The method of preparing xylo-oligosaccharide through high temperature degradation of xylan
One, technical field
The invention belongs to the functional food additives preparing technical field in the biological chemistry.
Two, background technology
Oligose claims oligosaccharides (oligosaccharide) again, is connected to form, has the general name of the low polymerization carbohydrate of straight or branched by 2~10 monose by glycosidic link, molecular weight about 300~2000.Functional oligose is meant to have special biological function, particularly can promote the propagation of bifidus bacillus in the enteron aisle, is of value to a class oligose of HUMAN HEALTH, promptly so-called bifidus factor.Abroad the principal item that comes into the market as commodity is low poly lactose, oligomeric galactose, oligomeric isomaltose, soybean oligosaccharide, oligofructose, palatinose, xylo-oligosaccharide etc.Domestic research mainly concentrates on the preparation of soybean oligosaccharide, oligomeric isomaltose, oligofructose and xylo-oligosaccharide and utilizes the aspect at present.
Xylo-oligosaccharide be by 2~10 wood sugars with β-1, the oligose that the 4-glycosidic link is formed by connecting.Compare with other functional oligose, xylo-oligosaccharide because have highly selective cultivation effect to bifidus bacillus, be difficult to by the human consumption enzyme system decompose, advantage such as unique acid acceptance and difficult fermentable and extremely people's favor.
Xylo-oligosaccharide adds the zytase degraded and makes xylo-oligosaccharide after can extracting from the plant fiber material (as corn cob, bagasse, birch, poplar etc.) that is rich in xylan and obtaining xylan under certain temperature, pH condition.Prepare xylo-oligosaccharide in this way, the enzyme activity of zytase and enzyme system constitute for the yield and the quality product influence of xylo-oligosaccharide very big.CN 02112568.6 " a plant fiber raw material enzyme liberating prepares the method for xylo-oligosaccharide " provides a kind of method that xylan is prepared the functional food additives xylo-oligosaccharide through enzyme liberating, it is characterized in that the xylan that extracts with plant fiber material is a raw material, degrading with the Trichodermareesei zytase, to obtain the polymerization degree be 2~5 xylo-oligosaccharide product.Also select for use after the preparation zytases such as other bacterium, actinomycetes and fungi, xylan is prepared the technology report of xylo-oligosaccharide through enzyme liberating.
Studies show that further the xylan that extracts mainly is 4-O-methyl-glucuronic acid sill glycan or Arabic glycosyl-4-O-methyl-glucuronic acid sill glycan from plant fiber material.Its main chain is by β-D-pyranose form xylosyl is with β-1, and the 4-glycosidic link is formed by connecting.Xylan is the same with Mierocrystalline cellulose and xylogen, can be at first softening under heating condition, more than softening temperature, carry out thermal destruction subsequently.The temperature that xylan begins thermal destruction is lower than Mierocrystalline cellulose and xylogen.The thermal destruction mechanism of discovering xylan can be divided into following three phases:
(1) at first carries out the cleacvage reaction of random chain;
(2) the reduction end xylosyl of chain cracking generation is because of peeling reaction is sloughed;
(3) unstable terminal group is stable gradually, until termination reaction.
In the thermal degradation process of xylan, random chain cleacvage reaction through the fs, the xylan of high-polymerization degree can effectively be degraded, simultaneously, degraded to a certain degree also can take place in the connection of xylogen-carbohydrate complex body, discharges the low xylan molecule of the free polymerization degree.If can control the process of xylan pyrolytic reaction by regulating suitable temperature and time, make it that random chain cleacvage reaction of fs only take place, just can adopt the method for high temperature degradation, make the β-1 of xylan, 4-glycosidic link fracture is 2~10 water-soluble xylo-oligosaccharide product thereby be degraded into the polymerization degree.But do not see up to now, the relevant report of this type of patented technology as yet.
