title: Partial characterization and flocculating behavior of an exopolysaccharide produced in nutrient-poor medium by a facultative oligotroph Klebsiella sp. PB12.
abstract: A facultative oligotrophic strain from the water sample of River Mahananda, Siliguri India was selected for its property to produce exopolysaccharide (EPS) in nutrient-poor (oligotrophic) medium. Viability assay of the strain was performed in sterile liquid LB, R2A, river water and diluted (10(-3)) LB at 30°C and pH 7 to understand oligotrophy. The selected strain was identified by 16S rRNA gene sequencing and designated as Klebsiella sp. PB12. Phylogenetic analysis showed its closest relationship with Klebsiella variicola ATCC BAA-830(T). Purification of EPS was performed by ethanol precipitation, dialysis and freeze-drying. Chemical analysis revealed that purified EPS was mainly composed of 72.32% (w/w) neutral sugar and 14.12% (w/w) uronic acids. Fourier transform infrared (FT-IR) spectroscopy indicated the presence of hydroxyl, carboxylic and methoxyl functional groups. The optimal dosages for flocculation of activated carbon suspension were 17 mg/l EPS and 4 mM CaCl(2). EPS showed flocculating rate of above 80% over a wide range of pH (pH 3-10) whereas, more than 90% rate was noted in the temperature range (10-50°C) tested in presence of CaCl(2). Moreover, EPS showed characteristic emulsifying activity with toluene (66.6%), n-hexadecane (65%), olive oil (63.3%) and kerosene (50%). The apparent molecular weight of the EPS was ~2 × 10(5) Da.
authors.affiliation: Department of Biotechnology, Omics Laboratory, University of North Bengal, Siliguri 734013, West Bengal, India.
authors.forename: Amit Kumar
authors.initials: AK
authors.lastname: Mandal
authors.forename: Krishna Kant
authors.initials: KK
authors.lastname: Yadav
authors.forename: Ipsita Kumar
authors.initials: IK
authors.lastname: Sen
authors.forename: Arvind
authors.initials: A
authors.lastname: Kumar
authors.forename: Soumyananda
authors.initials: S
authors.lastname: Chakraborti
authors.forename: Syed Sirajul
authors.initials: SS
authors.lastname: Islam
authors.forename: Ranadhir
authors.initials: R
authors.lastname: Chakraborty
mesh_terms: D003470:Culture Media / Q000378:metabolism*; D004655:Emulsions; D005427:Flocculation; D006863:Hydrogen-Ion Concentration; D007194:India; D007709:Klebsiella / Q000145:classification / Q000235:genetics / Q000378:metabolism*; D008970:Molecular Weight; D010802:Phylogeny; D011134:Polysaccharides / Q000096:biosynthesis* / Q000737:chemistry* / Q000302:isolation & purification; D045483:Rivers / Q000737:chemistry; D017550:Spectroscopy, Fourier Transform Infrared; D014574:Uronic Acids / Q000032:analysis
chemical_list: D003470:Culture Media; D004655:Emulsions; D011134:Polysaccharides; D014574:Uronic Acids