| Seed galactomannans are always preferred during production and application in industry, on account of their advantages in environment and cost. The seeds of Gleditsia sinensis and Gleditsia microphylla are an important and widespread source of galactomannans in China, whereas only a few studies focused on fractional purification and precipitate characterization of the polysaccharide gum. On this basis, Gleditsia sinensis galactomannan (GSG) and Gleditsia microphylla galactomannan (GMG) were precipitated by using different concentrations of ethanol and isopropanol.galactomannans of different sources were studied on the purification and enzymatic modification in micro-water-solid-phase. The relationship between the precipitation behavior and molecular structures of Gleditsia sinensis galactomannan (GSG) were clarified, which had a significant meaning for the purification of hydrophilic gel.Two galactomannans of Gleditsia sinensis galactomannan (GSG) and Gleditsia microphylla galactomannan (GMG) were fractionally precipitated from pure solutions by the addition of either ethanol or isopropanol. The GSG and GMG precipitated in different stages had different properties, including the morphological appearance, galactomannan recovery and content, mannose/galactose ratio, chemical composition, molecular weight, and They performed different precipitation behavior in the polar organic solvent-water systems. By adding more alcohol solvents, the concentration and purity of galactomannans were increased. And after the third precipitation, the galactomannan yield was up to 80%. The galactomannan recovery of GSG and GMG in 33.3% ethanol solvent was 81.7% and 82.5%, respectively, while that in 28.8% isopropanol solvent was 81.3% and 82.9%, respectively. To achieve the same precipitation efficiency, the usage amount of isopropanol was much lower than that of ethanol, owing to the low dielectric constant for isopropanol (20 vs.25). Our data demonstrate that to achieve the similar precipitation efficiency, the amount of isopropanol required was much lower than that of ethanol because of the low dielectric constant of isopropanol (20 vs.25 for ethanol). The precipitation behavior of galactomannans in polar organic solvents was dependent on the molecular structures and properties of the solvent. Purification of the crude samples of GSG and GMG can eliminate the impurities and endogenous enzymes, and improve the quality stability in the application process.Modification of galactomannan in micro-water-solid-phase is a innovative method proposed based on the swelling characteristics of the polysaccharide gums. While swelling in small amount of water, the chemical reagent was absorbed for the modification reaction, Imbibed endosperms were fluffy with snow flake after the pressure treatment. In this study, the micro water solid phase method has been used in the oxidation of Gleditsia sinensis galactomannan (GSG), H2O2 was used as the oxidizing reagents to prepare the oxidated Gleditsia sinensis galactomannan (OGSG). The degree of substitution (Ds), weight average molecular weight (Mw), viscosity of OGSG treat with different concentrations of H2O2 were investigated. The result showed that with the increasing of concentration of H2O2, a decrease in molar-mass values and the intrinsic viscosity and an increase in degree of substitution and polydispersity were observed. While the dosage of GSG and 30%H2O2 is 20g and 18g, respectively. The reaction temperature is 65℃, reaction time is 1 h. Under this condition, the Ds of product reached 1.22.The oxidation of Gleditsia sinensis galactomannan(GSG) can be achieved by the method of micro water solid phase oxidation modification under the condition of using fewer reaction reagent.the micro water solid phase method has been also used in the carboxymethylation of Gleditsia sinensis galactomannan (GSG), monochloroacetic acid and NaOH were used as the reagents to prepare the carboxymethylated Gleditsia sinensis galactomannan (CMGSG). The degree of substitution(Ds), Flocculation performance, weight average molecular weight (Mw), viscosity of CMGSG treat with different concentrations of NaOH were investigated. It indicated that in micro-water-solid-phase purity concentrations of NaOH had an important impact on the composition of modified products.after the modification, The product with flocculation performance can be used as flocculating agent.The micro-water-solid-phase physical method was used in the modification of GSG, adjusted pH of water, reacted in a high-pressure reaction kettle witg high temperature and high pressure. The product has different characteristics. This result shows that micro-water-solid-phase physical method can be used to improve the properties of the GSG.The micro-water-solid-phase chemical method and physical method are two new methods of modification of GSG modification of GSG in micro-water-solid-phase saves the cost of reagent. It is easily operated and successfully avoids the inconvenience of high viscosity of gum solution. This fresh method is suitable for the practical production and has a significant impact on the industrial application of polysaccharide gum modification. |
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