Classifications

• • 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
  • C12P19/14—Preparation of compounds containing saccharide radicals produced by the action of a carbohydrase (EC 3.2.x), e.g. by alpha-amylase, e.g. by cellulase, hemicellulase
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61L—METHODS OR APPARATUS FOR STERILISING MATERIALS OR OBJECTS IN GENERAL; DISINFECTION, STERILISATION OR DEODORISATION OF AIR; CHEMICAL ASPECTS OF BANDAGES, DRESSINGS, ABSORBENT PADS OR SURGICAL ARTICLES; MATERIALS FOR BANDAGES, DRESSINGS, ABSORBENT PADS OR SURGICAL ARTICLES
  • A61L15/00—Chemical aspects of, or use of materials for, bandages, dressings or absorbent pads
  • A61L15/16—Bandages, dressings or absorbent pads for physiological fluids such as urine or blood, e.g. sanitary towels, tampons
  • A61L15/22—Bandages, dressings or absorbent pads for physiological fluids such as urine or blood, e.g. sanitary towels, tampons containing macromolecular materials
  • A61L15/28—Polysaccharides or their derivatives
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61L—METHODS OR APPARATUS FOR STERILISING MATERIALS OR OBJECTS IN GENERAL; DISINFECTION, STERILISATION OR DEODORISATION OF AIR; CHEMICAL ASPECTS OF BANDAGES, DRESSINGS, ABSORBENT PADS OR SURGICAL ARTICLES; MATERIALS FOR BANDAGES, DRESSINGS, ABSORBENT PADS OR SURGICAL ARTICLES
  • A61L15/00—Chemical aspects of, or use of materials for, bandages, dressings or absorbent pads
  • A61L15/16—Bandages, dressings or absorbent pads for physiological fluids such as urine or blood, e.g. sanitary towels, tampons
  • A61L15/40—Bandages, dressings or absorbent pads for physiological fluids such as urine or blood, e.g. sanitary towels, tampons containing ingredients of undetermined constitution or reaction products thereof, e.g. plant or animal extracts
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61L—METHODS OR APPARATUS FOR STERILISING MATERIALS OR OBJECTS IN GENERAL; DISINFECTION, STERILISATION OR DEODORISATION OF AIR; CHEMICAL ASPECTS OF BANDAGES, DRESSINGS, ABSORBENT PADS OR SURGICAL ARTICLES; MATERIALS FOR BANDAGES, DRESSINGS, ABSORBENT PADS OR SURGICAL ARTICLES
  • A61L26/00—Chemical aspects of, or use of materials for, wound dressings or bandages in liquid, gel or powder form
  • A61L26/0009—Chemical aspects of, or use of materials for, wound dressings or bandages in liquid, gel or powder form containing macromolecular materials
  • A61L26/0023—Polysaccharides
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08B—POLYSACCHARIDES; DERIVATIVES THEREOF
  • C08B1/00—Preparatory treatment of cellulose for making derivatives thereof, e.g. pre-treatment, pre-soaking, activation
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08B—POLYSACCHARIDES; DERIVATIVES THEREOF
  • C08B37/00—Preparation of polysaccharides not provided for in groups C08B1/00 - C08B35/00; Derivatives thereof
  • C08B37/0006—Homoglycans, i.e. polysaccharides having a main chain consisting of one single sugar, e.g. colominic acid
  • C08B37/0057—Homoglycans, i.e. polysaccharides having a main chain consisting of one single sugar, e.g. colominic acid beta-D-Xylans, i.e. xylosaccharide, e.g. arabinoxylan, arabinofuronan, pentosans; (beta-1,3)(beta-1,4)-D-Xylans, e.g. rhodymenans; Hemicellulose; Derivatives thereof
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08B—POLYSACCHARIDES; DERIVATIVES THEREOF
  • C08B37/00—Preparation of polysaccharides not provided for in groups C08B1/00 - C08B35/00; Derivatives thereof
  • C08B37/006—Heteroglycans, i.e. polysaccharides having more than one sugar residue in the main chain in either alternating or less regular sequence; Gellans; Succinoglycans; Arabinogalactans; Tragacanth or gum tragacanth or traganth from Astragalus; Gum Karaya from Sterculia urens; Gum Ghatti from Anogeissus latifolia; Derivatives thereof
• • 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

Definitions

• the present invention is concerned with the production of gels from plant matter and the resulting gels.
