Antibacterial and antioxidant activities of β-glucans derived from Aureobasidium pullulans

Abstract

Polysaccharides from extracellular (PS_EX), cell wall (PS_CW), and intracellular (PS_IN) fractions of Aureobasidium pullulans CGMCC19650 were extracted and purified, respectively. Based on chemical composition analysis and spectral characterization using Fourier-transform infrared (FT-IR) and nuclear magnetic resonance (NMR) spectroscopy, it was confirmed that the three polysaccharides are β-1,3-1,6-glucans. However, results of molecular weight analysis, Congo red test, X-ray diffraction, and scanning electron microscopy revealed different molecular weight distributions, spatial configurations, and microstructure features. All three β-glucans exhibited potent antibacterial activities against both Escherichia coli and Staphylococcus aureus, but were ineffective against Candida albicans. Moreover, PS_EX, PS_CW, and PS_IN demonstrated robust scavenging activities against 1,1-diphenyl-2-picrylhydrazyl, 2,2′-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid), hydroxyl, and superoxide anion radicals in vitro. Additionally, these β-glucans protected RAW264.7 macrophages from H₂O₂-induced oxidative stress damage by lowering reactive oxygen species levels, increasing endogenous superoxide dismutase, catalase, and glutathione peroxidase activities, and decreasing intracellular malondialdehyde contents. These findings suggest that β-glucans derived from A. pullulans hold great potential for applications as natural antibacterial and antioxidant agents in food and medicine.