The structure-function relationship of a gellan family of polysaccharides, S-198 gum produced by Alcaligenes ATCC31853 was investigated in terms of rheological aspects. The flow curves of S-198 gum showed plastic beha...The structure-function relationship of a gellan family of polysaccharides, S-198 gum produced by Alcaligenes ATCC31853 was investigated in terms of rheological aspects. The flow curves of S-198 gum showed plastic behavior above 0.3%. Gelation did not occur in S-198 gum solution at low temperature (0℃), even at 0.8%. Both the viscosity and the elastic modulus remained constant with increasing temperature up to 80?C. The elastic modulus decreased a little with the addition of CaCl2 (6.8 mM), but then once again remained constant up to 80℃. The highest elastic modulus was observed for deacylated gellan gum with the addition of CaCl2 and increased slightly with increasing temperature up to 80℃, which was considered to be a transition temperature, after which it decreased rapidly. The elastic modulus of S-198 gum in the presence of urea (4.0 M) was lower than that in aqueous solution at low temperature (0℃), but remained constant with increasing temperature up to 80℃. The intramolecular associations, (hydrogen bonding and van der Waals forces of attraction), of S-198 gum molecules in aqueous solutions were proposed. The gellan family of polysaccharides, S-198, S-88, S-657, rhamsan, welan and gellan gum, provided a good opportunity to investigate the structure-function relationship for polysaccharides.展开更多
The polysaccharides, such as κ-carrageenan, ι-carrageenan, agarose (agar), gellan gum, amylose, curdlan, alginate, and deacetylated rhamsan gum, in water changed into an ice-like structure with hydrogen bonding betw...The polysaccharides, such as κ-carrageenan, ι-carrageenan, agarose (agar), gellan gum, amylose, curdlan, alginate, and deacetylated rhamsan gum, in water changed into an ice-like structure with hydrogen bonding between polymer and water molecules, and between water-water molecules even at a concentration range of 0.1% - 1.0% (W/V) at room temperature, resulting in gelation. Such dramatic changes from liquid into gels have been understood at the molecular level in principles. In this review, we describe the structure-function relationship of starch on the view point of rheological aspects and discuss gelatinization and retrogradation mechanism including water molecules at molecular level. The starch molecules (amylose and amylopectin) play a dominant role in the center of the tetrahedral cavities occupied by water molecules, and the arrangement is partially similar to a tetrahedral structure in a gelatinization process. The arrangement should lead to a cooperative effect stabilizing extended regions of ice-like water with hydrogen bonding on the surface of the polymer molecules, where hemiacetal oxygen and hydroxyl groups might participate in hydrogen bonding with water molecules. Thus, a more extended ice-like hydrogen bonding within water molecules might be achieved in a retrogradation process. Though many investigations not only include starch gelatinization and retrogradaion, but also the gelling properties of the polysaccharides have been undertaken to elucidate the structure-function relationship, no other researchers have established mechanism at the molecular level. There is reasonable consistency in our investigations.展开更多
A galactomannan was isolated from seeds of a leguminous plant, Desmanthus illinoensis, which is grown in Okinawa, Japan. D-Galactose (molar ratio, 1.0) and D-mannose (0.82) were identified via High-performance Anion E...A galactomannan was isolated from seeds of a leguminous plant, Desmanthus illinoensis, which is grown in Okinawa, Japan. D-Galactose (molar ratio, 1.0) and D-mannose (0.82) were identified via High-performance Anion Exchange Chromatography Coupled with a Pulse Amperometric Detector. The molecular mass and specific rotation were estimated to be 1000 kDa and +53.8°, respectively. The infrared spectrum indicated that the galactomannan was involved in both α- and β-linkages, and two types of α-linkages were detected at 814 and 830 cm-1. The 1H- and 13C-NMR spectra indicated that the majority of the β-D-mannan main chain was substituted with mono α-D-galactose or α-D-galacto-disaccharide-side chains. Methylation analysis was used to identify 2,3,4,6-tetra-O-methyl-D-galactose (molar ratio, 3.3), 2,3,4-tri-O-methyl- D-galactose (1.0) and 2,3-di-O-methyl-D-mannose (3.1). Specifically, unique 2,3,4-tri-O-methyl D-galactose residue was identified from mass spectrum. The results suggested that the galactomannan was 1,4-linked-β-D-mannan substituted with α-D-galactose or 1,6-linked-α-D-galacto-disaccharide side chains at C-6 on the main chain. The galactomannan isolated from D. illinoensis was an unusual highly branched polysaccharide, and its chemical structure was proposed. This work is the first to report on the galactomannan involving 1,6-linked α-D-galacto-disaccharide side chains in addition to α-D-galactose mono side chains.展开更多
