Abstract Lactobacillus paracasei that could release exopolysaccharide (EPS), was used as starter to prepare yoghurt under optimal fermented conditions. It was found that the viscosity of yoghurt increased exponentially with EPS production, and to elucidate this phenomen, the binding of EPS-S11 extracted and purified from yoghurt to casein was evaluated by turbidity and particle size analysis, zeta potential study, confocal laser scanning microscopy (CLSM) imaging, and isothermal titration calorimetry (ITC) determination. Results indicated that EPS-S11 with an average molecular weight of 1.68 × 107 Da, was mainly composed of mannose, glucose, galactose and glucuronic acid in a molar ratio of 0.87:0.92:1:0.24. Upon the addition of EPS-S11, the turbidity and particle size of casein solution both decreased in a dose-dependent manner, while the zeta potential was dose-dependently increased, suggesting that EPS-S11 might inhibit the aggregation of casein and thus enhanced its stability. ITC titration and CLSM imaging confirmed the existence of interactions between EPS-S11 and casein, which mainly involved in electrostatic interaction as well as hydrophobic interaction.

中文翻译：

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副干酪乳杆菌发酵酸奶的胞外多糖：生产、纯化及其与酪蛋白酸钠的结合

摘要 以可释放胞外多糖（EPS）的副干酪乳杆菌为发酵剂，在最佳发酵条件下制备酸奶。发现酸奶的粘度随着 EPS 的产生呈指数增加，为了阐明这一现象，通过浊度和粒度分析、zeta 电位研究、共聚焦激光扫描显微镜评估了从酸奶中提取和纯化的 EPS-S11 与酪蛋白的结合(CLSM) 成像和等温滴定量热法 (ITC) 测定。结果表明EPS-S11的平均分子量为1.68×107 Da，主要由甘露糖、葡萄糖、半乳糖和葡萄糖醛酸组成，摩尔比为0.87:0.92:1:0.24。加入EPS-S11后，酪蛋白溶液的浊度和粒径均呈剂量依赖性降低，而 zeta 电位呈剂量依赖性增加，表明 EPS-S11 可能抑制酪蛋白的聚集，从而增强其稳定性。ITC 滴定和 CLSM 成像证实了 EPS-S11 与酪蛋白之间存在相互作用，主要涉及静电相互作用和疏水相互作用。