Characterization and chemical modification of pullulan produced from a submerged culture of Aureobasidium pullulans ATCC 15233

Abstract

In this paper, the pullulan produced by A. pullulans ATCC 15233 was characterized and chemically modified. The pullulan derivative was synthesized with an acetylation reaction with a degree of substitution (DS) of 2.90. Its structural elucidation was performed using infrared (IR) and nuclear magnetic resonance (NMR) spectroscopy. The results showed signs of α (1–4) and α (1–6) glycosidic bonds, typical of pullulan. The molecular weight (MW) of pullulan was 93.47 kDa. The thermal analysis conducted indicated increased thermal stability (Td) and glass transition temperature (Tg) due to acetylation. Homogeneous morphologies of the samples under analysis were obtained using scanning electron microscopy (SEM). The mechanical properties of the pullulan film exhibited tensile strength (TS) values of 1.70 ± 0.48 MPa and an elongation at break (% E) of 11.89%. Likewise, the pullulan acetate film recorded a TS of 1.23 ± 0.09 MPa and a % E of 1.25%. The results suggest that the physicochemical properties of biosynthesized pullulan and pullulan derivatives can be considered in the development of biomaterials.

Keywords

• Pullulan
• Pullulan acetate
• Chemical modification
• Characterization
• Aureobasidium pullulans