CN1403591A - Prepn of oligoxylose - Google Patents

Abstract

The invention discloses a preparation method of xylooligosaccharide, which belongs to the field of food processing. The purpose is to realize the industrialized production method of converting hemicellulose in corncobs into high-quality xylo-oligosaccharides. The specific technical scheme includes pretreating raw corn cobs in aqueous alkali metal hydroxide solution; then performing direct thermal cracking under the action of weak acid catalysts such as acetic acid, formic acid, citric acid, etc.; Reaction, decolorization by activated carbon and removal of impurities by ion exchange resin, and then vacuum concentration, maltodextrin and the like can be used as excipients, and xylooligosaccharide powder is obtained by spray drying.

Description

The preparation method of xylo-oligosaccharide

The invention relates to a method for converting hemicellulose in corn cobs into xylooligosaccharides, belonging to the field of food processing.

Xylooligosaccharides, also known as xylooligosaccharides, are composed of 2 to 7 D-xyloses bound by β-1,4-xylosidic bonds, and are an important member of the functional oligosaccharide family. Its sweetness is lower than that of sucrose and glucose, similar to maltose, about 40% of sucrose. Xylo-oligosaccharides have good stability to pH and heat, and basically do not decompose even when heated under acidic conditions (pH=2.5-7), and are suitable for use in acidic beverages such as yogurt, lactic acid bacteria beverages, and carbonated beverages. The figure below shows the main components and chemical structure of xylooligosaccharides.

Xylo-oligosaccharides are extremely difficult to be digested and absorbed, and have a high residual rate in the intestinal tract. They have excellent proliferation of bifidobacteria, and their selective utilization is higher than that of other functional oligosaccharides. The physiological functions of xylooligosaccharides that have been confirmed by research mainly include: (1) provide low energy, meet the requirements of people who like sweets and worry about gaining weight, and can also be eaten by diabetics, obese patients and hypertensive patients; 2) activate bifidobacteria in the intestinal tract and promote their proliferation, inhibit pathogenic bacteria, and prevent diarrhea; (3) prevent constipation; (4) reduce serum cholesterol levels, lower blood pressure, generate nutrients, enhance body immunity and resist tumors; ( 5) It will not cause dental caries and is beneficial to oral health; (6) Remove intestinal toxins.

Xylo-oligosaccharides are generally made of plant resources rich in xylan, such as wood chips, corncobs, cottonseed hulls, rice husks, and rapeseed husks, which are hydrolyzed by endo-xylanase and then separated, Refined and made. my country is rich in corn cob resources, but there is no report about the method of extracting xylo-oligosaccharides from corn cobs.

The purpose of the present invention is to provide a kind of preparation method of the xylo-oligosaccharide that uses corn cob as raw material.

In order to achieve the purpose of the present invention, the technical scheme adopted includes the use of alkali metal hydroxide solution to pretreat corn cob powder, washing, dissolution of xylan in corn cob powder, xylanase hydrolysis reaction and xylooligosaccharide solution. Decolorization, impurity removal, concentration and drying technologies, including:

(1) The alkali metal hydroxide solution used in the pretreatment of corn cob flour is potassium hydroxide and sodium hydroxide

Equal solution, during pretreatment, the concentration of alkali metal hydroxide solution is 0.5% to 1.5%, and the treatment

 The temperature is 30℃～60℃, the time is 30min～120min, the corn cob powder and the alkali metal hydroxide are dissolved

The liquid weight ratio is 1:8～1:12;

(2) The dissolution of xylan in corncob powder adopts the method of direct heat cooking and cracking, and the cooking temperature is 155°C

～180°C, cooking time 30min～120min, the weight ratio of corncob flour to water is 1:6～1:

10. Weak acid catalysts such as acetic acid, formic acid, citric acid, etc. are used in the cooking process.

  0.2% to 1.5% of the weight of corncob flour;

(3) The enzymatic hydrolysis reaction uses sp.E-86 type xylan enzyme solution, and the enzymatic hydrolysis reaction temperature is 45°C to 60°C

℃, the enzymatic hydrolysis reaction time is 4h～10h, the ratio of xylan enzyme solution to corncob powder is

1ml/1.2g～1ml/1.6g, the enzyme activity of xylanase solution is 50UI/ml～70UI/ml;

(4) The decolorization of xylo-oligosaccharide solution adopts activated carbon powder, and the specific conditions are that the decolorization temperature is 80°C, and the activity

The volume ratio of charcoal to sugar solution is 0.5% to 1.5%, and the decolorization time is 25min to 40min;

(5) Xylo-oligosaccharide solution adopts strong acid cationic resin such as E306FG and macroporous weak base anion

Exchange resin such as D001 for impurity removal.

