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Cellulose is an
organic compound In chemistry Chemistry is the study of the properties and behavior of . It is a that covers the that make up matter to the composed of s, s and s: their composition, structure, properties, behavior and the changes they undergo during ...
with the
formula In , a formula is a concise way of expressing information symbolically, as in a mathematical formula or a . The informal use of the term ''formula'' in science refers to the . The plural of ''formula'' can be either ''formulas'' (from the mos ...
, a
polysaccharide Polysaccharides (), or polycarbohydrates, are the most abundant carbohydrate A carbohydrate () is a biomolecule , showing alpha helices, represented by ribbons. This poten was the first to have its suckture solved by X-ray crystallograp ...
consisting of a linear chain of several hundred to many thousands of β(1→4) linked
D-glucose
<small>D</small>-glucose
units. Cellulose is an important structural component of the primary
cell wall A cell wall is a structural layer surrounding some types of cells, just outside the cell membrane cell membrane vs. Prokaryotes The cell membrane (also known as the plasma membrane (PM) or cytoplasmic membrane, and historically referred to a ...
of
green plants Viridiplantae (literally "green plants") are a clade A clade (; from grc, , ''klados'', "branch"), also known as a monophyletic group or natural group, is a group of organisms that are monophyly, monophyletic—that is, composed of a common ...

green plants
, many forms of
algae Algae (; singular alga ) is an informal term for a large and diverse group of photosynthetic Photosynthesis is a process used by plants and other organisms to convert Conversion or convert may refer to: Arts, entertainment, and media * Co ...

algae
and the
oomycete Oomycota or oomycetes () form a distinct phylogenetic In biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, Biochemistry, chemical processes, Molecular biology, mole ...
s. Some species of
bacteria Bacteria (; common noun bacteria, singular bacterium) are ubiquitous, mostly free-living organisms often consisting of one Cell (biology), biological cell. They constitute a large domain (biology), domain of prokaryotic microorganisms. Typ ...

bacteria
secrete it to form
biofilm A biofilm comprises any Syntrophy, syntrophic consortium of microorganisms in which cell (biology), cells cell adhesion, stick to each other and often also to a surface. These adherent cells become embedded within a slimy extracellular matrix th ...

biofilm
s. Cellulose is the most abundant
organic polymer A polymer (; Greek ''poly- Poly, from the Greek :wikt:πολύς, πολύς meaning "many" or "much", may refer to: Businesses * China Poly Group Corporation, a Chinese business group, and its subsidiaries: ** Poly Property, a Hong Kong inco ...
on Earth. The cellulose content of
cotton Cotton is a soft, fluffy staple fiber Fiber or fibre (from la, fibra, links=no) is a natural Nature, in the broadest sense, is the natural, physical, material world or universe The universe ( la, universus) is all of s ...

cotton
fiber is 90%, that of
wood Wood is a porous and fibrous structural tissue found in the stems and roots of tree In botany, a tree is a perennial plant with an elongated Plant stem, stem, or trunk (botany), trunk, supporting branches and leaves in most species. ...

wood
is 40–50%, and that of dried
hemp Hemp, or industrial hemp, is a botanical class of ''Cannabis sativa ''Cannabis sativa'' is an annual herbaceous flowering plant The flowering plants, also known as Angiospermae (), or Magnoliophyta (), are the most diverse group of Embry ...
is approximately 57%. Cellulose is mainly used to produce
paperboard Paperboard is a thick paper Paper is a thin sheet material Material is a substance Substance may refer to: * Substance (Jainism), a term in Jain ontology to denote the base or owner of attributes * Chemical substance, a material with ...
and
paper Paper is a thin sheet material Material is a substance Substance may refer to: * Substance (Jainism), a term in Jain ontology to denote the base or owner of attributes * Chemical substance, a material with a definite chemical composition ...

paper
. Smaller quantities are converted into a wide variety of derivative products such as
cellophane Cellophane is a thin, transparent sheet made of regenerated cellulose. Its low permeability to air, oils, Fat, greases, bacteria, and water makes it useful for food packaging. Cellophane is highly permeable to water vapour, but may be coated with ...
and
rayon Rayon is a synthetic fiber Synthetic fiber or synthetic fibre (in British English British English (BrE) is the standard dialect A standard language (also standard variety, standard dialect, and standard) is a language variety that ...

rayon
. Conversion of cellulose from
energy crop Energy crops are low-cost and low-maintenance crops grown solely for energy production by combustion (not for food). The crops are processed into solid, liquid or gaseous fuels, such as pellets, bioethanol or biogas. The fuels are burned to gene ...
s into
biofuel Biofuel is fuel that is produced through contemporary processes from biomass, rather than by the very slow geological processes involved in the formation of fossil fuels, such as oil. Since biomass technically can be used as a fuel directly (e. ...

biofuel
s such as
cellulosic ethanol Cellulosic ethanol is (ethyl alcohol) produced from (the stringy fiber of a plant) rather than from the plant's s or . It can be produced from es, , , or other plants. It is generally discussed for use as a . The that plants offsets some of the ...
is under development as a
renewable fuelRenewable fuels are fuel A fuel is any material that can be made to react with other substances so that it releases energy as heat energy or to be used for work. The concept was originally applied solely to those materials capable of releasing ...
source. Cellulose for industrial use is mainly obtained from
wood pulp Pulp is a lignocellulosic fibrous material prepared by chemically or mechanically separating cellulose fiber Cellulose fibers () are fibers made with ethers or esters of cellulose, which can be obtained from the bark, wood or leaves of plants ...
and
cotton Cotton is a soft, fluffy staple fiber Fiber or fibre (from la, fibra, links=no) is a natural Nature, in the broadest sense, is the natural, physical, material world or universe The universe ( la, universus) is all of s ...

