A mannose-rich exopolysaccharide from Weissella cibaria SK01: Purification, characterization, antibiofilm, anticancer, and physicochemical properties.
TL;DR
Findings identify EPS-SK01 as a microbial exopolysaccharide with a distinct structure and biological activity, underscoring its potential for use in the fermented food processing industry.
Abstract
Among lactic acid bacteria (LAB) strains isolated from minced beef, an effective exopolysaccharide (EPS)-producing bacterium was identified using 16S rRNA gene sequencing as Weissella cibaria SK01. A distinctive EPS, designated EPS-SK01, was produced in relatively high yield (2.79 g/L) and purified to apparent homogeneity by consecutive chromatographic procedures. Structural characterization using monosaccharide composition analysis, FTIR, GPC, and one-dimensional NMR revealed that EPS-SK01 is mainly composed of α-linked mannose residues, necessitating further validation through advanced structural analyses. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) analyses revealed a hierarchical, porous-like architecture characterized by multiscale surface features ranging from nanoscale to microscale. Thermal investigations (DSC, DTG, and TGA) revealed well-defined thermal transitions and significant thermal stability, with a principal decomposition event occurring at around 273 °C. EPS-SK01 exhibited favorable physicochemical characteristics, such as high solubility, shear-thinning rheological properties, and efficient emulsifying and foaming abilities. EPS-SK01 showed concentration-dependent antioxidant activity (DPPH IC50 = 22.95 mg/mL) and antibacterial activity against methicillin-resistant Staphylococcus aureus (MRSA) (MIC of 5 mg/mL). Moreover, it could restrain MRSA biofilm formation by 55.3 ± 1.7%, which was associated with a significant reduction in the expression of biofilm-related genes (icaA, icaD, and srtA) and quorum-sensing regulatory genes. In MCF-7 breast cancer cells, EPS-SK01 exhibited dose-dependent antiproliferative activity with an IC50 value of 1313 μg/mL, while maintaining negligible cytotoxicity toward normal L929 fibroblasts. Taken together, these findings identify EPS-SK01 as a microbial exopolysaccharide with a distinct structure and biological activity, underscoring its potential for use in the fermented food processing industry.