JP5126728B2 - Lignocellulosic biomass processing method - Google Patents

Description

  The present invention relates to a method for treating lignocellulosic biomass for efficiently producing saccharides from biomass, particularly lignocellulosic biomass.

  It is known that biomass is used as a raw material and is subjected to steaming, chemical treatment, pulverization or explosion treatment, followed by hydrolysis with pressurized hot water or production of saccharides by enzymatic saccharification.

  By the way, lignocellulosic biomass is mainly composed of cellulose, hemicellulose, and lignin. When used as a raw material for saccharides, lignocellulosic biomass is usually subjected to saccharification treatment in order to separate lignin that is strongly bonded to cellulose or hemicellulose. Prior to this, steaming treatment and chemical treatment at high temperature and high pressure have been performed, and many methods have been proposed so far.

For example, after biomass is steamed under high temperature and high pressure, it is instantaneously released under the low temperature and low pressure conditions in the atmosphere or in the vicinity to explode, the explosive is extracted with water and an organic solvent, and a monosaccharide is extracted as a water extract. A method of separating lignin as an organic extract and obtaining cellulose as an extraction residue has been proposed (see Patent Document 1).
However, this method has a drawback that hemicellulose is excessively thermally decomposed and cannot be recovered as a saccharide.

In addition, in order to improve these disadvantages and to make better use of hemicellulose, lignocellulosic biomass is steamed under mild conditions, water is added to extract soluble components, and the extraction residue is steamed. In addition, a method (see Patent Document 2) that is subjected to a blasting treatment has also been proposed.
However, in this method, it is inevitable that the operation becomes complicated because a steaming process is required in addition to the explosion process.

  In addition, the present inventors also prepared a method for producing water-soluble oligosaccharides by hydrolyzing cellulose with pressurized hot water at 200 to 300 ° C. (see Patent Document 3), and pressurized heat at 240 to 340 ° C. for cellulose. A method of producing a water-insoluble polysaccharide by hydrolysis with water (see Patent Document 4), cellulose is hydrolyzed at 200 to 300 ° C. to produce a water-soluble oligosaccharide, and then this is enzymatically decomposed to produce a monosaccharide Have been proposed (see Patent Document 5), but these are all made from cellulose and not lignocellulosic biomass.

  On the other hand, organic components such as pulp sludge containing lignin and cellulose are hydrolyzed to hydrolyze the cellulose component into water-soluble saccharides, and the product is recovered from the liquid obtained by solid-liquid separation. However, in this method, it is known that lignin remains as a solid content without being decomposed and is not hydrolyzed.

JP 59-204997 (Claims and others) Japanese Patent Publication No. 7-121963 (Claims and others) JP-A-10-327900 (Claims and others) JP 2000-186102 A (Claims and others) JP-A-10-327900 (Claims and others) JP 2001-79595 A (Claims and others)

  The present invention has been made for the purpose of providing a method for efficiently producing saccharides using lignocellulosic biomass as a raw material.

  As a result of repeated researches to develop a method for efficiently producing saccharides using lignocellulosic biomass as a raw material, the present inventors have a structure in which cellulose is usually easily aggregated and fibrous. In order to accelerate the enzymatic saccharification reaction, cellulose crystals are formed because the structure of the crystallized structure is gathered to form microfibrils and form microfibrils. It is necessary to reduce the degree of conversion, and lignin is firmly bound to cellulose, and hemicellulose forms a cell wall around the microfibrils that make it, and this hemicellulose is also enzymatically saccharified. It is desirable to remove this hemicellulose in advance for the enzymatic saccharification reaction of cellulose, as this may cause a reaction inhibition. In addition, according to mechanical pulverization treatment, that is, mechanochemical treatment, cellulose fine particles of micro order obtained by ordinary dry pulverization become finer, and the crystallinity of cellulose gradually decreases with the pulverization time, and finally the degree of polymerization is about 220. It has been found that re-aggregation can be suppressed by adding a volatile organic solvent and an affinity polymer compound, and the present invention has been made based on these findings.

