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.

Production and Characterisation of an Exopolysaccharide by Bacillus amyloliquefaciens: Biotechnological Applications

“…The maximal production of the exopolysaccharide, namely, 490 mg/L, occurred at 24 h, during the exponential growth phase. However, this was previously observed as usually taking place at the beginning of the stationary phase [ 27 , 39 ].…”

“…The monosaccharide composition was determined with Bruker gas chromatography (EVOC GC–TQ) combined with mass spectrometry using the procedure described by Huang-Lin et al [ 39 ]. For this, EPS RT7 hydrolysis was conducted with 0.5 M trifluoroacetic acid (TFA) at 120 °C for 2 h. Subsequently, the samples were treated with N 2 .…”

“…The methodology used to create an injury model for HeLa cells was based on the procedure outlined by Huang-Lin et al [ 39 ]. HeLa cells were seeded at a density of 5 × 10 4 cells per well for 24 h. The medum was then removed and replaced with 100 µL of various concentrations of H 2 O 2 (0.25–2 mM) for 1 h at 37 °C under a 5% CO 2 atmosphere.…”

“…EPS RT7′ s ability to protect HeLa cells against oxidative stress was evaluated following the methods described by Huang-Lin et al [ 39 ]. HeLa cells were seeded at a concentration of 5 × 10 4 cell/well and incubated for 24 h. After that, the DMEM solutions were withdrawn and substituted with EPS RT7 diluted in DMEM at different concentrations (25–400 µg/mL).…”

The Immunostimulatory Effect of Probiotic Conditioned Medium on RAW264.7 Murine Macrophages

“…Moreover, lactic acid producing bacteria are known to secrete exopolysaccharides that have been found to obtain immunomodulatory potential 53 . Using J774A.1 macrophage cells, exopolysaccharides (from Bi dobacterium) was found to induce the secretion of TNF-α at a concentration of 5 µg/mL 54 .…”