Classifications

• • C—CHEMISTRY; METALLURGY
  • C12—BIOCHEMISTRY; BEER; SPIRITS; WINE; VINEGAR; MICROBIOLOGY; ENZYMOLOGY; MUTATION OR GENETIC ENGINEERING
  • C12N—MICROORGANISMS OR ENZYMES; COMPOSITIONS THEREOF; PROPAGATING, PRESERVING, OR MAINTAINING MICROORGANISMS; MUTATION OR GENETIC ENGINEERING; CULTURE MEDIA
  • C12N9/00—Enzymes; Proenzymes; Compositions thereof; Processes for preparing, activating, inhibiting, separating or purifying enzymes
  • C12N9/0004—Oxidoreductases (1.)
  • C12N9/0055—Oxidoreductases (1.) acting on diphenols and related substances as donors (1.10)
  • C12N9/0057—Oxidoreductases (1.) acting on diphenols and related substances as donors (1.10) with oxygen as acceptor (1.10.3)
  • C12N9/0061—Laccase (1.10.3.2)
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08B—POLYSACCHARIDES; DERIVATIVES THEREOF
  • C08B31/00—Preparation of derivatives of starch
• • C—CHEMISTRY; METALLURGY
  • C12—BIOCHEMISTRY; BEER; SPIRITS; WINE; VINEGAR; MICROBIOLOGY; ENZYMOLOGY; MUTATION OR GENETIC ENGINEERING
  • C12N—MICROORGANISMS OR ENZYMES; COMPOSITIONS THEREOF; PROPAGATING, PRESERVING, OR MAINTAINING MICROORGANISMS; MUTATION OR GENETIC ENGINEERING; CULTURE MEDIA
  • C12N9/00—Enzymes; Proenzymes; Compositions thereof; Processes for preparing, activating, inhibiting, separating or purifying enzymes
  • C12N9/0004—Oxidoreductases (1.)
  • C12N9/0065—Oxidoreductases (1.) acting on hydrogen peroxide as acceptor (1.11)
• • C—CHEMISTRY; METALLURGY
  • C12—BIOCHEMISTRY; BEER; SPIRITS; WINE; VINEGAR; MICROBIOLOGY; ENZYMOLOGY; MUTATION OR GENETIC ENGINEERING
  • C12P—FERMENTATION OR ENZYME-USING PROCESSES TO SYNTHESISE A DESIRED CHEMICAL COMPOUND OR COMPOSITION OR TO SEPARATE OPTICAL ISOMERS FROM A RACEMIC MIXTURE
  • C12P19/00—Preparation of compounds containing saccharide radicals
  • C12P19/04—Polysaccharides, i.e. compounds containing more than five saccharide radicals attached to each other by glycosidic bonds
• • D—TEXTILES; PAPER
  • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
  • D21H—PULP COMPOSITIONS; PREPARATION THEREOF NOT COVERED BY SUBCLASSES D21C OR D21D; IMPREGNATING OR COATING OF PAPER; TREATMENT OF FINISHED PAPER NOT COVERED BY CLASS B31 OR SUBCLASS D21G; PAPER NOT OTHERWISE PROVIDED FOR
  • D21H17/00—Non-fibrous material added to the pulp, characterised by its constitution; Paper-impregnating material characterised by its constitution
  • D21H17/005—Microorganisms or enzymes
• • D—TEXTILES; PAPER
  • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
  • D21H—PULP COMPOSITIONS; PREPARATION THEREOF NOT COVERED BY SUBCLASSES D21C OR D21D; IMPREGNATING OR COATING OF PAPER; TREATMENT OF FINISHED PAPER NOT COVERED BY CLASS B31 OR SUBCLASS D21G; PAPER NOT OTHERWISE PROVIDED FOR
  • D21H17/00—Non-fibrous material added to the pulp, characterised by its constitution; Paper-impregnating material characterised by its constitution
  • D21H17/20—Macromolecular organic compounds
  • D21H17/21—Macromolecular organic compounds of natural origin; Derivatives thereof
  • D21H17/24—Polysaccharides
• • D—TEXTILES; PAPER
  • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
  • D21H—PULP COMPOSITIONS; PREPARATION THEREOF NOT COVERED BY SUBCLASSES D21C OR D21D; IMPREGNATING OR COATING OF PAPER; TREATMENT OF FINISHED PAPER NOT COVERED BY CLASS B31 OR SUBCLASS D21G; PAPER NOT OTHERWISE PROVIDED FOR
  • D21H11/00—Pulp or paper, comprising cellulose or lignocellulose fibres of natural origin only
  • D21H11/12—Pulp from non-woody plants or crops, e.g. cotton, flax, straw, bagasse
• • D—TEXTILES; PAPER
  • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
  • D21H—PULP COMPOSITIONS; PREPARATION THEREOF NOT COVERED BY SUBCLASSES D21C OR D21D; IMPREGNATING OR COATING OF PAPER; TREATMENT OF FINISHED PAPER NOT COVERED BY CLASS B31 OR SUBCLASS D21G; PAPER NOT OTHERWISE PROVIDED FOR