• hemicelluloses Large numbers of plant sources contain hemicelluloses. w hich are composed of various arrangements of pentoses (such as xylose and arabinose). hexoses (such as mannose, glucose and galactose) and/or uronic acids (such as glucuronic and galacturonic acid).
• pentoses such as xylose and arabinose
• hexoses such as mannose, glucose and galactose
• uronic acids such as glucuronic and galacturonic acid
• hemicellulosic materials include xylans (such as arabinoxylan). mannans and galactans. which may be substituted by phenolic acid residues such as ferulic acid (4- hydroxy-3-methoxycinnam ⁇ c acid). coumaric acid (p-hydroxycmnamic acid) or vanillic acid (4-hydroxy-3-methoxyl benzoic acid).
• Such materials occur naturally in cereals such as maize, barley
• French patent specification 2545101 is concerned with modification of sugar beet pectins by reacting an oxidising system comprising an enzyme (such as peroxidase) and an oxidising agent (such as hydrogen peroxide) with pectins which have been isolated from sugar beet.
• the isolation of pectin comprises subjecting the sugar beet to acidic extraction and heat treatment.
• a method of producing a gel material which method comprises:
• the soluble hemicellulosic starting medium is typically prepared from waste testaceous plant material containing a significant quantity (such as at least about 10%. such as about 20%) of arabinoxylan or glucuronoarabinoxylan. which is present in nature primarily in the cell wall regions.
• waste materials which are rich in cell walls, such as cereal husk or bran, or legumes (pulses).
• Typical cereal husk or bran includes maize, barley, wheat, rice or oats, or malt or malt culms (dried germinated barley rootlets).
• the hemicellulosic starting medium is in a substantially ground form having a particle size of not more man about 100 microns.
• the plant material is therefore typically ground, either in dry or wet form (such as milling or wet grinding known as maceration) to the required particle size
• the ground material is typically air classified or sieved to remove starch-
• the method may comprise starch removal by suitable enzyme treatment, for example, with diatase (alpha and/or beta-amylase).
• the glucans are preferably removed from the plant material by enzyme digestion with carbohydrase enzymes such as glucanase.
• the insoluble enzyme treated material may then be dried (in air) before further processing.
• the plant material may have been pre-treated so as to remove the glucans prior to application of the present method, but it is preferred that the method according to the invention involves enzyme treatment so as to remove glucans following the above described grinding of the plant material.
• Suitable glucanases for use according to the invention are commercially available under the trade marks Viscozyme.
• Biofeed and Biofeed Plus which typically also have hemicellulase, cellulase, arabinase and xylanase activity. Viscozyme is currently preferred.
• the non-acidic extraction preferably comprises treatment with hot water or weak alkali typically of less than 0.5% by weight of the aqueous reagent.
• Preferred alkalies are NaOH and KOH.
• the alkali is preferably used in an amount of 0.1 to 10% (typically 0.5 to 2.5%) by weight of the aqueous reagent, for times ⁇ f from 20 minutes to 5 hours (typically about 2 hours).
• gels may be produced from wheat bran and barley dust or culms by using hot water in place of alkali.
• the alkaline extraction may be at a temperature of trom 30 to 100°C and is typically at a temperature of 60 to 90oC, generally for 10 minutes to 5 hours
• temperatures of 60 to 75°C are preferably used for 0.5 to I 5 hours: for weaker gels temperatures of 60 to 85oC are preferably used for 2 to 5 hours.
• Hot water extraction is carried out at temperatures of 50 to 80oC (typically 60 to 70oC) for 0.5 to 2 hours (typically 1 to 1.5 hours).
• the extraction is generally effected with gentle stirring.
• the resulting extracted material generally comprises insoluble cellulose and soluble hemicelluloses: the cellulose is typically removed by centrifugation. either with or without acidification.
• Alkaline extraction will produce an extracted material substantially tree of pectins as the latter are labile in alkaline conditions and are extractable by acidic reagents as described in FR 2545101.
• the hemicellulosic material which is rich in arabinoxylans and is substituted by phenolic acids, is preferably neutralised (for example, using hydrochloric, sulphuric, acetic or citric acid, of which citric acid is preferred).
• Neutralisation is advantageous in that it helps to preclude rapid hydrolysis of ferulic acid residues present in the extracted material: such hydrolysis would damage the gelling properties of the material.
• the solids can be removed from the neutralised extract by filtration or centrifugation which results in improved gel properties.
