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

Polysaccharides from extracellular (PSEX), cell wall (PSCW), and intracellular (PSIN) 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, PSEX, PSCW, and PSIN 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.

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Keywords

Aureobasidium pullulans

β-Glucan

Polysaccharide

Antimicrobial activity

Antioxidant activity

Oxidative stress

• Introduction

Microbial polysaccharides, a class of natural macromolecular compounds, are extensively utilized across the food, medical, and cosmetics industries, owing to their unique physical, chemical, and biological activities (Barcelos et al., 2020; Prasad & Purohit, 2023; Wei et al., 2024). Based on their composition, microbial polysaccharides can be categorized into hetero- and homo-polysaccharides, while based on their physiological activities, they can be classified as active and inactive polysaccharides (Wang et al., 2023b). Notably, polysaccharides featuring β-D-glucosidic linkages, known as β-glucan, are abundant in various types of active polysaccharides (Torres et al., 2024). β-Glucans are ubiquitous in algae, cereals, and mushrooms, as well as microorganisms such as brewer’s yeast, Candida albicans, Klebsiella spp., and Aureobasidium pullulans (Murphy et al., 2023; Shui et al., 20