Cellulose
Encyclopedia
Cellulose is an organic compound
with the formula
, a polysaccharide
consisting of a linear chain of several hundred to over ten thousand β(1→4) linked
D-glucose
units.
Cellulose is the structural component of the primary cell wall
of green plants, many forms of algae
and the oomycetes. Some species of bacteria
secrete it to form biofilm
s.
Cellulose is the most common organic compound on Earth. About 33% of all plant matter is cellulose (the cellulose content of cotton
is 90% and that of wood
is 40–50%).
For industrial use, cellulose is mainly obtained from wood pulp
and cotton
. It is mainly used to produce paperboard
and paper
; to a smaller extent it is converted into a wide variety of derivative products such as cellophane
and rayon
. Converting cellulose from energy crop
s into biofuel
s such as cellulosic ethanol
is under investigation as an alternative fuel source.
Some animals, particularly ruminant
s and termite
s, can digest
cellulose with the help of symbiotic
micro-organisms that live in their guts. Humans can digest cellulose to some extent, however it is often referred to as "dietary fiber
" or "roughage" (e.g. outer shell of maize
) and acts as a hydrophilic bulking agent for feces
.
, who isolated it from plant matter and determined its chemical formula. Cellulose was used to produce the first successful thermoplastic polymer
, celluloid
, by Hyatt Manufacturing Company in 1870. Hermann Staudinger
determined the polymer structure of cellulose in 1920. The compound was first chemically synthesized (without the use of any biologically derived enzyme
s) in 1992, by Kobayashi and Shoda.
, paperboard
, and card stock
and of textile
s made from cotton
, linen
, and other plant fibers.
Cellulose can be converted into cellophane
, a thin transparent film, and into rayon
, an important fiber that has been used for textiles since the beginning of the 20th century. Both cellophane and rayon are known as "regenerated cellulose fibers"; they are identical to cellulose in chemical structure and are usually made from dissolving pulp
via viscose
. A more recent and environmentally friendly method to produce rayon is the Lyocell
process.
Cellulose is the raw material in the manufacture of nitrocellulose
(cellulose nitrate) which is used in smokeless gunpowder
and as the base material for celluloid
used for photographic and movie films until the mid 1930s.
Cellulose is used to make water-soluble adhesives and binders
such as methyl cellulose and carboxymethyl cellulose
which are used in wallpaper paste
. Microcrystalline cellulose
(E460i
) and powdered cellulose (E460ii) are used as inactive fillers in tablets
and as thickeners and stabilizers in processed foods. Cellulose powder is for example used in Kraft's
Parmesan cheese to prevent caking inside the tube.
Cellulose is used in the laboratory as the stationary phase for thin layer chromatography
. Cellulose fibers are also used in liquid filtration
, sometimes in combination with diatomaceous earth
or other filtration media, to create a filter bed of inert material. Cellulose is further used to make hydrophilic and highly absorbent sponges.
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
.
component of non-food energy crop
s is cellulose, with lignin
second. Non-food energy crops are more efficient than edible energy crops (which have a large starch
component), but still compete with food crops for agricultural land and water resources. Typical non-food energy crops include industrial hemp
, switchgrass
, Miscanthus
, Salix (willow
), and Populus (poplar
) species.
Some bacteria can convert cellulose into ethanol
which can then be used as a fuel; see cellulosic ethanol
.
of 20–30, is insoluble in water
and most organic solvent
s, is chiral
and is biodegradable
. It can be broken down chemically into its glucose units by treating it with concentrated acids at high temperature.
Cellulose is derived from D-glucose units, which condense
through β(1→4)-glycosidic bond
s. This linkage motif contrasts with that for α(1→4)-glycosidic bonds present in starch
, glycogen
, and other carbohydrates. 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
on the glucose from one chain form 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
. This strength is important in cell walls, where the microfibrils are meshed into a carbohydrate matrix, conferring rigidity to plant cells.
Compared to starch, cellulose is also much more crystalline
. Whereas starch undergoes a crystalline to amorphous
transition when heated beyond 60-70 °C in water (as in cooking), cellulose requires a temperature of 320 °C and pressure of 25 MPa
to become amorphous in water.
Several different crystalline structures of cellulose are known, corresponding 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 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 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.
Plant-derived cellulose is usually found in a mixture with hemicellulose
, lignin
, pectin
and other substances, while microbial cellulose
is quite pure, has a much higher water content, and consists of long chains.
Cellulose is soluble in cupriethylenediamine (CED), cadmiumethylenediamine (Cadoxen), N-methylmorpholine N-oxide
and lithium chloride
/ dimethylformamide
. This is used in the production of regenerated celluloses (as viscose
and cellophane
) from dissolving pulp
.
Cellulose can be assay
ed using a method described by Updegraff in 1969, where the fiber is dissolved in acetic
and nitric acid
to remove lignin, hemicellulose, and xylosans. The resulting cellulose is allowed to react with anthrone
in sulfuric acid
. The resulting coloured compound is assayed spectrophotometrically
at a wavelength of approximately 635 nm
.
In addition, cellulose is represented by the difference between acid detergent fiber (ADF) and acid detergent lignin (ADL).
In vascular plant
s cellulose is synthesized at the plasma membrane by rosette terminal complexes (RTCs). The RTCs are hexameric
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
.
RTCs contain at least three different cellulose synthases, encoded by CesA genes, in an unknown stoichiometry
. Separate sets of CesA genes are involved in primary and secondary cell wall biosynthesis.
Cellulose synthesis requires chain initiation and elongation, and the two processes are separate.
CesA glucosyltransferase initiates cellulose polymerization using a steroid
primer, sitosterol
-beta-glucoside
, and UDP-glucose. Cellulose synthase
utilizes UDP
-D-glucose precursors to elongate the growing cellulose chain. A cellulase
may function to cleave the primer from the mature chain.
reaction. Because cellulose molecules bind strongly to each other, cellulolysis is relatively difficult compared to the breakdown of other polysaccharides. Processes do exist however for the breakdown of cellulose such as the Lyocell process which uses a combination of heated water and acetone
to break down the cellulose strands.
Most mammals have only very limited ability to digest dietary fibres such as cellulose. Some ruminant
s like cows and sheep contain certain symbiotic
anaerobic
bacteria (like Cellulomonas
) in the flora of the rumen, and these bacteria produce enzyme
s called cellulase
s that help the microorganism to break down 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). Similarly, lower termite
s contain in their hindgut
s certain flagellate
protozoa
which produce such enzymes; higher termites contain bacteria for the job. Some termites may also produce cellulase of their own. Fungi
, which in nature are responsible for recycling of nutrients, are also able to break down cellulose.
The enzymes utilized to cleave the glycosidic linkage in cellulose are glycoside hydrolase
s including endo-acting cellulase
s and exo-acting glucosidases. Such enzymes are usually secreted as part of multienzyme complexes that may include dockerin
s and carbohydrate-binding modules
.
is a polysaccharide
related to cellulose that comprises ca. 20% of the biomass of most plants. In contrast to cellulose, hemicellulose is derived from several sugars in addition to glucose
, especially xylose
but also including mannose
, galactose
, rhamnose
, and arabinose
. Hemicellulose consists of shorter chains – around 200 sugar units. Furthermore, hemicellulose is branched, whereas cellulose is unbranched.
groups (-OH) of cellulose can be partially or fully reacted with various reagent
s to afford derivatives with useful properties like mainly cellulose ester
s and cellulose ether
s (-OR). In principle, though 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
.
