The Structural Characterization of Extracellular Polysaccharide from Enterococcus faecium M20

HIGHLIGHTS

• The extracellular polysaccharide (EPS) from Enterococcus faecium M20 was characterized.

• The degradation of polysaccharide was in three steps and it was thermally stable.

• SAXS data showed that the bacterial EPS possessed the lamellar structure.

• The investigation of structure of its EPS may be extremely important to find a specific way for treatment of its infection.

Abstract

Enterococcus faecium is one of the well-known human pathogens producing biofilm. Todays, it is an important nosocomial infection agent and is spreading rapidly worldwide. As the first step of the infection, this bacterium adheres to tissue or devices with EPS fibrils, and then the biofilm grows. Therefore, investigation of structure of its EPS is extremely important to find a specific way for treatment of its infection. In this study, we isolated and investigated the physicochemical properties extracellular polysaccharide (EPS) from E. faecium M20 obtained from Denizli Public Hospital. The exopolysaccharide of M20 strain was purified by methanol/ethanol extraction method and then analyzed by SAXS, TGA, HPLC and SEM. Carbohydrate and protein were main compounds in the isolated EPS. Moreover, the uronic acid content was found to be high. The HPLC analysis indicated that the EPS consisted of glucose+maltitol, fructose and sorbitol+ksilitol. According to SAXS data, the EPS of M20 possessed a lamellar structure and prolate core shell with a major core radius of 1644.1 Å, a major shell thickness of 121.9 Å, and a bilayer thickness of 12.6 Å. The natural polysaccharide structure was more stable within aqueous (0.5%, w/v) and serum albumin solutions at room temperature. These results may be used to develop new strategies in future for eradicating biofilms of this pathogen bacterium.

Keywords:
enterococcus faecium; exopolysaccharide; SAXS; HPLC; SEM.