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Characterization of an extracellular polysaccharide produced by a Saharan bacterium Paenibacillus tarimensis REG 0201M

Boukhelata, Nadia, Taguett, Farida, Kaci, Yahia
Annals of microbiology 2019 v.69 no.2 pp. 93-106
Fourier transform infrared spectroscopy, Paenibacillus, agar, anion exchange chromatography, arabinose, bacteria, fructose, galactose, gel chromatography, industry, light scattering, moieties, molecular weight, nucleotide sequences, phenotype, polymers, rhamnose, rheological properties, ribosomal DNA, scanning electron microscopy, sucrose, water binding capacity, xanthan gum, zeta potential
The purpose of this paper is to highlight the novel molecular characteristics and rheological properties of the polysaccharide produced by a bacterium isolated from extremophilic environment (Algerian Sahara). Phenotypic and molecular characteristics of the REG 0201M bacterial strain retained for this research were studied. Extracellular polysaccharide produced by REG 0201M was purified, characterized and its production was investigated. Analysis of 16S rDNA gene sequence showed that strain REG 0201M belonged to the species Paenibacillus tarimensis. In sucrose agar medium, 1.31 g dry weight of the polysaccharide per liter was produced. Evaluation of water absorption capacity showed that this polysaccharide was able to absorb 1000 times more water than its own weight. The average molecular weight determined by high-performance size exclusion chromatography multiangle laser light scattering was 1.718 × 10⁶ g mol⁻¹. Analysis of the monosaccharide composition by high-performance anion exchange chromatography showed the presence of fructose (77.67%) as the main neutral sugar, followed by galactose (20.37%), arabinose (1.79%), and rhamnose (0.16%). Its global charge determined by the Zeta potential measurement was about −35.27 ± 0.66 mV. The main functional groups were elucidated by Fourier-Transform Infrared Spectroscopy while the surface morphology was resolved by scanning electron microscopy analysis. Moreover, the rheological data revealed shear thinning properties with the same general behavior of the studied polysaccharide compared to xanthan. These results show the great potential of this polysaccharide, which could help to promote its use in various industries by replacing synthetic polymers.