Yazhen Wu,Xiaoxiao Li,Zhengyu Jin,Birte Svensson,Yuxiang Bai
How to improve the solubility of linear dextrins (LD) and retain their characteristic helix amphiphilic cavities with flexible embedding capability, is a question worth exploring without adding new chemical groups. The strategy presented in this study is to attach a highly flexible (α-1 → 6) glucochain at the reducing end of LD by preparing a new type of dextrin, referred to as single-arm linear dextrin (SLD). In the actual synthesis, an (α-1 → 6) linked oligosaccharide of DP ¯ 10.7 (PDI = 1.28) was formed by extension of glucose units onto sucrose (2 M) by using L940W mutant of the glucansucrase GTF180-ΔN firstly. Next using γ-CD as glucosylation donor γ-CGTase extended this (α-1 → 6) glucochain with (α-1 → 4) bonds. SLD is a chimeric glucosaccharide comprising an (α-1 → 4) linked part ( DP ¯ 10.5) attached to the nonreducing end of an (α-1 → 6) glucochain as verified by enzyme fingerprinting and 1 H NMR. Furthermore, SLD was validated to show greatly improved solubility and dispersibility of resveratrol in water, as indicated by a 3.12-fold enhancement over the solubility in the presence of 0.014 M SLD. This study provided a new strategy for solving the solubility problem of LD and opens possibilities for new design of the fine structure of starch-like materials.
Yoghurt fermented by Leuconostoc mesenteroides XR1 from Kefir grains was found to produce a unique silk drawing phenomenon. This property was found to be associated with the exopolysaccharides (EPS), X-EPS, produced by strain XR1. In order to better understand the mechanism that produced this phenomenon, the X-EPS was extracted, purified and characterized. The molecular weight and monosaccharide composition were determined by size exclusion chromatography coupled with multi-angle laser light scattering (SEC-MALLS) and ion chromatography (IC) analysis, respectively. The results showed that its molecular weight was 4.183 × 10 6 g/mol and its monosaccharide composition was glucose, and glucuronic acid , with the contents of 567.6148 and 0.2096 μg/mg, respectively. FT-IR and NMR analyses showed that X-EPS was an α-pyranose polysaccharide and was composed of 92.22 % α-(1 → 6) linked d -glucopyranose units and 7.77 % α-(1 → 3) branching. Furthermore, it showed a chain-like microstructure with branches in atomic force microscopy (AFM) and scanning electron microscopy (SEM) experiments. These results suggested that the unique structure of X-EPS, gave the yoghurt a strong viscosity and cohesiveness, which resulted in the silk drawing phenomenon. This work suggested that X-EPS holds the potential for food and industrial applications.
危险品化学品经营许可证（带存储）