DK170810B1 - Process for the preparation of cellulose from lignin- containing raw 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

in DK 170810 B1

The present invention relates to a method for removing and / or converting lignin from lignocellulosic material.

For the production of cellulose or cellulose-like material, the lignocellulosic material such as wood or annual plants must be liberated for lignin as this greatly improves the mechanical and physicochemical properties of the paper produced from the cellulose. Conventional processes work at high pressures and temperatures using environmentally harmful chemicals.

Hitherto known biological methods for cellulose preparation 10 work with microorganisms, especially fungi. Thus, from DE-patent specification 3110117 a method for the extraction of cellulose from wood or other plant fiber materials is known, in which lignocellulose is broken down by white thread fungi. However, the microorganism processes have significant disadvantages. Thus, it has not hitherto been possible to obtain degradation and release of the lignin from the accompanying polymers (cellulose) without the simultaneous growth of the microorganisms concerned. The simultaneous growth of the fungus produces very long degradation times, which can last up to several weeks.

Due to the difficulties described by the use of microorganisms, the possibilities of using isolated enzyme systems have been investigated to a greater extent in recent years. In particular, the enzymes of the white thread fungus Phanerochaete chrysosporium have been studied and described in great detail. Thus, from "Biotechnology in the Pulp and Paper Industry, 3rd International Conference, Stockholm 1986" it is known that the equilibrium of the reaction in the decomposition of lignin without suitable enzyme systems lies on the polymerization side.

Furthermore, P.J. Harvey et al. investigated the role of radical cations in lignin degradation. In doing so, they observed that the in vitro method of veratrylal carbon can contribute to lignin degradation by means of Phanerochaete chrysosporium (Abstract Bulletin of the Institute of Paper Chemistry, vol. 57, January 7, Appleton, Wisconsin , USA) PJ Harvey et al .: "Lignin Degradation Enzymes and the Role of Radical Cations in Lignin Biodegradation, page 958,

Summary 8575, & STFI / SPCI Int. Conf. Biotehnol. Pulp & Paper 35 Ind. (Stockholm) 3rd: 11-12 (June 16-19, 1986). It is also known that fatty acids influence Phanerochaete chrysosporium. Thus, lignin production by Phanerochaete chrysosporium could be observed with the addition of Tween 80® (Abstract Bulletin of the Institute of 2 DK 170810 B1

Paper Chemistry, Vol. 57, No. 7, January 1987 (Appleton, Wisconsin, USA) M. Asther et al: "Production of ligninolytic enzymes of Phanerochaete chrysosporium INA-12 in submerged agitated cultures", pages 956-957, Zusammenfassung 8558, & STFI / SPCI Int. Conf. Biotechnol. Pulp & Paper 5 Ind. (Stockholm), 3rd: 152-153 (June 16-19, 1986).

In addition, the role of manganese in lignin mining has been dealt with (Abstract Bulletin of the Institute of Paper Chemistry, vol.

57, No. 7, January 1987 (Appleton, Wisconsin, USA) V.-B Huynh et al: "Oxidation of lignin model compounds by a manganese-dependent enzyme 10 from Phanerochaete chrysosporium as compared to chemically generated Mn (III)", page 959, Summary 8578, & STFI / SPCI Int. Conf.

Biotechnol. Pulp & Paper Ind. (Stockholm), 3rd: 42-45 (June 16-19, 1986). Hereby it was established that Phanerochaete chrysosporium produces a peroxidase which induces the oxidation of manganese (II) to manganese-15 (III). Manganese (III), in turn, induces oxidation of the lignin molecules. That is, Mn peroxidase production plays a crucial role in the degradation. On the other hand, it appears in “A.

Paszczgnski et al .: Composition of Ligninase-1 and Peroxidase-Mg from the White-Rot Fungus Phanerochaeta Chrysosporium. Arch. Biochem.

Biophys. Vol. 244. No. 2 "that the Mn-dependent peroxidase from

Phanerochaeta Chrysosporium is inhibited by the addition of reducing agents. Dithionite, on the other hand, acts as an activator.

Documents published in connection with the 3rd International Biotechnology Conference in Stockholm, 1986 (cf. under-25 search papers and present description, page 1, lines 20-27), in particular the contributions of M. Leisola et al. "Production and characterization of ligninolytic enzymes of Phanerochaete Chrysosporium" and M. Asther et al. "Production of ligninolytic enzymes of Phanerochaete Chrysosporium INA-12 in submerged agitated cultures" further demonstrates the use of 30 veratrylal carbon.

