Structural characterization and physicochemical properties of the exopolysaccharide produced by the moderately halophilic bacterium Chromohalobacter salexigens, strain 3EQS1.
Ibrahim M Ibrahim, Yuliya P Fedonenko, Elena N Sigida, Maxim S Kokoulin, Vyacheslav S Grinev, Ivan G Mokrushin, Gennady L Burygin, Andrey M Zakharevich, Alexander A Shirokov, Svetlana A Konnova
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引用次数: 1
Abstract
A strain, 3EQS1, was isolated from a salt sample taken from Lake Qarun (Fayoum Province, Egypt). On the basis of physiological, biochemical, and phylogenetic analyses, the strain was classified as Chromohalobacter salexigens. By 72 h of growth at 25 °C, strain 3EQS1 produced large amounts (15.1 g L-1) of exopolysaccharide (EPS) in a liquid mineral medium (initial pH 8.0) containing 10% sucrose and 10% NaCl. The EPS was precipitated from the cell-free culture medium with chilled ethanol and was purified by gel-permeation and anion-exchange chromatography. The molecular mass of the EPS was 0.9 × 106 Da. Chemical analyses, Fourier transform infrared spectroscopy, and nuclear magnetic resonance spectroscopy showed that the EPS was a linear β-D-(2 → 6)-linked fructan (levan). In aqueous solution, the EPS tended to form supramolecular aggregates with a critical aggregation concentration of 240 µg mL-1. The EPS had high emulsifying activity (E24, %) against kerosene (31.2 ± 0.4%), sunflower oil (76.9 ± 1.3%), and crude oil (98.9 ± 0.8%), and it also had surfactant properties. A 0.1% (w/v) aqueous EPS solution reduced the surface tension of water by 11.9%. The levan of C. salexigens 3EQS1 may be useful in various biotechnological processes.
期刊介绍:
Extremophiles features original research articles, reviews, and method papers on the biology, molecular biology, structure, function, and applications of microbial life at high or low temperature, pressure, acidity, alkalinity, salinity, or desiccation; or in the presence of organic solvents, heavy metals, normally toxic substances, or radiation.