Fermentation of Lactic Acid Bacteria (LAB) is considered to be a sustainable approach for polysaccharide production. Herein, exopolysaccharide (EPS)-producing LAB strain KM01 was isolated from Thai fermented dessert, Khao Mak, which was then identified as Leuconostoc holzapfelii. High-performance anion-exchange chromatography, nuclear magnetic resonance spectroscopy and Fourier-transform infrared spectroscopy suggested that the KM01 EPS comprises a-1,6-linked glucosides. The molecular weight of KM01 EPS was around 500?kDa, but it can form large aggregates formation (MW?>?2000?kDa) in an aqueous solution, judged by transmission electron microscopy and dynamic light scattering to be around 150?nm in size. Furthermore, this KM01 EPS form highly viscous hydrogels at concentrations above 5% (w/v). The formation of hydrogels and nanoparticle of KM01 EPS was found to be reversible. Finally, the suitability of KM01 EPS for biomedical applications was demonstrated by its’ lack of cytotoxicity and its’ ability to form complexes with quercetin. Unlike the common a-1,6-linked dextran, KM01 EPS can enhance the solubility of quercetin significantly.