  • D21H17/00—Non-fibrous material added to the pulp, characterised by its constitution; Paper-impregnating material characterised by its constitution
  • D21H17/20—Macromolecular organic compounds
  • D21H17/21—Macromolecular organic compounds of natural origin; Derivatives thereof
  • D21H17/24—Polysaccharides
  • D21H17/28—Starch
• • D—TEXTILES; PAPER
  • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
  • D21H—PULP COMPOSITIONS; PREPARATION THEREOF NOT COVERED BY SUBCLASSES D21C OR D21D; IMPREGNATING OR COATING OF PAPER; TREATMENT OF FINISHED PAPER NOT COVERED BY CLASS B31 OR SUBCLASS D21G; PAPER NOT OTHERWISE PROVIDED FOR
  • D21H17/00—Non-fibrous material added to the pulp, characterised by its constitution; Paper-impregnating material characterised by its constitution
  • D21H17/20—Macromolecular organic compounds
  • D21H17/21—Macromolecular organic compounds of natural origin; Derivatives thereof
  • D21H17/24—Polysaccharides
  • D21H17/28—Starch
  • D21H17/29—Starch cationic

Definitions

• the present invention provides a process for producing a lignocel- lulose-based product, e.g. paper, paperboard (such as cardboard and linerboard) , corrugated board and the like, from an ap ⁇ basementte lignocellulosic starting material, such as vegetable fibres (e.g. vegetable fibres originating from wood, flax, cotton, hemp, jute, bagasse, and the like) .
• a lignocel- lulose-based product e.g. paper, paperboard (such as cardboard and linerboard) , corrugated board and the like
• an ap ⁇ laminatete lignocellulosic starting material such as vegetable fibres (e.g. vegetable fibres originating from wood, flax, cotton, hemp, jute, bagasse, and the like) .
• vegetable fibres e.g. vegetable fibres originating from wood, flax, cotton, hemp, jute, bagasse, and the like
• Lignocellulose-based products prepared from lignocellulosic starting materials including products manufactured starting from vegetable fibre (e.g. wood fibre) prepared by mechanical (e.g. ther omechanical) pulping procedures, mechanical/-chemical pulping procedures (the latter often being denoted "semi-chemical” procedures) or chemical pulping procedures (such as kraft, sulfite or soda pulping), are indispensable everyday materials.
• vegetable fibre e.g. wood fibre
• mechanical/-chemical pulping procedures the latter often being denoted "semi-chemical” procedures
• chemical pulping procedures such as kraft, sulfite or soda pulping
• pulp hereafter denoted "semi-chemical pulp”
• unbleached chemical pulp or pulp made from recycled fibres i.e. pulp prepared from recycled paper, rags and the like
• various strengthening agents to the pulp in order to obtain an end product having adequate strength properties.
• the tensile strength and tear strength under dry and wet conditions are of primary importance; moreover, notably in the case of certain grades of cardboard (e.g. so-called unbleached board for the manufacture of corrugated cardboard boxes for packaging, transport and the like)
• the compression strength of the material is often also an important factor.
• EP 0 433 258 Al discloses a procedure for the production of mechanical pulp from a fibrous product using a chemical and/or enzymatic treatment in which a "binding agent" is linked with the lignin in the fibrous product via the formation of radicals on the lignin part of the fibrous product.
• a binding agent such as cationic starch, and/or proteins as examples of suitable binding agents.
• suitable enzymes laccase, lignin peroxidase and manganese peroxidase, and as examples of suitable chemical agents are mentioned hydrogen peroxide with ferro ions, chlorine dioxide, ozone, and mixtures thereof.
