Characterization of an extracellular biopolymer flocculant from a haloalkalophilic Bacillus isolate

SummaryA biopolymer flocculant, produced by a haloalkalophilic Bacillus sp. I-471 was isolated from a sea water sample from the tidal mud flats surrounding the city of Inchon, Korea. The bioflocculant (EPS471) was produced in late logarithmic growth phase, recovered by cold ethanol precipitation of the cell-free supernatant and purified by cetylpyridinium chloride treatment. Chemical analyses of EPS471 indicated that it was an acidic polysaccharide containing neutral sugars, namely, galactose, fructose, glucose (approximate ratio of 5:2:1) and uronic acids as major and minor components, respectively. SEM studies revealed that the polymer had a porous structure with small pore size distribution indicating the compactness of the polymer. Spectroscopic analyses of the polymer by nuclear magnetic resonance (NMR) and Fourier-transform infrared (FT-IR) spectroscopy revealed the presence of carboxyl and hydroxyl groups typical for a polysaccharide and that the polymer was a heteroglycan. The degradation temperature (Td) analyzed by thermogravimetry was 307 °C. The rheological analysis showed the pseudoplastic nature of the polymer with shear-thinning behaviour. The polymer EPS471 may find possible application as an polymer for environmental bioremediation and other biotechnological processes.

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