Potential Applications of an Exopolysaccharide Produced by Bacillus xiamenensis RT6 Isolated from an Acidic Environment

Abstract

The Bacillus xiamenensis RT6 strain was isolated and identified by morphological, biochemical and molecular tests from an extreme acidic environment, Rio Tinto (Huelva). Optimisation tests for exopolysaccharide (EPS) production in different culture media determined that the best medium was a minimal medium with glucose as the only carbon source. The exopolymer (EPSt) produced by the strain was isolated and characterised using different techniques (GC-MS, HPLC/MSMS, ATR-FTIR, TGA, DSC). The molecular weight of EPSt was estimated. The results showed that the average molecular weight of EPSt was approximately 2.71 × 104 Da and was made up of a heteropolysaccharide composed of glucose (60%), mannose (20%) and galactose (20%). The EPSt showed antioxidant capabilities that significantly improved cell viability. Metal chelation determined that EPSt could reduce the concentration of transition metals such as iron at the highest concentrations tested. Finally, the emulsification study showed that EPSt was able to emulsify different natural polysaccharide oils, reaching up to an 80% efficiency (olive and sesame oil), and was a good candidate for the substitution of the most polluting emulsifiers. The EPSt was found to be suitable for pharmaceutical and industrial applications.