Screening of Exopolysaccharide-producing Strains and Structural Analysis of the Exopolysaccharides

doi:10.13560/j.cnki.biotech.bull.1985.2016.05.022

Abstract

Abstract: This study aims to screen and identify strains producing exopolysaccharides（EPSs），to study the rheological properties of EPSs，and to analyze the structure of EPSs. The strains producing EPSs were screened from soil，and were identified based on their morphology and 16S rDNA gene sequencing. The viscosity changes of EPSs in different conditions were determined by viscometer to study its rheological properties. Then，GC，IR and NMR were used to analyze the structure of EPSs isolated and purified by ethanol precipitation，Sevag method and dialysis. As a result，a strain producing EPSs was identified as Enterobacter sp. WL113. The viscosity of the EPSs exponentially increased with the concentration of EPSs，i.e.，viscosity increased about 33 times when concentration of EPSs from 1 g/L to 10 g/L. The EPSs were sensitive to temperature，and viscosity decreased 89.8% when temperature from 25 ℃ to 100 ℃. The viscosity of EPSs remained relatively stable under the condition of acid，neutral and weak alkaline. The EPSs also well tolerated with metal ions such as Na+、K+、Mg2+ and Ca2+. The analysis of EPSs by GC，IR，and NMR indicated that the EPSs consisted of arabinose，mannose and glucose in a molar ratio of 1.63：3.16：2.38，also containing α-pyranose，β-pyranose and uronic acid.

Key words: exopolysaccharide, rheological properties, Enterobacter, structural analysis

LI Bin,CHEN Xiang-nan,ZHANG Jian-fa,WANG Shi-ming. Screening of Exopolysaccharide-producing Strains and Structural Analysis of the Exopolysaccharides[J]. Biotechnology Bulletin, 2016, 32(5): 165-171.

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