Ether derivatives include:
The sodium carboxymethyl cellulose can be cross-linked to give the croscarmellose sodium
(E468) for use as a disintegrant
in pharmaceutical formulations.
Organic compound
An organic compound is any member of a large class of gaseous, liquid, or solid chemical compounds whose molecules contain carbon. For historical reasons discussed below, a few types of carbon-containing compounds such as carbides, carbonates, simple oxides of carbon, and cyanides, as well as the...
with the formula
Chemical formula
A chemical formula or molecular formula is a way of expressing information about the atoms that constitute a particular chemical compound....
, a polysaccharide
Polysaccharide
Polysaccharides are long carbohydrate molecules, of repeated monomer units joined together by glycosidic bonds. They range in structure from linear to highly branched. Polysaccharides are often quite heterogeneous, containing slight modifications of the repeating unit. Depending on the structure,...
consisting of a linear chain of several hundred to over ten thousand β(1→4) linked
Glycosidic bond
In chemistry, a glycosidic bond is a type of covalent bond that joins a carbohydrate molecule to another group, which may or may not be another carbohydrate....
D-glucose
Glucose
Glucose is a simple sugar and an important carbohydrate in biology. Cells use it as the primary source of energy and a metabolic intermediate...
units.
Cellulose is the structural component of the primary cell wall
Cell wall
The cell wall is the tough, usually flexible but sometimes fairly rigid layer that surrounds some types of cells. It is located outside the cell membrane and provides these cells with structural support and protection, and also acts as a filtering mechanism. A major function of the cell wall is to...
of green plants, many forms of algae
Algae
Algae are a large and diverse group of simple, typically autotrophic organisms, ranging from unicellular to multicellular forms, such as the giant kelps that grow to 65 meters in length. They are photosynthetic like plants, and "simple" because their tissues are not organized into the many...
and the oomycetes. Some species of bacteria
Bacteria
Bacteria are a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria have a wide range of shapes, ranging from spheres to rods and spirals...
secrete it to form biofilm
Biofilm
A biofilm is an aggregate of microorganisms in which cells adhere to each other on a surface. These adherent cells are frequently embedded within a self-produced matrix of extracellular polymeric substance...
s.
Cellulose is the most common organic compound on Earth. About 33% of all plant matter is cellulose (the cellulose content of cotton
Cotton
Cotton is a soft, fluffy staple fiber that grows in a boll, or protective capsule, around the seeds of cotton plants of the genus Gossypium. The fiber is almost pure cellulose. The botanical purpose of cotton fiber is to aid in seed dispersal....
is 90% and that of wood
Wood
Wood is a hard, fibrous tissue found in many trees. It has been used for hundreds of thousands of years for both fuel and as a construction material. It is an organic material, a natural composite of cellulose fibers embedded in a matrix of lignin which resists compression...
is 40–50%).
For industrial use, cellulose is mainly obtained from wood pulp
Wood pulp
Pulp is a lignocellulosic fibrous material prepared by chemically or mechanically separating cellulose fibres from wood, fibre crops or waste paper. Wood pulp is the most common raw material in papermaking.-History:...
and cotton
Cotton
Cotton is a soft, fluffy staple fiber that grows in a boll, or protective capsule, around the seeds of cotton plants of the genus Gossypium. The fiber is almost pure cellulose. The botanical purpose of cotton fiber is to aid in seed dispersal....
. It is mainly used to produce paperboard
Paperboard
Paperboard is a thick paper based material. While there is no rigid differentiation between paper and paperboard, paperboard is generally thicker than paper. According to ISO standards, paperboard is a paper with a basis weight above 224 g/m2, but there are exceptions. Paperboard can be single...
and paper
Paper
Paper is a thin material mainly used for writing upon, printing upon, drawing or for packaging. It is produced by pressing together moist fibers, typically cellulose pulp derived from wood, rags or grasses, and drying them into flexible sheets....
; to a smaller extent it is converted into a wide variety of derivative products such as cellophane
Cellophane
Cellophane is a thin, transparent sheet made of regenerated cellulose. Its low permeability to air, oils, greases, bacteria and water makes it useful for food packaging...
and rayon
Rayon
Rayon is a manufactured regenerated cellulose fiber. Because it is produced from naturally occurring polymers, it is neither a truly synthetic fiber nor a natural fiber; it is a semi-synthetic or artificial fiber. Rayon is known by the names viscose rayon and art silk in the textile industry...
. Converting cellulose from energy crop
Energy crop
An energy crop is a plant grown as a low cost and low maintenance harvest used to make biofuels, or combusted for its energy content to generate electricity or heat. Energy crops are generally categorized as woody or herbaceous ....
s into biofuel
Biofuel
Biofuel is a type of fuel whose energy is derived from biological carbon fixation. Biofuels include fuels derived from biomass conversion, as well as solid biomass, liquid fuels and various biogases...
s such as cellulosic ethanol
Cellulosic ethanol
Cellulosic ethanol is a biofuel produced from wood, grasses, or the non-edible parts of plants.It is a type of biofuel produced from lignocellulose, a structural material that comprises much of the mass of plants. Lignocellulose is composed mainly of cellulose, hemicellulose and lignin...
is under investigation as an alternative fuel source.
Some animals, particularly ruminant
Ruminant
A ruminant is a mammal of the order Artiodactyla that digests plant-based food by initially softening it within the animal's first compartment of the stomach, principally through bacterial actions, then regurgitating the semi-digested mass, now known as cud, and chewing it again...
s and termite
Termite
Termites are a group of eusocial insects that, until recently, were classified at the taxonomic rank of order Isoptera , but are now accepted as the epifamily Termitoidae, of the cockroach order Blattodea...
s, can digest
Digestion
Digestion is the mechanical and chemical breakdown of food into smaller components that are more easily absorbed into a blood stream, for instance. Digestion is a form of catabolism: a breakdown of large food molecules to smaller ones....
cellulose with the help of symbiotic
Symbiosis
Symbiosis is close and often long-term interaction between different biological species. In 1877 Bennett used the word symbiosis to describe the mutualistic relationship in lichens...
micro-organisms that live in their guts. Humans can digest cellulose to some extent, however it is often referred to as "dietary fiber
Dietary fiber
Dietary fiber, dietary fibre, or sometimes roughage is the indigestible portion of plant foods having two main components:* soluble fiber that is readily fermented in the colon into gases and physiologically active byproducts, and* insoluble fiber that is metabolically inert, absorbing water as it...
" or "roughage" (e.g. outer shell of maize
Maize
Maize known in many English-speaking countries as corn or mielie/mealie, is a grain domesticated by indigenous peoples in Mesoamerica in prehistoric times. The leafy stalk produces ears which contain seeds called kernels. Though technically a grain, maize kernels are used in cooking as a vegetable...
) and acts as a hydrophilic bulking agent for feces
Feces
Feces, faeces, or fæces is a waste product from an animal's digestive tract expelled through the anus or cloaca during defecation.-Etymology:...
.
History
Cellulose was discovered in 1838 by the French chemist Anselme PayenAnselme Payen
Anselme Payen was a French chemist known for discovering the enzyme diastase, and the carbohydrate cellulose.Payen was born in Paris...
, who isolated it from plant matter and determined its chemical formula. Cellulose was used to produce the first successful thermoplastic polymer
Thermoplastic
Thermoplastic, also known as a thermosoftening plastic, is a polymer that turns to a liquid when heated and freezes to a very glassy state when cooled sufficiently...
