Studies On The Modification And Application Of Amylose, Guar Gum And Konjac Glucomannan

Nowadays, with the aggravation of environment and ecology crisis, people are enduring huge danger brought by synthetic polymers' bad biodegradability, while we are enjoying their advantages. At the same time, more and more people divert their attention to natural resources because of their excellent biologic reactivity, better biodegradability and environment compatibility.Due to the increasingly wide use of starch, guar gum and konjac in the fields of food, medicine and chemical industry et al, the three kinds of natural polysaccharides have become the most salable materials in China. Studies and exploitations on them get wide consideration. In this paper, amylose, guar gum and konjac have been modified by different methods such as esterification and sulfation. The properties of amylose maleic anhydride esters and anticoagulant bioactivities of guar gum sulfates and carboxymethylkonjac sulfates were investigated, which provided the scientific basis for developing the applications of those natural polysaccharides. The main contents and conclusions are presented as follows:1) Starch is used extensively in the production of both food and industrial products. Chemical modification of the starch is often required to better suit its properties to specific applications. Traditionally, starch esters with low degrees of substitution (DS) have been prepared in aqueous media. In this paper amylose maleic anhydride esters have been prepared in different reaction conditions. The effects of molar ratio of maleic anhydride to sugar unit, pH value, reaction time and temperature have been studied. It has been observed that the DS of amylose maleic anhydride ester was 0.130 and the viscosity has been improved by 5 times when molar ratio of maleic anhydride to sugar unit was 0.7 :1.0, pH value was 8.0, reaction time and temperature was 3 h and 30℃ respectively. The esterified amylose shows higher viscosity, better stability to heat and clarity compared to natural amylose. Also the structure of the product was investigated by FTIR spectrometry.2) The importance of heparin as an anticoagulant agent has stimulated, for over 20years, a great interest in the preparation of sulfated forms of many diverse polysaccharides exhibiting heparin-like properties. However, few studies have been devoted, as far as I know, to the sulfation reaction of guar gum. In this paper, guar gum was sulfated by chlorosulfonic acid (CISO3H) as a sulfation reagent. The optimum sulfation reaction was: molar ratio of CISO3H to sugar unit (CISO3H/SU) was 4: 1, reaction time and reaction temperature were 3h and 60 °C respectively . The characteristics of sulfated guar gums were investigated by GPC and FT-IR spectroscopy. Activated partial thromboplastin time (APTT) assay showed that although the anticoagulant bioactivity of guar gum sulfate is weaker than that of heparin, guar gum sulfate, whose DS is greater than 0.56, could inhibit the intrinsic coagulant pathway, which means that it has apparent anticoagulant bioactivity. The anticoagulant bioactivity strongly depended on DS and Mw of polysaccharides. DS > 0.56 was essential for anticoagulant bioactivity . The sulfated guar gum with DS of 0.85 and Mw of 3.40 X 104 had the best blood anticoagulant bioactivity. In addition, sulfation reactions of cationic, natural and anionic guar gum suggested that anticoagulant bioactivity has a good relation with the density of anionic electric charges on the polysaccharides' surfaces.3) Natural konjac glucomannans were modified by the methods of carboxymethylation and sulfation in the present of CISO3H/DMF. The effects of carboxymethylation DS, molar ratio of CISO3H/SU and reaction time have been studied. It has been observed that the sulfation DS of CMKGMS was higher when it was produced with the carboxymethylation DS 0.58, 4: 1 CISO3H/SU for 3 h. Activated partial thromboplastin time (APTT) assay showed that carboxymethylkonjac glucomannan sulfate whose sulfation DS is greater than 0.35 could inhibit the intrinsic coagulant pathway, which means that it has apparent anticoagulant bioactivity. The anticoagulant bioactivity strongly depended on not only the DS of carboxymethylation and sulfation but Mw of polysaccharides. The carboxymethylkonjac glucomannan sulfate withcarboxymethylation DS of 0.58, sulfation DS of 0.59 and Mw of 3.40X 104 had the best blood anticoagulant bioactivity.