cotton
. Some animals, particularly
ruminant Ruminants (suborder Ruminantia) are large ungulate, hoofed herbivorous grazing or browsing mammals that are able to acquire nutrients from plant-based food by Enteric fermentation, fermenting it in a specialized stomach prior to digestion, princi ...
s and
termite Termites are Eusociality, eusocial insects that are classified at the Taxonomy (biology), taxonomic rank of infraorder Isoptera, or alternatively as Taxonomic rank#All ranks, epifamily Termitoidae, within the order Blattodea (along with cockroa ...

termite
s, can
digest Digest may refer to: In biology: *Digestion of food *Restriction digest In literature or publication: *''The Digest'', formerly the English and Empire Digest *Digest size magazine format *Digest (Roman law), ''Digest'' (Roman law), also known as ...
cellulose with the help of
symbiotic Symbiosis (from Greek#REDIRECT Greek Greek may refer to: Greece Anything of, from, or related to Greece Greece ( el, Ελλάδα, , ), officially the Hellenic Republic, is a country located in Southeast Europe. Its population is approx ...

symbiotic
micro-organisms that live in their guts, such as '' Trichonympha''. In
human nutrition Human nutrition deals with the provision of essential nutrients in food that are necessary to support human life Life is a characteristic that distinguishes physical entities that have biological processes, such as signaling and self ...
, cellulose is a non-digestible constituent of
insoluble In chemistry Chemistry is the science, scientific study of the properties and behavior of matter. It is a natural science that covers the Chemical element, elements that make up matter to the chemical compound, compounds composed of atom ...
dietary fiber Dietary fiber (British spelling fibre) or roughage is the portion of plant-derived food that cannot be completely broken down by human digestive enzyme Digestive may refer to: Biology *Digestion Digestion is the breakdown of large insolub ...
, acting as a
hydrophilic A hydrophile is a molecule File:Pentacene on Ni(111) STM.jpg, A scanning tunneling microscopy image of pentacene molecules, which consist of linear chains of five carbon rings. A molecule is an electrically neutral group of two or more atoms ...
bulking agent for
feces Feces ( or faeces) is the solid or semi-solid remains of food that was not digested in the small intestine The small intestine or small bowel is an organ (anatomy), organ in the human gastrointestinal tract, gastrointestinal tract where mos ...

feces
and potentially aiding in
defecation frame, Human anatomy of the ''anorecturm'' (anus and rectum">anus.html" ;"title="Human anatomy of the ''anorecturm'' (anus">Human anatomy of the ''anorecturm'' (anus and rectum) Defecation (or defaecation) is the final act of digestion, by whi ...
.


History

Cellulose was discovered in 1838 by the French chemist
Anselme Payen Anselme Payen (; 6 January 1795 – 12 May 1871) was a French chemist A chemist (from Greek ''chēm(ía)'' alchemy; replacing ''chymist'' from Medieval Latin ''alchemist'') is a scientist A scientist is a person who conducts Scientific m ...

Anselme Payen
, who isolated it from plant matter and determined its chemical formula. Cellulose was used to produce the first successful
thermoplastic polymer A thermoplastic, or thermosoftening plastic, is a plastic polymer A polymer (; Greek '' poly-'', "many" + '' -mer'', "part") is a substance or material consisting of very large molecule File:Pentacene on Ni(111) STM.jpg, A scanning tunne ...
,
celluloid Celluloids are a class of materials produced by mixing nitrocellulose Nitrocellulose (also known as cellulose nitrate, flash paper, flash cotton, guncotton, pyroxylin and flash string, depending on form) is a highly flammable compound formed ...

celluloid
, by Hyatt Manufacturing Company in 1870. Production of
rayon Rayon is a synthetic fiber Synthetic fiber or synthetic fibre (in British English British English (BrE) is the standard dialect A standard language (also standard variety, standard dialect, and standard) is a language variety that ...

rayon
("artificial
silk Silk is a natural Nature, in the broadest sense, is the natural, physical, material world or universe The universe ( la, universus) is all of space and time and their contents, including planets, stars, galaxies, and all o ...

silk
") from cellulose began in the 1890s and
cellophane Cellophane is a thin, transparent sheet made of regenerated cellulose. Its low permeability to air, oils, Fat, greases, bacteria, and water makes it useful for food packaging. Cellophane is highly permeable to water vapour, but may be coated with ...
was invented in 1912.
Hermann Staudinger Hermann Staudinger (; 23 March 1881 – 8 September 1965) was a German organic chemist who demonstrated the existence of macromolecule macromolecule A macromolecule is a very large molecule File:Pentacene on Ni(111) STM.jpg, A scanning tu ...

Hermann Staudinger
determined the polymer structure of cellulose in 1920. The compound was first chemically synthesized (without the use of any biologically derived
enzyme Enzymes () are proteins that act as biological catalysts (biocatalysts). Catalysts accelerate chemical reactions. The molecules upon which enzymes may act are called substrate (chemistry), substrates, and the enzyme converts the substrates in ...

enzyme
s) in 1992, by Kobayashi and Shoda.