Three, summary of the invention
The goal of the invention of present technique is, according to xylan mainly by wood sugar (monose) through β-1, the 4-glycosidic link is formed by connecting and is the thermal destruction mechanism of the constructional feature of polymkeric substance and xylan, seek a kind of method and make β-1 with high temperature degradation, 4-glycosidic link fracture, thus make the xylan degrading of high-polymerization degree become the processing method that the polymerization degree is 2~10 xylo-oligosaccharide product.
Technical solution of the present invention is: with the xylan that extracts in the wood fibre plant is raw material, adopts high temperature degradation technology to produce the xylo-oligosaccharide product, and the optimal reaction temperature that it is characterized in that high temperature degradation is 180 ± 2 ℃, and optimum reacting time is 30 ± 5min.
The gentle soaking time of strict control liquid is extremely important.The liquid temperature is low excessively, the β of xylan-1, and the 4-glycosidic link is difficult to fracture, and the xylo-oligosaccharide yield is very low; The liquid temperature is too high, and not only the xylo-oligosaccharide of Sheng Chenging continues to decompose easily, and other components such as xylogen in the raw material also can degrade, and purifies to product separation and brings difficulty.Soaking time is too short, the cleacvage reaction deficiency of random chain, and xylan degrading is incomplete; Soaking time is long, and high temperature degradation enters second and third stage, and consequently the xylo-oligosaccharide yield reduces, and low molecular impurity content increases.Therefore, be under the condition of 30 ± 5min in 180 ± 2 ℃ of liquid temperature, soaking time, can be so that the xylo-oligosaccharide yield be the highest, and the content of low molecular impurity is minimum.Adopt above method, the 100g xylan can make xylo-oligosaccharide 40~45g.
Four, description of drawings
Fig. 1 analyzes collection of illustrative plates for the high performance liquid chromatography (HPLC) of xylan xylo-oligosaccharide in the supernatant liquor that 180 ℃ of high temperature degradation 30min obtain, the polymerization degree at each peak is followed successively by 1~10 from right to left among the figure, and the big peak of Far Left is high xylan of the polymerization degree and lignin degradation product;
Fig. 2 is xylan high temperature degradation 10~50min under 160 ℃ of conditions, and the xylan of the xylo-oligosaccharide in the supernatant liquor, the xylan in the solid slag and loss is with the change curve in reaction times;
Fig. 3 is xylan high temperature degradation 10~50min under 170 ℃ of conditions, and the xylan of the xylo-oligosaccharide in the supernatant liquor, the xylan in the solid slag and loss is with the change curve in reaction times;
Fig. 4 is xylan high temperature degradation 10~50min under 180 ℃ of conditions, and the xylan of the xylo-oligosaccharide in the supernatant liquor, the xylan in the solid slag and loss is with the change curve in reaction times.
Five, embodiment
Embodiment 1: the extraction of xylan
It is particle about 0.5cm that 1000g over dry corn cob meal is broken into particle diameter, adds sodium hydroxide 400g, and water 7000g is in 85~90 ℃ of boiling 3h.Press filtration separates cooking liquor and corn cob solid slag.Cooking liquor is neutralized to pH5.0 with sulfuric acid.The neutralizer molecular weight cut-off is 6000 polysulfone hollow fibre ultrafiltration post desalination, and inorganic salt more than 95% and low molecular compound can see through liquid with ultrafiltration and remove, and xylan is then stayed in the ultrafiltration mother liquor.With decompression evaporator the ultrafiltration mother liquor is concentrated, make that the concentrated solution solid content is about 100g/L.Analysis revealed, 1000g over dry corn cob is in the solid substance 295.0g that above processing obtains, and xylan is 220.4g, accounts for 74.7% of solid substance; Sodium sulfate is 18.8g, accounts for 6.4%, and all the other are impurity such as lignin degradation product.
