Structural and Functional Characterization of Exopolysaccharide Produced by a Novel Isolate Bacillus sp. EPS003

An exopolysaccharide (EPS)-producing soil bacterium was isolated and characterized using 16S rRNA as Bacillus sp. EPS003. EPS was precipitated using ethanol and % composition of total carbohydrate, and protein was determined. Monosaccharide composition was identified using thin layer chromatography (TLC), and it was found to be a levan. Fourier transform infrared (FTIR) spectrum revealed the peaks for carboxyl, hydroxyl, and amide functional groups. ¹H nuclear magnetic resonance (NMR) spectrum further confirmed the presence of fructose monomer. Field emission scanning electron microscopic images (FE-SEM) revealed porous and amorphous characteristics of EPS which was further confirmed with broad peaks in X-ray diffraction (XRD) spectrum. Elemental composition was determined using energy-dispersive X-ray analysis (EDAX). Thermogravimetric analysis (TGA) of EPS resulted in a residual mass of 33.81% at 548 °C indicating high thermal stability. In addition, solubility index and water-holding capacity of EPS were found to be 56% and 264%, respectively, making EPS suitable for various applications. Further, antioxidant potential of EPS was studied using hydroxyl and DPPH radical scavenging assays. In vitro cytotoxicity assessment using L929 cells and SK-MEL-3 cell lines clearly indicated that the EPS produced by the novel isolate Bacillus sp. EPS003 could serve as a potential anticancer agent.