Scleroglucan is a neutral β-glucan exopolysaccharide secreted by fungi such as Sclerotium rolfsii. It is distinguished by its rigid triple-helical structure and remarkable rheological stability. This polysaccharide is part of a broader family of microbial and marine polysaccharides, alongside alginate, dextran, levan, pullulan, xanthan gum, gellan gum, and fucoidan, widely studied for their physicochemical and biological properties.
Molecular Structure
Scleroglucan is composed of a linear β-(1→3)-D-glucopyranose backbone with single β-(1→6)-D-glucose side chains attached to every third glucose unit. This arrangement forms a repeating pentasaccharide structure and promotes the formation of a stable triple-helical conformation in aqueous solutions. The molecular weight typically ranges from 5 × 106 to 15 × 106 Da. The helical structure imparts high rigidity and mechanical strength, while exposure to temperatures above 120°C or alkaline conditions induces a transition to single coils that can reversibly reform upon cooling.
Production and Properties
Scleroglucan is produced via submerged fermentation using glucose or sucrose substrates by S. rolfsii, typically conducted at 28–30°C and pH 4–6. Following fermentation, the broth is clarified through filtration or centrifugation, and the polysaccharide is recovered by precipitation with solvents such as isopropanol or acetone before drying. Scleroglucan exhibits exceptional shear-thinning viscosity, high elasticity, and outstanding stability across a broad pH range (2–13), elevated temperatures up to 140°C, and high salt or electrolyte concentrations. Its low biodegradability and thermoreversible behavior make it particularly effective in harsh industrial and biomedical environments, often outperforming xanthan gum.
Biomedical Applications
In biomedical research, scleroglucan functions as a β-glucan immunomodulator capable of enhancing innate immune responses. It has demonstrated antitumor activity, vaccine adjuvant potential, and anti-infective properties. Additionally, scleroglucan forms biocompatible hydrogels suitable for controlled drug delivery, wound healing scaffolds, and therapies for dysphagia by mimicking natural bolus rheology. When blended with polymers such as gellan gum, it can generate co-crosslinked hydrogel matrices that support sustained and targeted therapeutic delivery.
