What is the chemical formula for cellulose

Cellulose

The Cellulose (often also cellulose) is the main component of plant cell walls (mass fraction approx. 50%) and thus the most common organic compound and also the most common polysaccharide (polysaccharide). It is unbranched and consists of several hundred to ten thousand β-D.-Glucose molecules (β-1,4-glycosidic bond) or cellobiose units. The cellulose molecules accumulate to form higher structures which, as tear-resistant fibers in plants, often have static functions. Cellulose is important as a raw material for paper production, but also in the chemical industry and other areas.

history

Cellulose was discovered in 1838 by the French chemist Anselme Payen, who isolated it from plants and determined their chemical formula.[2] Cellulose was made by in 1870 Hyatt Manufacturing Company used to produce the first plastomer, celluloid. Hermann Staudinger determined the structure of cellulose in 1920. In 1992, cellulose was chemically synthesized for the first time by Kobayashi and Shoda (without the help of biologically based enzymes).[3]

chemistry

Cellulose is a polymer (Polysaccharide 'Multiple sugar') from the monomer cellobiose, a disaccharide ('double sugar'). The monomers are linked to one another by β-1,4-glycosidic bonds. Cellobiose itself consists of two molecules of the monosaccharide ('simple sugar') glucose. Here, too, there is a β-1,4-glycosidic bond, so that glucose is often also defined as a monomer of cellulose.

The monomers are linked by a condensation reaction in which two hydroxyl groups (-OH) form a water molecule (H.2O) and the remaining oxygen atom connects the ring-shaped basic structure (pyran ring) of the two monomers. In addition to this strong, covalent bond, the less strong hydrogen bonds are also formed intramolecularly.[4] A cellulose molecule often consists of several thousand glucose units.

properties

Cellulose is insoluble in water and in most organic solvents. Solvents such as dimethylacetamide / lithium chloride or dimethyl sulfoxide / tetrabutylammonium fluoride and ammonia / Cu2+ (Schweizer's reagent) can, however, dissolve cellulose. It can be split by strong acids. With concentrated acids at elevated temperatures, the cellulose can be broken down into glucose by cleaving the glycosidic bonds.

The chemical company BASF has developed an injection process in which cellulose is physically dissolved in an ionic liquid. This solution can be used for chemical syntheses that were previously not possible.[5]

biosynthesis

Schematic representation of the cell wall, cellulose microfibrils in light blue

In most plants, cellulose is of fundamental importance as a structural substance. Fibers in woody and non-woody plants consist of a large number of fibrils, which in turn consist of numerous cellulose molecules arranged parallel to one another. Cellulose microfibrils are synthesized in the plasma membrane of a cell in so-called rosette complexes. These contain the enzyme cellulose synthase, which produces β-D-glucans (D-glucose polymers with β-bond) and thereby links the first carbon atom of one D-glucose molecule with the fourth carbon atom of another D-glucose molecule. The production of the glucan chain requires two essential steps. First, sucrose synthase splits the disaccharide (double sugar) sucrose into its monomers glucose and fructose to provide glucose. The glucose is now linked by the cellulose synthase with uridine diphosphate (UDP) to form UDP-glucose. In a further step, the bound glucose is now transferred to the non-reducing sugar of the growing glucan chain. The glucan chain or the enzyme then moves on so that a further synthesis step can take place.

Cellulose is formed in the plasma membrane and interlinks to form fibrous structures. Then the spatial arrangement of the cellulose fibrils takes place by means of microtubules.

use

Plant material consisting mainly of cellulose has been used by humans as fuel for cooking and heating since at least the Paleolithic Age. Cellulose is also an important raw material for material uses, but is also important as a natural or added component of food and feed. Since cellulose is also found in almost all types of plant biomass, it is also important in many other areas, such as e.g. B. in wood (lignocellulose) as a building material etc.

raw material

Cellulose is an important raw material for paper production. Wood, which is rich in lignin and cellulose, is used as the raw material. From this pulp is made, which is used for paper of less high quality. By removing the lignin content, pulp can be used, which consists mainly of cellulose and can be used for higher quality papers.

In the clothing industry, the plant fibers, which mainly consist of cellulose, are used for various fabrics. Examples are cotton and bast fibers from flax, which are processed into linen.

Another regenerated cellulose material is cellophane (cellulose hydrate), which is a widely used packaging material in the form of foils. Synthetic cellulose fibers ("rayon") can also be produced. For this, an alkaline solution of xanthogenized cellulose ("viscose solution") is processed into threads, the so-called regenerated fibers (e.g. viscose).

A wide variety of cellulose derivatives are used in a variety of ways, such as. B. methyl cellulose, cellulose acetate and cellulose nitrate in the construction, textile and chemical industries. Celluloid, the first thermoplastic, is derived from cellulose nitrate.

Since cellulose is available in large quantities in nature, attempts are being made to use this renewable raw material e.g. B. to make cellulosic ethanol available as biofuel. Intensive research is currently being carried out to develop plant biomass, especially wood and straw, for this purpose.

