pullulan

Pullulan is a water-soluble extracellular polysaccharide produced by the black yeast-like fungus Aureobasidium pullulans. It is a linear glucan in which maltotriose units (three glucose residues) are joined by α-1,6 glycosidic bonds, yielding a polymer composed of repeating maltotriose blocks. The polymer exhibits a broad molecular weight range, typically from about 10^5 to 2×10^6 Da, reflecting differences in fermentation conditions and strain.

Pullulan is produced commercially by fermentation of sugars such as glucose or sucrose, followed by purification from the culture broth. It forms transparent, colorless, odorless films when cast from aqueous solution and is edible. It is highly water-soluble and has exceptional oxygen barrier properties in film form, while being relatively permeable to water vapor, which influences its use in packaging where moisture control is important.

Applications include edible coatings and films for food and pharmaceutical capsules. Its film-forming and barrier properties make it attractive for packaging, coatings, and controlled-release formulations. In addition, pullulan is used as a thickener, stabilizer, and binder in foods and cosmetics; it is generally recognized as safe (GRAS) in several jurisdictions.

Pullulan is not digestible by human enzymes but can be fermented by certain gut microbiota, contributing to dietary fiber-like effects. It is considered biocompatible and has ongoing research in drug delivery systems, nanocomposites, and biodegradable packaging.