  That is, the present invention is a method for producing saccharides from lignocellulosic biomass, in which the other constituent components are separated and removed from cellulose as a constituent component of lignocellulosic biomass by temperature-controlled pressurized hot water. A hydrothermal treatment process, after the hydrothermal treatment is completely dried, and mechanically pulverized to mechanically activate the cellulose until it is crushed and the crystallinity of the cellulose is reduced to 10% or less. And a saccharification treatment step of saccharifying the mechanically pulverized product with an enzyme.

  And in this lignocellulosic biomass treatment method, after the hydrothermally treated product is completely dried, it is preferably mechanically pulverized in the presence of a volatile organic solvent or an affinity polymer compound. The organic solvent is preferably a volatile organic hydroxyl compound, and the affinity polymer compound is preferably a water-soluble natural polymer compound or synthetic polymer compound.

Next, the present invention will be described in detail.
The method for treating lignocellulosic biomass of the present invention includes three steps of a hydrothermal treatment step, a mechanical pulverization treatment step, and a saccharification treatment step.

In the method of the present invention, lignocellulosic biomass is used as a raw material, and this biomass originally means a biological organic resource excluding fossil fuel, and therefore lignocellulosic biomass is mainly composed of lignocellulose. Means biomass.
Typical examples of this lignocellulosic biomass include woody materials such as wood, inawara, wheat straw, bagasse, bamboo, and pulp, and waste products such as waste paper.

  These lignocellulosic biomass used in the method of the present invention may be a dried product or a wet product, but it is preferably used after coarsely pulverizing or chopping to a size of 100 to 1000 μm in order to increase the processing speed. The rough pulverization or chopping can be performed using a machine commonly used for coarse pulverization or chopping of various materials such as a ball mill, a vibration mill, a cutter mill, a hammer mill, a wheel mill, and a jet mill.

  Next, in the above hydrothermal treatment step, lignocellulosic biomass to be used as a raw material is treated with pressurized hot water, and intracellular components that are components other than cellulose that is a constituent component of lignocellulosic biomass can be easily solubilized. It is a process for separating and recovering the contained component, hemicellulose and some lignin, which includes a temperature in the range of room temperature to 140 ° C. and 1.0 to 3.0 times the saturated vapor pressure (about 1 to 3 MPa). First, cell-containing components are extracted by contacting with pressurized hot water having pressure, and then pressurized hot water having a temperature in the range of 140 to 220 ° C. and a pressure of 1.0 to 3.0 times the saturated vapor pressure. A two-stage system in which the hemicellulose component is separately separated and recovered by contact with the liquid, and contact with pressurized hot water having a temperature in the range of 140 to 220 ° C. and a pressure in the range of about 1 to 3 MPa. The There is a method in which at the time of separation and recovery.

  In this step, unstable lignin can also be separated and recovered. And by performing such a process, the lignin which bind | bonds firmly with a cellulose and inhibits an enzyme reaction, and the hemicellulose which forms a cell wall around the microfibrin of a cellulose and inhibits an enzyme reaction are removed.

  In this hydrothermal treatment step, the cell-containing component extracted at less than 140 ° C. contains useful pigments and physiologically active components, so various useful substances can be separated and recovered from this fraction. On the other hand, in the temperature range of 140 to 220 ° C., hemicellulose is hydrolyzed and oligosaccharides composed of pentasaccharides are extracted. This oligosaccharide can be isolated according to a conventional method and used as a functional food material.

  This oligosaccharide can also be enzymatically degraded to produce a monosaccharide (xylose), which is in increasing demand recently. The hydrolyzed product of hemicellulose can be used as it is as an aqueous solution containing a water-soluble oligosaccharide, but can also be concentrated or evaporated and dried as desired.

  In the above hydrothermal treatment step, a treatment product containing cellulose as a main component is obtained, which is then subjected to a mechanical pulverization step. This mechanical pulverization pulverizes cellulose in the product obtained by hydrothermal treatment to reduce its crystallinity and polymerization degree, and it is mechanochemically activated to facilitate enzyme reaction in the subsequent process. Make it easier to receive.