Structure and properties

Cellulose has no taste, is odorless, is
hydrophilic A hydrophile is a molecule File:Pentacene on Ni(111) STM.jpg, A scanning tunneling microscopy image of pentacene molecules, which consist of linear chains of five carbon rings. A molecule is an electrically neutral group of two or more atoms ...
with the
contact angle The contact angle is the angle In Euclidean geometry Euclidean geometry is a mathematical system attributed to Alexandrian Greek mathematics , Greek mathematician Euclid, which he described in his textbook on geometry: the ''Euclid's Eleme ...

contact angle
of 20–30 degrees, is insoluble in
water Water (chemical formula H2O) is an Inorganic compound, inorganic, transparent, tasteless, odorless, and Color of water, nearly colorless chemical substance, which is the main constituent of Earth's hydrosphere and the fluids of all known li ...

water
and most organic
solvent A solvent (from the Latin Latin (, or , ) is a classical language belonging to the Italic languages, Italic branch of the Indo-European languages. Latin was originally spoken in the area around Rome, known as Latium. Through the power of the ...

solvent
s, is
chiral Chirality is a property of important in several branches of science. The word ''chirality'' is derived from the (''kheir''), "hand", a familiar chiral object. An object or a system is ''chiral'' if it is distinguishable from its ; that is, i ...
and is
biodegradable Biodegradation is the breakdown of organic matter by microorganisms, such as bacteria and fungi. Mechanisms The process of biodegradation can be divided into three stages: biodeterioration, biofragmentation, and assimilation (biology), assimila ...
. It was shown to melt at 467 °C in pulse tests made by Dauenhauer ''et al.'' (2016). It can be broken down chemically into its glucose units by treating it with concentrated mineral acids at high temperature. Cellulose is derived from units, which
condense Condensation is the change of the state of matter In physics Physics is the natural science that studies matter, its Elementary particle, fundamental constituents, its Motion (physics), motion and behavior through Spacetime, space ...
through β(1→4)-
glycosidic bond A glycosidic bond or glycosidic linkage is a type of covalent bond that joins a carbohydrate (sugar) molecule to another group, which may or may not be another carbohydrate. A glycosidic bond is formed between the hemiacetal or hemiketal group ...
s. This linkage motif contrasts with that for α(1→4)-glycosidic bonds present in
starch Starch or amylum is a polymeric A polymer (; Greek '' poly-'', "many" + '' -mer'', "part") is a substance Substance may refer to: * Substance (Jainism), a term in Jain ontology to denote the base or owner of attributes * Chemical substance ...
and
glycogen Glycogen is a multibranched polysaccharide Polysaccharides (), or polycarbohydrates, are the most abundant found in . They are long chain carbohydrates composed of units bound together by . This carbohydrate can react with water () usi ...

glycogen
. Cellulose is a straight chain polymer. Unlike starch, no coiling or branching occurs and the molecule adopts an extended and rather stiff rod-like conformation, aided by the equatorial conformation of the glucose residues. The multiple
hydroxyl groups A hydroxy or hydroxyl group is a functional group with the chemical formula -OH and composed of one oxygen Oxygen is the chemical element Image:Simple Periodic Table Chart-blocks.svg, 400px, Periodic table, The periodic table of the ...

hydroxyl groups
on the glucose from one chain form
hydrogen bond A hydrogen bond (or H-bond) is a primarily electrostatic Electrostatics is a branch of physics Physics is the that studies , its , its and behavior through , and the related entities of and . "Physical science is that department ...

hydrogen bond
s with oxygen atoms on the same or on a neighbor chain, holding the chains firmly together side-by-side and forming ''microfibrils'' with high
tensile strength Ultimate tensile strength (UTS), often shortened to tensile strength (TS), ultimate strength, or F_\text within equations, is the maximum stress that a material can withstand while being stretched or pulled before breaking. In brittle tensi ...
. This confers tensile strength in
cell wall A cell wall is a structural layer surrounding some types of cells, just outside the cell membrane cell membrane vs. Prokaryotes The cell membrane (also known as the plasma membrane (PM) or cytoplasmic membrane, and historically referred to a ...
s where cellulose microfibrils are meshed into a polysaccharide ''matrix''. The high tensile strength of plant stems and of the tree wood also arises from the arrangement of cellulose fibers intimately distributed into the
lignin Lignin is a class of complex organic polymers that form key structural materials in the support tissues of most plants. Lignins are particularly important in the formation of cell walls, especially in wood and Bark (botany), bark, because they l ...

lignin
matrix. The mechanical role of cellulose fibers in the wood matrix responsible for its strong structural resistance, can somewhat be compared to that of the
reinforcement bar Rebar (short for reinforcing bar), known when massed as reinforcing steel or reinforcement steel, is a steel Steel is an alloy of iron with typically a few tenths of a percent of carbon to improve its strength of materials, strength and fract ...
s in
concrete Concrete is a composite material A composite material (also called a composition material or shortened to composite, which is the common name) is a material Material is a substance Substance may refer to: * Substance (Jainism), a ter ...