, celluloid
Celluloid
Celluloid is the name of a class of compounds created from nitrocellulose and camphor, plus dyes and other agents. Generally regarded to be the first thermoplastic, it was first created as Parkesine in 1862 and as Xylonite in 1869, before being registered as Celluloid in 1870. Celluloid is...
, by Hyatt Manufacturing Company in 1870. Hermann Staudinger
Hermann Staudinger
- External links :* Staudinger's * Staudinger's Nobel Lecture *....
determined the polymer structure of cellulose in 1920. The compound was first chemically synthesized (without the use of any biologically derived enzyme
Enzyme
Enzymes are proteins that catalyze chemical reactions. In enzymatic reactions, the molecules at the beginning of the process, called substrates, are converted into different molecules, called products. Almost all chemical reactions in a biological cell need enzymes in order to occur at rates...
s) in 1992, by Kobayashi and Shoda.
Commercial products
Cellulose is the major constituent of paperPaper
Paper is a thin material mainly used for writing upon, printing upon, drawing or for packaging. It is produced by pressing together moist fibers, typically cellulose pulp derived from wood, rags or grasses, and drying them into flexible sheets....
, paperboard
Paperboard
Paperboard is a thick paper based material. While there is no rigid differentiation between paper and paperboard, paperboard is generally thicker than paper. According to ISO standards, paperboard is a paper with a basis weight above 224 g/m2, but there are exceptions. Paperboard can be single...
, and card stock
Card stock
Card stock, also called cover stock or pasteboard, is a paper stock that is thicker and more durable than normal writing or printing paper, but thinner and more flexible than other forms of paperboard. Card stock is often used for business cards, postcards, playing cards, catalog covers,...
and of textile
Textile
A textile or cloth is a flexible woven material consisting of a network of natural or artificial fibres often referred to as thread or yarn. Yarn is produced by spinning raw fibres of wool, flax, cotton, or other material to produce long strands...
s made from cotton
Cotton
Cotton is a soft, fluffy staple fiber that grows in a boll, or protective capsule, around the seeds of cotton plants of the genus Gossypium. The fiber is almost pure cellulose. The botanical purpose of cotton fiber is to aid in seed dispersal....
, linen
Linen
Linen is a textile made from the fibers of the flax plant, Linum usitatissimum. Linen is labor-intensive to manufacture, but when it is made into garments, it is valued for its exceptional coolness and freshness in hot weather....
, and other plant fibers.
Cellulose can be converted into cellophane
Cellophane
Cellophane is a thin, transparent sheet made of regenerated cellulose. Its low permeability to air, oils, greases, bacteria and water makes it useful for food packaging...
, a thin transparent film, and into rayon
Rayon
Rayon is a manufactured regenerated cellulose fiber. Because it is produced from naturally occurring polymers, it is neither a truly synthetic fiber nor a natural fiber; it is a semi-synthetic or artificial fiber. Rayon is known by the names viscose rayon and art silk in the textile industry...
, an important fiber that has been used for textiles since the beginning of the 20th century. Both cellophane and rayon are known as "regenerated cellulose fibers"; they are identical to cellulose in chemical structure and are usually made from dissolving pulp
Dissolving pulp
Dissolving pulp is a bleached wood pulp that has a high cellulose content . It is produced chemically from the pulpwood, in a process that has a low yield...
via viscose
Viscose
Viscose is a viscous organic liquid used to make rayon and cellophane. Viscose is becoming synonymous with rayon, a soft material commonly used in shirts, shorts, coats, jackets, and other outer wear.-Manufacture:...
. A more recent and environmentally friendly method to produce rayon is the Lyocell
Lyocell
Lyocell is a regenerated cellulose fiber made from dissolving pulp . It was first manufactured in 1987 by Courtaulds Fibres UK at their pilot plant S25...
process.
Cellulose is the raw material in the manufacture of nitrocellulose
Nitrocellulose
Nitrocellulose is a highly flammable compound formed by nitrating cellulose through exposure to nitric acid or another powerful nitrating agent. When used as a propellant or low-order explosive, it is also known as guncotton...
(cellulose nitrate) which is used in smokeless gunpowder
Smokeless powder
Smokeless powder is the name given to a number of propellants used in firearms and artillery which produce negligible smoke when fired, unlike the older gunpowder which they replaced...
and as the base material for celluloid
Celluloid
Celluloid is the name of a class of compounds created from nitrocellulose and camphor, plus dyes and other agents. Generally regarded to be the first thermoplastic, it was first created as Parkesine in 1862 and as Xylonite in 1869, before being registered as Celluloid in 1870. Celluloid is...
used for photographic and movie films until the mid 1930s.
Cellulose is used to make water-soluble adhesives and binders
Binder (material)
-See also:*Adhesive or Glue*Cement*Paint...
such as methyl cellulose and carboxymethyl cellulose
Carboxymethyl cellulose
Carboxymethyl cellulose or cellulose gum is a cellulose derivative with carboxymethyl groups bound to some of the hydroxyl groups of the glucopyranose monomers that make up the cellulose backbone...
which are used in wallpaper paste
Wallpaper paste
Wallpaper adhesive or wallpaper paste is a specific adhesive, based on modified starch or methylcellulose, used to fix wallpaper to walls.Wallpaper pastes have a typical shear thinning viscosity and a high wet adhesive tack...
. Microcrystalline cellulose
Microcrystalline cellulose
Microcrystalline cellulose is a term for refined wood pulp and is used as a texturizer, an anti-caking agent, a fat substitute, an emulsifier, an extender, and a bulking agent in food production. The most common form is used in vitamin supplements or tablets...
(E460i
E number
E numbers are number codes for food additives that have been assessed for use within the European Union . They are commonly found on food labels throughout the European Union. Safety assessment and approval are the responsibility of the European Food Safety Authority...
) and powdered cellulose (E460ii) are used as inactive fillers in tablets
and as thickeners and stabilizers in processed foods. Cellulose powder is for example used in Kraft's
Kraft Foods
Kraft Foods Inc. is an American confectionery, food and beverage conglomerate. It markets many brands in more than 170 countries. 12 of its brands annually earn more than $1 billion worldwide: Cadbury, Jacobs, Kraft, LU, Maxwell House, Milka, Nabisco, Oscar Mayer, Philadelphia, Trident, Tang...
Parmesan cheese to prevent caking inside the tube.
Cellulose is used in the laboratory as the stationary phase for thin layer chromatography
Chromatography
Chromatography is the collective term for a set of laboratory techniques for the separation of mixtures....
. Cellulose fibers are also used in liquid filtration
Filtration
Filtration is commonly the mechanical or physical operation which is used for the separation of solids from fluids by interposing a medium through which only the fluid can pass...
, sometimes in combination with diatomaceous earth
Diatomaceous earth
Diatomaceous earth also known as diatomite or kieselgur/kieselguhr, is a naturally occurring, soft, siliceous sedimentary rock that is easily crumbled into a fine white to off-white powder. It has a particle size ranging from less than 1 micrometre to more than 1 millimetre, but typically 10 to...
or other filtration media, to create a filter bed of inert material. Cellulose is further used to make hydrophilic and highly absorbent sponges.