文摘The structure-function relationship of a gellan family of polysaccharides, S-198 gum produced by Alcaligenes ATCC31853 was investigated in terms of rheological aspects. The flow curves of S-198 gum showed plastic behavior above 0.3%. Gelation did not occur in S-198 gum solution at low temperature (0℃), even at 0.8%. Both the viscosity and the elastic modulus remained constant with increasing temperature up to 80?C. The elastic modulus decreased a little with the addition of CaCl2 (6.8 mM), but then once again remained constant up to 80℃. The highest elastic modulus was observed for deacylated gellan gum with the addition of CaCl2 and increased slightly with increasing temperature up to 80℃, which was considered to be a transition temperature, after which it decreased rapidly. The elastic modulus of S-198 gum in the presence of urea (4.0 M) was lower than that in aqueous solution at low temperature (0℃), but remained constant with increasing temperature up to 80℃. The intramolecular associations, (hydrogen bonding and van der Waals forces of attraction), of S-198 gum molecules in aqueous solutions were proposed. The gellan family of polysaccharides, S-198, S-88, S-657, rhamsan, welan and gellan gum, provided a good opportunity to investigate the structure-function relationship for polysaccharides.
文摘The polysaccharides, such as κ-carrageenan, ι-carrageenan, agarose (agar), gellan gum, amylose, curdlan, alginate, and deacetylated rhamsan gum, in water changed into an ice-like structure with hydrogen bonding between polymer and water molecules, and between water-water molecules even at a concentration range of 0.1% - 1.0% (W/V) at room temperature, resulting in gelation. Such dramatic changes from liquid into gels have been understood at the molecular level in principles. In this review, we describe the structure-function relationship of starch on the view point of rheological aspects and discuss gelatinization and retrogradation mechanism including water molecules at molecular level. The starch molecules (amylose and amylopectin) play a dominant role in the center of the tetrahedral cavities occupied by water molecules, and the arrangement is partially similar to a tetrahedral structure in a gelatinization process. The arrangement should lead to a cooperative effect stabilizing extended regions of ice-like water with hydrogen bonding on the surface of the polymer molecules, where hemiacetal oxygen and hydroxyl groups might participate in hydrogen bonding with water molecules. Thus, a more extended ice-like hydrogen bonding within water molecules might be achieved in a retrogradation process. Though many investigations not only include starch gelatinization and retrogradaion, but also the gelling properties of the polysaccharides have been undertaken to elucidate the structure-function relationship, no other researchers have established mechanism at the molecular level. There is reasonable consistency in our investigations.
文摘A galactomannan was isolated from seeds of a leguminous plant, Desmanthus illinoensis, which is grown in Okinawa, Japan. D-Galactose (molar ratio, 1.0) and D-mannose (0.82) were identified via High-performance Anion Exchange Chromatography Coupled with a Pulse Amperometric Detector. The molecular mass and specific rotation were estimated to be 1000 kDa and +53.8°, respectively. The infrared spectrum indicated that the galactomannan was involved in both α- and β-linkages, and two types of α-linkages were detected at 814 and 830 cm-1. The 1H- and 13C-NMR spectra indicated that the majority of the β-D-mannan main chain was substituted with mono α-D-galactose or α-D-galacto-disaccharide-side chains. Methylation analysis was used to identify 2,3,4,6-tetra-O-methyl-D-galactose (molar ratio, 3.3), 2,3,4-tri-O-methyl- D-galactose (1.0) and 2,3-di-O-methyl-D-mannose (3.1). Specifically, unique 2,3,4-tri-O-methyl D-galactose residue was identified from mass spectrum. The results suggested that the galactomannan was 1,4-linked-β-D-mannan substituted with α-D-galactose or 1,6-linked-α-D-galacto-disaccharide side chains at C-6 on the main chain. The galactomannan isolated from D. illinoensis was an unusual highly branched polysaccharide, and its chemical structure was proposed. This work is the first to report on the galactomannan involving 1,6-linked α-D-galacto-disaccharide side chains in addition to α-D-galactose mono side chains.