concrete
,
lignin Lignin is a class of complex organic polymers that form key structural materials in the support tissues of most plants. Lignins are particularly important in the formation of cell walls, especially in wood and Bark (botany), bark, because they l ...

lignin
playing here the role of the hardened cement paste acting as the "glue" in between the cellulose fibers. Mechanical properties of cellulose in primary plant cell wall are correlated with growth and expansion of plant cells. Live fluorescence microscopy techniques are promising in investigation of the role of cellulose in growing plant cells. Compared to starch, cellulose is also much more
crystalline A crystal or crystalline solid is a solid Solid is one of the four fundamental states of matter (the others being liquid, gas and plasma). The molecules in a solid are closely packed together and contain the least amount of kinet ...
. Whereas starch undergoes a crystalline to
amorphous In condensed matter physics Condensed matter physics is the field of that deals with the macroscopic and microscopic physical properties of , especially the and which arise from forces between s. More generally, the subject deals with " ...
transition when heated beyond 60–70 °C in water (as in cooking), cellulose requires a temperature of 320 °C and pressure of 25
MPa MPA or mPa may refer to: Academia Academic degrees * Master of Performing Arts * Master of Professional Accountancy * Master of Public Administration * Master of Public Affairs Schools * Mesa Preparatory Academy * Morgan Park Academy * Mounds ...
to become amorphous in water. Several types of cellulose are known. These forms are distinguished according to the location of hydrogen bonds between and within strands. Natural cellulose is cellulose I, with structures Iα and Iβ. Cellulose produced by bacteria and algae is enriched in Iα while cellulose of higher plants consists mainly of Iβ. Cellulose in regenerated cellulose fibers is cellulose II. The conversion of cellulose I to cellulose II is irreversible, suggesting that cellulose I is
metastable In chemistry and physics, metastability denotes an intermediate energetic state within a dynamical system other than the system's ground state, state of least energy. A ball resting in a hollow on a slope is a simple example of metastability. I ...

metastable
and cellulose II is stable. With various chemical treatments it is possible to produce the structures cellulose III and cellulose IV. Many properties of cellulose depend on its chain length or
degree of polymerizationThe degree of polymerization, or DP, is the number of monomeric units in a macromolecule or polymer or oligomer molecule. For a homopolymer, there is only one type of monomeric unit and the ''number-average'' degree of polymerization is given by DP ...

degree of polymerization
, the number of glucose units that make up one polymer molecule. Cellulose from wood pulp has typical chain lengths between 300 and 1700 units; cotton and other plant fibers as well as bacterial cellulose have chain lengths ranging from 800 to 10,000 units. Molecules with very small chain length resulting from the breakdown of cellulose are known as cellodextrins; in contrast to long-chain cellulose, cellodextrins are typically soluble in water and organic solvents. The chemical formula of cellulose is (C6H10O5)n where n is the degree of polymerization and represents the number of glucose groups. Plant-derived cellulose is usually found in a mixture with
hemicellulose A hemicellulose (also known as polyose) is one of a number of heteropolymer, heteropolymers (matrix polysaccharides), such as arabinoxylans, present along with cellulose in almost all embryophyte, terrestrial plant cell walls.Scheller HV, Ulvskov H ...

hemicellulose
,
lignin Lignin is a class of complex organic polymers that form key structural materials in the support tissues of most plants. Lignins are particularly important in the formation of cell walls, especially in wood and Bark (botany), bark, because they l ...

lignin
,
pectin Pectin (from grc, πηκτικός ', "congealed, curdled") is a structural acidic heteropolysaccharide contained in the primary and middle lamella The middle lamella is a layer that cements together the primary cell wall A cell wall is a ...

pectin
and other substances, while bacterial cellulose is quite pure, has a much higher water content and higher tensile strength due to higher chain lengths. Cellulose consists of fibrils with
crystalline A crystal or crystalline solid is a solid Solid is one of the four fundamental states of matter (the others being liquid, gas and plasma). The molecules in a solid are closely packed together and contain the least amount of kinet ...

crystalline
and
amorphous In condensed matter physics Condensed matter physics is the field of that deals with the macroscopic and microscopic physical properties of , especially the and which arise from forces between s. More generally, the subject deals with " ...
regions. These cellulose fibrils may be individualized by mechanical treatment of cellulose pulp, often assisted by chemical
oxidation Redox (reduction–oxidation, pronunciation: or ) is a type of chemical reaction A chemical reaction is a process that leads to the chemical transformation of one set of chemical substance A chemical substance is a form of matter ...

oxidation
or
enzymatic Enzymes () are protein Proteins are large biomolecules and macromolecules that comprise one or more long chains of amino acid residue (biochemistry), residues. Proteins perform a vast array of functions within organisms, including Enzyme ...

enzymatic
treatment, yielding semi-flexible generally 200 nm to 1 μm in length depending on the treatment intensity. Cellulose pulp may also be treated with strong acid to
hydrolyze Hydrolysis (; ) is any chemical reaction in which a molecule of water breaks one or more chemical bonds. The term is used broadly for substitution, elimination, and solvation reactions in which water is the nucleophile In chemistry, a nucleop ...
the amorphous fibril regions, thereby producing short rigid a few 100 nm in length. These s are of high technological interest due to their
self-assembly File:Iron oxide nanocube.jpg, upright=1.2, Transmission electron microscopy image of an iron oxide nanoparticle. Regularly arranged dots within the dashed border are columns of Fe atoms. Left inset is the corresponding electron diffraction pattern. ...