• EP 0 565 109 Al discloses a method for achieving binding of mechanically produced wood fragments via activation of the lignin in the middle lamella of the wood cells by incubation with phenol-oxidizing enzymes. The use of a separate binder is thus avoided by this method.
• US 4,432,921 describes a process for producing a binder for wood products from a phenolic compound having phenolic groups, and the process in question involves treating the phenolic compound with enzymes to activate and oxidatively polymerize the phenolic compound, thereby converting it into the binder.
• strengthened lignocellulose-based products e.g. paper and paperboard
• a procedure involving the use of a combination of a polysaccharide which is substituted with at least substituents containing a phenolic hydroxy group in the following often simply denoted a "phenolic polysaccharide"
• an oxidizing agent and an enzyme capable of catalyzing the oxidation of phenolic groups by the oxidizing agent in this manner exhibit strength properties at least comparable to, and often sig ⁇ nificantly better than, those achievable using previously known processes.
• PCT application No. PCT/DK95/00318 discloses a process for the manufacture of a lignocellulose-based product from a lignocellulosic material, the process comprising treating the lignocellulosic material and a phenolic polysaccharide with an enzyme capable of catalyzing the oxidation of phenolic groups, in the presence of an oxidizing agent.
• phenolic substituents in phenolic polysaccharides suited for use in the context of the invention described therein may suitably be linked to the polysaccharide species by ester linkages or ether linkages.
• Types of phenolic polysaccharides mentioned in PCT/DK95/00318 include those in which the phenolic substituent of the phenolic polysaccharide is a substituent derived from a phenolic compound which occurs in one of the following plant-biosynthetic pathways: from p-coumaric acid to p-coumaryl alcohol, from p-coumaric acid to coniferyl alcohol and from p-coumaric acid to sinapyl alcohol; p-coumaric acid itself and the three mentioned "end products" of the latter three biosynthetic pathways are also mentioned in this respect.
• relevant "intermediate" compounds formed in these biosynthetic pathways are caffeic acid, ferulic acid (i.e. 4-hydroxy-3-methoxycinnamic acid) , 5-hydroxy-ferulic acid and sinapic acid.
• PCT/DK95/00318 discloses the following types of phenolic polysaccharides as being suitable in the context of the invention described therein:
• the present invention thus provides a process for the manufacture of a lignocellulose-based product from a lignocellulosic material, the process comprising treating (i) said lignocellulosic material and (ii) a phenolic polysaccharide other than those specifically disclosed in PCT/DK95/00318 ( vide supra) with (iii) an enzyme capable of catalyzing the oxidation of phenolic groups, in the presence of (iv) an oxidizing agent (more specifically an oxidizing agent appropriate for use with the enzyme in question, in general an oxidizing agent which in conjunction with the enzyme is capable of bringing about oxidation of phenolic groups) .
• Enzymes of the type(s) employed in the process of the present invention i.e. enzymes capable of catalyzing the oxidation of phenolic groups, are believed to lead to the formation, in the presence of an appropriate oxidizing agent, of radicals in the aromatic moieties of phenolic substituents, such as the phenolic functionalities in phenolic polysaccharides and in the lignin part of a lignocellulosic substrate.
• a reaction of central importance in the process of the invention is a reaction between phenolic substituents (especially those on the lignocellulosic material and the phenolic polysaccharide, respectively) which have been "activated" by radical formation as described above.
• the order of mixing/contacting the four components i.e. the lignocellulosic material, the phenolic polysaccharide, the enzyme and the oxidizing agent, is not critical as long as the process set-up ensures that the "activated” lignocellulosic material and the "activated” phenolic polysaccharide are brought together in a way that enables them to react in the desired manner.
• the enzyme and the oxidizing agent may be mixed with, or otherwise brought into contact with, the lignocellulosic material before or after being mixed with the phenolic polysaccharide.
• a technically very satisfactory embodiment of the process of the invention involves the continuous spraying of a solution of the phenolic polysaccharide and a laccase [or another enzyme of the oxidase type which catalyzes oxidation of phenolic groups by oxygen (vide infra) ] at ambient temperature (e.g. about 20-25°C) or a higher temperature (e.g. a temperature in the vicinity of 40°C) onto a thin layer of the moving lignocellulosic material (pulp) on the papermaking machine, in the presence of atmospheric air as oxygen source.