Cellulose can also serve as a natural insulation material.[6] For this purpose, sorted newsprint is first shredded in a mechanical process. The cellulose insulation material obtained can be blown in seamlessly and used for thermal insulation and soundproofing. The blowing process has been used in Canada and the USA since around 1940. The advantage of this insulation material is the environmentally friendly production and the further use of sorted newsprint.

In the laboratory, it can be used as a filling material for column chromatography when separating mixtures of substances.

food

In contrast to starch, all higher living organisms, including the typical herbivores, cannot break down cellulose themselves in the intestine, although both molecules are made up of glucose molecules. They only own the enzymes that α-1,4- or α1,6-glycosidic bonds (e.g. in starch) can cleave (amylases), but not those with a different structure β-1,4-glycosidic bonds of cellulose. This is why these creatures (e.g. cows) can only use the high energy content of this carbohydrate with the help of symbiotic bacteria that provide the appropriate cellulases and that live in their intestines.

Humans also have no digestive enzymes to break down cellulose. With the help of anaerobic bacteria in the first part of the large intestine, the appendix and the ascending colon, only part of the cellulose from food is broken down into short-chain fatty acids. They are absorbed through the colon mucosa and used by the metabolism. In addition to hemicelluloses, pectin and lignin, cellulose is an important vegetable fiber in human nutrition.

Other living beings with a similarly structured digestive system (monogastric animals), such as pigs, cannot digest cellulose effectively either.

Ruminants digest a large part of the cellulose and other polysaccharides in the rumen. Here, too, anaerobic bacteria are involved, which convert the cellulose into fatty acids. The same applies to horses and water fowl, where processing takes place in the large intestine. Some insects, such as the silverfish (Lepisma), are able to digest cellulose with the body's own cellulases and do not depend on endosymbionts.

Most bacteria and fungi, however, can only break down cellulose through their cellulases down to the glucose dimer-cellobiose. A few protozoa and fungi like Aspergillus, Penicillium and FusariumSpecies also have the necessary β-1,4-glucosidases or Cellobiaseswhich break down the cellobiose into glucose.[7] Some wood-decomposing mushrooms like Ceriporiopsis subvermispora can also use cellobiose via the Cellobiose dehydrogenase (CDH), an extracellular hemoflavoenzyme, oxidatively break down. This creates gluconic acid instead of glucose.[8]

Food additive

Cellulose or cellulose derivatives are also used in the food and pharmaceutical industries, e.g. B. as a thickener, carrier, filler, release agent, coating agent and foam agent. As a food additive, cellulose has the designations E 460 to E 466:

E 460i - microcrystalline cellulose
E 460ii - cellulose powder
E 461 - methyl cellulose
E 463 - hydroxypropyl cellulose
E 464 - hydroxypropyl methyl cellulose
E 465 - ethyl methyl cellulose
E 466 - carboxymethyl cellulose

The detection is carried out by means of an iodine-zinc chloride solution (blue color).

See also

literature

  • Hans-Werner Heldt, Birgit Piechulla, Fiona Heldt: Plant biochemistry 4th edition, Spektrum, Heidelberg / Berlin 2008, ISBN 978-3-8274-1961-3.
  • Peter Schopfer, Axel Brennicke: Plant physiology, 7th edition, Spektrum, Heidelberg / Berlin 2010, ISBN 978-3-8274-2351-1.
  • Lincoln Taiz, Eduardo Zeiger: Plant Physiology (Original title: Plant physiology translated by Uta Dreßer), Spektrum, Heidelberg / Berlin 2000, ISBN 3-8274-0537-8.
  • Dieter Hess: Plant physiology. 11th, completely revised and redesigned edition, UTB 8393 / Ulmer, Stuttgart 2008 ISBN 978-3-8252-8393-3 (UTB) / ISBN 978-3-8001-2885-3 (Ulmer).

Web links

Individual evidence

  1. 1,01,11,21,31,41,51,6data sheet CELLULOSE for column chromatography from Carl Roth, accessed December 27, 2012.
  2. Crawford, R. L .: Lignin biodegradation and transformation. New York: John Wiley and Sons 1981, ISBN 0-471-05743-6
  3. Dieter Klemm, Brigitte Heublein, Hans-Peter Fink, Andreas Bohn: Cellulose: Fascinating Biopolymer and Sustainable Raw Material. In: ChemInform. 36, No. 36, 2005. doi: 10.1002 / chin.200536238.
  4. ↑ Stryer, Lubert: biochemistry, Spektrum der Wissenschaft Verlag, 4th edition, corrected reprint, Heidelberg, 1999, ISBN 3-86025-346-8, p.497
  5. ↑ Neue Zürcher Zeitung, online edition of Nov 21, 2007: Chemicals from the biorefinery.
  6. ↑ Fraunhofer Information Center for Space and Construction (Baufachinformation.de): Organic insulation materials
  7. ↑ M. Weidenbörner: Lexicon of food mycology. Springer, 1999, ISBN 978-3-540-65241-0
  8. ↑ E. Duenhofen: Fermentation, purification and characterization of cellobiose dehydrogenase from Ceriporiopsis subvermispora. Diploma thesis at the University of Natural Resources and Life Sciences, Vienna, 2005