Abstract：
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 × 106 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.
摘要：
发现由开菲尔谷物中肠明串珠菌XR1发酵的酸奶会产生独特的拉丝现象。发现此特性与胞外多糖（EPS）有关，X-EPS,由菌株XR1产生。为了更好地理解产生这种现象的机制，提取了X-EPS，纯化和表征。通过尺寸排阻色谱结合多角度激光散射（SEC-MALLS）和离子色谱（IC）分析确定分子量和单糖组成，分别。结果表明,其分子量为4.183×106g/mol,单糖组成为葡萄糖,和葡萄糖醛酸，含量分别为567.6148和0.2096μg/mg，分别。FT-IR和NMR分析表明，X-EPS是α-吡喃糖多糖，由92.22％的α-（1→6）连接的d-吡喃葡萄糖单元和7.77％的α-（1→3）分支组成。此外，在原子力显微镜（AFM）和扫描电子显微镜（SEM）实验中显示出带分支的链状微观结构。这些结果表明，X-EPS的独特结构，使酸奶具有很强的粘度和粘结性，这导致了拉丝现象。这项工作表明X-EPS具有食品和工业应用的潜力。