Cellulose insulation
Cellulose insulation
The word cellulose comes from the French word for a living cellule and glucose, which is sugar. Building insulation is low-thermal-conductivity material used to separate the internal climate and sounds of a building from external climate and sounds...
made from recycled paper is becoming popular as an environmentally preferable material for building insulation
Building insulation
building insulation refers broadly to any object in a building used as insulation for any purpose. While the majority of insulation in buildings is for thermal purposes, the term also applies to acoustic insulation, fire insulation, and impact insulation...
. It can be treated with boric acid
Boric acid
Boric acid, also called hydrogen borate or boracic acid or orthoboric acid or acidum boricum, is a weak acid of boron often used as an antiseptic, insecticide, flame retardant, as a neutron absorber, and as a precursor of other chemical compounds. It exists in the form of colorless crystals or a...
as a fire retardant
Fire retardant
A fire retardant is a substance other than water that reduces flammability of fuels or delays their combustion. This typically refers to chemical retardants but may also include substances that work by physical action, such as cooling the fuels; examples of these include fire-fighting foams and...
.
Cellulose source and energy crops
The major combustibleCombustion
Combustion or burning is the sequence of exothermic chemical reactions between a fuel and an oxidant accompanied by the production of heat and conversion of chemical species. The release of heat can result in the production of light in the form of either glowing or a flame...
component of non-food energy crop
Energy crop
An energy crop is a plant grown as a low cost and low maintenance harvest used to make biofuels, or combusted for its energy content to generate electricity or heat. Energy crops are generally categorized as woody or herbaceous ....
s is cellulose, with lignin
Lignin
Lignin or lignen is a complex chemical compound most commonly derived from wood, and an integral part of the secondary cell walls of plants and some algae. The term was introduced in 1819 by de Candolle and is derived from the Latin word lignum, meaning wood...
second. Non-food energy crops are more efficient than edible energy crops (which have a large starch
Starch
Starch or amylum is a carbohydrate consisting of a large number of glucose units joined together by glycosidic bonds. This polysaccharide is produced by all green plants as an energy store...
component), but still compete with food crops for agricultural land and water resources. Typical non-food energy crops include industrial hemp
Hemp
Hemp is mostly used as a name for low tetrahydrocannabinol strains of the plant Cannabis sativa, of fiber and/or oilseed varieties. In modern times, hemp has been used for industrial purposes including paper, textiles, biodegradable plastics, construction, health food and fuel with modest...
, switchgrass
Switchgrass
Panicum virgatum, commonly known as switchgrass, is a perennial warm season bunchgrass native to North America, where it occurs naturally from 55°N latitude in Canada southwards into the United States and Mexico...
, Miscanthus
Miscanthus
Miscanthus is a genus of about 15 species of perennial grasses native to subtropical and tropical regions of Africa and southern Asia, with one species Miscanthus is a genus of about 15 species of perennial grasses native to subtropical and tropical regions of Africa and southern Asia, with one...
, Salix (willow
Willow
Willows, sallows, and osiers form the genus Salix, around 400 species of deciduous trees and shrubs, found primarily on moist soils in cold and temperate regions of the Northern Hemisphere...
), and Populus (poplar
Poplar
Populus is a genus of 25–35 species of deciduous flowering plants in the family Salicaceae, native to most of the Northern Hemisphere. English names variously applied to different species include poplar , aspen, and cottonwood....
) species.
Some bacteria can convert cellulose into ethanol
Ethanol
Ethanol, also called ethyl alcohol, pure alcohol, grain alcohol, or drinking alcohol, is a volatile, flammable, colorless liquid. It is a psychoactive drug and one of the oldest recreational drugs. Best known as the type of alcohol found in alcoholic beverages, it is also used in thermometers, as a...
which can then be used as a fuel; see cellulosic ethanol
Cellulosic ethanol
Cellulosic ethanol is a biofuel produced from wood, grasses, or the non-edible parts of plants.It is a type of biofuel produced from lignocellulose, a structural material that comprises much of the mass of plants. Lignocellulose is composed mainly of cellulose, hemicellulose and lignin...
.
Structure and properties
Cellulose has no taste, is odorless, is hydrophilic with the contact angleContact angle
The contact angle is the angle at which a liquid/vapor interface meets a solid surface. The contact angle is specific for any given system and is determined by the interactions across the three interfaces. Most often the concept is illustrated with a small liquid droplet resting on a flat...
of 20–30, is insoluble in water
Water
Water is a chemical substance with the chemical formula H2O. A water molecule contains one oxygen and two hydrogen atoms connected by covalent bonds. Water is a liquid at ambient conditions, but it often co-exists on Earth with its solid state, ice, and gaseous state . Water also exists in a...
and most organic solvent
Solvent
A solvent is a liquid, solid, or gas that dissolves another solid, liquid, or gaseous solute, resulting in a solution that is soluble in a certain volume of solvent at a specified temperature...
s, is chiral
Chirality (chemistry)
A chiral molecule is a type of molecule that lacks an internal plane of symmetry and thus has a non-superimposable mirror image. The feature that is most often the cause of chirality in molecules is the presence of an asymmetric carbon atom....
and is biodegradable
Biodegradation
Biodegradation or biotic degradation or biotic decomposition is the chemical dissolution of materials by bacteria or other biological means...
. It can be broken down chemically into its glucose units by treating it with concentrated acids at high temperature.
Cellulose is derived from D-glucose units, which condense
Condensation reaction
A condensation reaction is a chemical reaction in which two molecules or moieties combine to form one single molecule, together with the loss of a small molecule. When this small molecule is water, it is known as a dehydration reaction; other possible small molecules lost are hydrogen chloride,...
through β(1→4)-glycosidic bond
Glycosidic bond
In chemistry, a glycosidic bond is a type of covalent bond that joins a carbohydrate molecule to another group, which may or may not be another carbohydrate....
s. This linkage motif contrasts with that for α(1→4)-glycosidic bonds present in starch
Starch
Starch or amylum is a carbohydrate consisting of a large number of glucose units joined together by glycosidic bonds. This polysaccharide is produced by all green plants as an energy store...
, glycogen
Glycogen
Glycogen is a molecule that serves as the secondary long-term energy storage in animal and fungal cells, with the primary energy stores being held in adipose tissue...
, and other carbohydrates. 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
Hydroxyl
A hydroxyl is a chemical group containing an oxygen atom covalently bonded with a hydrogen atom. In inorganic chemistry, the hydroxyl group is known as the hydroxide ion, and scientists and reference works generally use these different terms though they refer to the same chemical structure in...
on the glucose from one chain form hydrogen bond
Hydrogen bond
A hydrogen bond is the attractive interaction of a hydrogen atom with an electronegative atom, such as nitrogen, oxygen or fluorine, that comes from another molecule or chemical group. The hydrogen must be covalently bonded to another electronegative atom to create the 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
Tensile strength
Ultimate tensile strength , often shortened to tensile strength or ultimate strength, is the maximum stress that a material can withstand while being stretched or pulled before necking, which is when the specimen's cross-section starts to significantly contract...
. This strength is important in cell walls, where the microfibrils are meshed into a carbohydrate matrix, conferring rigidity to plant cells.
Compared to starch, cellulose is also much more crystalline
Crystallinity
Crystallinity refers to the degree of structural order in a solid. In a crystal, the atoms or molecules are arranged in a regular, periodic manner. The degree of crystallinity has a big influence on hardness, density, transparency and diffusion. In a gas, the relative positions of the atoms or...