• Purification of the hemicellulosic material may then be carried out by precipitation with an alcohol such as methanol or ethanol (or industrial methy lated spirit). or iso-propanol (propan-2-ol). Such alcohols may be added in amounts of from 1 .5 to 3.5 volumes according to the fraction desired by molecular weight.
• the hemicellulosic material may alternatively be purified by passage through an activated carbon column and subsequently concentrated by precipitation with ammonium sulphate at 70-80% saturation or any of the above alcohols used for precipitation Alternatively the concentration of the eluate may involve drying (such spray or vacuum rotary drying) and redissolving of the eluate.
• the hemicellulosic material may be further purified by ion-exchange treatment, preferably with a cation exchange resin to remove cationic impurities.
• Differential precipitation or selection by molecular weight cut-off can provide fractions of the polysaccharide which vary in molecular weight and exhibit different rheological properties and consequently viscoelastic properties of the gels they produce.
• precipitation with ammonium sulphate at saturations of between 60 and 80% yields fractions differing in molecular weight; similarly addition of ethanol of 1.7 to 3 volumes yields the same range of fractions.
• a second precipitation may be carried out by addition of 2 to 4 volumes of alcohol.
• the fraction obtained may be filtered (and dried on the filler using ether) or redissolved in water and lyophilised.
• the salt content may be lowered if wished (for example, if the final gel is to be used in foodstuffs), typically by dialysis or tangential flow ultrafiltration.
• the de-salted material may be separated on an anion exchange resin such as Purolite A500 to produce fractions differing in charge (dependent on uronic acid content). Selection of fractions at this stage can further control the rheological/viscoclastic properties of the final product.
• the resulting material may be dried (for example, by spray drying, freeze drying, vacuum rotary drying or drying on a filter using diethyl ether) at this stage; the resulting dried material may be rehydrated prior to treatment with an oxidising system as described below.
• the rehydrated material (or. if relevant, the non-dried material) is then treated with a peroxide (such as H 2 O 2 ) and a peroxidase (such as horseradish peroxidase).
• a peroxide such as H 2 O 2
• a peroxidase such as horseradish peroxidase
• the gel properties may be further modified by the conditions used in peroxidase treatment.
• the treatment with a peroxidase (with a small amount of the peroxide) can result in a weak to strong clear gel at concentrations of 0 05 to 10% (preferably 0.5 to 2.5 %).
• the balance is generally water Polyvalent metal cations (such as Ca 2+ , Cu 2 + , Zn 2+ , Fe 3 + or Al 3+ ) added prior to peroxide/peroxidase treatment w i ll modify the gels, for example such that they can subsequently break into sols.
• the resulting gel which is constituted of cross-linked fibrous material comprising a phenolic acid substituted polysaccharide network, typically rich in arabinoxylans, is highly thermostable and may be autoclaved ( For example, the gel may withstand 15 psi at 122°C for 15 minutes)
• the purified gels m particular can be made with reproducible viscoelastic and rheological properties
• Further control over the viscoelastic properties may be exercised by addition of sugar, salts or alcohols, or by treatment with carbohydrase enzymes.
• the peroxidase is typically used in an amount of 1 to 100 micrograms per gram of substrate; the peroxide is typically used in an amount of the order of one tenth of the amount of peroxidase.
• a gel material obtainable from a hemicellulosic starting medium, said gel material being substantially free of glucans and pectins and comprising a polysaccharide network which comprises:
• the gel material according to the first aspect of the present invention is characterised by infra-red absorbance both in the wavelength range of 1550- 1600 cm -1 and in the wavelength range of 1100 - 1 160 cm -1
• a gel material obtainable from a hemicellulosic starting medium, said material comprising a polysaccharide matrix having a substantially regular array of cross-linking bridges and being characterised by infra-red absorbance both in the wavelength range of 1550 - 1600 cm -1 and in the wavelength range of 1100 - 1 160 cm -1 .
• the gel material according to the second aspect of the present invention is preferably substantially free of glucans and pectins.
• the absence of these relatively large sugar units facilitates the formation of cross-linking bridges within the polysaccharide matrix.
• the polysaccharide matrix preferably comprises a multiplicity of polysaccharide chain segments joined by means of the cross-linking bridges.
