Cellulose

Cellulose is a biopolymer composed exclusively of β-glucose molecules (from hundreds to several thousand units), as it is a homopolysaccharide. Cellulose is the most abundant organic biomolecule since it forms the majority of the terrestrial biomass.

It can also be produced by some living beings that belong to the kingdom protista.

History

Cellulose was discovered in 1838 by the French chemist Anselme Payen, who isolated it from plant matter and determined its chemical formula. Cellulose was used by the Hyatt Manufacturing Company to produce the first successful thermoplastic polymer in 1870, celluloid. The production of rayon (“artificial silk”) from cellulose began in the 1890s, and cellophane was invented in 1912. Hermann Staudinger determined the polymer structure of cellulose in 1920. The compound was first synthesized chemically (without the use of any enzyme of biological origin) in 1992, by Kobayashi and Shoda.

Structure

Cellulose is present in all plants.

The arrangement of cellulose and other polysaccharides on a plant cell wall.

Cellulose is formed by the union of β-D-glucose molecules through β-1,4-O-glucosidic bonds. When completely hydrolyzed, glucose is obtained. Cellulose is a long polymeric chain of variable molecular weight, with the empirical formula (C₆H₁₀O₅)_n, with a minimum value of n = 200.

Cellulose structure; to the left, β-glucosa; to the right, several β-glucosa joined.

It has a linear or fibrous structure, in which multiple hydrogen bonds are established between the hydroxyl groups of different juxtaposed glucose chains, making them impenetrable to water, which makes it insoluble in water, and originating compact fibers that constitute the cell wall of plant cells.

Function

Hydrogen links between contiguous cellulose chains

Cellulose is a structural polysaccharide in plants, as it is part of the supporting tissues. The wall of a young plant cell contains approximately 40% cellulose; wood is 50%, while the purest example of cellulose is cotton, with a percentage greater than 90%. Although it is made up of glucose, animals cannot use cellulose as an energy source, since they do not have cellulase, the enzyme necessary to break β-1,4-glucosidic bonds, and therefore cannot digest it However, it is important to include it in the human diet (dietary fiber) because when mixed with feces it facilitates digestion and can prevent constipation.

In the digestive system of ruminants (pre-stomachs), other herbivores and termites, there are microorganisms, many methanogens, that do have cellulase and manage to break the β-1,4-glucosidic bond and when this polysaccharide is hydrolyzed glucose molecules are available as an energy source.

There are microorganisms (bacteria and fungi) that live free and are also capable of hydrolyzing cellulose. They are of great ecological importance, as they recycle cellulosic materials such as paper, cardboard and wood. Among them, the fungus Trichoderma reesei stands out, capable of producing four types of cellulases: 1,4-β-D-glucancellobiohirolases CBH i and CBH II and endo-1,4-β -D-glucanase EG I and EG II. Biotechnological techniques produce these enzymes that can be used in paper recycling, reducing the economic cost and pollution.

Discovery and uses

Cellulose is the substance most frequently found in plant cell walls, and it was discovered in 1838.

Cellulose is the raw material for paper and natural fiber fabrics. It is also used in the manufacture of explosives (the best known is nitrocellulose or "gunpowder"), celluloid, artificial silk, varnishes and is used as thermal and acoustic insulation, as a by-product of shredded recycled paper. Through vegetable cellulose, water treatment systems could be designed and implemented, since this polysaccharide has the ability to adsorb heavy metals