. Whereas starch undergoes a crystalline to amorphous
Amorphous solid
In condensed matter physics, an amorphous or non-crystalline solid is a solid that lacks the long-range order characteristic of a crystal....
transition when heated beyond 60-70 °C in water (as in cooking), cellulose requires a temperature of 320 °C and pressure of 25 MPa
Pascal (unit)
The pascal is the SI derived unit of pressure, internal pressure, stress, Young's modulus and tensile strength, named after the French mathematician, physicist, inventor, writer, and philosopher Blaise Pascal. It is a measure of force per unit area, defined as one newton per square metre...
to become amorphous in water.
Several different crystalline structures of cellulose are known, corresponding 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 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 polymerization
Degree of polymerization
The degree of polymerization, or DP, is usually defined as the number of monomeric units in a macromolecule or polymer or oligomer molecule.For a homopolymer, there is only one type of monomeric unit andthe number-average degree of polymerization is given by...
, 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.
Plant-derived cellulose is usually found in a mixture with hemicellulose
Hemicellulose
A hemicellulose is any of several heteropolymers , such as arabinoxylans, present along with cellulose in almost all plant cell walls. While cellulose is crystalline, strong, and resistant to hydrolysis, hemicellulose has a random, amorphous structure with little strength...
, lignin
Lignin
Lignin or lignen is a complex chemical compound most commonly derived from wood, and an integral part of the secondary cell walls of plants and some algae. The term was introduced in 1819 by de Candolle and is derived from the Latin word lignum, meaning wood...
, pectin
Pectin
Pectin is a structural heteropolysaccharide contained in the primary cell walls of terrestrial plants. It was first isolated and described in 1825 by Henri Braconnot...
and other substances, while microbial cellulose
Microbial cellulose
Microbial cellulose is a form of cellulose that is produced by bacteria. It is widely used in the traditional Filipino dessert Nata de coco. Microbial cellulose was first confirmed as cellulose in 1886.- Production :...
is quite pure, has a much higher water content, and consists of long chains.
Cellulose is soluble in cupriethylenediamine (CED), cadmiumethylenediamine (Cadoxen), N-methylmorpholine N-oxide
N-Methylmorpholine N-oxide
N-Methylmorpholine-N-oxide, NMO or NMMO is an organic compound. This heterocyclic amine oxide and morpholine derivative is used in organic chemistry as a co-oxidant and sacrificial catalyst in oxidation reactions for instance in osmium tetroxide oxidations and the Sharpless asymmetric...
and lithium chloride
Lithium chloride
Lithium chloride is a chemical compound with the formula LiCl. The salt is a typical ionic compound, although the small size of the Li+ ion gives rise to properties not seen for other alkali metal chlorides, such as extraordinary solubility in polar solvents and its hygroscopic...
/ dimethylformamide
Dimethylformamide
Dimethylformamide is an organic compound with the formula 2NCH. Commonly abbreviated as DMF , this colourless liquid is miscible with water and the majority of organic liquids. DMF is a common solvent for chemical reactions...
. This is used in the production of regenerated celluloses (as viscose
Viscose
Viscose is a viscous organic liquid used to make rayon and cellophane. Viscose is becoming synonymous with rayon, a soft material commonly used in shirts, shorts, coats, jackets, and other outer wear.-Manufacture:...
and cellophane
Cellophane
Cellophane is a thin, transparent sheet made of regenerated cellulose. Its low permeability to air, oils, greases, bacteria and water makes it useful for food packaging...
) from dissolving pulp
Dissolving pulp
Dissolving pulp is a bleached wood pulp that has a high cellulose content . It is produced chemically from the pulpwood, in a process that has a low yield...
.
Assaying a Cellulose-containing Material
Given a cellulose-containing material, the carbohydrate portion that does not dissolve in a 17.5% solution of sodium hydroxide at 20 °C is α cellulose, which is true cellulose. Acidification of the extract precipitates β cellulose. The portion that dissolves in base but does not precipitate with acid is γ cellulose.Cellulose can be assay
Assay
An assay is a procedure in molecular biology for testing or measuring the activity of a drug or biochemical in an organism or organic sample. A quantitative assay may also measure the amount of a substance in a sample. Bioassays and immunoassays are among the many varieties of specialized...
ed using a method described by Updegraff in 1969, where the fiber is dissolved in acetic
Acetic acid
Acetic acid is an organic compound with the chemical formula CH3CO2H . It is a colourless liquid that when undiluted is also called glacial acetic acid. Acetic acid is the main component of vinegar , and has a distinctive sour taste and pungent smell...
and nitric acid
Nitric acid
Nitric acid , also known as aqua fortis and spirit of nitre, is a highly corrosive and toxic strong acid.Colorless when pure, older samples tend to acquire a yellow cast due to the accumulation of oxides of nitrogen. If the solution contains more than 86% nitric acid, it is referred to as fuming...
to remove lignin, hemicellulose, and xylosans. The resulting cellulose is allowed to react with anthrone
Anthrone
Anthrone is a tricyclic aromatic ketone. It is used for a popular cellulose assay and in the colorometric determination of carbohydrates....
in sulfuric acid
Sulfuric acid
Sulfuric acid is a strong mineral acid with the molecular formula . Its historical name is oil of vitriol. Pure sulfuric acid is a highly corrosive, colorless, viscous liquid. The salts of sulfuric acid are called sulfates...
. The resulting coloured compound is assayed spectrophotometrically
Spectrophotometry
In chemistry, spectrophotometry is the quantitative measurement of the reflection or transmission properties of a material as a function of wavelength...
at a wavelength of approximately 635 nm
1 E-9 m
To help compare different orders of magnitudes this page lists lengths between 10−9 metres and 10−8 metres .Distances shorter than 1 nanometre*1 nm = 1 nanometre = 1000 picometres = 10 angstroms...
.
In addition, cellulose is represented by the difference between acid detergent fiber (ADF) and acid detergent lignin (ADL).
Biosynthesis
Vascular plant
Vascular plants are those plants that have lignified tissues for conducting water, minerals, and photosynthetic products through the plant. Vascular plants include the clubmosses, Equisetum, ferns, gymnosperms and angiosperms...
s cellulose is synthesized at the plasma membrane by rosette terminal complexes (RTCs). The RTCs are hexameric
Oligomer
In chemistry, an oligomer is a molecule that consists of a few monomer units , in contrast to a polymer that, at least in principle, consists of an unlimited number of monomers. Dimers, trimers, and tetramers are oligomers. Many oils are oligomeric, such as liquid paraffin...
protein structures, approximately 25 nm
Nanometre
A nanometre is a unit of length in the metric system, equal to one billionth of a metre. The name combines the SI prefix nano- with the parent unit name metre .The nanometre is often used to express dimensions on the atomic scale: the diameter...
in diameter, that contain the cellulose synthase
Synthase
In biochemistry, a synthase is an enzyme that catalyses a synthesis process.Following the EC number classification, they belong to the group of ligases, with lyases catalysing the reverse reaction....
enzymes that synthesise the individual cellulose chains. Each RTC floats in the cell's plasma membrane and "spins" a microfibril into the cell wall
Cell wall
The cell wall is the tough, usually flexible but sometimes fairly rigid layer that surrounds some types of cells. It is located outside the cell membrane and provides these cells with structural support and protection, and also acts as a filtering mechanism. A major function of the cell wall is to...
.
