Pullulan

Description

Pullulan is a water-soluble, linear homopolysaccharide of glucose that is produced extracellularly by certain strains of the Aureobasidium pullulans fungus. This polysaccharide possesses adhesive properties and can be utilized to create strong, compression moldings, fibers, and oxygen-impermeable films. In the food industry, pullulan films are frequently used as coating or packaging material for dried foods, as a binder for tobacco, plant fertilizers, and seed coatings, as a low-viscosity filler in sauces and beverages, as well as a stabilizer and binder in food pastes. Additionally, this polysaccharide is often used to halt fungal growth in food. As for pharmaceutical applications, pullulan is used as a denture adhesive and an ingredient in sugar-coated pharmaceutical compositions to prevent the development of brownish coloring. Finally, pullulan finds application in lotions, shampoos, and cosmetics.

Chemical Properties

It is a white, tasteless, and odorless non-crystalline powder that dissolves easily in water and dimethylformamide, but not in alcohol, ether, or oil. Its solution is viscous, stable, and neutral, with no gelling effect. The viscosity of the solution is the same as that of gum arabic, and it has a very good thickening effect of salt resistance, enzyme resistance, heat resistance, and pH value change resistance. It has strong film-forming properties, and the film formed after its aqueous solution is dried on a metal plate has strong gas barrier properties to oxygen and nitrogen. Moreover, it is suitable for making water-soluble edible films and is compatible with other water-soluble polymers.

Uses

Pullulan has been used in a study to assess bone tissue engineering. It has also been used in a study that investigated anti-fog applications.

Definition

pullulan: A water-soluble polysaccharidecomposed of glucose unitsthat are polymerized in such a wayas to make it viscous and impermeableto oxygen. Pullulan is used in adhesives, food packaging, andmoulded articles. It is derived fromthe fungus Aureobasidium pullulans.

Application

Pullulan is a hemocompatible, nonimmunogenic, and noncarcinogenic agent. In the food industry are mainly filler, edible, and tasteless polymers. Furthermore, in pharmaceuticals and electronics pullulan is used in tissue engineering, drug and gene delivery systems, as a coating agent, and as a film- and fiber-forming agent, due to its excellent physicochemical properties. Pullulan is the backbone of a polymeric system capable of forming hydrogels and nanogels. These systems show potential applications in the preparation of green smart materials, biomimetics, biosensors, artificial muscles, drug delivery systems, and chemical separations. Pullulan-based nanosystems can act as carriers of different drugs. It has been used as a carrier for oral, nasal, and lung transmucosal drug delivery systems because it is not attacked by the digestive enzymes in the human gut[3-4].

Production Methods

Pullulan is produced by fermentation from a food-grade hydrolyzed search with a non-toxin-producing strain of Aureobasidium pullulans. After fermentation, the fungal biomass is removed by microfiltration, the filtrate is heat-sterilized, and pigments and other impurities are removed by adsorption and ion exchange chromatography. The product contains not less than 90% glucan on a dried basis. The main impurities from the starting material are mono-, di-, and oligosaccharides. The average relative molecular mass of pullulan varies considerably depending on the conditions of the culture. A commercially available product has an average relative molecular mass of 200 000 Da.

Biological Functions

Pullulan is a polysaccharide polymer that is derived from the Aureobasidium pullulans yeast and consists of D-Maltotriose units. It is used as a binder and film former in a variety of formulation categories (skin, make-up, and hair). Pullulan has been used in a study to assess bone tissue engineering. Addition of pullulan has improved the elongation at break of gelatin based edible film when the amount was 50% (wt. %).

General Description

Pullulan Standards are mostly used to obtain molecular mass distribution of cellulosic samples. It mainly consists of polymaltotriose units linked together by α-(1→6) linkages. Pullulan is a biodegradable polysaccharide made by yeast fermentation, originally developed in Japan. Its adhesive and oxygen impermeable properties enable it to be used to coat pharmaceutical products. It is water soluble, odorless, and edible.

Structure and conformation

Pullulan is a naturally occurring, fungal polysaccharide produced by fermentation of liquefied corn starch by Aureobasidium pullulans, a ubiquitous yeast-likefungus. It has a linear structure consisting predominantly of repeating maltotriose units, which are made up of three o-1,4-linked glucose molecules linked by a-1,6-glycosidic bonds. The maltotriose units are interspersed with about 6% maltotetraose units consisting of four o-1,4-linked glucose molecules; rarely, branch points occur, at which poly-maltotriose side chains are attached to the main chain by a 1,3-glycosidic bond.

References

[1] Timothy D. Leathers, Biopolymers Online, 2005,
[2] Ram S. Singh, Gaganpreet K. Saini and John F. Kennedy, Pullulan: Microbial sources, production and applications, Carbonhydrate Polymers, 2008, vol. 73, 515-531.
[3] Nasrollahzadeh M, et al. Green Nanotechnology. Interface Science and Technology, 2019; 28: 145-198.
[4] Narayanaswamy R, et al. Basics to different imaging techniques, different nanobiomaterials for image enhancement. Nanobiomaterials in Medical Imaging, 2016; 101-129.