Pullulan: Microbial sources, production and applications

Pullulan is a water-soluble glucan gum produced aerobically by growing a yeast like fungus Aureobasidium pullulans. It is a regularly repeating copolymer with the chemical structure {→6)-α-d-glucopyranosyl-(1→4)-α-d-glucopyranosyl-(1→4)-α-d-glucopyranosyl-(1→}n. Thus the polysaccharide is viewed as a succession of α-(1→6)-linked (1→4)-α-d-triglucosides i.e. maltotriose (G3). Pullulan have a wide range of commercial and industrial applications in many fields like food science, health care, pharmacy and even in lithography. Due to its strictly linear structure, pullulan is also very valuable in basic research as well as a well-defined model substance. This review attempts to critically appraise the current literature on fungal exopolysaccharide (EPS) 'pullulan' considering its microbial sources, structural geometry, upstream processing, downstream processing, peculiar characteristics and applications.