... Karin Bongaerts and Harry Reynaers. Laboratory of Macromolecular Structural Chemistry, Depart... more ... Karin Bongaerts and Harry Reynaers. Laboratory of Macromolecular Structural Chemistry, Department of Chemistry, KULeuven, Celestijnenlaan 200F, Heverlee, Belgium. Flavio Zanetti. POLY-tech SCrl, AREA Science Park, Padriciano ...
The scope of the present work was to assess and compare different methods to determine molecular ... more The scope of the present work was to assess and compare different methods to determine molecular weight (MW) averages and molecular weight distributions (MWD) of two samples of sodium alginate of different composition. Weight average (~lw) and number average (~In) molecular weights were determined by totally integrated laser light scattering (LLS), both at wide angles' (WA) and at a low angle (LA), and membrane osmometo', respectively. The two alginates were fractionated by preparative and analytical size exclusion chromatography.
ABSTRACT A large number of light-scattering data indicate that the sulfated polysaccharide κ-carr... more ABSTRACT A large number of light-scattering data indicate that the sulfated polysaccharide κ-carrageenan undergoes an intramolecular conformational transition under suitable conditions from a semiflexible, disordered conformation to a rather rigid, helical one. By varying the parameters controlling the conformational phase diagram (i.e., by increasing the concentration of polymer or that of the supporting electrolyte, or both, or by decreasing temperature), a tertiary structure is manifested, through a progressive increase of the weight-average molar mass (M̄w) as determined by light scattering. This can be very well explained in terms of a reversible association of stretches of such intramolecular helical structures and quantitatively described by a model of “open association” of two or more chains. The association of κ-carrageenan was demonstrated to take place at around room temperature also in the presence of iodide ions, as long as their concentration is ≥0.20 M. In this way the apparent inconsistency of a number of published M̄w results can be reconciled. Additional light-scattering results indicated that the demonstrated thermodynamic tendency to reversible interchain association may lead to an irreversible aggregation of polymer chains if an improper solution preparation procedure is used.
The insoluble organic fraction (humin-like material, HLM) from rice hull-dairy cattle compost is ... more The insoluble organic fraction (humin-like material, HLM) from rice hull-dairy cattle compost is well converted into water soluble HLM-sulphonate by reaction in liquid SO3. Microanalytical, potentiometric, molecular weight, and NMR data are consistent with a highly homogeneous polymeric arylsulphonate having 4000 Da MW, 1.3 sulphonic groups per aromatic ring and significant content of carboxylic and phenolic groups. By comparison with structure-property relationships for commercial lignosulphonates derived from the pulp and paper industry, the above arylsulphonate is likely to be a candidate at a variety of applications in the chemical industry and in agriculture. Therefore, sulphonation is a means for upgrading composts HLM to the same uses as for commercial lignosulphonates.
Succinoglycan production by Agrobacterium tumefaciens was increased from 9.5 g/l to 14 g/l when t... more Succinoglycan production by Agrobacterium tumefaciens was increased from 9.5 g/l to 14 g/l when the microorganism was cultivated under fed-batch condition, as compared to batch fermentation. Cells and broth impurities were removed from the fermentation broth with activated charcoal at a temperature of 90 • C, yielding a clear and odorless solution of the polymer. Viscosity mesurement, NMR spectroscopy and Mw determination proved that the polymer retains its main features, practically unaffected by the heat treatment.
... Karin Bongaerts and Harry Reynaers. Laboratory of Macromolecular Structural Chemistry, Depart... more ... Karin Bongaerts and Harry Reynaers. Laboratory of Macromolecular Structural Chemistry, Department of Chemistry, KULeuven, Celestijnenlaan 200F, Heverlee, Belgium. Flavio Zanetti. POLY-tech SCrl, AREA Science Park, Padriciano ...
ABSTRACT A large number of light-scattering data indicate that the sulfated polysaccharide κ-carr... more ABSTRACT A large number of light-scattering data indicate that the sulfated polysaccharide κ-carrageenan undergoes an intramolecular conformational transition under suitable conditions from a semiflexible, disordered conformation to a rather rigid, helical one. By varying the parameters controlling the conformational phase diagram (i.e., by increasing the concentration of polymer or that of the supporting electrolyte, or both, or by decreasing temperature), a tertiary structure is manifested, through a progressive increase of the weight-average molar mass (M̄w) as determined by light scattering. This can be very well explained in terms of a reversible association of stretches of such intramolecular helical structures and quantitatively described by a model of “open association” of two or more chains. The association of κ-carrageenan was demonstrated to take place at around room temperature also in the presence of iodide ions, as long as their concentration is ≥0.20 M. In this way the apparent inconsistency of a number of published M̄w results can be reconciled. Additional light-scattering results indicated that the demonstrated thermodynamic tendency to reversible interchain association may lead to an irreversible aggregation of polymer chains if an improper solution preparation procedure is used.