self-assembly
into cholesteric liquid crystals, production of
hydrogel A hydrogel is a crosslinked hydrophilic A hydrophile is a molecule File:Pentacene on Ni(111) STM.jpg, A scanning tunneling microscopy image of pentacene molecules, which consist of linear chains of five carbon rings. A molecule is an electr ...

hydrogel
s or
aerogel Aerogel is a Manufacturing, synthetic porous ultralight material derived from a gel, in which the liquid component for the gel has been replaced with a gas without significant collapse of the gel structure. The result is a solid with extremely l ...

aerogel
s, use in
nanocompositeNanocomposite is a multiphase solid material where one of the phases has one, two or three dimensions of less than 100 nanometers (nm) or structures having nano-scale repeat distances between the different phases that make up the material. The idea ...
s with superior thermal and mechanical properties, and use as Pickering stabilizers for
emulsions An emulsion is a mixture In chemistry, a mixture is a material made up of two or more different chemical substances which are not chemically combined. A mixture is the physical combination of two or more substances in which the identities are ...

emulsions
.


Processing


Biosynthesis

In
plant Plants are predominantly photosynthetic Photosynthesis is a process used by plants and other organisms to Energy transformation, convert light energy into chemical energy that, through cellular respiration, can later be released to fuel ...
s cellulose is synthesized at the
plasma membrane The cell membrane (also known as the plasma membrane (PM) or cytoplasmic membrane, and historically referred to as the plasmalemma) is a biological membrane A biological membrane, biomembrane or cell membrane is a selectively permeable membra ...
by rosette terminal complexes (RTCs). The RTCs are
hexameric In chemistry and biochemistry, an oligomer () is a molecule that consists of a few similar or identical repeating units which could be derived, actually or conceptually, from copies of a smaller molecule, its monomer. Quote: ''Oligomer molecule: A m ...
protein structures, approximately 25 nm in diameter, that contain the cellulose synthase enzymes that synthesise the individual cellulose chains. Each RTC floats in the cell's plasma membrane and "spins" a microfibril into the
cell wall A cell wall is a structural layer surrounding some types of cells, just outside the cell membrane cell membrane vs. Prokaryotes The cell membrane (also known as the plasma membrane (PM) or cytoplasmic membrane, and historically referred to a ...
. RTCs contain at least three different cellulose synthases, encoded by ''CesA'' (''Ces'' is short for "cellulose synthase") genes, in an unknown
stoichiometry Stoichiometry refers to the relationship between the quantities of reactant 200px, Reactants, such as sulfur (''pictured''), are the starting materials that are used in chemical reactions. A reagent is a substance or compound added to a sy ...
. Separate sets of ''CesA'' genes are involved in primary and secondary cell wall biosynthesis. There are known to be about seven subfamilies in the plant ''CesA'' superfamily, some of which include the more cryptic, tentatively-named ''Csl'' (cellulose synthase-like) enzymes. These cellulose syntheses use UDP-glucose to form the β(1→4)-linked cellulose. Bacterial cellulose is produced using the same family of proteins, although the gene is called ''BcsA'' for "bacterial cellulose synthase" or ''CelA'' for "cellulose" in many instances. In fact, plants acquired ''CesA'' from the endosymbiosis event that produced the
chloroplast A chloroplast is a type of membrane-bound organelle In cell biology, an organelle is a specialized subunit, usually within a cell (biology), cell, that has a specific function. The name ''organelle'' comes from the idea that these structure ...

chloroplast
. All cellulose synthases known belongs to
glucosyltransferaseGlucosyltransferases are a type of glycosyltransferase Most glycosyltransferase enzymes form one of two folds: GT-A or GT-B Glycosyltransferases (GTFs, Gtfs) are enzyme Enzymes () are proteins that act as biological catalysts (biocatalysts). C ...
family 2 (GT2). Cellulose synthesis requires chain initiation and elongation, and the two processes are separate. Cellulose synthase (''CesA'') initiates cellulose polymerization using a
steroid A steroid is a biologically active organic compound In chemistry Chemistry is the study of the properties and behavior of . It is a that covers the that make up matter to the composed of s, s and s: their composition, structure, ...

steroid
primer,
sitosterol β-Sitosterol (beta-sitosterol) is one of several phytosterolPhytosterols, which encompass plant sterols and stanols, are phytosteroid Phytosteroids, also known as plant steroids, are naturally occurring steroid , a steroid with 27 carbon a ...

sitosterol
-beta-
glucoside A glucoside is a glycoside In chemistry Chemistry is the science, scientific study of the properties and behavior of matter. It is a natural science that covers the Chemical element, elements that make up matter to the chemical compoun ...
, and UDP-glucose. It then utilizes
UDP UDP may refer to: Political parties * Ulster Democratic Party, in Northern Ireland * ''União Democrática Popular'' (People's Democratic Union (Portugal)) * ''Unidad Democrática y Popular'' (Democratic and Popular Union), a former Bolivian umbr ...