• ambient temperature e.g. about 20-25°C
• a higher temperature e.g. a temperature in the vicinity of 40°C
• reaction medium containing the lignocellulosic material, phenolic polysaccharide and enzyme in the presence of oxidizing agent for a period of at least a few minutes.
• An incubation time in the range of from 1 minute to 10 hours will generally be suitable, although a period of from 1 minute to 2 hours is preferable.
• the process of the invention is well suited to the production of a variety of types of lignocellulose-based products, e.g. various paper and paperboard products (such as cardboard, linerboard and the like) .
• the lignocellulosic starting material employed in the method of the invention can be in any appropriate form, e.g. in the form of vegetable fibre (such as fibres from wood, flax, cotton, hemp, bagasse, jute and the like) , depending on the type of product to be manufactured.
• vegetable fibre such as fibres from wood, flax, cotton, hemp, bagasse, jute and the like
• the lignocellulosic material in question in an amount corresponding to a weight percentage of dry lignocellulosic material [dry substance (DS)] in the medium in the range of 0.1-90%.
• the temperature of the reaction mixture in the process of the invention may suitably be in the range of 10-120°C, as ap ⁇ basementte; however, a temperature in the range of 15-90°C i ⁇ generally to be preferred.
• the reactions involved in a process of the invention may take place very satisfactorily at ambient temperatures around 25°C.
• the phenolic polysaccharide employed in the process of the present invention is a phenolic polysaccharide other than those specifically disclosed in PCT/DK95/00318.
• phenolic substituent(s) in phenolic polysaccharides suited for use in the context of the present invention may suitably be linked to the polysaccharide species by, e.g., ester linkages or ether linkages.
• Particularly suitable phenolic polysaccharides are those which exhibit good solubility in water, and thereby in aqueous media in the context of the invention.
• polysaccharide in the context of the present invention refers not only polysaccharides per se, but also to derivatives - often synthetic derivatives - thereof, especially derivatives which exhibit greater water solubility than the "parent" polysaccharide.
• phenolic polysac ⁇ charides for use in the process of the present invention include the following:
• Phenolic starches other than those specifically mentioned in PCT/DK95/00381 i.e. other than those in which the phenolic substituents are acyl-type substituents derived from 2-, 3- or 4-hydroxybenzoic acid; and phenolic starch derivatives (i.e. starch derivatives into which phenolic substituents have been introduced by chemical or enzymatic means) .
• the "parent" starch from which a phenolic starch or phenolic starch derivative employed in the context of the present invention is derived may, for example, suitably be any of the commercially available types of starch. These include starch from potato, corn (maize) , waxy corn (waxy maize) , wheat, rice, sorghum, waxy sorghum, sago, arrowroot and tapioca (cassava, manioc) . Relevant types of starch thus include both high-amylose starches (such as starch from so-called "high-amylose corn”) and high-amylopectin starches (such as starch from waxy maize, waxy sorghum or glutinous rice) . Potato starch is a very suitable "parent" starch in the context of the invention.
• the starch derivative from which a phenolic starch derivative employed in the context of the present invention is derived may, for example, be a starch ester (e.g. a starch acetate) or an hydroxyalkylstarch (e.g. an hydroxyethyl- or hydroxypropylstarch) .
• Particularly interesting starch derivatives are so-called "cationic starches", such as those wherein the cationic functionality is of the quaternary ammonium type.
• Cationic starches of the quaternary ammonium type are themselves widely used in the paper industry as so-called “wet-end additives” for improving, inter alia, strength and drainage, and as binders in coatings;
• one example of a commercially available cationic starch product of the quaternary ammonium type is CerestarTM CC Bond, available through Cerestar Scandinavia A/S, Holte, Denmark.
• paper, cardboard, linerboard and the like is obtainable when a phenolic cationic starch is used in the preparation thereof in the manner according to the present invention.
• Phenolic celluloses and phenolic cellulose derivatives i.e. celluloses and cellulose derivatives into which phenolic substituents have been introduced by chemical or enzymatic means.
• Some examples of relevant phenolic celluloses are celluloses into which have been introduced phenolic substituents of one or more of the types disclosed in PCT/DK95/00381 and listed above ( vide supra) , e.g. ferulyl substituents, or 2-, 3- or 4-hydroxybenzoyl substituents.
• phenolic cellulose derivatives which are derived from water-soluble cellulose derivatives.