In the above-mentioned preparation method of xylo-oligosaccharides, the optimal alkali metal hydroxide used in the pretreatment of corncob powder is sodium hydroxide, the optimal concentration is 0.7%, the optimal temperature is 55° C., and the optimal treatment time is 60 min. The optimum material-to-liquid weight ratio is 1:10.

In the above-mentioned preparation method of xylo-oligosaccharides, when the corn cob powder is subjected to direct heat cooking and cracking, the optimal cooking temperature is 165° C., the cooking time is 120 min, the optimal catalyst is acetic acid, and the addition amount is 0.5% of the weight of the corn cob powder.

In the above-mentioned preparation method of xylo-oligosaccharides, the optimal temperature of xylanase hydrolysis reaction is 55°C, the reaction time is 8h, the ratio of xylanase liquid to corncob powder is 1ml/1.45g, and the xylanase liquid The enzyme activity is 60UI/ml.

In the decolorization process of the above xylooligosaccharide preparation method, the optimal volume ratio of activated carbon to sugar solution is 1%, and the decolorization time is 30min.

In the above-mentioned preparation method of xylo-oligosaccharides, double-effect vacuum concentration is adopted, and the first concentration is at 75° C., and the xylo-oligosaccharide liquid is concentrated to a syrup with a total sugar content of 15% to 20%; At 75°C, the xylooligosaccharide liquid is concentrated to a syrup with a total sugar content of 55% to 75%.

In the preparation method of above-mentioned xylo-oligosaccharide, can adopt spray drying method to prepare xylo-oligosaccharide powder, the inlet temperature of hot air is 130 ℃～160 ℃ during spray drying, and outlet temperature is 65 ℃～85 ℃, and material flow rate is 0.8-1.2m ³ /h, the residence time in the tower is 10-20 seconds, and the excipient is maltodextrin, β-cyclodextrin or corn starch.

In the above-mentioned preparation method of xylo-oligosaccharide, the most suitable excipient for preparing xylo-oligosaccharide powder is maltodextrin.

In the above preparation method, the selection of xylanase and the preparation process, as well as the selection of catalyst and reaction conditions in the direct heat steam explosion cracking process are the key.

The present invention has the following advantages:

(1) Use alkali metal hydroxides such as potassium hydroxide, sodium hydroxide and other solutions at a certain temperature and time

Pretreatment of corncobs under in-situ conditions removes most of the lignin in corncobs,

And make its organizational structure relatively loose, which is conducive to the dissolution of xylan in corn cobs;

(2) The combination of high temperature cooking and direct heat steam explosion, that is, direct heat cooking and cracking, is used to process corn

cob, which can dissolve the xylan in the corncob to the maximum extent, which improves the work efficiency,

 It also reduces the cost of the equipment, making the industrial production of xylo-oligosaccharides relatively easy and simple

Convenience;

(3) The xylanase solution produced by the spE-86 strain was selected to hydrolyze the product obtained by direct heat cooking and cracking corn cobs.

The obtained xylan liquid can obtain xylooligosaccharide products mainly composed of xylobiose.

Detailed flow chart of the present invention is as follows:

Corn cob

↓ ↓

removal of impurities

↓ ↓

smash

↓ ↓

Preprocessing

↓ ↓

                         

↓ ↓

               

↓ ↓

        High temperature cooking cracking

↓ ↓

Vapor-liquid separation

↓ ↓

Xylanase hydrolysis

The invention provides a method for converting hemicellulose in corncob flour into xylooligosaccharides by means of combining enzyme method and physical chemistry. The method comprises the steps of pretreating raw corncobs in aqueous solutions of alkali metal hydroxides such as potassium hydroxide and sodium hydroxide at a certain temperature of 30°C to 60°C and for a time of 30min to 120min; pretreating the pretreated corncobs Under the action of weak acid catalysts such as acetic acid, formic acid, citric acid, etc., use direct heat steam at 155°C to 180°C for 30min to 120min; Under the action of carbohydrase solution, react for 4h-10h, then heat up to 90°C-105°C, keep warm for 10min-30min; decolorize the obtained xylo-oligosaccharide sugar solution through activated carbon and remove impurities with cation exchange resins such as E306FG and anion exchange resins such as D001 , and then vacuum concentrated to 55% to 75% sugar solution, using maltodextrin, β-cyclodextrin or corn starch as excipients, spray-dried to obtain xylooligosaccharides with a total sugar content of 20% to 50% powder.

The sp.E-86 type xylanase liquid used in the present invention is prepared by liquid fermentation of Streptomyces sp.E-86 strain.

In order to better remove the color of the obtained xylo-oligosaccharide liquid, the decolorization of activated carbon of the present invention can be performed twice.

