Characterization of exopolysaccharide derived from Enterobacter ludwigii and its possible role as an emulsifier.

Enterobacter ludwigii is an oral growing bacteria responsible for teeth blackening. It can form biofilm. The exopolysaccharide (EPS) cluster associated with biofilm formation was isolated using ethanol precipitation and the formaldehyde-sodium hydroxide method. The chemical characterization of EPS was done using UV spectroscopy, Fourier transforms infrared spectroscopy, and gas chromatography-mass spectrometry. Energy-dispersive X-ray spectroscopy (EDS) analysis of  EPS has revealed the presence of carbon > boron > nitrogen > phosphorous > calcium > sulfur > iron > potassium > magnesium. The carbon content was quite high (72.72-77.63%) in the EPS due to polysaccharide composition. The study showed the presence of different monosaccharides glucose (16.91%), galactose (4.25%), mannose (4.04%), and xylose (8.06%) as the major components of EPS. It appears such as thin filaments with three-dimensional structure, compact, irregular lumps and stacked flakes of polysaccharides. The EPS was also examined using different 1D, 2D Nuclear Magnetic Resonance (NMR) spectroscopy techniques (1H NMR, 13C NMR, 1H-1H COSY, 1H-13C HSQC, 1H-13C HMBC) with different deuterated solvents (Protic and aprotic solvents for exchangeable protons), which showed eight distinguished monomers (seven confirmed by HSQC spectrum and one from 1H spectrum). Semi-crystalline nature and thermal stability were confirmed by X-ray diffractogram and differential scanning calorimetry analysis, respectively. The EPS further shows antioxidant potential in a concentration-dependent manner. It can form a stable emulsion against different edible oil that makes it promising alternative for use in food, and pharmaceutical industries. Supplementary Information: The online version contains supplementary material available at 10.1007/s13205-022-03279-z. © King Abdulaziz City for Science and Technology 2022, Springer Nature or its licensor holds exclusive rights to this article under a publishing agreement with the author(s) or other rightsholder(s); author self-archiving of the accepted manuscript version of this article is solely governed by the terms of such publishing agreement and applicable law.