FI95289B - Method for producing cellulose from lignin-containing materials - Google Patents

Abstract

A process and apparatus for transforming and/or extracting lignin or its decomposition products from lignin-cellulosic materials. For this purpose, a redox potential in the 200-500 mV range is set by adding oxidizing and/or reducing agents and/or salts and/or phenolic compounds to an acid aqueous solution of the lignin-containing raw materials. The lignin-decomposing reaction is initiated with bleaching by adding enzymes, micro-organisms, animal or vegetable cells. The reaction is maintained for several hours at a redox potential value oscillating around a constant value, at a constant temperature and with constant agitation.

Description

95239

Method for producing cellulose from lignin-containing materials

The invention relates to a process for removing and / or modifying lignin or its degradation products from a lignocellulosic material.

In order to produce cellulose or a cellulose-like material, lignin must be removed from a cellulosic material, such as wood or annual plants, because thus the mechanical and physicochemical properties of the cellulosic paper are considerably improved. Traditional methods work at high pressures and temperatures using chemicals that pollute the environment.

Microorganisms, in particular fungi, are used in hitherto known biological methods for the production of cellulose. Thus, German Pat. No. 3,110,117 discloses a process for producing cellulose from wood or other vegetable fiber materials, in which lignocellulose is decomposed by means of white fungi. However, methods using microorganisms have significant drawbacks. Thus, until now, it has not been possible to achieve the degradation and leaching of lignin from any of the accompanying polymers (cellulose) without the co-growth of the respective microorganism.

Due to the co-cultivation of the fungus, there are very long disintegration times, which can take several weeks.

In recent years, due to the described difficulties in the use of microorganisms, the use of highly isolated enzyme systems has been investigated. In particular, the enzymes of the white fungus, Phaneroachaete Chrysosporium, were studied and many details were elucidated. Thus, it is known from "Biotechnology in the Pulp and Paper 35 Indistry, 3rd International Conference, Stockholm 1986", 95289 2 that in the decomposition of lignin without a suitable enzyme system, the equilibrium of the reaction is on the polymerization side. On the other hand, it is known from "Paszczgnski, A. et al .: Com-parision of Ligninase-1 and Peroxidase-M2 from the White-5 Rot Fungus Phanerochaete Chrysosporium. Arch. Biochem. Biophys. Vol. 244, no. 2" that the addition of reducing agents substances Phanerochaete Chrysosporium Mn-dependent peroxidase is inhibited. Dithionite, on the other hand, acts as an activator.

It is now an object of the present invention to provide a method for removing and / or modifying lignin from a lignocellulosic material which avoids the above disadvantages of the use of microorganisms, enzymes and chemicals. This object is achieved according to the invention by adding a redox potential in the range of 200 to 500 mV by adding one or more oxidants, reducing agents, salts and phenolic compounds to the aqueous solution of lignin-containing raw materials; then, by adding the lignolytic enzyme, a lignin-degrading reaction is initiated with simultaneous bleaching; the reaction is maintained at a redox potential of 200 to 500 mV, at a constant temperature of 20 to 60 eC, at a constant pH of 2 to 5 and with constant stirring for 2 to 6 hours; and the redox potential is continuously indicated by the redox electrode and is maintained between 200 and 500 mV throughout the reaction by means of a regulator and an actuator with the addition of oxidants, reducing agents, salts, phenolic compounds and organic acids.

The redox potential is preferably 250 to 350 mv. In the process according to the invention, it can be detected by means of a redox electrode and kept constant by means of a regulator and a control part (Stellglied) throughout the reaction by adding oxidants, reducing agents, salts, phenolic compounds and organic acids. The oxidants used are preferably hydrogen peroxide, oxygen or ozone. Suitable reducing agents are preferably MnSO 4 and / or FeCl 2. As the phenolic compound, veratzyl alcohol can be used. Suitable organic acids are, for example, lactic acid.

As enzymes, lignolytic enzymes are preferably used in the process according to the invention. Preferably, these include phenol oxidases, lallaases and peroxidases. The efficiency of the method according to the invention can be increased by adding pectinases and / or hemicellulases. In particular, enzymes obtained from the white fungus Phanerochaete Chrysosporium can be used according to the invention. Optionally, Phanerochaete chrysosporium itself can also be used for the degradation process.