UDP
-D-glucose precursors to elongate the growing cellulose chain. A
cellulase Cellulase is any of several enzymes Enzymes () are proteins that act as biological catalysts (biocatalysts). Catalysts accelerate chemical reactions. The molecules upon which enzymes may act are called substrate (chemistry), substrates, a ...
may function to cleave the primer from the mature chain. Cellulose is also synthesised by
tunicate A tunicate is a marine invertebrate animal, a member of the subphylum Tunicata (). It is part of the Chordata, a phylum which includes all animals with dorsal nerve cords and notochords (including vertebrates). The subphylum was at one time cal ...
animals, particularly in the
test Test(s), testing, or TEST may refer to: * Test (assessment), an educational assessment intended to measure the respondents' knowledge or other abilities Arts and entertainment * Test (2013 film), ''Test'' (2013 film), an American film * Test ( ...
s of
ascidian Ascidiacea, commonly known as the ascidians, tunicate A tunicate is a marine invertebrate animal, a member of the subphylum Tunicata . It is part of the Chordata, a phylum which includes all animals with dorsal nerve cords and notochords (incl ...

ascidian
s (where the cellulose was historically termed "tunicine" (tunicin)).


Breakdown (cellulolysis)

Cellulolysis is the process of breaking down cellulose into smaller polysaccharides called cellodextrins or completely into
glucose Glucose is a simple with the . Glucose is the most abundant , a subcategory of s. Glucose is mainly made by and most during from water and carbon dioxide, using energy from sunlight, where it is used to make in s, the most abundant carbohydr ...

glucose
units; this is a
hydrolysis Hydrolysis (; ) is any chemical reaction in which a molecule of water breaks one or more chemical bonds. The term is used broadly for substitution Substitution may refer to: Arts and media *Chord substitution, in music, swapping one chord fo ...

hydrolysis
reaction. Because cellulose molecules bind strongly to each other, cellulolysis is relatively difficult compared to the breakdown of other
polysaccharide Polysaccharides (), or polycarbohydrates, are the most abundant carbohydrate A carbohydrate () is a biomolecule , showing alpha helices, represented by ribbons. This poten was the first to have its suckture solved by X-ray crystallograp ...
s. However, this process can be significantly intensified in a proper
solvent A solvent (from the Latin Latin (, or , ) is a classical language belonging to the Italic languages, Italic branch of the Indo-European languages. Latin was originally spoken in the area around Rome, known as Latium. Through the power of the ...

solvent
, e.g. in an
ionic liquid An ionic liquid (IL) is a salt Salt is a mineral In geology and mineralogy, a mineral or mineral species is, broadly speaking, a solid chemical compound with a fairly well-defined chemical composition and a specific crystal structure ...
. Most mammals have limited ability to digest dietary fiber such as cellulose. Some
ruminant Ruminants (suborder Ruminantia) are large ungulate, hoofed herbivorous grazing or browsing mammals that are able to acquire nutrients from plant-based food by Enteric fermentation, fermenting it in a specialized stomach prior to digestion, princi ...
s like cows and sheep contain certain
symbiotic Symbiosis (from Greek#REDIRECT Greek Greek may refer to: Greece Anything of, from, or related to Greece Greece ( el, Ελλάδα, , ), officially the Hellenic Republic, is a country located in Southeast Europe. Its population is approx ...

symbiotic
Anaerobic organism, anaerobic bacteria (such as ''Cellulomonas'' and ''Ruminococcus'' species, spp.) in the flora of the rumen, and these bacteria produce
enzyme Enzymes () are proteins that act as biological catalysts (biocatalysts). Catalysts accelerate chemical reactions. The molecules upon which enzymes may act are called substrate (chemistry), substrates, and the enzyme converts the substrates in ...

enzyme
s called
cellulase Cellulase is any of several enzymes Enzymes () are proteins that act as biological catalysts (biocatalysts). Catalysts accelerate chemical reactions. The molecules upon which enzymes may act are called substrate (chemistry), substrates, a ...
s that hydrolyze cellulose. The breakdown products are then used by the bacteria for proliferation. The bacterial mass is later digested by the ruminant in its digestive system (stomach and small intestine). Horses use cellulose in their diet by hindgut fermentation, fermentation in their hindgut. Some
termite Termites are Eusociality, eusocial insects that are classified at the Taxonomy (biology), taxonomic rank of infraorder Isoptera, or alternatively as Taxonomic rank#All ranks, epifamily Termitoidae, within the order Blattodea (along with cockroa ...

termite
s contain in their hindguts certain flagellate protozoa producing such enzymes, whereas others contain bacteria or may produce cellulase. The enzymes used to wikt:cleave, cleave the glycosidic linkage in cellulose are glycoside hydrolases including endo-acting
cellulase Cellulase is any of several enzymes Enzymes () are proteins that act as biological catalysts (biocatalysts). Catalysts accelerate chemical reactions. The molecules upon which enzymes may act are called substrate (chemistry), substrates, a ...
s and exo-acting glucosidases. Such enzymes are usually secreted as part of multienzyme complexes that may include dockerins and carbohydrate-binding modules.