• the regular array of cross-linking bridges typically consists essentially of ferulate bridges disposed at bonding locations at substantially regular intervals along the chain segments of the polysaccharide matrix-
• the ferulate moieties are responsible for the characteristic infra-red absorbance both in the wavelength range of 1550 - 1600 cm -1 and in the wavelength range of 1100 -1160 cm -1 exhibited by the gel material.
• the frequency of ferulate bridges within the polysaccharide network influences the properties of the resulting gel.
• the extent of ferulate cross-linking can be substantially controlled by selected reaction conditions during treatment with the peroxide and oxygenase, wherein ferulic acid residues are ox ⁇ datively coupled to form the di-ferulate cross-links.
• a gel material provided with a substantially regular arrangement of ferulate bridges as described above closely approximates an "ideal gel system".
• the term "ideal gel system” as used herein denotes a gel of substantially ordered macromelecular structure, the production of which is desirable due to the substantially predictable properties of the resultant gel.
• a gel according to the present invention is preferably obtained from a hemicellulosic starting medium according to a method substantially as hereinbefore described.
• the present invention therefore allows the production of an ideal gel system from a naturally occurring biological material.
• the above definition of a gel according to the present invention also encompasses a gel material obtained by chemical synthesis techniques.
• the polysaccharide network comprises a plurality of discrete polysaccharide chains linked by means of the ferulate bridges.
• the polysaccharide chain segments are preferably rich in arabinoxylan or glucuronoarabmoxyian moieties.
• the molecular integrity of the arabinoxylan or glucuronoarabmoxyian moieties is substantially disrupted as a result of enzyme treatment of the hemicellulosic starting medium.
• the enzyme treatment typically nn oKes treatment by suitable glucanases, such as glucanases commercially available under the trade marks Viscozyme. Bi ⁇ feed and Biofeed Plus.
• the gel material may further comprise an aqueous liquid, such as water, which is preferably present in an amount of 98-99.9% by weight. There may further be present in the gel material metal cations as hereinbefore described.
• the molecular weight of the gel material according to the present invention is typically in the range of 80 to 600 kdaltons (more generally 90 to 500 kdaltons).
• Viscous solutions rather than gels can be produced by either further limitation of the peroxide concentration or by using a solution having a hemicellulosic concentration below the critical gel-forming concentration of about 0.05 %
• solutions of viscosity varying between 100 and 500 cP ma ⁇ be produced f rom a 0. 1 % hemicellulosic concentration by limiting the peroxide concentration to levels below those which form gels
• extract material derived from maize in the method according to the invention may be blended with extract material derived from other cereals (such as wheat, malt or barley) in the method according to the invention, in proportions m which neither would form a firm gel alone, but a firm gel is formed w ith the two materials
• a firm gel can be obtained with 0.7 to 3 % of material derived from maize and about 2% of material derived from wheat (all the above proportions being on a solids basis).
• the gel material according to the invention may have a wide variety of uses, of which the following are exemplary: 1.
• medicinal compositions for example as a topical formulation or wound dressing (such as for treatment of burns) or debriding agent, as a carrier for iron or zinc, as a lubricant, or a thickener for parenteral compositions, or as an encapsulating agent, or as a slow release vehicle for drug delivery (either for oral, parenteral or anal delivery), or for use for implants and prosthesis purposes for orthopaedic purposes (such as pressure-relief gels), for ocular purposes or suppository uses.
• a particularly preferred medicinal application of the gel is for use as a wound dressing, and there is further provided by the present invention a wound dressing having a surface contact region comprising a gel as hereinbefore described.
• the wound dressing consists essentially of a gel material substantially as hereinbefore described.
• a cold setting gel for use as a stabiliser for ice cream or the like, as a suspending agent for particles such as coconut, as a glazing agent for meat or the like, as a setting agent for jams, or a thickening agent for gravies, purees, sweets, soups or the like, as a soluble fibre, as a food lubricant, as a viscosity agent for flavours, as a canning gel, functional food or fish bait.
• a suspending agent for particles such as coconut, as a glazing agent for meat or the like, as a setting agent for jams, or a thickening agent for gravies, purees, sweets, soups or the like, as a soluble fibre, as a food lubricant, as a viscosity agent for flavours, as a canning gel, functional food or fish bait.
• a gelling agent for example as a gelling agent, a spore biocontainer or a culture biocontainer.