The pH in the process according to the invention is between two and five. Particularly preferred is a pH of 3. The temperature is 20 to 60 ° C, preferably the reaction is carried out at 40 ° C

When the described conditions of the method according to the invention are met, the redox potential of 250 to 350 mV can be adjusted. Thus, it is possible to decompose, for example, wheat 20 straw (lignin content about 18%) to a lignin content close to 0%. It is possible to decompose spruce ground (lignin content about 28-30%) to similar final values. These results can be achieved surprisingly in 2-6 hours, in many cases even within two hours. In this case, physical and / or chemical pretreatment, which is necessary especially when using wood or annual plants, is not included.

The redox potential is adjusted by the ratio of the various substances added in the reaction vessel. By measuring and adjusting the addition of oxidants and reducing agents, salts and phenolic compounds, a certain redox potential can be maintained throughout the reaction. The purpose of using a redox system thus regulated is to prevent the polymerization of lignin.

4 95289 For the first time, this biodegradation principle has succeeded in developing a lignin removal process that operates in a very short time (2-6 hours) at physiological temperatures (40 ° C) without pressure and with the least possible addition of chemicals and, above all, environmentally friendly. In addition, a good yield of cellulose or cellulose-like material is an advantage. In the case of annual plants, the yield is about 80% and in the case of wood about 70%, calculated on the basis of as-10 whey after pre-treatment.

The process also has a significant bleaching effect during the decomposition and / or modification reaction, which makes it possible to operate with substantially less environmentally bleaching agents. The process according to the invention is thus also suitable as a bleaching or post-bleaching process for various processes. Thus, the process can also be used for biological bleaching and for the biological treatment of effluents from the pulp industry and other effluents. In particular, the method can be used wherever decolorization and detoxification of wastewater should be achieved.

A further advantage of the method according to the invention is the possibility of continuous method execution. Particularly economically, the process can be carried out when the enzymes used are reprocessed and recycled to the reaction process. This goal can be achieved by affinity chromatography. In this case, after completion of the reaction, the enzyme is passed to a separation column, purified there and passed again to the reaction process. Purification of the Ent-30 enzyme is performed on the separation column by affinity chromatography. To this end, new specific types of ligands were developed, which are used in conjunction with the corresponding enzymological know-how. Such ligands are described in patent application PCT / EP 87/00214.

35 In the present case, for example, 95289 phenolic compounds can be used. Protein-specific ligands are also contemplated. An example is tannin.

The process according to the invention for removing and / or converting lignin or its decomposition products from lignocellulosic material can be carried out in a plant consisting of a reactor, an apparatus for adding microorganisms or enzymes, an apparatus for adding oxidants, reducing agents, salts or phenolic compounds, a reactor ka, spent oxidants, reducing agents, salts, phenolic compounds, enzymes and microorganisms, from the apparatus for the separation of dissolved and insoluble substances, from an affinity chromatography column in which the enzymes are reprocessed for reactivation of the lignin decomposition reaction and back-reaction. Filters or precipitators, for example, can be used as the device for separating dissolved and insoluble substances.

• · 20 The following illustrates the image with the above facility in mind. Through the inlet stream 7, microorganisms or enzymes are introduced into the reactor. Microorganisms or enzymes can possibly also be immobilized in the reactor. Conventional excipients and carriers can be used for immobilization. Oxidants, reducing agents, salts or phenolic compounds can be dispensed through the inlet stream 4. The dosage can be adjusted depending on the respective redox potential. For this purpose, a redox electrode (not shown) must be attached to the reactor, with an intermediate. . At 30 times, the redox potential can be read continuously. In connection with the corresponding control device, the redox potential can then be kept constant throughout the reaction. Raw materials can be further added via the inlet flow 7. In this case, all kinds of other substances of lignin-35 can be considered. In particular, chemically and / or physically pretreated straw and wood are suitable. However, lignin-containing waste liquors and effluents can also be treated in the plant used in the invention. In the reactor, the lignin is decomposed by lignolytic enzymes or microorganisms. Suitable enzymes are, in particular, those obtained from the fungus Pha-norochaete Chrysosporium. Particularly suitable microorganisms are cellulase- and hemicellulase-free mutants. In particular, Phanerochaete chrysosporium mutants 10 are useful. Upon completion of the lignin decomposition, the reacted feedstock flows out of the reactor through the outlet pipe 8 together with the chemicals, microorganisms or enzymes used. The mixture of substances is passed, for example, through a filter 3, in which the dissolved and insoluble substances are separated from each other. The enzyme-containing solution is passed through chromatography column 2. This column operates on the principle of affinity chromatography. Here, the enzymes are reprocessed and then passed through line 5 again to the reaction process. The substances separated from the enzymes are discharged via a pipe 6. Specific enzyme-specific ligands, especially phenolic compounds, are used for affinity chromatography. Protein-specific ligands, especially tannin, can also be used.

