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

**Enrique Sánchez-León <sup>1</sup> , Elisa Huang-Lin 1, Ricardo Amils 1,2 and Concepción Abrusci 1,2,\***


**\*** Correspondence: concepcion.abrusci@uam.es; Tel.: +34-91-497-82-57

**Abstract:** The *Bacillus amyloliquefaciens* RT7 strain was isolated from an extreme acidic environment and identified. The biodegradation capabilities of the strain using different carbon sources (glucose, oleic acid, Tween 80, PEG 200, and the combination of glucose–Tween 80) were evaluated via an indirect impedance technique. The glucose–Tween 80 combination was further studied using nuclear magnetic resonance (NMR). The exopolysaccharide (EPSRT7) that had been produced with the strain when biodegrading glucose–Tween 80 was isolated and characterised using different techniques (GC–MS, HPLC/MSMS, ATR–FTIR, TGA, and DSC), and its molecular weight was estimated. The results show that the average molecular weight of EPSRT7 was approximately 7.0794 <sup>×</sup> 104 Da and a heteropolysaccharide composed of mannose, glucose, galactose, and xylose (molar ratio, 1:0.5:0.1:0.1) with good thermostability. EPSRT7 showed good emulsifying activity against different natural oils and hydrocarbons at high concentrations (2 mg/mL) and at the studied pH range (3.1–7.2). It also presented good emulsifying activity compared to that of commercial emulsifiers. Lastly, EPSRT7 showed antioxidant capacity for different free radicals, a lack of cytotoxicity, and antioxidant activity at the cellular level. EPSRT7 has promising applications in bioremediation processes and other industrial applications.

**Keywords:** exopolysaccharide; biodegradation; *Bacillus*; emulsifying; antioxidant
