Production and Characterisation of an Exopolysaccharide by Zn11_249 Isolated from Salar de Uyuni (Bolivia).

The extremophilic strain Zn11_249 was isolated from Salar de Uyuni, an environment with high salinity, among other extreme factors. This study researched the optimised production, characterisation, antioxidant activity, and cytotoxicity of exopolysaccharides (EPS) produced by this strain under different ionic stresses. Zn11_249 was cultured in a minimal medium with glucose as the sole carbon source as a control, and under kosmotropic (NaCl, 1 M) and chaotropic (LiCl, 0.3 M) conditions, yielding EPS, EPS, and EPS, respectively. Maximum EPS production (336 mg/L) occurred under chaotropic conditions after 96 h. EPSs were characterised using the following techniques: Gas chromatography (GC-MS); Attenuated Total Reflectance Fourier Transform Infrared Spectroscopy (ATR-FTIR); Thermogravimetric Analysis (TGA); and Differential Scanning Calorimetry, (DSC). The results showed differences between the molecular weights for EPS (3.9 × 10 Da), EPS (3.9 × 10 Da), and EPS (5.85 × 10 Da). Their monosaccharide molar ratios (%) were 40/25/25/10 in EPS, 10/30/30/30 in EPS, and 25/25/25/25 in EPS, composed of mannose, galactose, rhamnose, and glucose, respectively. Functional group analysis confirmed their heteropolysaccharide nature. Thermal profiles suggest the potential of these exopolysaccharides as biomaterials. Antioxidant tests demonstrated significant activity against DPPH, OH, and O radicals, while cytotoxicity assays showed no toxicity. These results highlight the biotechnological potential of EPSs from Zn11_249 for biomedical and cosmetic uses.