• a cellulose derivative from which a phenolic cellulose derivative employed in the context of the present invention is derived may, for example, suitably be an hydroxyalkylcellulose (e.g. an hydroxyethyl- or hydroxypropylcellulose) , or a carboxymethyl ⁇ cellulose (CMC) or salt thereof (e.g. sodium salt, sometimes known as carmellose sodium) .
• hydroxyalkylcellulose e.g. an hydroxyethyl- or hydroxypropylcellulose
• CMC carboxymethyl ⁇ cellulose
• salt thereof e.g. sodium salt, sometimes known as carmellose sodium
• pectins of non- chenopodi a ceae origin notably pectins which do not naturally contain phenolic substituents, such as citrus pectin
• galactomannans such as guar gum or locust bean gum (ceratonia)
• - arabinogalactan e.g. from western larch timber
• dextrans acacia gum (g
• Preferred types of phenolic substituents in phenolic polysac ⁇ charides employed in the context of the present invention include benzyloxy (i.e. phenyImethoxy) groups having an hydroxy substituent in the aromatic ring. Examples hereof are 2-, 3- and 4-hydroxybenzyloxy.
• the aromatic ring may optionally further be substituted with one or more other substituents, e.g. one or more lower alkyl groups (such as methyl, ethyl, l-propyl or 2-propyl) , one or more lower alkoxy groups (such as methoxy, ethoxy, 1- propoxy or 2-propoxy) and/or one or more further hydroxy groups.
• An example of a suitable alkoxy-substituted 4-hydroxybenzyloxy substituent is 3,5-dimethoxy-4-hydroxybenzyloxy (also known as "syringyl”) .
• 4-Hydroxybenzyloxy and related substituents may be readily introduced into, for example, starches by a simple and straight- tforward chemical procedure (vide infra) employing relatively mild reaction conditions.
• the amount of phenolic polysaccharide employed in the process of the invention will generally be in the range of 0.01-20 weight per cent (%w/w) , typically 0.01-10 % w/w, based on the weight of lignocellulosic material (calculated as dry lignocellulosic material), and amounts in the range of about 0.02-6 % w/w (calcu ⁇ lated in this manner) will often be very suitable.
• any type of enzyme capable of catalyzing oxidation of phenolic groups may be employed in the process of the invention.
• Preferred enzymes are, however, oxidases [e.g. laccases
• laccases have proved to be well suited for use in the method of the invention.
• villo ⁇ u ⁇ Coriolus pin ⁇ i tu ⁇ ] , Polyporu ⁇ , Rhizoctonia (e.g. R. ⁇ olani ) , Coprinu ⁇ (e.g. C. plicatili ⁇ ) , P ⁇ atyrella, Myceliophthora (e.g. M. thermophila) , Schytalidium, Phlebia (e.g. P. radita; see WO 92/01046), Coriolus (e.g. C. hirsutu ⁇ ; see JP 2-238885), Pyricularia or Rigidoporus .
• laccases in the context of the invention include laccase obtainable from Tramete ⁇ villosa and laccase obtainable from My eel i oph thora thermophi 1a.
• Peroxidase enzymes (EC 1.11.1) employed in the method of the invention are preferably peroxidases obtainable from plants (e.g. horseradish peroxidase or soy bean peroxidase) or from microorganisms, such as fungi or bacteria.
• plants e.g. horseradish peroxidase or soy bean peroxidase
• microorganisms such as fungi or bacteria.
• some preferred fungi include strains belonging to the subdivision Deuteromycotina, class Hyphomycetes, e.g.
• fungi include strains belonging to the subdivision Basidiomycotina, class Basidiomycetes, e.g. Coprinu ⁇ , Phanerochaete, Coriolu ⁇ or Tramete ⁇ , in particular Coprinu ⁇ cinereu ⁇ f. micro ⁇ poru ⁇ (IFO 8371), Coprinu ⁇ macrorhizu ⁇ , Phanerochaete chry ⁇ o ⁇ porium (e.g. NA-12) or Trametes ver ⁇ icolor (e.g. PR4 28-A) .
• Basidiomycotina class Basidiomycetes
• Coprinu ⁇ e.g. Coprinu ⁇ , Phanerochaete, Coriolu ⁇ or Tramete ⁇
• Coprinu ⁇ cinereu ⁇ f. micro ⁇ poru ⁇ IFO 8371
• Coprinu ⁇ macrorhizu ⁇ Phanerochaete chry ⁇ o ⁇ porium
• Trametes ver ⁇ icolor e.g. PR4 28
• fungi include strains belonging to the sub ⁇ division Zygomycotina, class Mycoraceae, e.g. Rhizopus or ⁇ ucor, in particular Mucor hiemalis .