  This mechanical pulverization is preferably performed in a state where water remains in a treated product from which intracellular components and hemicellulose components have been removed by anhydrous treatment. The amount of water remaining at this time is in the range of 10 to 100% by mass, preferably 20 to 50% by mass, based on the dry mass.

  This mechanical pulverization can be performed using, for example, a vibration ball mill, a rotating ball mill, a planetary ball mill, a roll mill, a disk mill, a high-speed rotating blade mixer, a homomixer, or the like.

  Usually, it is performed until the average particle diameter of the hot water treated product is 10 μm or less, preferably 5 μm or less. By the pulverization treatment, the crystallinity of cellulose in the hydrothermally treated product is reduced to 10% or less, preferably 0 to 5%, or the polymerization degree is reduced to 250 or less, preferably 220 or less. This usually requires a processing time of 2 hours or more, preferably 4 hours or more.

When the mechanical pulverization is performed for a long time in a dry process, the fine powder once generated causes reagglomeration. Therefore, in the method of the present invention, it is preferable to carry out in the presence of water, a volatile organic solvent or an affinity polymer compound. As this volatile organic solvent, hydroxyl compounds such as methanol, ethanol, propanol, ethylene glycol and the like are particularly used. The affinity polymer compound may be a natural polymer compound such as starch or amylose, or a synthetic polymer compound such as polyethylene glycol or polyvinyl alcohol. These addition amounts are selected in the range of 1 to 100% by mass, preferably 20 to 50% by mass, based on the mass of the hydrothermal treatment product.
By performing such mechanical pulverization treatment, the enzymatic saccharification reaction of the hydrothermal treatment product is promoted twice or more as compared with the untreated one.

  Next, the saccharification treatment step in the method of the present invention is performed by allowing a hydrolase, such as cellulase, to act on the processed product of the mechanical pulverization treatment. This reaction can be carried out under the conditions used in a method for decomposing ordinary cellulose into glucose. The nature of this cellulase varies slightly depending on the type of microorganism producing it, but the optimum pH range is 3.5 to 5.5 and the optimum temperature range is 45 to 55 ° C., so the pH is 3.3 to 5. Cellulase is added to the mechanically pulverized product dissolved in the buffer solution 5 and the saccharification treatment is performed by maintaining at 45 to 55 ° C. for 10 to 30 hours. This saccharification treatment may be performed batchwise or continuously using a bioreactor containing an immobilized enzyme.

  At this time, if the saccharification reaction solution is irradiated with ultrasonic waves, the enzyme adsorbed on the cellulose is peeled off, so that the saccharification reaction is promoted. In addition, when cellulases derived from different microorganisms are added, a synergistic effect is produced and the enzyme reaction can be promoted. In addition, when a parallel saccharification and fermentation system is used, in which fermentation is performed simultaneously with saccharification, cellobiose and glucose produced by decomposing cellulose are accumulated and fermented, so that product inhibition does not occur and the overall saccharification rate is increased. be able to.

Next, specific embodiments of the method of the present invention will be described with reference to the accompanying drawings.
FIG. 1 is an example of a flow sheet for carrying out the present invention. The lignocellulosic biomass 1 as a raw material is treated with pressurized hot water in the solubilization treatment step 2 after pulverization. The treated biomass is divided into an aqueous solution 4 containing oligosaccharide and a residue 5 of the solubilization process by solid-liquid separation 3, and the residue 5 of the solubilization process is pulverized in the pulverization process 6. In practical use, the total amount of the aqueous solution (liquid component) 4 containing the oligosaccharide produced by the solubilization treatment step 2 and the residue (solid component) 5 of the solubilization treatment step 5 without the solid-liquid separation step 3 is provided. It is also possible to perform pulverization. Next, the pulverized biomass is subjected to enzymatic saccharification in the enzymatic saccharification step 7 and separated into an enzymatic saccharification residue 9 and an aqueous sugar solution 10 in the solid-liquid separation step 8.

