You Xiu, Yang Lin, Zhao Xiaojuan, Ma Kai, Chen Xiaohong, Zhang Changliang, Wang Guangxian, Dong Mingsheng, Rui Xin, Zhang Qiuqin, Li Wei
College of Food Science and Technology, Nanjing Agricultural University, Nanjing, Jiangsu 210095, PR China.
Food Science College, Tibet Agriculture & Animal Husbandry University, Nyingchi, Tibet 860000, PR China.
Int J Biol Macromol. 2020 May 7;158:408-419. doi: 10.1016/j.ijbiomac.2020.05.027.
In this study, three strains of lactic acid bacteria isolated from Tibetan kefir grains, including two strains of Lactobacillus pentosus LZ-R-17 and L. helveticus LZ-R-5, and one strain of Lactococcus lactis subsp. lactis LZ-R-12. The ability of three strains to produce exopolysaccharide (EPS) was tested, and L. pentosus LZ-R-17 was found to have the highest EPS yield. One EPS (R-17-EPS) was isolated from the fermented milk by L. pentosus LZ-R-17 and purified by DEAE-52 anion exchange chromatography. Furthermore, R-17-EPS preliminary structure and macrophage immunomodulatory activity in vitro were investigated. On the basis of the analytical results of ultraviolet-visible spectrum, Fourier transform-infrared spectrum, monosaccharide composition analysis and one-dimensional and two-dimensional nuclear magnetic resonance (NMR) spectra, R-17-EPS was found to have an average molecular weight of 1.20 × 10 Da and was composed of galactose and glucose residues with a molar ratio of 1.00:3.15. NMR analysis revealed that the R-17-EPS was a linear hetero-galactoglucan containing repeating units of →2)-α-D-Galp-(1 → 4)-β-D-Glcp-(1 → 4)-β-D-Glcp-(1 → 4)-β-D-Glcp-(1→. In addition, R-17-EPS could effectively enhanced the proliferation, phagocytosis, nitric oxide and cytokines production of RAW264.7 cells, suggesting that R-17-EPS had potent immunostimulatory activity and could be explored as immunomodulator in functional food and/or medicine fields.
在本研究中，从西藏开菲尔粒中分离出三株乳酸菌，包括两株戊糖乳杆菌LZ-R-17和瑞士乳杆菌LZ-R-5，以及一株乳酸乳球菌乳酸亚种LZ-R-12。测试了这三株菌产生胞外多糖（EPS）的能力，发现戊糖乳杆菌LZ-R-17的EPS产量最高。从戊糖乳杆菌LZ-R-17发酵的牛奶中分离出一种EPS（R-17-EPS），并通过DEAE-52阴离子交换色谱法进行纯化。此外，还研究了R-17-EPS的初步结构和体外巨噬细胞免疫调节活性。根据紫外可见光谱、傅里叶变换红外光谱、单糖组成分析以及一维和二维核磁共振（NMR）光谱的分析结果，发现R-17-EPS的平均分子量为1.20×10 Da，由半乳糖和葡萄糖残基组成，摩尔比为1.00:3.15。NMR分析表明，R-17-EPS是一种线性杂半乳葡聚糖，含有→2)-α-D-半乳糖-(1→4)-β-D-葡萄糖-(1→4)-β-D-葡萄糖-(1→4)-β-D-葡萄糖-(1→的重复单元。此外，R-17-EPS可有效增强RAW264.7细胞的增殖、吞噬作用、一氧化氮和细胞因子的产生，表明R-17-EPS具有强大的免疫刺激活性，可在功能性食品和/或医药领域作为免疫调节剂进行探索。