• Some preferred bacteria include strains of the order Actino- mycetales, e.g. Streptomyces spheroides (ATTC 23965), Streptomyces thermoviolaceu ⁇ (IFO 12382) or Streptoverticillum verticillium ssp. verticillium.
• Actino- mycetales e.g. Streptomyces spheroides (ATTC 23965), Streptomyces thermoviolaceu ⁇ (IFO 12382) or Streptoverticillum verticillium ssp. verticillium.
• Bacillus pumilu ⁇ ATCC 12905
• Bacillus stearothermophilus Rhodobacter sphaeroides
• Rhodomona ⁇ palu ⁇ tri Streptococcu ⁇ lactis
• Pseudomonas purrocinia ATCC 15958
• Pseudomonas fluorescens NRRL B-ll
• bacteria include strains belonging to Myxococcus, e.g. M. virescen ⁇ .
• an amount in the range of 0.0001-30 mg of oxidase, e.g. laccase, per gram of dry lignocellulosic material will generally be suitable. More typical amounts will be amounts in the range of 0.001-10 mg of oxidase (e.g. laccase) per gram of dry lignocellulosic material.
• laccases in the context of the invention include Tramete ⁇ villosa laccase, and when using this laccase in the process of the invention it will generally be appropriate to employ an amount in the range of 0.02-2000 laccase units (LACU) , such as 0.01-1000 LACU, per gram of dry lignocellulosic material.
• LACU laccase units
• peroxidases When employing peroxidases in the process of the invention, an amount thereof in the range of 0.00001-30 mg of peroxidase (calculated as pure enzyme protein) per gram of dry lignocellulosic material will generally be suitable. More typical amounts will be amounts in the range of 0.0001-10 mg, such as 0.001-1 mg, of peroxidase (calculated as pure enzyme protein) per gram of dry lignocellulosic material.
• preferred peroxidases in the context of the invention include Coprinus peroxidases, such as the previously mentioned C. cinereu ⁇ peroxidase.
• peroxidase units such as 0.1-2000 PODU, e.g. 0.1-1000 PODU, per gram of dry lignocellulosic material.
• T. villosa laccase activity Determination of T. villosa laccase activity and Coprinus peroxidase activity: The determination of T. villosa laccase activity is based on the oxidation of syringaldazin to tetramethoxy azo bis-methylene quinone under aerobic conditions, and 1 LACU is the amount of enzyme which converts 1 ⁇ M of syringaldazin per minute under the following conditions: 19 ⁇ M syringaldazin, 23.2 mM acetate buffer, 30°C, pH 5.5, reaction time 1 minute, shaking; the reaction is monitored spectrophotometric ⁇ ally at 530 nm.
• 1 PODU is the amount of enzyme which catalyses the conversion of 1 ⁇ mol of hydrogen peroxide per minute under the following conditions: 0.88 mM hydrogen peroxide, 1.67 mM 2,2' -azinobis(3-ethylbenzothiazoline-6-sulfonate) , 0.1 M phosphate buffer, pH 7.0, incubation at 30°C; the reaction is monitored photometrically at 418 nm.
• the enzyme(s) and oxidizing agent(s) used in the process of the invention should clearly be matched to one another, and it is clearly preferable that the oxidizing agent(s) in question participate(s) only in the oxidative reaction involved in the binding process, and does/do not otherwise exert any deleterious effect on the substances/materials involved in the process.
• Oxidases e.g. laccases
• Oxidases are, among other reasons, well suited in the context of the invention since they catalyze oxidation by molecular oxygen.
• reactions taking place in vessels open to the atmosphere and involving an oxidase as enzyme will be able to utilize atmospheric oxygen as oxidant; it may, however, be desirable to forcibly aerate the reaction medium with air or another oxygen-containing gas (e.g. oxygen-enriched air or, if ap ⁇ intestinalte, substantially pure oxygen) during the reaction to ensure an adequate supply of oxygen.
• oxygen-containing gas e.g. oxygen-enriched air or, if ap ⁇ basementte, substantially pure oxygen
• hydrogen peroxide is a preferred peroxide in the context of the invention and is suitably employed in a concentration (in the reaction medium) in the range of 0.01- 100 mM.
