AU605215B2

AU605215B2 - Process for producing cellulose from lignin-containing raw materials

Info

Publication number: AU605215B2
Application number: AU82303/87A
Authority: AU
Inventors: Hans-Peter Call
Original assignee: Individual
Current assignee: Individual
Priority date: 1986-10-24
Filing date: 1987-10-24
Publication date: 1991-01-10
Anticipated expiration: 2007-10-24
Also published as: DE3636208A1; FI891909A0; EP0327576B1; BR8707844A; HUT50894A; HU202938B; AU8230387A; NO175104C; DE3784515D1; EP0327576A1; ATE86318T1; FI891909A; JPH02500990A; JPH0718108B2; DK344888A; WO1988003190A1; NO882808L; DK170810B1; NO175104B; FI95289C

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

AU-Al-02303/87 PTWELTORGANISATION FOJR GEISTIES EIETMl INTERNATIONALE ANMVELDUNG VEROFFENTLICHT NACH DEM VERTRAG OJBER DIE INTERNATIONALE ZUSAMMENARI3EIT AUF DEM GEBIET DES PATENTWESENS (PCT) (51) Internatioiale Patentklassifikation 4: D21C 3/00, 9/10, C12N 1/22 ftional Ve lichungsnurnmer: W~O 88/ 03190 ei~nti~iigdaum 5, Mai 1988 (05,05.88 (21) lnteriiationales Aktenzeichcn: PCT/EP87/00635 (22) Internationales Anineldedatum: 24, Oktober 1987 (24.10.87) (31) Prioritiitsaktenzeichen: P 36 36208,5 (32) Prioritiitsdatuim: (33) Prioritiitslanid: 24, Oktober 1986 (24..0.86)

DE

CALL, Hlans-Peter (DE/ 14A, D-5132 Oba-.;-PalenrtA (GAP! Patent), GB (europflisches Patent), HU, IT (europgisches Patent), JP, KR, LU (europilisehes Patent), MG, ML (GAP! Patent), MR (GAP! Patent), MW, NL (europtiisches Patent), NO, RO, SD, SE (europfiisrhes Patent), SN (OALP. Patent), SU', TD (GA- P! Patent), TG (GAP! Patent), US.

Vcriiffentlich- H'!it inen~inln Rechierelienberich t.

Vor Ablauf derlirh Anderuige,: der Ansprtiche zugelassenen Frist. Ver6ffewlichung wvird wviederhot Its Anderungen eintreffen, ThsdcmntCn;n mnIdnents nmade Lnd PATCN io1 Anmelder und Erfinder; DEJ; Heinsberger Straae berg (DE), (74) Anwah: COHAUSZ FLORACK; Postfach 14 01 47, D,4000 Dtlsseldorf I (DE), (81) Bcstimmungsstaitten- AT (europitisches Paitent), AU, B3E (europtlisches Patent), BG, BJ (GAP! Patent), BR, CF (GAP! Patent), CG (GAP! Patent), CH- (europflischies Patent), CM (QAP1 Patent), DE (europilisches Patent), DK, Fl, FR (europiiisches Patent), P. 2 3 JUNV 1988 (54)TItie: PROCESS FOR PRODQ'ING CELLULOSE FROM LIGNIN-CONTAINING RAW MATERIALS (54) Bezechnutig: V4iRFAHREN ZUR HERSTELLUNG VON ZELLSTOFF AU LIGNINHIALTIGEN ROHSTOF-

FEN

(57) Abstract A process and apparatus ror transforming and/or extracting lignin or its dqoompogition producto from lignin-cellulo'sic materials, For this purpose, a redox potential in tbe 200-500 mV range is set by adding oxidizing and/or reducing agents and/o~r salts and/or phenolic compounds to an acid aqueous solution of the lignlri'containilng raw materials. The ligin-ldecomposing reaction is Iiilated wittL bleaching by adding enymes, micro-organisms, animal or vegetable ceilk, The reaction Is maintained for several houies at a redox potential value oscillating around at constant value, at a constant temperature and with constant agitation, (57) Zoisarnieiiassiing Verfahren und Gerii zur Entfernting und/oder Urnvandlung von Lign t n oder dessen Abbauprodukten aus lgnocellulosehaltigem Material, 1Hierbd( wind em durch Zusatz von oxidation- und/oder Reduktionsmi tteln und/ odor Salzen und/oder phenolischen Verbindungen zu elner saureni wlissrigen Lfisung der Itgninhalgen Rohistoffe emn Redoxpoteotial im Bereich von 200 S500 mY eingesteilt. Durch Zugabe von Enzymen, Mikroorganismen, tierischen oder pflarinlichen Zellen wird die ligninabbauende Reaktion mit gleichzeiger 13!eichung gestantet, Die Reaktlon wird bei einem urn einen konstantern Redoxpotentilwert schwlngenden Went, konstantet i'empenatur und tinter stindigemh Ralhren fiber mehrere SbItnden aufrecliterhalten, COMMONWEALTH OF AUSTRALIA PATENTS ACT 1952 COMPLETE SPECIFICATION NAME ADDRESS OF APPLICANT: Hans-Peter Call Heinsberger Strasse 14A Ubach-Palenberg D-5132 Federal Republic of Germany NAME(S) OF INVENTOR(S): Hans-Peter CALL ADDRESS FOR SERVICE: DAVIES COLISON Patent Attorneys 1 Little Collin Street, Melbourne, 3000.