RTCs contain at least three different cellulose synthases, encoded by CesA genes, in an unknown stoichiometry
Stoichiometry
Stoichiometry is a branch of chemistry that deals with the relative quantities of reactants and products in chemical reactions. In a balanced chemical reaction, the relations among quantities of reactants and products typically form a ratio of whole numbers...
. Separate sets of CesA genes are involved in primary and secondary cell wall biosynthesis.
Cellulose synthesis requires chain initiation and elongation, and the two processes are separate.
CesA glucosyltransferase initiates cellulose polymerization using a steroid
Steroid
A steroid is a type of organic compound that contains a characteristic arrangement of four cycloalkane rings that are joined to each other. Examples of steroids include the dietary fat cholesterol, the sex hormones estradiol and testosterone, and the anti-inflammatory drug dexamethasone.The core...
primer, sitosterol
Beta-sitosterol
β-Sitosterol is one of several phytosterols with chemical structures similar to that of cholesterol. Sitosterols are white, waxy powders with a characteristic odor...
-beta-glucoside
Glucoside
A glucoside is a glycoside that is derived from glucose. Glucosides are common in plants, but rare in animals. Glucose is produced when a glucoside is hydrolysed by purely chemical means, or decomposed by fermentation or enzymes....
, and UDP-glucose. Cellulose synthase
Cellulose synthase (UDP-forming)
In enzymology, a cellulose synthase is an enzyme that catalyzes the chemical reactionThus, the two substrates of this enzyme are UDP-glucose and a chain of 1,4-beta-D-glucosyl residues, whereas its two products are UDP and an elongated chain of glucosyl residues...
utilizes UDP
Uridine diphosphate
Uridine diphosphate, abbreviated UDP, is a nucleoside diphosphate. It is an ester of pyrophosphoric acid with the nucleoside uridine. UDP consists of the pyrophosphate group, the pentose sugar ribose, and the nucleobase uracil.-See also:* Nucleoside...
-D-glucose precursors to elongate the growing cellulose chain. A cellulase
Cellulase
400px|thumb|right|alt = Colored dice with checkered background|Ribbon representation of the Streptomyces lividans beta-1,4-endoglucanase catalytic domain - an example from the family 12 glycoside hydrolases...
may function to cleave the primer from the mature chain.
Breakdown (cellulolysis)
Cellulolysis is the process of breaking down cellulose into smaller polysaccharides called cellodextrins or completely into glucose units; this is a hydrolysisHydrolysis
Hydrolysis is a chemical reaction during which molecules of water are split into hydrogen cations and hydroxide anions in the process of a chemical mechanism. It is the type of reaction that is used to break down certain polymers, especially those made by condensation polymerization...
reaction. Because cellulose molecules bind strongly to each other, cellulolysis is relatively difficult compared to the breakdown of other polysaccharides. Processes do exist however for the breakdown of cellulose such as the Lyocell process which uses a combination of heated water and acetone
Acetone
Acetone is the organic compound with the formula 2CO, a colorless, mobile, flammable liquid, the simplest example of the ketones.Acetone is miscible with water and serves as an important solvent in its own right, typically as the solvent of choice for cleaning purposes in the laboratory...
to break down the cellulose strands.
Most mammals have only very limited ability to digest dietary fibres such as cellulose. Some ruminant
Ruminant
A ruminant is a mammal of the order Artiodactyla that digests plant-based food by initially softening it within the animal's first compartment of the stomach, principally through bacterial actions, then regurgitating the semi-digested mass, now known as cud, and chewing it again...
s like cows and sheep contain certain symbiotic
Symbiosis
Symbiosis is close and often long-term interaction between different biological species. In 1877 Bennett used the word symbiosis to describe the mutualistic relationship in lichens...
anaerobic
Anaerobic organism
An anaerobic organism or anaerobe is any organism that does not require oxygen for growth. It could possibly react negatively and may even die if oxygen is present...
bacteria (like Cellulomonas
Cellulomonas
Cellulomonas is a genus of Gram-positive rod-shaped bacteria. One of their main distinguishing features is their ability to degrade cellulose, using enzymes such as endoglucanase and exoglucanase. They are members of the actinobacteria....
) in the flora of the rumen, and these bacteria produce enzyme
Enzyme
Enzymes are proteins that catalyze chemical reactions. In enzymatic reactions, the molecules at the beginning of the process, called substrates, are converted into different molecules, called products. Almost all chemical reactions in a biological cell need enzymes in order to occur at rates...
s called cellulase
Cellulase
400px|thumb|right|alt = Colored dice with checkered background|Ribbon representation of the Streptomyces lividans beta-1,4-endoglucanase catalytic domain - an example from the family 12 glycoside hydrolases...
s that help the microorganism to break down 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). Similarly, lower termite
Termite
Termites are a group of eusocial insects that, until recently, were classified at the taxonomic rank of order Isoptera , but are now accepted as the epifamily Termitoidae, of the cockroach order Blattodea...
s contain in their hindgut
Hindgut
The hindgut is the posterior part of the alimentary canal. In mammals, it includes the distal third of the transverse colon and the splenic flexure, the descending colon, sigmoid colon and rectum.-Blood flow:...
s certain flagellate
Flagellate
Flagellates are organisms with one or more whip-like organelles called flagella. Some cells in animals may be flagellate, for instance the spermatozoa of most phyla. Flowering plants do not produce flagellate cells, but ferns, mosses, green algae, some gymnosperms and other closely related plants...
protozoa
Protozoa
Protozoa are a diverse group of single-cells eukaryotic organisms, many of which are motile. Throughout history, protozoa have been defined as single-cell protists with animal-like behavior, e.g., movement...
which produce such enzymes; higher termites contain bacteria for the job. Some termites may also produce cellulase of their own. Fungi
Fungus
A fungus is a member of a large group of eukaryotic organisms that includes microorganisms such as yeasts and molds , as well as the more familiar mushrooms. These organisms are classified as a kingdom, Fungi, which is separate from plants, animals, and bacteria...
, which in nature are responsible for recycling of nutrients, are also able to break down cellulose.
The enzymes utilized to cleave the glycosidic linkage in cellulose are glycoside hydrolase
Glycoside hydrolase
Glycoside hydrolases catalyze the hydrolysis of the glycosidic linkage to release smaller sugars...
s including endo-acting cellulase
Cellulase
400px|thumb|right|alt = Colored dice with checkered background|Ribbon representation of the Streptomyces lividans beta-1,4-endoglucanase catalytic domain - an example from the family 12 glycoside hydrolases...
s and exo-acting glucosidases. Such enzymes are usually secreted as part of multienzyme complexes that may include dockerin
Dockerin
Dockerin is a protein domain found in the Cellulosome cellular structure. It is part of endoglucanase enzymes. The dockerin's binding partner is the cohesin domain. This interaction is essential to the construction of the Cellulosome complex . The Dockerin domain has two in-tandem repeats of a...
s and carbohydrate-binding modules
Carbohydrate-binding module
In molecular biology, a carbohydrate-binding module is a protein domain found in carbohydrate-active enzymes . The majority of these domains have carbohydrate-binding activity. Some of these domains are found on cellulosomal scaffoldin proteins. CBMs were previously known as cellulose-binding...
.