Clinical and environmental strains of Burkholderia cenocepacia belonging to the recA lineages III... more Clinical and environmental strains of Burkholderia cenocepacia belonging to the recA lineages IIIA and IIIB were examined for exopolysaccharide (EPS) production. The exopolysaccharides structure was determined using mainly gas chromatography coupled to mass spectrometry and NMR spectroscopy. All the strains produced Cepacian, a highly branched polysaccharide constituted of a heptasaccharide repeating unit, composed of one rhamnose, one glucose, one glucuronic acid, one mannose and three galactose residues. This polymer is the most common exopolysaccharide produced by strains of the Burkholderia cepacia (Bcc) complex. One clinical strain produced also another polysaccharide constituted of three galactose units and one 3-deoxy-D-manno-2-octulosonic acid residues, a polymer that was previously isolated from two strains of B. cepacia genomovar I and B. cenocepacia IIIA.
A strain of Agrobacterium tumefaciens isolated from soil was cultivated under various conditions ... more A strain of Agrobacterium tumefaciens isolated from soil was cultivated under various conditions in shake flasks to study exopolysaccharides (EPS) production. NMR analysis revealed that the EPS obtained was a succinoglycan-like polymer. Optimal yields of EPS were obtained using sucrose and lysine as the carbon and nitrogen sources, respectively. Supplementation of the medium with various chemicals resulted in a more or less marked effect on the polymer yield and properties: in particular, high phosphate levels and non-ionic surfactants led to the production of polymers of different molecular sixes in yields up to 13.7 g/l. Oxygen availability also affected the polymer yield and quality. The chemical structure was substantially unaffected by the various fermentation conditions tested. A fermentation carried out in a laboratory-scale fermentor yielded 9.6 g/l succinoglycan from 15 g/Z sucrose in the basic medium without further supplements.
Aqueous extracts of Codium fragile ssp. atlanticum possess marked anticoagulant activity. The com... more Aqueous extracts of Codium fragile ssp. atlanticum possess marked anticoagulant activity. The compounds responsible appear to be proteoglycans with molecular weights, determined by a low angle, laser light-scattering method, of 1.8 x 106 daltons, with a polydispersity value of 1.2.
... Karin Bongaerts and Harry Reynaers. Laboratory of Macromolecular Structural Chemistry, Depart... more ... Karin Bongaerts and Harry Reynaers. Laboratory of Macromolecular Structural Chemistry, Department of Chemistry, KULeuven, Celestijnenlaan 200F, Heverlee, Belgium. Flavio Zanetti. POLY-tech SCrl, AREA Science Park, Padriciano ...
The scope of the present work was to assess and compare different methods to determine molecular ... more The scope of the present work was to assess and compare different methods to determine molecular weight (MW) averages and molecular weight distributions (MWD) of two samples of sodium alginate of different composition. Weight average (~lw) and number average (~In) molecular weights were determined by totally integrated laser light scattering (LLS), both at wide angles' (WA) and at a low angle (LA), and membrane osmometo', respectively. The two alginates were fractionated by preparative and analytical size exclusion chromatography.
ABSTRACT A large number of light-scattering data indicate that the sulfated polysaccharide κ-carr... more ABSTRACT A large number of light-scattering data indicate that the sulfated polysaccharide κ-carrageenan undergoes an intramolecular conformational transition under suitable conditions from a semiflexible, disordered conformation to a rather rigid, helical one. By varying the parameters controlling the conformational phase diagram (i.e., by increasing the concentration of polymer or that of the supporting electrolyte, or both, or by decreasing temperature), a tertiary structure is manifested, through a progressive increase of the weight-average molar mass (M̄w) as determined by light scattering. This can be very well explained in terms of a reversible association of stretches of such intramolecular helical structures and quantitatively described by a model of “open association” of two or more chains. The association of κ-carrageenan was demonstrated to take place at around room temperature also in the presence of iodide ions, as long as their concentration is ≥0.20 M. In this way the apparent inconsistency of a number of published M̄w results can be reconciled. Additional light-scattering results indicated that the demonstrated thermodynamic tendency to reversible interchain association may lead to an irreversible aggregation of polymer chains if an improper solution preparation procedure is used.