COMPLETE SPECIFICATION FOR THE INVENTION ENTITLED: Process for producing cellulose from lignin-containing raw materials The following statement is a full description of this invention, including the best method of performing it known to me/us:r -la- The present invention relates to a process and a plant capable of removing and/or transforming lignin present in lignocellulosic material.

The production of cellulose or of cellulose-like material requires that lignin be removed from the lignocellulosic material such as wood or annual plant matter, in order to thereby significantly improve the mechanical and physical-chemical properties of paper produced from cellulose. Conventional methods use high pressures and temperatures and employ environmentally harmful chemicals.

Prior art biological processes employed in cellulose production use microorganisms, especially fungi. A process used to recover cellulose from wood or other plant fibre materials, in which the lignocellulose is degraded with the aid of wood rot fungi, is known from the German patent specification 3110117. Methods employing microorganisms have, however, great disadvantages. It has not been possible, until the present time, to achieve the degradation and separation of lignin from its accompanying polymers (cellulose) without inciting the simultaneous growth of the microorganisms involved. Very long degradation tires, up to several weeks in length, can result from such simultaneous growth.

In recent years, the possibility of employing isolated enzyme systems has been actively investigated in response to problems arising from the use of microorganisms. In particular the enzymes of wood rot fungi Phanerochaete chrysosporium were investigated and their role identified. Known, from "Biotechnology for the Pulp and Paper Industry 3. International Conference, Stockholm, 1986" is that, during the degradation of lignin in the absence of suitable enzyme systems, the equilibrium of the reaction shifts towards -2the polymer. On the other hand it is known from "Paszczgnski, A. et al: Comparison of Ligninasee-1 and Peridoxase-M 2 from the White Rot Fungus Phanerochaeta Chrysosporium. Arch. Biochem. Biophys.

Vol. 244 No. 2" that the Mn-dependent peroxidase of Phanerochaeta chrysosporium is inhibited by reducing agents. By contrast, dithionite acts as an activator.

The object of the present invention is a process and a plant suitable for the removal and/or transformation of lignin present in material containing lignocellulose and wherein the above mentioned disadvantages arising from the use of microorganisms, enzymes and chemicals, are eliminated. This obje'ct is accomplished by the addition of one or a plurality of oxiding and/or reducing agents and/or salts and/or phenolic compounds to an acid aqueous solution containing lignin raw materials in such a manner that a redox potential can be set between 200 and 500 mV. A lignin degradation reaction accompanied by a simultaneous bleaching process is subsequently initiated by the addition of enzymes, microorganisms, animal or plant cells. The reaction is maintained for several hours at a value that fluctuates about a constant redox potential value, constant temperature and constant pH value with continuous stirring.

The preferred redox potential lies between 250 and 350 mV. In accordance with the proposed process, such a redox potential can be reached with the help of a redox electrode a regulator and adjustment mechanism, and maintained at a constant value throughout the reaction period by the addition of oxidizing and/or reducing agents and/or salts and/or phenolic compounds and/or organic acids. Used preferably as oxidizing agents are hydrogen peroxide, oxygen and ozone; used as reducing

I

-3agents are ascorbic acid, dithionite and sodium bisulphite. Suitable salts are MnSO 4 and/or FeCl 2 Veratryl alcohol can serve as the phenolic compound.

Lactic acid can, for example, be employed as the organic acid.

In accordance with the proposed process, ligneous enzymes are preferred. Examples of such preferred enzymes are phenol oxidase, lallases and peroxidase.

The effectiveness of the proposed process can be increased by the addition of pectinase and/or hemicellulose. In accordance with the proposed process, in particular enzymes derived from the wood rot fungi, Phanerochaete chrysosporium, can be used. The latter may, if required, be employed in the degradation process.

The pH value lies, in accordance with the proposed process, between 2 and 5. The most preferred pH value is 3. The reaction is carried out at a temperature lying between 200 and 60 0 C, and preferably at 40 0

C.

