Chapter 8 - Production and applications of pullulan

Abstract

Pullulan is a linear, extracellular glucose polysaccharide produced by fermentation using fungus, Aureobasidium pullulans. It is a nonionic, biocompatible, nonmutagenic, water-soluble, and edible polymer with film-forming properties displaying diverse applications in food preservation and packaging, biomedical, pharmaceutical, and waste remediation. The structure of pullulan comprises bonds of α-(1→6)-linked (1→4)-α-d-triglucosides, that is, maltotriose in a successive manner giving it properties like adhesion, film, and fiber formation. The reactive sites present in its structure enhance the chances for chemical modifications further widening its application scope in different arenas. Selected raw materials, fermentation conditions and product recovery steps majorly impact the productivity and properties of pullulan. To lower the production cost, researchers in the past have reported the utilization of low-cost raw materials as a source of carbon and nitrogen. Many conventional and novel fermentation systems have been widely studied for the production of this exopolysaccharide to achieve high productivity at lower process costs. During the downstream processing (DSP), removal of melanin pigment co-produced during fermentation is an important step to obtain a pure biopolymer. This article presents an overview of various literature on pullulan biosynthesis, structure, chemical modifications, different substrates, microbial sources, upstream processing, DSP, and applications of pullulan in various fields.