylooligosaccharides in the acid hydrolysis process is 7.5%, and the total yield of xylooligosaccharides reaches 50.1%.

Example 2

The preparation, enzymatic hydrolysis, purification steps and related parameters of xylan in this example are the same as those in Example 1. In the subsequent steps, 0.8% (v/v) acetic acid was used for acid hydrolysis at 140° C. for 60 minutes.

It was determined that under this condition, the yield of xylooligosaccharides in the acid hydrolysis process was 6.4%, the total yield of xylooligosaccharides reached 49%, and the total yield of monosaccharides reached 11.2%, that is, the total yield of sugars was 60.2%.

Example 3

The preparation, enzymatic hydrolysis, purification steps and related parameters of xylan in this example are the same as those in Example 1. In the subsequent steps, 1% (v/v) acetic acid was used for acid hydrolysis at 160° C. for 120 minutes.

It was determined that under this condition, the yield of xylooligosaccharides in the acid hydrolysis process was 9.7%, the total yield of xylooligosaccharides reached 52.3%, and the total yield of monosaccharides reached 14.6%, that is, the yield of total sugars was 66.9%.

Claims (2)

1. A method for improving xylo-oligosaccharide yield, characterized in that comprising the following processing steps: a Raw material preparation: After the straw is air-dried, use a pulverizer to crush it until the particle size is below 2mm; b Raw material treatment: put the above corn stalk powder into a heat-resistant container, soak in boiling water for 1-3h, separate the solid and liquid to take the filter residue, and soak in 75-95% (v/v) ethanol for 1-3h again to remove the corn stalk For water-soluble and fat-soluble impurities in the raw materials, the treated mixture is separated from solid and liquid, and the filter residue is taken, dried at 40-80°C until the solid content is greater than 90%, and then the solid-liquid ratio is 1:10-15 (w/v) Add 6% (w/v) sodium chlorite, and use 8%-12% (w/v) acetic acid to adjust the pH to 3.6-3.8, then treat at 75°C for 2-4h; c xylan preparation: use 8-15% (w/v) NaOH solution to treat the above-mentioned treated stalks at 90-160°C for 0.5- 2h, take the filtrate after solid-liquid separation; d Adjust the pH of the filtrate to 6-8 with concentrated HCl, desalt after concentration, and obtain the xylan extract; e enzyme hydrolysis: the above-mentioned xylan solid is dissolved in deionized water with 1.5-2.5% (w/v) substrate concentration, and 1% (w/w) commercial xylanase preparation is added by substrate weight, and the enzyme The hydrolysis temperature is 45-55°C, and the enzymatic hydrolysis is 4-24h under stirring conditions; f acid treatment: separate the liquid from the solid of the enzymolysis liquid, prepare the enzymolysis residue as a 1-2% (w/v) mixture as the acid treatment substrate, use 0.8-1.2% (v/v) acetic acid at 140-160°C Under the reaction 60-120min; g Purification: Combine the enzymatic hydrolysis solution of step e and the acid hydrolysis solution of step f, adjust the pH to 4.0, use 4% (w/v) activated carbon to adsorb, and then use 15%, 30%, and 60% of 1 volume ethanol for eluting and concentrating under reduced pressure to obtain a xylooligosaccharide liquid, which is then freeze-dried to obtain a xylooligosaccharide product. 2. a kind of method for improving xylo-oligosaccharide yield as claimed in claim 1, is characterized in that described straw refers to corn straw, wheat straw, rice straw, sorghum straw, sunflower straw.