Embodiment 2: the high temperature degradation of xylan
Get the xylan concentrated solution that embodiment 1 obtains, thin up is inserted in the hydrolytic decomposition pot that volume is 35ml to containing xylan 5.85%, seals.Contain xylan 2.05g in this hydrolytic decomposition pot.Oil bath is warming up to 180 ℃, puts into the said hydrolyzed jar, treat to pick up counting when temperature rises to 180 ℃ once more, make that material is at 180 ℃ of reaction 30min in the hydrolytic decomposition pot.After reaction finishes, place cold water to cool off hydrolytic decomposition pot immediately, with termination reaction.Carefully open hydrolytic decomposition pot, reaction solution is centrifugal, collect supernatant liquor and solid slag respectively.Measure pH value, mean polymerisation degree and the total reducing sugars of supernatant liquor, and total reducing sugars is converted to xylo-oligosaccharide.Measure the total reducing sugars of solid slag, and total reducing sugars is converted to undegradable xylan.The xylan that loses in the reaction by reaction before xylan total amount (2.05g) deduct xylo-oligosaccharide in the supernatant liquor and the xylan in the solid slag and get.Measurement result is as shown in table 1.
Table 1 xylan is in the result of 180 ℃ of high temperature degradation 30min
The mensuration project | Measure numerical value |
Supernatant liquor | The pH value | ????4.7 |
Xylo-oligosaccharide (g) | ????0.872 |
Account for the ratio (%) of the preceding xylan of reaction | ????42.5 |
Mean polymerisation degree | ????2.0 |
Solid slag | Xylan (g) | ????0.784 |
Account for the ratio (%) of the preceding xylan of reaction | ????38.2 |
Loss | Xylan (g) | ????0.394 |
Account for the ratio (%) of the preceding xylan of reaction | ????19.2 |
Table 1 is the result show, under above-mentioned experiment condition, through 180 ℃ of high temperature degradation 30min, 42.5% xylan is degraded into the xylo-oligosaccharide of solubility, and its mean polymerisation degree is 2.0; 38.2% xylan remains in the solid slag, is not degraded; Yin Gaowen destroys and the xylan of loss accounts for 19.2% in the reaction.
Xylo-oligosaccharide in the supernatant liquor is done high performance liquid chromatography (HPLC) analysis, and chromatographic operational condition is as follows:
Sugar post: Bio-Rad Aminex HPX-42A (300 * 7.8mm);
Guard column: Micro-Guard Carbo-P and Micro-Guard Deashing Cartridges;
Column temperature: 85 ℃;
Moving phase: high purity water, ultrasonic degas; Flow velocity: 0.6ml/min;
Detector: differential refractometer detector (RI).
Analytical results shows, the xylo-oligosaccharide in the supernatant liquor is that 2~10 xylo-oligosaccharide is formed by the polymerization degree mainly, as shown in Figure 1.
Embodiment 3: differential responses temperature and reaction times are to the influence of xylo-oligosaccharide yield
Adopt different temperature of reaction and reaction times, all the other conditions can obtain differential responses temperature shown in the accompanying drawing 2~4 and the reaction times influence curve to the xylo-oligosaccharide yield with embodiment 2.
By accompanying drawing 2~4 as can be known, in 160~180 ℃, boiling temperature is high more, and the ratio that the interior xylan of identical soaking time is converted into xylo-oligosaccharide is big more, and xylan loss simultaneously is also big more.With boiling 50min is example, is respectively 25.1%, 28.1% and 46.3% at 160,170 and 180 ℃ of following boiling xylan transformation efficiencys, and the xylan loss is respectively 6.0%, 21.6% and 34.2%.Under same boiling temperature, the xylan transformation efficiency improves with holding time prolonging, and xylan loss simultaneously also increases with holding time prolonging.The change curve of comprehensive accompanying drawing 2~4 xylan transformation efficiencys and xylan loss can determine that it is 180 ℃ ± 2 ℃ that the xylan high temperature degradation is produced the optimum reaction condition of xylo-oligosaccharide, and optimum reacting time is 30 ± 5min.
The present invention produces xylo-oligosaccharide technology with enzyme liberating and compares, and technical process is shortened greatly, and reaction process is obviously accelerated, and is easy to form the large-scale industrial production ability more.