Hemicellulose
HemicelluloseHemicellulose
A hemicellulose is any of several heteropolymers , such as arabinoxylans, present along with cellulose in almost all plant cell walls. While cellulose is crystalline, strong, and resistant to hydrolysis, hemicellulose has a random, amorphous structure with little strength...
is a polysaccharide
Polysaccharide
Polysaccharides are long carbohydrate molecules, of repeated monomer units joined together by glycosidic bonds. They range in structure from linear to highly branched. Polysaccharides are often quite heterogeneous, containing slight modifications of the repeating unit. Depending on the structure,...
related to cellulose that comprises ca. 20% of the biomass of most plants. In contrast to cellulose, hemicellulose is derived from several sugars in addition to glucose
Glucose
Glucose is a simple sugar and an important carbohydrate in biology. Cells use it as the primary source of energy and a metabolic intermediate...
, especially xylose
Xylose
Xylose is a sugar first isolated from wood, and named for it. Xylose is classified as a monosaccharide of the aldopentose type, which means that it contains five carbon atoms and includes an aldehyde functional group. It is the precursor to hemicellulose, one of the main constituents of biomass...
but also including mannose
Mannose
Mannose is a sugar monomer of the aldohexose series of carbohydrates. Mannose is a C-2 epimer of glucose. It is not part of human metabolism, but is a component of microbial cell walls, and is therefore a target of the immune system and also of antibiotics....
, galactose
Galactose
Galactose , sometimes abbreviated Gal, is a type of sugar that is less sweet than glucose. It is a C-4 epimer of glucose....
, rhamnose
Rhamnose
Rhamnose is a naturally occurring deoxy sugar. It can be classified as either a methyl-pentose or a 6-deoxy-hexose. Rhamnose occurs in nature in its L-form as L-rhamnose . This is unusual, since most of the naturally occurring sugars are in D-form...
, and arabinose
Arabinose
Arabinose is an aldopentose – a monosaccharide containing five carbon atoms, and including an aldehyde functional group.For biosynthetic reasons, most saccharides are almost always more abundant in nature as the "D"-form, or structurally analogous to D-glyceraldehyde.For sugars, the D/L...
. Hemicellulose consists of shorter chains – around 200 sugar units. Furthermore, hemicellulose is branched, whereas cellulose is unbranched.
Derivatives
The hydroxylHydroxyl
A hydroxyl is a chemical group containing an oxygen atom covalently bonded with a hydrogen atom. In inorganic chemistry, the hydroxyl group is known as the hydroxide ion, and scientists and reference works generally use these different terms though they refer to the same chemical structure in...
groups (-OH) of cellulose can be partially or fully reacted with various reagent
Reagent
A reagent is a "substance or compound that is added to a system in order to bring about a chemical reaction, or added to see if a reaction occurs." Although the terms reactant and reagent are often used interchangeably, a reactant is less specifically a "substance that is consumed in the course of...
s to afford derivatives with useful properties like mainly cellulose ester
Ester
Esters are chemical compounds derived by reacting an oxoacid with a hydroxyl compound such as an alcohol or phenol. Esters are usually derived from an inorganic acid or organic acid in which at least one -OH group is replaced by an -O-alkyl group, and most commonly from carboxylic acids and...
s and cellulose ether
Ether
Ethers are a class of organic compounds that contain an ether group — an oxygen atom connected to two alkyl or aryl groups — of general formula R–O–R'. A typical example is the solvent and anesthetic diethyl ether, commonly referred to simply as "ether"...
s (-OR). In principle, though not always in current industrial practice, cellulosic polymers are renewable resources.
Ester derivatives include:
| Cellulose ester | Reagent | Example | Reagent | Group R |
|---|---|---|---|---|
| Organic esters | Organic acids | Cellulose acetate Cellulose acetate Cellulose acetate , first prepared in 1865, is the acetate ester of cellulose. Cellulose acetate is used as a film base in photography, as a component in some adhesives, and as a frame material for eyeglasses; it is also used as a synthetic fiber and in the manufacture of cigarette filters and... |
Acetic acid Acetic acid Acetic acid is an organic compound with the chemical formula CH3CO2H . It is a colourless liquid that when undiluted is also called glacial acetic acid. Acetic acid is the main component of vinegar , and has a distinctive sour taste and pungent smell... and acetic anhydride Acetic anhydride Acetic anhydride, or ethanoic anhydride, is the chemical compound with the formula 2O. Commonly abbreviated Ac2O, it is the simplest isolatable acid anhydride and is a widely used reagent in organic synthesis... |
H or -(C=O)CH3 |
| Cellulose triacetate Cellulose triacetate Cellulose triacetate, also known simply as triacetate, CTA and TAC, is manufactured from cellulose and a source of acetate esters, typically acetic anhydride... |
Acetic acid and acetic anhydride | -(C=O)CH3 | ||
| Cellulose propionate | Propanoic acid | H or -(C=O)CH2CH3 | ||
| Cellulose acetate propionate | Acetic acid and propanoic acid | H or -(C=O)CH3 or -(C=O)CH2CH3 | ||
| Cellulose acetate butyrate | Acetic acid and butyric acid Butyric acid Butyric acid , also known under the systematic name butanoic acid, is a carboxylic acid with the structural formula CH3CH2CH2-COOH. Salts and esters of butyric acid are known as butyrates or butanoates... |
H or -(C=O)CH3 or -(C=O)CH2CH2CH3 | ||
| Inorganic esters | Inorganic acids | Nitrocellulose Nitrocellulose Nitrocellulose is a highly flammable compound formed by nitrating cellulose through exposure to nitric acid or another powerful nitrating agent. When used as a propellant or low-order explosive, it is also known as guncotton... (cellulose nitrate) |
Nitric acid Nitric acid Nitric acid , also known as aqua fortis and spirit of nitre, is a highly corrosive and toxic strong acid.Colorless when pure, older samples tend to acquire a yellow cast due to the accumulation of oxides of nitrogen. If the solution contains more than 86% nitric acid, it is referred to as fuming... or another powerful nitrating agent |
H or -NO2 |
| Cellulose sulfate | Sulfuric acid Sulfuric acid Sulfuric acid is a strong mineral acid with the molecular formula . Its historical name is oil of vitriol. Pure sulfuric acid is a highly corrosive, colorless, viscous liquid. The salts of sulfuric acid are called sulfates... or another powerful sulfuring agent |
H or -SO3H |
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
Camphor
Camphor is a waxy, white or transparent solid with a strong, aromatic odor. It is a terpenoid with the chemical formula C10H16O. It is found in wood of the camphor laurel , a large evergreen tree found in Asia and also of Dryobalanops aromatica, a giant of the Bornean forests...
, nitrocellulose gives celluloid
Celluloid
Celluloid is the name of a class of compounds created from nitrocellulose and camphor, plus dyes and other agents. Generally regarded to be the first thermoplastic, it was first created as Parkesine in 1862 and as Xylonite in 1869, before being registered as Celluloid in 1870. Celluloid is...
.
