Department of Microbial Biotechnology, Bharathiar University, Coimbatore 641046, India.
Department of Food Science and Technology, Pondicherry University, Pondicherry 605014, India.
Int J Biol Macromol. 2018 Oct 15;118(Pt B):1667-1675. doi: 10.1016/j.ijbiomac.2018.07.015. Epub 2018 Jul 11.
Exopolysaccharide (EPS) producing probiotic strain Enterococcus hirae KX577639 were isolated from the feces of South Indian Irula tribes. EPS yield was 18.57 g/L (dry weight) at 48 h in 2% sucrose supplemented MRS medium. TLC and GC-MS analysis confirmed the presence of predominant glucose monomer indicating the homopolysaccharide nature of EPS. FTIR and NMR studies revealed that the EPS were branched α-D-glucan polymer with α-(1 → 6) and α-(1 → 3) linkages. SEM analysis of glucan-EPS revealed porous and starch like cracked granules of aggregation. AFM studies proved spherical lumps and dense, grainy like network. The thermal behavior of glucan-EPS showed degradation temperature of 315.98 °C and melting point of 296.67 °C. The XRD analysis confirmed the amorphous nature of EPS with a crystalline index of 0.48. The water solubility index and water holding capacity of glucan-EPS showed 46.5% and 202.04%. These distinctive features of the glucan EPS could find its potential application in functional food products as the α-(1 → 3) linkage are resistant to human digestive enzymes and can serve as a nutrient to gut bacteria. This the first study reporting the EPS production by Enterococcus hirae.
从印度南部 Irula 部落的粪便中分离出产胞外多糖 (EPS) 的益生菌菌株屎肠球菌 KX577639。在 2%蔗糖补充的 MRS 培养基中，48 小时时 EPS 的产量为 18.57 g/L（干重）。TLC 和 GC-MS 分析证实了主要葡萄糖单体的存在，表明 EPS 具有均多糖性质。FTIR 和 NMR 研究表明，EPS 是支链α-D-葡聚糖聚合物，具有α-(1→6)和α-(1→3)键。葡聚糖-EPS 的 SEM 分析显示出多孔和淀粉样开裂的聚集颗粒。AFM 研究证明了球形块状物和密集、粒状的网络。葡聚糖-EPS 的热行为显示出 315.98°C 的降解温度和 296.67°C 的熔点。XRD 分析证实了 EPS 的无定形性质，结晶指数为 0.48。葡聚糖-EPS 的水溶性指数和持水能力分别为 46.5%和 202.04%。葡聚糖 EPS 的这些独特特性可能使其在功能性食品产品中具有潜在的应用，因为α-(1→3)键对人体消化酶具有抗性，并且可以作为肠道细菌的营养物质。这是首次报道屎肠球菌产生 EPS 的研究。