Here, however, veratry alcohol serves only to promote the formation of 1 anti-degrading enzymes.

The present invention has for its object to provide a method for removing and / or converting lignin from lignocellulosic material, thereby avoiding the disadvantages described above using microorganisms, enzymes and chemicals. This is achieved by a method which is peculiar to the characterizing part of claim 1. One or more oxidizing and / or reducing agents are added to an acidic aqueous solution of the lignin-containing raw materials, the redox potential is adjusted in the range of 200-500 mV, then a 1 ignitively decomposes reaction with simultaneous bleaching by the addition of enzymes, microorganisms or 5 animal or plant cells and the reaction is maintained at a constant redox potential, oscillating value, constant temperature, constant pH and under constant stirring for several hours.

The redox potential is preferably at 250-350 mV. In the method of the invention, the redox potential can be measured by a redox electrode and kept constant throughout the reaction time by means of a regulator and an adjusting device through the addition of oxidizing and / or reducing agents and / or salts and / or phenol compounds. / or organic acids. Preferably, as the oxidizing agent, hydrogen peroxide, oxygen and ozone are used. As the reducing agent, ascorbic acid, dithionite and sodium bisulfite can be used. Preferably as salt, MnSO4 and / or FeCl2 are suitable. As a phenol compound, veratrylal carbon can be used. As organic acid, e.g. lactic acid is used.

In the process of the invention, as enzyme, preferably 1 in gnolyte enzymes is used. These preferably include phenol oxidases, laccases and peroxidases. The efficiency of the process of the invention may be increased by the addition of pectinases and / or hemicellulases. In particular, according to the invention, such enzymes derived from the white thread fungus Phanerochaete chrysosporium can be used. Optionally, Pha-nerochaete chrysosporium itself may also be added by the degradation process.

In the process of the invention, the pH is between 2 and 5. Particularly preferred is a pH of 3. The temperature is 20-60 ° C. Preferably, the reaction is carried out at 40 ° C.

If the stated conditions of the method according to the invention are complied with, the setting will have a redox potential of 250-350 mV.

Hereby, the lignin content of e.g. wheat straw (about 18% lignin content) decomposes to almost 0%. Spruce gravel (1% content of about 28-30%) can be broken down to similar final values. Surprisingly, these results can be achieved within 2-6 hours, often even within 2 hours. The physical and / or chemical pretreatment required especially when using wood or 35 annual plants is not included here.

The redox potential is adjusted through the ratio of the various added materials in the reaction vessel. By appropriately measuring and regulating the addition of the oxidizing and reducing agents, salts and phenol compounds, a certain redox potential can be maintained throughout the course of the reaction. The purpose of maintaining the redox system thus set up is to prevent the lignin from repolymerizing.

With this biological degradation system, it has for the first time succeeded in developing a process useful for the removal of lignin, which within a very short period (2-6 hours) at physiological temperatures (40 ° C), without pressure and with minimal chemical additives work economically and above all gentle on the environment. A further advantage is the high yield of cellulose or cellulose-like material. At 10 annual plants the yield is approx. 80% and wood approx. 70% of the dry matter after the pre-treatment.

The process according to the invention also has a significant bleaching effect during degradation and / or conversion reaction, which makes it possible to work with bleaching agents which have a significantly lesser impact on the environment. The process according to the invention is therefore also suitable as a bleaching or bleaching method in various processes. Therefore, the method can also be used for biological bleaching and biological wastewater treatment of wastewater from the cellulose industry and other wastewater. In particular, the method can be used wherever a decolorization and wastewater detoxification is the goal.

A further advantage of the method according to the invention is the possibility of continuous practice of the method. The process can be practiced in a particularly economical way when the spent enzymes are recovered and returned to the reaction process. This objective can be achieved by affinity chromatography. Hereby, after the reaction is complete, the enzyme is passed over a chromatography column where it is purified and then returned to the reaction process. The enzyme purification is performed in the chromatography column by affinity chromatography. For this purpose, special ligand types have been developed which can be used in connection with the corresponding enzyme technological know-how. Such ligands are described in patent application PCT / EP87 / 00214. In the present, e.g. phenol is used past several. In addition, protein-specific ligands can be used. An example is tannin.