The method according to the invention is illustrated in more detail on the basis of the following example.

Example 20 g of Atro (<110 ° C) shredded straw, 10 to 20 mm long, are treated with 400 ml of 1 to 2% NaOH for 24 to 48 hours. The straw is then filtered off and washed with 1200 ml of hot • «

of water. The filtered straw is placed in the Jokrumylly. Then 250 ml of water are added. It is then ground for 5-10 minutes at 150 rpm. Then take 1 g of straw, calculated on the dry weight basis, into 90 ml of vet-35. The pH is adjusted to 0.2 M with stirring while stirring

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7 95289 with HCl. When the pH is reached, make up to 100 ml with water. H 2 O 2 (60 μΐ of a solution containing 49 ml of H 2 O -f 4 ml of H 2 O 2) is then added. An equimolar amount of ascorbic acid is added as a reducing agent. Addition of 5 enzymes obtained from Phanerochaete chrysosporium (7000 U, 1 U 1 1 pmol conversion from veratryl alcohol to veratryl aldehyde / l / min) starts the reaction. The reaction is carried out at 40 ° C. After two hours, about 33% of the lignin had decomposed.

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Claims (14)

A process for removing and / or converting ligation or its degradation products from lignocellulosic material using lignolytic enzymes, characterized in that a) by the addition of one or more oxidizing agents, reducing agents, acids and phenolic compounds 1 an aqueous solution of the lignin-containing raw materials sets a redox potential in the range of 200-500 mV; mV, at constant temperature 20 - 60 eC, at constant pH 2-5 and with constant stirring for 2-6 hours, and d) continuously announces the redox potential by means of a redox electrode and pours it within the range 200 - 500 mV 20 by means of a regulator and an adjustment portion during the total reaction time by the addition of oxidizing agents, reducing agents, salts, phenolic a compounds and organic acids. 2. A method according to claim 1, characterized in that 25, the redox potential is set within the range 250 - 350 mV. 3. A process according to claim 1 or 2, characterized in that H 2 O 2, O 2 or ozone are used as the oxidizing agent. 30 4. A process according to any one of claims 1-3, characterized in that ascorbic acid, dithionite or sodium bisulfite are used as reducing agents. Process according to any of claims 1-4, characterized in that MnSO4 and / or FeCl2 are used as a site. Il 95289 Process according to any of claims 1-5, characterized in that the phenolic compound is used as a veratryl alcohol. 7. A process according to any one of claims 1-6, characterized in that lignolytic enzymes extracted from citrus fungi (Phanernerochaete chrysosporium) are used. Process according to any of claims 1-7, characterized in that the pH is 3. Method according to any of claims 1-8, characterized in that the temperature is at 40 ° C. Process according to any of claims 1-9, characterized in that after completion of the reaction, the enzyme is passed over a separation column, purified in it and then returned to the reaction process. 11. A process according to claim 10, characterized in that the enzyme purification is carried out in the separation column by affinity chromatography. i · 20 12. A process according to claim 11, characterized in that affinity chromatography is carried out with enzyme-specific ligands, especially with phenolic compounds. 13. A method according to claim 12, characterized in that affinity chromatography is carried out with protein-specific ligands, especially with tannin. Process according to any of claims 1-13, characterized in that it is further bleached with suitable bleaching agents, such as sodium hypochlorite, chlorine, ozone, O 2, chlorine dioxide. • »•».