A novel exopolysaccharide from cold-adapted yeast Rhodotorula glutinis, along with structural, rheological, antioxidant, and antibiofilm properties

In the present study, a novel exopolysaccharide EPS-BMD26 produced by cold-adapted yeast Rhodotorula glutinis was structurally examined, along with its rheological, antioxidant, and antibiofilm properties. High-performance liquid chromatography (HPLC) analysis revealed glucose and galactose as two monosaccharide constituents. The functional groups within the EPS-BMD26 structure were detected by Fourier transform infrared (FT-IR) spectroscopy. The ¹H and ¹³C nuclear magnetic resonance (NMR) spectra of EPS-BMD26 also confirmed its β-D-glucan type with galactose residues with an average molecular weight of 118 kDa. Differential scanning calorimetry (DSC) analysis revealed that EPS-BMD26 had a high level of thermal stability, up to 326.16 °C. Scanning electron microscopy (SEM) analysis demonstrated that EPS-BMD26 had a porous microstructure with fissures. X-ray diffraction (XRD) analysis revealed its semi-crystalline nature. EPS-BMD26 showed moderate and concentration-dependent antioxidant potential recruiting different methods, including •OH, DPPH•, CUPRAC, and ABTS radical scavenging activities. Water-soluble EPS-BMD26 exhibited high water holding capacity of 190 ± 0.22% with a water solubility index of 60.6 ± 8.3%. At 1.25 mg mL^-1, EPS-BMD26 inhibited biofilm formation of Staphylococcus aureus ATCC 25923 by 79.5%. Rheological characterization revealed that the aqueous solution of EPS-BMD26 had shear thinning and pseudoplastic behavior. Given these properties, EPS-BMD26 may be a promising bio-hydrocolloid, antibiofilm agent, and food additive for industrial applications.