In the following, the apparatus for carrying out the method 35 according to the invention is elucidated with reference to the drawing. Microorganisms or enzymes are supplied to the reactor via the conduit 7. The microorganisms or enzymes may also be immobile in the reactor. Conventional filler and carrier materials may be used for immobilisation. Oxidizing agent, reducing agent, salts or phenol compounds can be dosed via the conduit 4. The dosage can be controlled depending on the current redox potential. For this purpose, a redox electrode is placed in the reactor (not shown in the drawing) by means of which a continuous measurement of the redox potential can be performed. By means of a connection with a corresponding control device, the redox potential can then be kept constant throughout the course of the reaction. In addition, the raw materials are added via the conduit 7. These may be 1ignin-containing materials of any kind. In particular, chemical 10 and / or physically pretreated straw and wood are considered. However, lignin-containing liquor from effluent and wastewater can also be treated in the apparatus. In the reactor, the lignin is broken down by lignolytic enzymes or microorganisms. As enzymes in particular, those derived from the fungus Phanerochaeta chrysosporium are considered. As microorganisms, cellulase- and hemicellulase-free mutants are particularly suitable. In particular, mutants of Phanerochaeta Chrysosporium can be used. When the ignition decomposition is complete, the converted feedstock is discharged via the outlet 8 together with the chemicals, microorganisms or enzymes used away from the reactor. For example, the material mixing is conducted. through a filter 3 where 20 dissolved and unresolved materials are separated. The enzyme-containing solution is passed through a chromatography column 2. This column operates according to the affinity chromatography principle. Here, the enzymes are recovered and then returned to the reaction process via the conduit 5. The materials separated from the enzymes are diverted via conduit 6. For affinity chromatography, particular enzyme-specific ligands, especially phenolic compounds, are used. Also, protein-specific ligands, especially tannin, can be used.

The method according to the invention is further illustrated by the following example.

Example 20 g of cut atro (= dried at 110 ° C) straw with a length of 10-20 mm is treated for 24-48 hours with 400 ml of 1-2% NaOH. The cut straw is then filtered off and washed with 1200 ml of warm water. The filtered straw is transferred to a Jokru mill. Then add 250 ml of water. Paint 35 at 150 rpm for 5-10 minutes. Subsequently, an amount of straw corresponding to a dry weight of 1 g in 90 ml of water is taken up. With constant stirring, the pH is adjusted to 3 with 0.2 M HCl. After adjusting the pH, water is added to 100 ml. Then H2O2 (60 µl of a solution, containing 49 ml of HgO + 4 ml of HgOg) is added as a reducing agent, an equimolar amount of ascorbic acid is added. By adding enzymes extracted from Phanerochaete chrysosporium (7000 U, 1 U = conversion of 1 μΜοΙ veratrylal carbon to veratryl aldehyde per liter per minute). Reaction 5 was carried out at 40 ° C. After 2 hours, 33% of the lignin had broken down.

Claims (11)

1. A process for the removal and / or conversion of lignin or its degradation products from lignocellulosic material by means of recovered lignolytic enzymes, characterized in that: the lignin-containing raw materials set a redox potential in the range of 200 to 500 mV, b) then, upon addition of the lignolytic enzymes, 10 initiates an intrinsic breakdown reaction with simultaneous bleaching; C and 60 ° C, constant pH between 2 and 5 and with constant stirring for 2 to 6 hours; d) continuously measuring the redox potential by means of a redox electrode and holding it between 200 and 500 mV by means of a regulator and adjusting device throughout the reaction by the addition of oxidizing agents, reducing agents, salts, phenol compounds and organs e) upon completion of the reaction, the enzyme passes through a chromatography column where it is purified and then returned to the reaction process. 2. A method according to claim 1, characterized in that the redox potential is set in the range of 250 to 350 mV. 25 3. A process according to claims 1-3, characterized in that H 2, O 2 or ozone are used as the oxidizing agent. 4. A process according to claims 1-3, characterized in that ascorbic acid, dithionite or sodium bisulfite are used as reducing agent. 5. A process according to claims 1-4, characterized in that veratryl alcohol is used as a phenol compound. Process according to claims 1-5, characterized in that the pH is adjusted to 3. 8 DK 170810 B1 Process according to claims 1-6, characterized in that the temperature is adjusted to 40 ° C. 7 DK 170810 B1 8. A process according to claims 1-7, characterized in that enzyme purification 5 is performed by affinity chromatography in the chromatography column. 9. A method according to claim 8, characterized in that the affinity chromatography is performed with enzyme-specific ligands, especially phenol compounds. 10 10. A process according to claim 9, characterized in that the affinity chromatography is performed with protein-specific ligands, especially tannin. 11. A process according to claims 1-10, characterized in that it is also bleached with conventional bleaching agents such as sodium hypochlorite, chlorine, ozone, and or chlorine dioxide.