The impurity removal process of the ion exchange resin of the present invention is positive and negative, the temperature of the xylo-oligosaccharide sugar solution is less than 45°C, the flow rate of the xylo-oligosaccharide sugar solution per hour is 1 to 2 times the volume of the resin, and the conductivity of the obtained sugar solution is less than 50VS/ cm, pH 4.5-6.0.

The invention is illustrated with the following examples:

Example 1

Weigh 500kg of 40-mesh-60mesh corn cob powder, add it into 4000L solution containing 0.7% sodium hydroxide, stir evenly at 75rpm, and stir at 55°C for 60min. After centrifugal filtration, the filter cake was washed with water until the pH was 7.0. Slurry the filter cake with water, the solid-to-liquid ratio is 1:8, add 2.5kg of acetic acid, cook and crack at 160°C for 2 hours, enter the enzymolysis tank through a vapor-liquid separator, and cool to 55°C. Regulate the pH of reaction solution to 5.5 with the sodium hydroxide solution of 1mol/ml hydrochloric acid solution and 1mol/ml respectively, add sp.E-86 type xylanase solution by the amount of 1ml enzyme solution/1.45g corncob powder, its The enzyme activity is 60UI/ml. After 8 hours of enzymatic hydrolysis reaction, inactivate at 90°C for 15 minutes, cool to 60°C for frame filtration. Add activated carbon powder with a total volume of 1% to the sugar liquid, stir and decolorize at 80° C. for 30 minutes, filter, and concentrate the sugar liquid at 75° C. to a xylooligosaccharide syrup with a total sugar content of 15%. The 15% syrup was decolorized for the second time, and the decolorization conditions were the same as the first time. Then put the decolorized syrup twice on the ion exchange resin column to remove impurities, the conductivity of the sugar solution is less than 50VS/cm, and the pH is 5.0. Finally, at 75°C, the sugar solution was concentrated to light yellow viscous xylooligosaccharide syrup with a total sugar content of 70%, with a yield of 8.8%.

Example 2

Weigh 500kg of 40-mesh-60mesh corn cob powder, add it into 4000L solution containing 0.5% sodium hydroxide, stir evenly at 75rpm, and stir at 55°C for 60min. After centrifugal filtration, the filter cake was washed with water until the pH was 7.0. Make the filter cake into a slurry with water, the solid-to-liquid ratio is 1:8, add 2.0kg of citric acid, cook and crack at 160°C for 2 hours, enter the enzymolysis tank through a vapor-liquid separator, and cool to 55°C. Regulate the pH of reaction solution to 5.5 with the sodium hydroxide solution of 1mol/ml hydrochloric acid solution and 1mol/ml respectively, according to the amount sp.E-86 type xylan enzyme solution of 1ml enzyme solution/1.3g corncob powder, its enzyme The activity is 70UI/ml. After 6 hours of enzymatic hydrolysis, inactivate at 90°C for 15 minutes, cool to 60°C for frame filtration. Add activated carbon powder with a total volume of 1% to the sugar solution, stir and decolorize at 80° C. for 30 minutes, filter, and concentrate the sugar solution at 75° C. to xylooligosaccharide syrup with a total sugar content of 20%. The 20% syrup is decolorized for the second time, and the decolorization conditions are the same as the first time. Then put the decolorized syrup twice on the ion exchange resin column to remove impurities, the conductivity of the sugar solution is less than 50VS/cm, and the pH is 5.0. Finally, at 75°C, the sugar solution was concentrated to light yellow viscous xylo-oligosaccharide syrup with a total sugar content of 70%, with a yield of 8.5%.

Example 3

Weigh 500kg of 40-mesh-60mesh corn cob powder, add it into 4000L solution containing 0.7% sodium hydroxide, stir evenly at 75rpm, and stir at 55°C for 60min. After centrifugal filtration, the filter cake was washed with water until the pH was 7.0. Slurry the filter cake with water, the solid-to-liquid ratio is 1:8, cook and crack at 165°C for 2 hours, enter the enzymolysis tank through a vapor-liquid separator, and cool to 55°C. Regulate the pH of reaction solution to 5.5 with the sodium hydroxide solution of 1mol/ml hydrochloric acid solution and 1mol/ml respectively, add sp.E-86 type xylanase solution by the amount of 1ml enzyme solution/1.45g corncob powder, its The enzyme activity is 60UI/ml. After 8 hours of enzymatic hydrolysis reaction, inactivate at 90°C for 15 minutes, cool to 60°C for frame filtration. Add activated carbon powder with a total volume of 1% to the sugar liquid, stir and decolorize at 80° C. for 30 minutes, filter, and concentrate the sugar liquid at 75° C. to a xylooligosaccharide syrup with a total sugar content of 15%. The 15% syrup was decolorized for the second time, and the decolorization conditions were the same as the first time. Then put the decolorized syrup twice on the ion exchange resin column to remove impurities, the conductivity of the sugar solution is less than 50VS/cm, and the pH is 5.0. Finally, at 75°C, the sugar solution was concentrated to light yellow viscous xylooligosaccharide syrup with a total sugar content of 70%, with a yield of 7.6%.

