Isolation, Characterization, and Pharmaceutical Applications of an Exopolysaccharide from Aerococcus Uriaeequi.

Chunlei Wang,Lujiang Hao,Jie Zhang,Wen Hao,Yanrui Xu,Qiuping Fan,Xiaofei Zhang,Xiaoping Lu,Wenxing Zhu

doi:10.3390/md16090337

Abstract

Many marine bacteria secrete exopolysaccharides (EPSs), which are made up of a substantial component of the macro-molecules surrounding cells. Recently, the wide demand for EPSs for food, cosmetics, pharmaceutical and other applications has led to great interest in them. In this study, an EPS produced by marine bacteria Aerococcus uriaeequi HZ strains (EPS-A) was isolated and purified to examine its structure and biological function. The molecular weight of EPS-A analyzed by high-performance liquid gel filtration chromatography (HPGFC) is found to have a number average of 2.22 × 105 and weight average of 2.84 × 105, respectively. High-performance liquid chromatography (HPLC) and Fourier-transform–infrared (FT–IR) analysis indicate that EPS-A was a polysaccharide composed of glucose and a little mannose. In addition, the flocculating rate of sewage of EPS-A was 79.90%. The hygroscopicity studies showed that hygroscopicity of EPS-A was higher than chitosan but lower than that of sodium hyaluronate. The moisture retention of EPS-A showed similar retention activity to both chitosan and sodium hyaluronate. EPS-A also can scavenge free radicals including both OH• free radical and O2•− free radical and the activity to O2•− free radical is similar to vitamin C. Safety assessment on mice indicated that the EPS-A is safe for external use and oral administration. EPS-A has great potential for applications in medicine due to its characteristics mentioned above.

Highlights

Microbial exopolysaccharides are critical for the biofilm formation, which is involved in the protection of bacteria against a harmful environment and in the adherence
To analyze if the bacteria can produce EPSs, A. uriaeequi was fermented and the EPS-A was isolated by Diethylaminoethano (DEAE) ion exchange chromatography and gel filtration chromatography
high-performance liquid gel filtration chromatography (HPGFC) results showed that the purified product forms a single and symmetric peak, which indicated that EPS-A was purified with high quality

Summary

Introduction

Microbial exopolysaccharides are critical for the biofilm formation, which is involved in the protection of bacteria against a harmful environment and in the adherence. The EPS layers with high viscosity are formed by accumulating various types of polymeric substances. They tend to be hygroscopic and aerophytic bacteria, and often contain more water than the surrounding environment [1]. It is known that certain marine bacterial polysaccharides have features such as hygroscopicity and moisture resistance, ability to scavenge free radicals, oxidation resistance, and the adsorption of heavy metal ions. The EPS from Pseudoalteromonas SM20310 enables the strain to adapt to the environments such as low temperature, high salt concentration, and freeze–thaw cycles. In addition to its functions in the strain, the EPS obviously increased the tolerance of Escherichia coli to repeated freeze–thaw cycles [2].

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Discussion

Conclusion