When the conditions required by proposed process are met, the redox potential can be set between 250 and 350 mV. The lignin content of wheat straw (ca. 18% lignin content) can, for example, be reduced to approximately 0% by this method. Fir wood pulp (ca. 28-30% lignin content) can also be broken down to similar end values. Surprisingly, such results can be achieved within 2 to 6 hours, and in many cases within 2 hours. Not taken into account in this case is the physical and/or chemical pretreatment which is especially important if wood or annual plants are to be processed.

The redox potential is set by varying the ratio of the different materials added to the reaction vessel.

L

-4- Appropriate measurement and regulation of the added oxidizing and reducing agents, salts and phenolic compounds, permit the maintenance of a specific redox potential throughout the reaction. The aim of such an adjustable redox system is that of preventing the lignin fromrepolymerizing.

This biological degradation principle has, for the first time, enabled the development of an economical process capable of removing lignin and involving a very short reaction time (2 to 6 hours) at physiological temperatures (40 0 ambient pressure and a minimal addition of chemicals. Above all, the process is not harmful to the environment. An additional advantage conferred by the present process is a high yieldof cellulose or cellulose-like material. For annual plants, the yield is approximately 80% and for wood, about 70%, based on the dry mass after pretreatment.

During the degradation and/or transformation reaction, the present process has a bleaching effect that permits the use of smaller quantities of environmentally-harmful bleaching agents. The proposed method is therefore capable of serving in the bleaching or post-bleaching procedure employed in conjunction with various processes. This bleaching characteristic also permits the proposed method to be used in biological bleaching processes and in the biological treatment of effluents produced by the cellulose industry as well as other effluents. The present method may also be particularly useful wherever the discoloration or decontamination of effluents is required.

An additional advantage of the proposed process is its continuous mode of operation. The process can be managed very economically if spent enzymes are regenerated and afterwards returned to the reaction.

This object is achieved by affinity chromatography.

In this procedure, the enzyme is, upon termination of the reaction, passed through a separating column, purified therein and then returned to the reaction process. The purification of the enzyme is carried out in the separating column by means of affinity chromatography. For this purpose, new specific ligand types have been developed, and are currently being used in the context of state-of-the-art enzyme technology. Such ligands are described in patent application PCT/EP 87/00214. In the present process, phenolic compounds can also be used. Similarly, protein-specific ligands, such as tannin, might also be suitable.

Another object of the proposed process is a plant suitable for removing and/or transforming lignin or its degradation products present in material containing lignocellulose. Such a plant comprises a reaction vessel; a device for adding microorganisms or enzymes, a device for adding oxiding agents, reducing agents, salt or phenolic compounds; an outlet to receive converted raw materials, spent oxiding agents, reducing agents, salts, phenolic compounds, enzymes and microrganisms; a device capable of separating dissolved and undissolved substances; a column suitable for affinity chromatography, wherein enzymes used in the lignin degradation reaction are regenerated; and a reflux for feeding the regenerated enzymes to the reaction vessel. Devices suitable for separating dissolved and undissolved substances can either be filters or concentrating apparatuses.

There now follows a detailed description of the proposed plant as shown in the diagram. Microorganisms or enzymes are introduced into the reaction vessel through supply line 7. The microorganisms or enzymes can, if required, be immobilized inside the reaction vessel.

II

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C~r i _1 F II -6- Commonly used fillers and carriers can be used for immobilization. Oxidizing agents, reducing agents, salts or phenolic compounds can be added in small doses through supply line 4. The dosage can be regulated according to the prevailing redox potential. To this end, an electrode, not shown in the diagram, can be installed on the reaction vessel, wherewith the redox potential is continuously monitored. By connecting this electrode to a suitable regulating system, it is possible to maintain the redox potential at a constant value throughout the reaction.

The raw materials are also fed through supply line 7. Such raw materials can be lignin-containing substances of any type, particularly suitable examples of which are straw and wood that have undergone chemical and/or physical pretreatment. Lignin-containing spent liquor and effluent'. can similarly be treated in the proposed plant. Lignin is degraded in the reaction vessel with the aid of lignolytic enzymes or microorganisms. The enzymes employed are in particular those derived from the fungus Phanerochaete chrysosporium. Suitable microorganisms for the above reaction are mutants of cellulase and those free of hemicellulase. Mutant of Phanerochaete chrysosporium are particularly suitable in this regard. The converted raw material is, at the conclusion of the lignin degradation, discharged from the reaction vessel through discharge line 8 together with the spent chemicals, microorganisms and enzymes. For example the liquid is directed to a filter, 3, where dissolved and, undissolved substances are separated out. The enzymic solution is directed through a chromatographic colmn 2 that operates according to the principle of affinity chromatography.

In this column, the enzymes adre regenerated and then returned to the reaction process through line 5. The 4 L -7substances, once having been separated from the enzymes, are expelled through line 6. Ligands having an affinity for enzymes, of which a particularly suitable example are phenolic compounds, are used in the affinity chromatography procedure. Similarly, ligands having a specific affinity for proteins, especially tannin, can also be used.