  FIG. 2 is a hot water circulation type reaction system for separating and recovering lignocellulosic biomass constituents by pressurized hot water treatment. As biomass, 24-42 mesh rice husk powder was used. 10 g of dried rice husk powder is charged into a stainless steel reactor 17 having an internal volume of 28 ml, which is capped at both ends with a sintered filter having a pore diameter of 5 μm and is provided with a line heater 16 for heat insulation. Moreover, the distilled water in the water tank 11 is filled with the pump 12 in the heating coil 14 for preparing hot water. After setting the pressure holding valve 19 so that the pressure in the system becomes a predetermined value, the valve 13 is closed so that the water in the heating coil 14 does not bump, and then the valves 13 'and 13 "are opened, and the nitrogen cylinder 21 Then, nitrogen gas was sent to pressurize the system. Next, after closing the valves 13 'and 13' ', the valve 13 was opened and the preheating oil bath 15 heated to a predetermined temperature was raised with the jack 25, The preheating coil 14 is immersed in this to heat the water inside.

  Next, distilled water is supplied from the water tank 11 by the pump 12, and the reaction is terminated from the water tank 11 ′ when the temperature measured by the thermocouple 23 provided immediately below the reactor 17 starts to rise rapidly. Of cooling water is started to flow using the pump 12 '. This cooling water comes into direct contact with the hot water flowing out from the upper part of the reactor to rapidly cool the hot water, and the mixed water is further cooled to about 30 ° C. in the cooler 18 and then passes through the pressure holding valve 19. And flows into the receiver 20. The time when the pressure in the system reaches a predetermined value and water begins to flow out from the pressure-holding valve 19 is taken as the reaction start time, and the decomposition products are collected in the receiver 20 at regular intervals. In FIG. 2, 22 and 22 ′ are pressure gauges, and 24 is a pressure gauge indicated by the pressure gauge 22 and a temperature recorder indicated by the thermocouple 23.

  According to the present invention, hemicellulose can be produced from lignocellulosic biomass at a efficiency that is at least twice as high as that of the conventional method, and it is a raw material for producing cell-containing components and pentose containing pigments and bioactive components. Can be separated and recovered.

  Next, the best mode for carrying out the present invention will be described by way of examples, but the present invention is not limited by these.

(1) Hydrothermal treatment step In FIG. 2, as a reactor 17, a fixed-bed reactor made of stainless steel having an internal volume of 28 ml, which is capped with a silver-plated nickel sintered filter (pore diameter 5 μm) at both ends, is 5 μm. Into this, 10 g of 24-42 mesh rice husk was charged, and the components contained in the cells were extracted and removed by flowing pressurized water at 128 ° C. and 1 MPa for 30 minutes at 15 ml / min, and then added at 205 ° C. and 2 MPa. Hemicellulose was saccharified by flowing pressurized hot water at 15 ml / min for 30 minutes. The obtained hemicellulose section contained about 30% lignin and ash in addition to the hemicellulose degradation product. The rice husk residue excluding the hemicellulose fraction aqueous solution contained about 40% lignin and ash in addition to cellulose.

(2) Mechanical pulverization process Part of the rice husk residue after hydrothermal treatment was completely dried by vacuum drying, and then subjected to mechanochemical treatment by a planetary ball mill pulverizer (Fritsch, P-5). . The mechanocal treatment uses a zirconia container with an internal volume of 500 ml and a zirconia ball (20 mmφ), puts 50 g of completely dry rice husk residue per container, pulverizes for 10 minutes at a revolution speed of 250 rpm and pauses for 10 minutes. And then pulverized for 4 hours. From the powder X-ray diffraction measurement of the obtained processed product, the cellulose was in an amorphous state (crystallinity 0%). From the laser diffraction particle size distribution measurement, the average particle size was 8.5 μm.

