Isolation And Identification Of Extracellular Polysaccharides Producing Bacteria

Microbial extracellular polysaccharides, such as Xanthan, Gellan and Curdlan, which have been confirmed with many important biological activities and physiological functions, are increasingly and widely used in food, textile, petroleum and chemical industry. Indeed, microbial EPSs are much cheaper than those from plants for their convenient large-scale fermentation.In order to enlarge their industrial applications, fundamental studies on microbial EPSs including isolating new EPS-producing strains and discovering novel EPSs are necessarily emphasized.In this study, samples from some different environment were used to isolating and screening 349 EPS-producing bacterial strains via a selective medium containing aniline blue stain.89 of 349 strains, which gave extracellular polysaccharides sediments after fermented in liquid medium, were carried on Gram stain and performed physiological and biochemical analysis. Considering their sample source, characters and EPS yields,,8 strains were selected to carry on 16SrDNA sequencing and comparison, phylogenetic tree construction. Finally these 8 strains were identified preliminarily,1CH117,QS51 and SS22 were categorized as Bacillus megateriμm；6CH13 might be a strain of Bacillus thuringiensis；while SJH21,TY33,CDG45 and 6CH15 showed 76%的similarity with strains of Pseudomonas sp.. The results also showed that:there are divergent abundance of EPS-producing bacteria in different environments, active sludge is better sample for EPS-producing bacteria screening; Bacillus is the more common genus for EPS-producing bacteria; aniline blue selective medium is suitable medium for EPS-producing bacteria but accurate reexamination is needed; composite analysis and more complete control strains are necessary to construct phylogenetic tree and confirm the candidate's genus.