Breakdown (thermolysis)

At temperatures above 350 °C, cellulose undergoes thermolysis (also called 'pyrolysis'), decomposing into solid char, vapors, aerosols, and gases such as carbon dioxide. Maximum yield of vapors which condense to a liquid called ''bio-oil'' is obtained at 500 °C. Semi-crystalline cellulose polymers react at pyrolysis temperatures (350–600 °C) in a few seconds; this transformation has been shown to occur via a solid-to-liquid-to-vapor transition, with the liquid (called ''intermediate liquid cellulose'' or ''molten cellulose'') existing for only a fraction of a second. Glycosidic bond cleavage produces short cellulose chains of two-to-seven monomers comprising the melt. Vapor bubbling of intermediate liquid cellulose produces aerosols, which consist of short chain anhydro-oligomers derived from the melt. Continuing decomposition of molten cellulose produces volatile compounds including levoglucosan, furans, pyrans, light oxygenates and gases via primary reactions. Within thick cellulose samples, volatile compounds such as levoglucosan undergo 'secondary reactions' to volatile products including pyrans and light oxygenates such as glycolaldehyde.


Hemicellulose

Hemicelluloses are
polysaccharide Polysaccharides (), or polycarbohydrates, are the most abundant carbohydrate A carbohydrate () is a biomolecule , showing alpha helices, represented by ribbons. This poten was the first to have its suckture solved by X-ray crystallograp ...
s related to cellulose that comprise about 20% of the biomass of embryophyte, land plants. In contrast to cellulose, hemicelluloses are derived from several sugars in addition to
glucose Glucose is a simple with the . Glucose is the most abundant , a subcategory of s. Glucose is mainly made by and most during from water and carbon dioxide, using energy from sunlight, where it is used to make in s, the most abundant carbohydr ...

glucose
, especially xylose but also including mannose, galactose, rhamnose, and arabinose. Hemicelluloses consist of shorter chains – between 500 and 3000 sugar units. Furthermore, hemicelluloses are branched, whereas cellulose is unbranched.


Regenerated cellulose

Cellulose is soluble in several kinds of media, several of which are the basis of commercial technologies. These dissolution process is reversible and are used in the production of regenerated celluloses (such as viscose and
cellophane Cellophane is a thin, transparent sheet made of regenerated cellulose. Its low permeability to air, oils, Fat, greases, bacteria, and water makes it useful for food packaging. Cellophane is highly permeable to water vapour, but may be coated with ...
) from dissolving pulp. The most important solubilizing agent is carbon disulfide in the presence of alkali. Other agents include Schweizer's reagent, N-Methylmorpholine N-oxide, ''N''-methylmorpholine ''N''-oxide, and lithium chloride in dimethylacetamide. In general these agents modify the cellulose, rendering it soluble. The agents are then removed concomitant with the formation of fibers. Cellulose is also soluble in many kinds of ionic liquids. The history of regenerated cellulose is often cited as beginning with George Audemars, who first manufactured regenerated nitrocellulose fibers in 1855. Although these fibers were soft and strong -resembling silk- they had the drawback of being highly flammable. Hilaire de Chardonnet perfected production of nitrocellulose fibers, but manufacturing of these fibers by his process was relatively uneconomical. In 1890, L.H. Despeissis invented the Cuprammonium rayon, cuprammonium process – which uses a cuprammonium solution to solubilize cellulose – a method still used today for production of artificial silk. In 1891, it was discovered that treatment of cellulose with alkali and carbon disulfide generated a soluble cellulose derivative known as viscose. This process, patented by the founders of the Viscose Development Company, is the most widely used method for manufacturing regenerated cellulose products. Courtaulds purchased the patents for this process in 1904, leading to significant growth of viscose fiber production. By 1931, expiration of patents for the viscose process led to its adoption worldwide. Global production of regenerated cellulose fiber peaked in 1973 at 3,856,000 tons. Regenerated cellulose can be used to manufacture a wide variety of products. While the first application of regenerated cellulose was as a clothing textile, this class of materials is also used in the production of disposable medical devices as well as fabrication of Synthetic membrane, artificial membranes.


Cellulose esters and ethers

The hydroxyl groups (−OH) of cellulose can be partially or fully reacted with various reagents to afford derivatives with useful properties like mainly cellulose esters and cellulose ethers (−OR). In principle, although not always in current industrial practice, cellulosic polymers are renewable resources. Ester derivatives include: The cellulose acetate and cellulose triacetate are film- and fiber-forming materials that find a variety of uses. The nitrocellulose was initially used as an explosive and was an early film forming material. With camphor, nitrocellulose gives
celluloid Celluloids are a class of materials produced by mixing nitrocellulose Nitrocellulose (also known as cellulose nitrate, flash paper, flash cotton, guncotton, pyroxylin and flash string, depending on form) is a highly flammable compound formed ...

celluloid
. Ether derivatives include: The sodium carboxymethyl cellulose can be cross-linked to give the croscarmellose sodium (E468) for use as a Excipient, disintegrant in pharmaceutical formulations.