Ether derivatives include:
| Cellulose ethers | Reagent | Example | Reagent | Group R = H or | Water solubility | Application | E number E number E numbers are number codes for food additives that have been assessed for use within the European Union . They are commonly found on food labels throughout the European Union. Safety assessment and approval are the responsibility of the European Food Safety Authority... |
|---|---|---|---|---|---|---|---|
| Alkyl | Halogenoalkanes | Methylcellulose Methylcellulose Methyl cellulose is a chemical compound derived from cellulose. It is a hydrophilic white powder in pure form and dissolves in cold water, forming a clear viscous solution or gel. It is sold under a variety of trade names and is used as a thickener and emulsifier in various food and cosmetic... |
Chloromethane Chloromethane Chloromethane, also called methyl chloride, R-40 or HCC 40, is a chemical compound of the group of organic compounds called haloalkanes. It was once widely used as a refrigerant. It is a colorless extremely flammable gas with a minorly sweet odor, which is, however, detected at possibly toxic levels... |
-CH3 | Cold water soluble | E461 | |
| Ethylcellulose | Chloroethane Chloroethane Chloroethane or monochloroethane, commonly known by its old name ethyl chloride, is a chemical compound with chemical formula , once widely used in producing tetraethyllead, a gasoline additive... |
-CH2CH3 | Water insoluble | A commercial thermoplastic used in coatings, inks, binders, and controlled-release drug tablets | E462 | ||
| Ethyl methyl cellulose | Chloromethane and chloroethane | -CH3 or -CH2CH3 | E465 | ||||
| Hydroxyalkyl | Epoxide Epoxide An epoxide is a cyclic ether with three ring atoms. This ring approximately defines an equilateral triangle, which makes it highly strained. The strained ring makes epoxides more reactive than other ethers. Simple epoxides are named from the parent compound ethylene oxide or oxirane, such as in... s |
Hydroxyethyl cellulose Hydroxyethyl cellulose Hydroxyethyl cellulose is a gelling and thickening agent derived from cellulose. It is widely used in cosmetics, cleaning solutions, and other household products.... |
Ethylene oxide Ethylene oxide Ethylene oxide, also called oxirane, is the organic compound with the formula . It is a cyclic ether. This means that it is composed of two alkyl groups attached to an oxygen atom in a cyclic shape . This colorless flammable gas with a faintly sweet odor is the simplest epoxide, a three-membered... |
-CH2CH2OH | Cold/hot water soluble | Gelling and thickening agent | |
| Hydroxypropyl cellulose Hydroxypropyl cellulose Hydroxypropyl cellulose is a derivative of cellulose with both water solubility and organic solubility. It is used as a topical ophthalmic protectant and lubricant.-Chemistry:... (HPC) |
Propylene oxide Propylene oxide Propylene oxide is an organic compound with the molecular formula CH3CHCH2O. This colourless volatile liquid is produced on a large scale industrially, its major application being its use for the production of polyether polyols for use in making polyurethane plastics... |
-CH2CH(OH)CH3 | Cold water soluble | E463 | |||
| Hydroxyethyl methyl cellulose Hydroxyethyl methyl cellulose Hydroxyethyl methyl cellulose is a gelling and thickening agent derived from cellulose.... |
Chloromethane and ethylene oxide | -CH3 or -CH2CH2OH | Cold water soluble | Production of cellulose films | |||
| Hydroxypropyl methyl cellulose (HPMC) | Chloromethane and propylene oxide | -CH3 or -CH2CH(OH)CH3 | Cold water soluble | Viscosity modifier, gelling, foaming and binding agent | E464 | ||
| Ethyl hydroxyethyl cellulose | Chloroethane and ethylene oxide | -CH2CH3 or—CH2CH2OH | E467 | ||||
| Carboxyalkyl | Halogenated carboxylic acids | Carboxymethyl cellulose Carboxymethyl cellulose Carboxymethyl cellulose or cellulose gum is a cellulose derivative with carboxymethyl groups bound to some of the hydroxyl groups of the glucopyranose monomers that make up the cellulose backbone... (CMC) |
Chloroacetic acid Chloroacetic acid Chloroacetic acid, industrially known as monochloroacetic acid is the organochlorine compound with the formula ClCH2CO2H. This carboxylic acid is a useful building-block in organic synthesis.-Production:... |
-CH2COOH | Cold/Hot water soluble | Often used as its sodium Sodium Sodium is a chemical element with the symbol Na and atomic number 11. It is a soft, silvery-white, highly reactive metal and is a member of the alkali metals; its only stable isotope is 23Na. It is an abundant element that exists in numerous minerals, most commonly as sodium chloride... salt, sodium carboxymethyl cellulose (NaCMC) |
E466 |
The sodium carboxymethyl cellulose can be cross-linked to give the croscarmellose sodium
Croscarmellose sodium
Croscarmellose sodium is an internally cross-linked sodium carboxymethylcellulose for use as a disintegrant in pharmaceutical formulations.-Background:...
(E468) for use as a disintegrant
Excipient
An excipient is generally a pharmacologically inactive substance used as a carrier for the active ingredients of a medication. In many cases, an "active" substance may not be easily administered and absorbed by the human body; in such cases the substance in question may be dissolved into or...
in pharmaceutical formulations.
See also
- Cell wallCell wallThe cell wall is the tough, usually flexible but sometimes fairly rigid layer that surrounds some types of cells. It is located outside the cell membrane and provides these cells with structural support and protection, and also acts as a filtering mechanism. A major function of the cell wall is to...
- CellulaseCellulase400px|thumb|right|alt = Colored dice with checkered background|Ribbon representation of the Streptomyces lividans beta-1,4-endoglucanase catalytic domain - an example from the family 12 glycoside hydrolases...
- Cellulose insulationCellulose insulationThe word cellulose comes from the French word for a living cellule and glucose, which is sugar. Building insulation is low-thermal-conductivity material used to separate the internal climate and sounds of a building from external climate and sounds...
- Cellulose fiberCellulose fiberCellulose fibers are fibres of cellulose from any source, either natural or manufactured.-Textile:In the textile industry regenerated cellulose is used as fibers such as rayon, . Cellulose fibers are manufactured from dissolving pulp...
- Cellulosic ethanolCellulosic ethanolCellulosic ethanol is a biofuel produced from wood, grasses, or the non-edible parts of plants.It is a type of biofuel produced from lignocellulose, a structural material that comprises much of the mass of plants. Lignocellulose is composed mainly of cellulose, hemicellulose and lignin...
- HemicelluloseHemicelluloseA hemicellulose is any of several heteropolymers , such as arabinoxylans, present along with cellulose in almost all plant cell walls. While cellulose is crystalline, strong, and resistant to hydrolysis, hemicellulose has a random, amorphous structure with little strength...
- Microbial celluloseMicrobial celluloseMicrobial cellulose is a form of cellulose that is produced by bacteria. It is widely used in the traditional Filipino dessert Nata de coco. Microbial cellulose was first confirmed as cellulose in 1886.- Production :...
- NanocelluloseNanocelluloseNanocellulose or microfibrillated cellulose , is a material composed of nanosized cellulose fibrils with a high aspect ratio . Typical dimensions are 5–20 nanometers width and length up to 2000 nanometers. It is pseudo-plastic...
External links
- Structure and morphology of cellulose by Serge Pérez and William Mackie, CERMAV-CNRS
- Cellulose, by Martin Chaplin, London South Bank UniversityLondon South Bank UniversityLondon South Bank University is a university in south London. With over 25,000 students and 1,700 staff, it is based in the London Borough of Southwark, near the South Bank of the River Thames, from which it takes its name...
- Clear description of a cellulose assay method at the Cotton Fiber Biosciences unit of the USDAUnited States Department of AgricultureThe United States Department of Agriculture is the United States federal executive department responsible for developing and executing U.S. federal government policy on farming, agriculture, and food...
. - Cellulose films could provide flapping wings and cheap artificial muscles for robots - TechnologyReview.com
- Using cellulase enzymes in the bioethanol process
- A list of cellulolytic bacteria