• Figure 1 is a graphic comparison of the hardness, elasticity and brittleness properties of a gel according to the present invention (identified as G.B. Gel), a pectin gel and gelatin:
• Figure 2 illustrates the variation of elasticity and brittleness with polysaccharide concentration of a gel according to the present invention:
• Figure 3 illustrates the variation of hardness and adhesiveness with polysaccharide concentration of a gel according to the present invention
• Figure 4 illustrates the UV spectra of (i) a ferulic acid solution ( Figure 4a). and (ii) a gel according to the present invention ( Figure 4b):
• Figure 5 is a UV reference spectra from which the extent of di ferulate cross- linking in a gel according to the present invention can be estimated:
• Figure 6 illustrates IR spectra of (i) an ungelled polysaccharide (Figure 6a), and (ii) a gel according to the present invention ( Figure 6b).
• Corn bran was subjected to grinding which involved initial wet milling followed by dry milling to an average particle size in the range 80-300 microns.
• a cytase enzyme at 45oC for 2 to 24 hours depending on raw material type and textures (e.g. for milled corn bran a period of about 6 hours).
• the insoluble material consisting mainly of cellulose, was removed by centrifugation at 2500 rpm.
• the supernatant was carefully decanted, neutralised with hydrochloric acid (or citric acid) and dialysed against funning tap water for 2 days.
• the concentration of the dialysed extract was adjusted to 3% w/v with deionised water. 100ml of this solution was taken and 1ml of 100 micrograms/ml horseradish peroxidase mixed in thoroughly. When distributed. 0.5ml of hydrogen peroxide at 40 micrograms H 2 O 2 /ml was added and mixed in; the mixture was then left to set at ambient temperature (5-15 min) or at a higher temperature ( 1-2 min at 40oC).
• An Instron Texture Profile Analyser was used to measure the hardness, brittleness and elasticity of the following:- a gel produced by the above example, gelatin and a pectin gel cross-linked with diferulic acid which was prepared according to the teaching of French patent specification 2545101.
• the gel according to the present invention had superior hardness compared to gelatin and the pectin gel. Similar elasticity to gelatin and was less brittle than either of the other two gels.
• Figures 2 and 3 respectively show the variation of elasticity and brittleness. hardness and adhesiveness with polysaccharide concentration of the gel (w/v).
• An extract of corn bran was prepared as in steps 1-4 of Example 1.
• the supernatant was neutralised w ith acid (hydrochloric or citric ) and dialysed against running water for 2 days.
• the extract was neutralised with hydrochloric acid to pH 6 -6.5 and diluted to about 1.5 % dry matter with water 2.
• the extract was desalted by dialysis against running water for 3 days.
• this step may involve tangential flow ultrafiltration.
• the extract was then passed through a column containing activated carbon at a rate of 2 - 4 bed volumes per hour until the capacity of the column was exhausted.
• An eluate which was substantially free of mono and oligosaccharides. free ferulic and diferulic acids, and other organic compounds which contribute to colour and odour, was obtained.
• the eluate was concentrated by precipitation with ammonium sulphate (other precipitating reagents such as ethanol. IMS propan-2-ol or methanol could have been used). Alternatively the concentration could have been carried out by drying (spray or vacuum rotary drying) and redissolving of the eluate.
• ammonium sulphate other precipitating reagents such as ethanol. IMS propan-2-ol or methanol could have been used.
• concentration could have been carried out by drying (spray or vacuum rotary drying) and redissolving of the eluate.
• the redissolved precipitate produced in stage 4 was subjected to alcohol precipitation by adding 2.8 volume of alcohol.
• the redissolved precipitate was added to water to produce a gelling medium of hemicellulosic concentration between 0.05 and 3.0% w/v. 30 - 100 micromoles of peroxide per gram of the polysaccharide and 100 - 200 microgram of peroxidase enzyme were added to the medium.
• the diferulate cross-linking was further investigated by infra-red spectrophotometry.
• Substituted aromatic acids have many characteristic bands of absorbance between wave numbers 1480 and 1700 cm -1 and between wave numbers 1000 and 1250 cm -1 .

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• 1992
  • 1992-11-16 AU AU29335/92A patent/AU2933592A/en not_active Abandoned
  • 1992-11-16 WO PCT/GB1992/002125 patent/WO1993010158A1/en active IP Right Grant
  • 1992-11-16 RU RU94030463A patent/RU2119758C1/ru active
  • 1992-11-16 WO PCT/GB1992/002122 patent/WO1993010157A1/en active IP Right Grant
  • 1992-11-16 AU AU29488/92A patent/AU670420B2/en not_active Ceased
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