The insoluble organic fraction (humin-like material, HLM) from rice hull-dairy cattle compost is ... more The insoluble organic fraction (humin-like material, HLM) from rice hull-dairy cattle compost is well converted into water soluble HLM-sulphonate by reaction in liquid SO3. Microanalytical, potentiometric, molecular weight, and NMR data are consistent with a highly homogeneous polymeric arylsulphonate having 4000 Da MW, 1.3 sulphonic groups per aromatic ring and significant content of carboxylic and phenolic groups. By comparison with structure-property relationships for commercial lignosulphonates derived from the pulp and paper industry, the above arylsulphonate is likely to be a candidate at a variety of applications in the chemical industry and in agriculture. Therefore, sulphonation is a means for upgrading composts HLM to the same uses as for commercial lignosulphonates.
Succinoglycan production by Agrobacterium tumefaciens was increased from 9.5 g/l to 14 g/l when t... more Succinoglycan production by Agrobacterium tumefaciens was increased from 9.5 g/l to 14 g/l when the microorganism was cultivated under fed-batch condition, as compared to batch fermentation. Cells and broth impurities were removed from the fermentation broth with activated charcoal at a temperature of 90 • C, yielding a clear and odorless solution of the polymer. Viscosity mesurement, NMR spectroscopy and Mw determination proved that the polymer retains its main features, practically unaffected by the heat treatment.
... Karin Bongaerts and Harry Reynaers. Laboratory of Macromolecular Structural Chemistry, Depart... more ... Karin Bongaerts and Harry Reynaers. Laboratory of Macromolecular Structural Chemistry, Department of Chemistry, KULeuven, Celestijnenlaan 200F, Heverlee, Belgium. Flavio Zanetti. POLY-tech SCrl, AREA Science Park, Padriciano ...
ABSTRACT A large number of light-scattering data indicate that the sulfated polysaccharide κ-carr... more ABSTRACT A large number of light-scattering data indicate that the sulfated polysaccharide κ-carrageenan undergoes an intramolecular conformational transition under suitable conditions from a semiflexible, disordered conformation to a rather rigid, helical one. By varying the parameters controlling the conformational phase diagram (i.e., by increasing the concentration of polymer or that of the supporting electrolyte, or both, or by decreasing temperature), a tertiary structure is manifested, through a progressive increase of the weight-average molar mass (M̄w) as determined by light scattering. This can be very well explained in terms of a reversible association of stretches of such intramolecular helical structures and quantitatively described by a model of “open association” of two or more chains. The association of κ-carrageenan was demonstrated to take place at around room temperature also in the presence of iodide ions, as long as their concentration is ≥0.20 M. In this way the apparent inconsistency of a number of published M̄w results can be reconciled. Additional light-scattering results indicated that the demonstrated thermodynamic tendency to reversible interchain association may lead to an irreversible aggregation of polymer chains if an improper solution preparation procedure is used.
Clinical and environmental strains of Burkholderia cenocepacia belonging to the recA lineages III... more Clinical and environmental strains of Burkholderia cenocepacia belonging to the recA lineages IIIA and IIIB were examined for exopolysaccharide (EPS) production. The exopolysaccharides structure was determined using mainly gas chromatography coupled to mass spectrometry and NMR spectroscopy. All the strains produced Cepacian, a highly branched polysaccharide constituted of a heptasaccharide repeating unit, composed of one rhamnose, one glucose, one glucuronic acid, one mannose and three galactose residues. This polymer is the most common exopolysaccharide produced by strains of the Burkholderia cepacia (Bcc) complex. One clinical strain produced also another polysaccharide constituted of three galactose units and one 3-deoxy-D-manno-2-octulosonic acid residues, a polymer that was previously isolated from two strains of B. cepacia genomovar I and B. cenocepacia IIIA.
A strain of Agrobacterium tumefaciens isolated from soil was cultivated under various conditions ... more A strain of Agrobacterium tumefaciens isolated from soil was cultivated under various conditions in shake flasks to study exopolysaccharides (EPS) production. NMR analysis revealed that the EPS obtained was a succinoglycan-like polymer. Optimal yields of EPS were obtained using sucrose and lysine as the carbon and nitrogen sources, respectively. Supplementation of the medium with various chemicals resulted in a more or less marked effect on the polymer yield and properties: in particular, high phosphate levels and non-ionic surfactants led to the production of polymers of different molecular sixes in yields up to 13.7 g/l. Oxygen availability also affected the polymer yield and quality. The chemical structure was substantially unaffected by the various fermentation conditions tested. A fermentation carried out in a laboratory-scale fermentor yielded 9.6 g/l succinoglycan from 15 g/Z sucrose in the basic medium without further supplements.
Aqueous extracts of Codium fragile ssp. atlanticum possess marked anticoagulant activity. The com... more Aqueous extracts of Codium fragile ssp. atlanticum possess marked anticoagulant activity. The compounds responsible appear to be proteoglycans with molecular weights, determined by a low angle, laser light-scattering method, of 1.8 x 106 daltons, with a polydispersity value of 1.2.
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