Partial Characterization and Immunomodulatory Effects of Exopolysaccharides from Streptococcus thermophilus SBC8781 during Soy Milk and Cow Milk Fermentation

Hajime Nakata; Yoshiya Imamura; Sudeb Saha; René Emanuel Lobo; Shugo Kitahara; Shota Araki; Mikado Tomokiyo; Fu Namai; Masanori Hiramitsu; Takashi Inoue; Keita Nishiyama; Julio Villena; Haruki Kitazawa

doi:10.3390/foods12122374

Partial Characterization and Immunomodulatory Effects of Exopolysaccharides from Streptococcus thermophilus SBC8781 during Soy Milk and Cow Milk Fermentation

Foods. 2023 Jun 15;12(12):2374. doi: 10.3390/foods12122374.

Authors

Hajime Nakata^{1

2}, Yoshiya Imamura^{1

3}, Sudeb Saha^{1

3

4}, René Emanuel Lobo⁵, Shugo Kitahara¹, Shota Araki^{1

3}, Mikado Tomokiyo^{1

3}, Fu Namai^{1

3}, Masanori Hiramitsu², Takashi Inoue², Keita Nishiyama^{1

3}, Julio Villena⁶, Haruki Kitazawa^{1

3}

Affiliations

¹ Food and Feed Immunology Group, Laboratory of Animal Food Function, Graduate School of Agricultural Science, Tohoku University, Sendai 980-8572, Japan.
² Pokka Sapporo Food and Beverage Ltd., Nagoya 460-0008, Japan.
³ Livestock Immunology Unit, International Education and Research Centre for Food and Agricultural Immunology (CFAI), Graduate School of Agricultural Science, Tohoku University, Sendai 980-8572, Japan.
⁴ Department of Dairy Science, Faculty of Veterinary, Animal and Biomedical Sciences, Sylhet Agricultural University, Sylhet 3100, Bangladesh.
⁵ Institute of Analytical Chemistry (Cátedra de Química Analítica III), Faculty of Biochemistry, Chemistry, and Pharmacy, National University of Tucumán, Tucuman 4000, Argentina.
⁶ Laboratory of Immunobiotechnology, Reference Centre for Lactobacilli (CERELA-CONICET), Tucuman 4000, Argentina.

Abstract

The immunomodulatory properties of exopolysaccharides (EPSs) produced by Streptococcus thermophilus have not been explored in depth. In addition, there are no comparative studies of the functional properties of EPSs produced by streptococci in different food matrices. In this work, EPSs from S. thermophilus SBC8781 were isolated after soy milk (EPS-s) or cow milk (EPS-m) fermentation, identified, and characterized in their abilities to modulate immunity in porcine intestinal epithelial cells. Fresh soy milk and cow milk were inoculated with S. thermophilus SBC8781 (7 log CFU/mL) and incubated at 37 °C for 24 h. The extraction of EPSs was performed by the ethanol precipitation method. Analytical techniques, including NMR, UV-vis spectroscopy, and chromatography, identified and characterized both biopolymer samples as polysaccharides with high purity levels and similar Mw. EPS-s and EPS-m had heteropolysaccharide structures formed by galactose, glucose, rhamnose, ribose, and mannose, although with different monomer proportions. On the other hand, EPS-s had higher quantities of acidic polymer than EPS-m. The biopolymer production of the SBC8781 strain from the vegetable culture broth was 200-240 mg/L, which was higher than that produced in milk, which reached concentrations of 50-70 mg/L. For immunomodulatory assays, intestinal epithelial cells were stimulated with 100 µg/mL of EPS-s or EPS-m for 48 h and then stimulated with the Toll-like receptor 3 agonist poly(I:C). EPS-s significantly reduced the expression of IL-6, IFN-β, IL-8, and MCP-1 and increased the negative regulator A20 in intestinal epithelial cells. Similarly, EPS-m induced a significant reduction of IL-6 and IL-8 expressions, but its effect was less remarkable than that caused by EPS-s. Results indicate that the structure and the immunomodulatory activity of EPSs produced by the SBC8781 strain vary according to the fermentation substrate. Soy milk fermented with S. thermophilus SBC8781 could be a new immunomodulatory functional food, which should be further evaluated in preclinical trials.

Keywords: Streptococcus thermophilus SBC8781; cow milk; exopolysaccharides; immunomodulatory activities; intestinal epithelial cells; soy milk.

Abstract

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