Commercial applications

Cellulose for industrial use is mainly obtained from
wood pulp Pulp is a lignocellulosic fibrous material prepared by chemically or mechanically separating cellulose fiber Cellulose fibers () are fibers made with ethers or esters of cellulose, which can be obtained from the bark, wood or leaves of plants ...
and from
cotton Cotton is a soft, fluffy staple fiber Fiber or fibre (from la, fibra, links=no) is a natural Nature, in the broadest sense, is the natural, physical, material world or universe The universe ( la, universus) is all of s ...

cotton
. * Paper products: Cellulose is the major constituent of
paper Paper is a thin sheet material Material is a substance Substance may refer to: * Substance (Jainism), a term in Jain ontology to denote the base or owner of attributes * Chemical substance, a material with a definite chemical composition ...

paper
,
paperboard Paperboard is a thick paper Paper is a thin sheet material Material is a substance Substance may refer to: * Substance (Jainism), a term in Jain ontology to denote the base or owner of attributes * Chemical substance, a material with ...
, and card stock. Electrical insulation paper: Cellulose is used in diverse forms as insulation in transformers, cables, and other electrical equipment. * Fibers: Cellulose is the main ingredient of textiles. Cotton and synthetics (nylons) each have about 40% market by volume. Other plant fibers (jute, sisal, hemp) represent about 20% of the market. Rayon,
cellophane Cellophane is a thin, transparent sheet made of regenerated cellulose. Its low permeability to air, oils, Fat, greases, bacteria, and water makes it useful for food packaging. Cellophane is highly permeable to water vapour, but may be coated with ...
and other "regenerated cellulose fibers" are a small portion (5%). * Consumables: Microcrystalline cellulose (E number, E460i) and powdered cellulose (E460ii) are used as inactive Excipient#Fillers and diluents, fillers in drug tablets and a wide range of soluble cellulose derivatives, E numbers E461 to E469, are used as emulsifiers, thickeners and stabilizers in processed foods. Cellulose powder is, for example, used in processed cheese to prevent caking inside the package. Cellulose occurs naturally in some foods and is an additive in manufactured foods, contributing an indigestible component used for texture and bulk, potentially aiding in
defecation frame, Human anatomy of the ''anorecturm'' (anus and rectum">anus.html" ;"title="Human anatomy of the ''anorecturm'' (anus">Human anatomy of the ''anorecturm'' (anus and rectum) Defecation (or defaecation) is the final act of digestion, by whi ...
. * Building material: Hydroxyl bonding of cellulose in water produces a sprayable, moldable material as an alternative to the use of plastics and resins. The recyclable material can be made water- and fire-resistant. It provides sufficient strength for use as a building material. Cellulose insulation made from recycled paper is becoming popular as an environmentally preferable material for building insulation. It can be treated with boric acid as a fire retardant. * Miscellaneous: Cellulose can be converted into
cellophane Cellophane is a thin, transparent sheet made of regenerated cellulose. Its low permeability to air, oils, Fat, greases, bacteria, and water makes it useful for food packaging. Cellophane is highly permeable to water vapour, but may be coated with ...
, a thin transparent film. It is the base material for the
celluloid Celluloids are a class of materials produced by mixing nitrocellulose Nitrocellulose (also known as cellulose nitrate, flash paper, flash cotton, guncotton, pyroxylin and flash string, depending on form) is a highly flammable compound formed ...

celluloid
that was used for photographic and movie films until the mid-1930s. Cellulose is used to make water-soluble adhesives and binder (material), binders such as methyl cellulose and carboxymethyl cellulose which are used in wallpaper paste. Cellulose is further used to make
hydrophilic A hydrophile is a molecule File:Pentacene on Ni(111) STM.jpg, A scanning tunneling microscopy image of pentacene molecules, which consist of linear chains of five carbon rings. A molecule is an electrically neutral group of two or more atoms ...
and highly absorbent sponge (tool), sponges. Cellulose is the raw material in the manufacture of nitrocellulose (cellulose nitrate) which is used in smokeless powder, smokeless gunpowder. *Pharmaceuticals: Cellulose derivatives, such as microcrystalline cellulose (MCC), have the advantages of retaining water, being a stabilizer (chemistry), stabilizer and thickening agent, and in reinforcement of drug tablets.


Aspirational

Energy crops: The major combustion, combustible component of non-food
energy crop Energy crops are low-cost and low-maintenance crops grown solely for energy production by combustion (not for food). The crops are processed into solid, liquid or gaseous fuels, such as pellets, bioethanol or biogas. The fuels are burned to gene ...
s is cellulose, with
lignin Lignin is a class of complex organic polymers that form key structural materials in the support tissues of most plants. Lignins are particularly important in the formation of cell walls, especially in wood and Bark (botany), bark, because they l ...

lignin
second. Non-food energy crops produce more usable energy than edible energy crops (which have a large
starch Starch or amylum is a polymeric A polymer (; Greek '' poly-'', "many" + '' -mer'', "part") is a substance Substance may refer to: * Substance (Jainism), a term in Jain ontology to denote the base or owner of attributes * Chemical substance ...
component), but still compete with food crops for agricultural land and water resources. Typical non-food energy crops include hemp, industrial hemp, switchgrass, ''Miscanthus'', ''Salix'' (willow), and ''Populus'' (Populus, poplar) species. A strain of ''Clostridium'' bacteria found in zebra dung, can convert nearly any form of cellulose into butanol fuel.


See also

* Gluconic acid * Isosaccharinic acid, a degradation product of cellulose * Lignin * Zeoform


References


External links

*
Structure and morphology of cellulose
by Serge Pérez and William Mackie, CERMAV-CNRS
Cellulose
by Martin Chaplin, London South Bank University
Clear description of a cellulose assay method
at the Cotton Fiber Biosciences unit of the United States Department of Agriculture, USDA.
Cellulose films could provide flapping wings and cheap artificial muscles for robots
– TechnologyReview.com {{Authority control Cellulose, Excipients Papermaking Polysaccharides E-number additives