Isolation, purification, characterization and immunostimulatory activity of an exopolysaccharide produced by Lactobacillus pentosus LZ-R-17 isolated from Tibetan kefir

Xiu You; Lin Yang; Xiaojuan Zhao; Kai Ma; Xiaohong Chen; Changliang Zhang; Guangxian Wang; Mingsheng Dong; Xin Rui; Qiuqin Zhang; Wei Li

doi:10.1016/j.ijbiomac.2020.05.027

Isolation, purification, characterization and immunostimulatory activity of an exopolysaccharide produced by Lactobacillus pentosus LZ-R-17 isolated from Tibetan kefir

Int J Biol Macromol. 2020 May 7:158:408-419. doi: 10.1016/j.ijbiomac.2020.05.027. Online ahead of print.

Authors

Xiu You¹, Lin Yang², Xiaojuan Zhao¹, Kai Ma³, Xiaohong Chen¹, Changliang Zhang³, Guangxian Wang³, Mingsheng Dong¹, Xin Rui¹, Qiuqin Zhang¹, Wei Li⁴

Affiliations

¹ College of Food Science and Technology, Nanjing Agricultural University, Nanjing, Jiangsu 210095, PR China.
² Food Science College, Tibet Agriculture & Animal Husbandry University, Nyingchi, Tibet 860000, PR China.
³ Jiangsu Biodep Biotechnology Co., Ltd., Jiangyin, Jiangsu 214400, PR China; Probiotics Australia Pty, Ormeau, Queensland 4208, Australia.
⁴ College of Food Science and Technology, Nanjing Agricultural University, Nanjing, Jiangsu 210095, PR China. Electronic address: lw1981@njau.edu.cn.

PMID: 32389648
DOI: 10.1016/j.ijbiomac.2020.05.027

Abstract

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 × 10⁶ 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.

Keywords: Exopolysaccharide (EPS); Immunostimulatory activity; Tibetan kefir grains.