Example 4

In the 100kg 40% xylooligosaccharide syrup made by the conditions and steps in Example 1, adding content is 120kg of 98% maltodextrin, at 145°C of inlet temperature, 85°C of outlet temperature, the material flow rate is 1.0m ³ /h under the condition of spray-drying, to obtain a xylo-oligosaccharide powder product with a content of 25%.

Claims (8)

1, a kind of preparation method of xylo-oligosaccharide comprises adopting alkali metal hydroxide solution to pretreat corncob powder, washing, the stripping of xylan in corncob powder, xylanase hydrolysis reaction and xylo-oligosaccharide solution Decolorization, impurity removal, concentration and drying technologies, including: (1) The alkali metal hydroxide solution used in the pretreatment of corn cob flour is potassium hydroxide and sodium hydroxide Equal solution, during pretreatment, the concentration of alkali metal hydroxide solution is 0.5% to 1.5%, and the treatment  The temperature is 30℃～60℃, the time is 30min～120min, the corn cob powder and the alkali metal hydroxide are dissolved The liquid weight ratio is 1:8～1:12; (2) The dissolution of xylan in corncob powder adopts the method of direct heat cooking and cracking, and the cooking temperature is 155°C ～180°C, cooking time 30min～120min, the weight ratio of corncob flour to water is 1:6～1: 10. Weak acid catalysts such as acetic acid, formic acid, citric acid, etc. are used in the cooking process.   0.2% to 1.5% of the weight of corncob flour; (3) The enzymatic hydrolysis reaction uses sp.E-86 type xylan enzyme solution, and the enzymatic hydrolysis reaction temperature is 45°C to 60°C ℃, the enzymatic hydrolysis reaction time is 4h～10h, the ratio of xylan enzyme solution to corncob powder is 1ml/1.2g～1ml/1.6g, the enzyme activity of xylanase solution is 50UI/ml～70UI/ml; (4) The decolorization of xylo-oligosaccharide solution adopts activated carbon powder, and the specific conditions are that the decolorization temperature is 80°C, and the activity The volume ratio of charcoal to sugar solution is 0.5% to 1.5%, and the decolorization time is 25min to 40min; (5) Xylo-oligosaccharide solution adopts strong acid cationic resin such as E306FG and macroporous weak base anion Exchange resin such as D001 for impurity removal. 2. The preparation method of xylo-oligosaccharide according to claim 1, wherein the optimal alkali metal hydroxide used in the pretreatment of corn cob powder is sodium hydroxide, the optimal concentration is 0.7%, and the optimal temperature is 55°C. The optimal treatment time is 60 minutes, and the optimal material-liquid weight ratio is 1:10. 3. The preparation method of xylo-oligosaccharide according to claim 1, when the corncob powder is subjected to direct heat cooking and cracking, the optimal cooking temperature is 165°C, the cooking time is 120min, the optimal catalyst is acetic acid, and the addition amount is corn 0.5% by weight of core powder. 4. The preparation method of xylo-oligosaccharides according to claim 1, wherein the optimal temperature of xylanase hydrolysis reaction is 55°C, the reaction time is 8h, and the ratio of xylanase liquid to corncob powder is 1ml/1.45 g, the enzyme activity of xylanase solution is 60UI/ml. 5. The preparation method of xylo-oligosaccharides according to claim 1, wherein the optimal volume ratio of activated carbon to sugar solution is 1% during the decolorization process, and the decolorization time is 30 minutes. 6. The preparation method of xylo-oligosaccharide according to claim 1, the present invention adopts double-effect vacuum concentration, the first concentration is at 75°C, and the xylo-oligosaccharide liquid is concentrated to a total sugar content of 15% to 20%. % syrup; the second concentration is at 75°C, concentrate the xylooligosaccharide liquid to a syrup with a total sugar content of 55% to 75%. 7. The preparation method of xylooligosaccharide according to claim 1, the present invention can prepare xylooligosaccharide powder by spray drying method, the inlet temperature of the hot air during spray drying is 130°C to 160°C, and the outlet temperature is 65°C. ℃～85℃, the material flow rate is 0.8～1.2m ³ /h, the residence time in the tower is 10 seconds～20 seconds, and the excipient is maltodextrin, β-cyclodextrin or corn starch. 8. According to the preparation method of xylooligosaccharide according to claim 7, the most suitable excipient for preparing xylooligosaccharide powder is maltodextrin.