title: Structural investigation and response surface optimisation for improvement of kefiran production yield from a low-cost culture medium.
abstract: Kefiran, a water-soluble heteropolysaccharide with molecular weight of 1.35×10(6)Da and a specific optical rotation of +64° (c 1.0, H2O), was isolated from kefir grains grown in cheese whey and further purified through DEAE-Sepharose XK26. Response surface methodology was employed to optimise the culture conditions for kefiran production from kefir grains to be lactose concentration 67 g/l, yeast extract 13g/l, pH 5.7 and temperature 24°C. Intrinsic viscosity was 5.84 dl/g using the Huggins extrapolation and 5.53 dl/g using the Kramer extrapolation. Monosaccharide analysis revealed that kefiran is composed of glucose (Glc) and galactose (Gal) in a relative molar ratio of 1.0:1.1. Its structural features were elucidated by a combination of FT-IR, methylation and GC-MS analysis, periodate oxidation-Smith degradation, partial acid hydrolysis and NMR spectroscopy ((1)H, (13)C and HMBC). The data obtained indicated that kefiran possessed a backbone of (1→6)-linked Glc, (1→3)-linked Gal, (1→4)-linked Gal, (1→4)-linked Glc and (1→2,6)-linked Gal, with a branch attached to O-2 of Gal residues and terminated with Glc residues.
authors: Department of Food Science, Engineering and Technology, Faculty of Agricultural Engineering and Technology, University of Tehran, Iran. Electronic address: mghasemlou@ut.ac.ir.
authors: Mehran
authors: M
authors: Ghasemlou
authors: Department of Food Science, Engineering and Technology, Faculty of Agricultural Engineering and Technology, University of Tehran, Iran.
authors: Faramarz
authors: F
authors: Khodaiyan
authors: Shahrood University of Technology, Faculty of Agriculture, School of Agricultural Engineering, Shahrood, Iran.
authors: Kambiz
authors: K
authors: Jahanbin
authors: Department of Food Science, Engineering and Technology, Faculty of Agricultural Engineering and Technology, University of Tehran, Iran.
authors: Seyed Mohammad Taghi
authors: SM
authors: Gharibzahedi
authors: Chemistry and Chemical Engineering Research Center of Iran, P.O. Box 14335-186, Tehran, Iran.
authors: Salman
authors: S
authors: Taheri
mesh_terms: D003470:Culture Media; D043302:Cultured Milk Products / Q000737:chemistry*; D008401:Gas Chromatography-Mass Spectrometry / Q000379:methods*; D006868:Hydrolysis; D009005:Monosaccharides; D010084:Oxidation-Reduction; D011134:Polysaccharides / Q000737:chemistry*; D014867:Water / Q000737:chemistry*
chemical_list: D003470:Culture Media; D009005:Monosaccharides; D011134:Polysaccharides; D014867:Water; C050180:kefir grain polysaccharide
keywords: Cheese whey; Exopolysaccharide; Kefiran; Response surface methodology; Structural analysis