The composition of Tibetan kefir grain TKG-Y and the antibacterial potential and milk fermentation ability of S. warneri KYS-164 screened from TKG-Y.

This study utilized high-throughput sequencing and SEM observation to elucidate the microbial composition of a Tibetan herder's homemade kefir grain named TKG-Y. Subsequently, S. warneri KYS-164 was isolated from TKG-Y, which can produce mixed protein substances with antibacterial activity, namely bacteriocin-like inhibitory substances (BLIS). BLIS can significantly reduce the growth rate of Escherichia coli 366-a, Staphylococcus aureus CICC 10384 and mixed strains at low concentrations (1 × MIC). The presence of the warnericin-centered gene cluster in KYS-164 may explain the antibacterial properties of the BLIS. Pepsin and an acidic environment can reduce the number of colonies of KYS-164 by 2.5 Log10 CFU mL-1 within 1 h, and reduce the antibacterial activity of BLIS by 21.48%. S. warneri KYS-164 showed no antibiotic resistance and biological toxicity after 80 subcultures, while BLIS produced by 40 generations of the strain retained their inhibitory efficacy against pathogenic bacteria. After 48-hour fermentation of milk with KYS-164, volatile compounds such as aldehydes, phenols, esters, and alcohols, giving it a floral, fruity, milky, oily, and nutty aroma, were released, enriching the sensory characteristics of dairy products. This study not only revealed the bacterial colony composition information of home-made kefir grain TKG-Y but also discovered and proved that S. warneri KYS-164 has the potential to inhibit bacteria and ferment dairy products. This will provide a basis for subsequent applied research on KYS-164.

Selenium-containing tea polysaccharides ameliorate DSS-induced ulcerative colitis via enhancing the intestinal barrier and regulating the gut microbiota.

Both tea polysaccharides and selenium have certain remission potential for ulcerative colitis (UC), but few reports focused on natural selenium-containing tea polysaccharides. The purpose of this study was to isolate a selenium-containing tea polysaccharide (ASeTP) and determine its structure and effects on UC. Results showed that ASeTP was primarily composed of three purified, ß-pyranoside-linked, protein-binding polysaccharides (SeTP-1, SeTP-2, and SeTP-3) with SeOC, OSeO, and SeO linkages. Specifically, SeTP-1 was a neutral heteropolysaccharide principally composed of mannose, glucose, galactose, xylose, and arabinose, while SeTP-2 and SeTP-3 were acidic heteropolysaccharides due to the existence of glucuronic acid. ASeTP effectively alleviated the symptoms of weight loss, colon shortens, and disease activity index scores increase in dextran sodium sulfate (DSS)-induced colitis mice. ASeTP attenuated the histological damage and maintained the colonic mucosal barrier via up-regulating the expression of occludin, claudin-1, and zona occludens-1 (ZO-1). ASeTP suppressed the levels of pro-inflammatory cytokines and enhanced the antioxidant capacity of colon tissue. Besides, ASeTP beneficially increased the selenium content of the colon. Furthermore, ASeTP remodeled the gut microbiota by accelerating the proliferation of beneficial bacteria and inhibiting pathogenic microorganisms. Thus, ASeTP has the potential to be a functional food against colitis.