The proposed process is explained in detail with the aid of the following example.

EXAMPLE

dry (dried at 1100C) and chopped straw of 10-20 nfi length is treated with 400 ml 1 to 2% NaOH for 24-48 hours. Next, the chopped straw is filtered and washed with 1200 ml hot water. The filtered straw is placed in a Jokru mill to which 250 ml water is added and the contents ground at 150 rpm for 5-10 minutes.

At this point, Ig straw based on dry weight is placed in 90 ml water. While the mixture is being continuously stirred, the pH of the solution is adjusted to a pH value of 3 by the addition of 0.2M HCL. Once the desired pH value has been reached, water is added to the solution, bringing it to 100 ml. Then H 2 0 2 is added (60 ml of a solution containing 49 ml H 2 0 4 ml H 2 0 2 An equimolar amount of ascorbic acid is next added as a reducing agent. The reaction is initiated by the addition of enzymes derived from Phanerochaete thrysosporium (7000 U 1 lU=uMol conversion of veratryl alcohol to veratryl aldehyde/l/ min). This reaction was carried out at 40 0 C. After 2 hours, approximately 33% lignin was degraded.

Claims

1. Process suitable for removing and/or transforming lignin and its degradation products present in material containing lignocellulose, wherein a redox potential is set in the range 200 and 500 mV by the addition of one or a plurality of oxidizing agents and/or reducing agents and/or salts and/or phenolic compounds to an acid aqueous solution of raw materials containing lignin; a lignin degradation reaction and simultaneous bleaching are accomplished by the addition of enzymes, nicroorganisms, animal cells or plant cells; and the reaction is maintained by continuous stirring for several hours at a redox value in the range 200 to 500 mV, a temperature between 20 and 60°C and a pH value between 2 and Process in accordance with claim 1 wherein the redox pot ',tial is within the range 250 and 350 mV,

3. Process in accordance with claim 1 or 2, wherein the redox potential is continuously monitored with the aid of a redox electrode and maintained at a constant value *t a4 I throughout said reaction by the addition of oxidizing agents and/or reducing agents and/or salts and/or phenolic compounds and/or organic acids, said addition being aided by a regulator and an adjustment member.

4. Process in accordance with any one of claims 1 to 3, wherein H 2 0 2 0 or ozone is employed as an oxidizing agent. Process in accordance with any one of claims 1 to 4, wherein ascorbic acid, dithionite or sodium bisulphite is employed as the reducing agent. 90too3,immdaLOS9,a,82303caLrcs,8 I- I 1 -9-

6. Process in accordance with any one of claims 1 to wherein MnS0 4 and/or FeCl 2 are employed as the salt.

7. Process in accordance with any one of claims 1 to 6, wherein veratryl alcohols are employed as the phenolic compound.

8. Process in accordance with any one of claims 1 to 7, wherein lignolytic enzymes are employed. *e S

9. Process in accordance with claim 8, wherein the *So lignolytic enzyme is derived from wood rot fungi Phanerochaete chrysosporium). 0 10 Process in accordance with any one of claims 1 to 9, wherein pectinases and/or hemicellulases are employed,

11. Process in accordance with any one of claims 1 to 10, wherein Phanerochaete chrysosporium, which acts as a lignin degrading organism, is added.

12. Process in accordance with any one of claims 1 to 11, wherein the pH value is about 3. et S* 13. Process in accordance with any one of claims 1 to 12, wherein the temperature is about

14. Process in accordance with any one of claims 1 to 9 or 12 or 13, wherein after the reaction, the enzyme is transferred to a separating column, purified therein and then returned to the reaction. Process in accordance with claim 14, wherein the enzymes are purified in the separating column by means of affinity chromatography. T. oo. S 4 9. S S S 6* 0 S S S. *5 S S. 'e.g S 4* 5 55,. 5 9*9* 0* 45 S C 10

16. Process in accordance with claim 15, wherein affinity chromatography is accomplished with the aid of enzyme-specific ligands, in particular phenolic compounds.

17. Process in accordance with claim 16, wherein affinity chromatography is accomplished with the aid of protein-speclific ligands, in particular tannin.

18. Process in accordance with any one of claims 1 to 17, wherein supplementary bleaching is carried out with conventional bleaching agents such as sodium hypochiorite, chlorine, ozone, 02 and chlorine dioxide,

19. A process for re wving and/or transforminp lignin and its degradation produQts substantially as hereinbefore described with reference to the Example and/or drawings.

20. cellulose material produced following the 'pr~ooss of any preceding claim. DATED this 3rd day Of October 1990. HANS-PETER CALLi By His Patent Attorneys DAVIES COLLISON V