• the pH in the aqueous medium (reaction medium) in which the process of the invention takes place will be in the range of 3-10, preferably in the range 4-9.
• the present invention also relates to a lignocellulose-based product obtained by, or obtainable by, a process according to the invention as disclosed herein.
• the potato starch (potato flour) employed as described in the following was a standard Danish food-grade retail product manufactured from Danish potatoes and having a declared content of ca. 80% of potato starch, the balance being water.
• the cationic starch (often abbreviated hereafter as CS) employed was obtained through Cerestar Scandinavia A/S, Holte, Denmark.
• 4-Acetoxybenzyl acetate was prepared from 4-hydroxybenzyl alcohol (Fluka, "purum”) as described below.
• the laccase employed was Tramete ⁇ villo ⁇ a laccase, produced by Novo Nordisk A/S, Bagsvaerd, Denmark.
• thermomechanical pulp prepared from mixed Scandinavian softwood (spruce) was obtained from SCA AB, Sundsvall, Sweden.
• TMP thermomechanical pulp
• 4-acetoxybenzyl acetate (4-ABA) 4-Hydroxybenzyl alcohol (50 grams) was dissolved in pyridine (100 ml) . Acetic anhydride (100 ml) was added, and the solution was kept at room temperature overnight. The reaction mixture was then evaporated to remove the bulk of volatile components (e.g. acetic anhydride, acetic acid and pyridine) , and remaining traces of pyridine were removed by co-distillation with toluene. The resulting crude 4-ABA was used without further purification.
• 4-ABA 4-acetoxybenzyl acetate
• a solution containing phenolic starch was prepared as follows:
• a 2% w/w solution of potato starch was prepared by boiling potato starch in the appropriate amount of water for 2 hours. The pH of the solution was adjusted to 10-11 by addition of concentrated (ca. 33% w/w w ca. 11.5M) aqueous NaOH. A quantity of 4- acetoxybenzyl acetate corresponding to 5% w/w of the dry weight of the amount of starch employed was added in the form of a 10% w/w solution in ethyl acetate. The resulting mixture was then stirred at 60°C for 16 hours. The reaction mixture was allowed to cool to ambient temperature, and the pH thereof was then adjusted to 5.5 by addition of glacial acetic acid.
• Example 2 Comparison of PS/laccase and CS in paper manufacture Standard handsheets (ca. 60 g/m 2 ) were prepared fom TMP in accor ⁇ dance with the SCAN standard C26:76. Four dried sheets were then immersed and soaked in a freshly prepared aqueous solution (1.2% w/w,- temperature 25°C) of PS (prepared as described in Example 1, above) to which laccase (157 LACU/liter) had been added immediately prior to the immersion. A second set of four dried sheets was treated in the same way except that laccase was not added to the PS solution. The sheets were removed from the respective solutions and left at ambient temperature for 5 minutes. They were then pressed (0 -> 4 bar) in a sheet press and dried at ca. 105°C using a hot-plate drier.
• a third set of four sheets was treated in a manner completely analogous to that described above for the second set of sheets (i.e. in the absence of laccase), but using cationic starch (CS) instead of phenolic starch (PS) .
• CS cationic starch
• PS phenolic starch
• a fourth set of four dried, but otherwise completely untreated, handsheets was employed as control.
• the tear-strength and tensile strength of the 4 sheets in each of the four sets was measured according to SCAN Pll:73 and SCAN P38:80, respectively.
• the weight increase due to uptake of the "modified starch" in question (PS + laccase, PS alone, or CS alone) for the first three sets of sheets was also determined. All strength and weight measurements were made after equilibrating/conditioning the sheets at 50% relative humidity and 25°C for a minimum of 12 hours.
• PS and PCS can be prepared straightforwardly and relatively cheaply from starch (vide supra) and cationic starch, respectively, and since the use of laccases at the levels required in the process of the invention is relatively inexpensive, strength enhancement using embodiments of the process according to the present invention, exemplified here, can thus provide an attractive alternative to the more "traditional" approach employing cationic starch.

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• 1996
  • 1996-11-08 EP EP96938023A patent/EP0870088A1/de not_active Withdrawn
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  • 1996-11-08 BR BR9611393A patent/BR9611393A/pt not_active Application Discontinuation
  • 1996-11-08 WO PCT/DK1996/000463 patent/WO1997017492A1/en not_active Application Discontinuation
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