In order to suppress the reaggregation of the generated particles and proceed the pulverization more efficiently, ethanol was added as a compound containing a hydroxyl group at the time of pulverization. 20% by mass of ethanol was added to 50 g of completely dried rice husk residue, and allowed to stand at room temperature for 12 hours to uniformly adsorb the whole. In this case, the added ethanol was completely adsorbed and could be pulverized in the same manner as the dried product without becoming a slurry. In the mechanochemically processed product obtained by ball milling using the same method as described above, cellulose had a crystallinity of 5% and an average particle size of 5 μm.
The crystallinity of cellulose was calculated from the diffraction peak around 2θ = 15 ° according to the method of Isogai Usuda [“Journal of the Fiber Society”, Vol. 46, p. 324 (1990)].

(3) Saccharification treatment process 50 mM acetic acid at 45 ° C. using as a substrate a rice husk residue (crystallinity: 44%) treated with hydrothermal treatment or a rice husk residue (crystallinity: 0%) further mechanically treated after hydrothermal treatment. A final concentration of 5% (w / v) was added to a 1 ml sodium acetate buffer reaction solution. As the enzyme, a commercially available cellulase preparation (trade name: Acremonium cellulase, manufactured by Meiji Seika Co., Ltd.) is added to the reaction solution to a final concentration of 0.05% (w / v), and further commercially available in the reaction solution. β-glucosidase (trade name: Novozyme, manufactured by Novozyme) was added in an amount corresponding to 0.63 unit. Using such a reaction solution composition as a standard composition, a saccharification reaction was performed at a reaction temperature of 45 ° C. for 24 hours.
The total amount of reducing sugar in the saccharified solution after solid-liquid separation using a centrifugal separation (12,000 rpm, 5 minutes) of the saccharide-containing solution obtained after the saccharification reaction was measured using the Somogi-Nelson reaction. Moreover, the amount of glucose in the saccharified solution was measured using a glucose test Wako.
From these results, if only hemicellulose is removed by pressurized hot water treatment, only 9% by mass of cellulose in the rice husk is converted to glucose. When the crystallinity was lowered to an amorphous state, 21% by mass of cellulose in the rice husk was converted to glucose, and the saccharification reaction was accelerated more than twice.
In the case of mechanical pulverization treatment with a crystallinity of 5% and an average particle size of 5 μm obtained by adding ethanol, the saccharification reaction was promoted more than twice as described above.

  The method of the present invention is useful as a method for producing saccharides using lignocellulosic biomass as a raw material.

Process drawing of an example of this invention method. The flow sheet figure of an apparatus suitable for enforcing the method of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Lignocellulosic biomass 2 Solubilization process 3 Solid-liquid separation process 4 Aqueous solution of oligosaccharides 5 Solubilization process residue 6 Grinding process 7 Enzyme saccharification process 8 Solid-liquid separation process 9 Enzyme saccharification residue 10 Aqueous solution 11 of sugar, 11 'water tank 12, 12' pump 13, 13 ', 13 "valve 14 preheating coil 15 preheating oil bath 16 heat retaining heater 17 reactor 18 cooler 19 pressure retaining valve 20 receiver 21 nitrogen cylinder 22, 22' pressure gauge 23 Thermocouple 24 Recorder 25 Jack

Claims (4)

A method for producing saccharides from lignocellulosic biomass, which is a hydrothermal treatment step that is a step of separating and removing other constituent components from cellulose as a constituent component of lignocellulosic biomass by temperature-controlled pressurized hot water, A mechanical pulverization process in which the hydrothermally treated product is completely dried and then mechanically pulverized, whereby the cellulose is pulverized and mechanochemically activated until the crystallinity of the cellulose is reduced to 10% or less. and, lignocellulosic biomass processing method characterized by comprising the saccharification process step of saccharification its mechanical pulverized product with an enzyme. The lignocellulosic biomass treatment method according to claim 1, wherein the hydrothermally treated product is subjected to mechanical drying in the presence of a volatile organic solvent or an affinity polymer compound after being completely dried. The method for treating lignocellulosic biomass according to claim 2, wherein the volatile organic solvent is a volatile organic hydroxyl compound. The method for treating a lignocellulosic biomass according to claim 2, wherein the affinity polymer compound is a water-soluble natural polymer compound or a synthetic polymer compound.

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