High Acyl Gellan Networks Probed by Rheology and Atomic Force Microscopy

The network structure of high acyl gellan polysaccharide was investigated using dynamic viscoelasticity and steady flow viscosity measurements, as well as atomic force microscopy (AFM). Time-temperature superposition (TTS) of mechanical spectra of aqueous dispersions having a gellan concentration of 0.1% w/w revealed a gel-like response at the lower end of the frequency range. The TTS master curve of the steady flow data exhibited a power-law relationship between shear viscosity and shear rate at the lower end of the shear rate range, instead of a Newtonian plateau. These rheological characteristics suggest the existence of an effective yield stress arising from the presence of a percolated network. AFM images of high acyl gellan revealed micrometer-sized networks composed of double-stranded helices laterally associated to varying degrees. These associated helices did not dissociate fully on heating at 90°C, suggesting that they are partially preserved native networks secreted by gellan-producing bacteria.

[1]  S. Kasapis.  Relation between the structure of matrices and their mechanical relaxation mechanisms during the glass transition of biomaterials: A review , 2012 .

[2]  L. Benyahia,et al.  Rheology of xanthan solutions as a function of temperature, concentration and ionic strength , 2010 .

[3]  S. Mallapragada,et al.  Rheological properties of methylcellulose aqueous gels under dynamic compression: Frequency sweep and validity of scaling law , 2010 .

[4]  K. Nishinari,et al.  Molecular structures of gellan gum imaged with atomic force microscopy (AFM) in relation to the rheological behavior in aqueous systems in the presence of sodium chloride , 2009 .

[5]  K. Nishinari,et al.  Molecular structures of gellan gum imaged with atomic force microscopy in relation to the rheological behavior in aqueous systems. 1. Gellan gum with various acyl contents in the presence and absence of potassium , 2008 .

[6]  Alexander B. Morgan,et al.  Rheological characterization of polystyrene–clay nanocomposites to compare the degree of exfoliation and dispersion , 2005 .

[7]  K. Nishinari,et al.  Atomic force microscopy studies on cation-induced network formation of gellan , 2004 .

[8]  M. Nickerson,et al.  Time–temperature studies of gellan polysaccharide gelation in the presence of low, intermediate and high levels of co-solutes , 2004 .

[9]  S. Turgeon,et al.  Associative phase separation of beta-lactoglobulin/pectin solutions: a kinetic study by small angle static light scattering. , 2004, Colloids and surfaces. B, Biointerfaces.

[10]  M. Rinaudo,et al.  Role of substituents on the properties of some polysaccharides. , 2004, Biomacromolecules.

[11]  T. Camesano,et al.  Polysaccharide properties probed with atomic force microscopy , 2003, Journal of microscopy.

[12]  K. Nishinari,et al.  Microstructure of aggregated and nonaggregated kappa-carrageenan helices visualized by atomic force microscopy. , 2001, Biomacromolecules.

[13]  T. Camesano,et al.  Single molecule study of xanthan conformation using atomic force microscopy. , 2001, Biomacromolecules.

[14]  K. Nishinari,et al.  "Weak gel"-type rheological properties of aqueous dispersions of nonaggregated kappa-carrageenan helices. , 2001, Journal of agricultural and food chemistry.

[15]  L M Harvey,et al.  Gellan Gum , 2000, Critical reviews in biotechnology.

[16]  H. Seki,et al.  Multinuclear NMR study on the sol-gel transition of gellan gum , 1999 .

[17]  M. Rinaudo,et al.  Conformational transition of native and modified gellan. , 1999, International journal of biological macromolecules.

[18]  Y. Yuguchi,et al.  The sol-gel transition of gellan gum aqueous solutions in the presence of various metal salts , 1999 .

[19]  K. Nishinari,et al.  Rheological and thermal properties near the sol-gel transition of gellan gum aqueous solutions , 1999 .

[20]  S. Matsukawa,et al.  Structural change of polymer chains of gellan monitored by circular dichroism , 1999 .

[21]  R. Clark,et al.  Gelatin alternatives for the food industry , 1999 .

[22]  A. P. Gunning,et al.  Atomic force microscopy of plant cell walls, plant cell wall polysaccharides and gels. , 1997, International journal of biological macromolecules.

[23]  A. P. Gunning,et al.  Investigation of gellan networks and gels by atomic force microscopy , 1996 .

[24]  E. Morris,et al.  Conformational and rheological transitions of welan, rhamsan and acylated gellan , 1996 .

[25]  M. Mikolajczak,et al.  Linkage of genes essential for synthesis of a polysaccharide capsule in Sphingomonas strain S88 , 1996, Journal of bacteriology.

[26]  E. Morris,et al.  Native ordered structure of welan polysaccharide: conformational transitions and gel formation in aqueous dimethyl sulphoxide. , 1994, Carbohydrate research.

[27]  T. J. Pollock.  Gellan-related polysaccharides and the genus Sphingomonas , 1993 .

[28]  R. Chandrasekaran,et al.  Roles of potassium ions, acetyl and L-glyceryl groups in native gellan double helix: an X-ray study. , 1992, Carbohydrate research.

[29]  A. Dell,et al.  Identification and location of l-glycerate, an unusual acyl substituent in gellan gum , 1986 .

[30]  V. Morris.  Gelation of Polysaccharides , 1986 .

[31]  Per-Erik Jansson,et al.  Structural studies of gellan gum, an extracellular polysaccharide elaborated by Pseudomonas elodea , 1983 .

[32]  M. O’Neill,et al.  Structure of the acidic extracellular gelling polysaccharide produced by Pseudomonas elodea , 1983 .