Ulcerative colitis (UC) is a chronic inflammatory bowel disease. The purpose of this study was to investigate the ameliorating effects of three yeast strains, Saccharomyces cerevisiae I4, Clavispora lusitaniae 30 and Pichia kudriavzevii 11, isolated from traditional fermented dairy food in Xinjiang, China, on the ulcerative colitis symptoms of Balb/c mice treated by dextran sulfate sodium (DSS). Among which, S. cerevisiae I4 had good tolerance to simulated gastrointestinal juice and strong adhesion to HT−29 cells monolayers. Furthermore, the three yeast strains were oral administered to Balb/c mice with DSS induced colitis. The weight loss, colon shortening and histological injury of colitis mice were ameliorated. Then, oral administration of S. cerevisiae I4 improved the immune state by reducing the contents of TNF−α, IL−6 and IL−1β and increasing immunoglobulin. The relative expression of intestinal barrier proteins Claudin−1, Occludin and Zonula Occludins−1 (ZO−1) of the mice enhanced, and the short chain fatty acids (SCFAs) content such as Propionic acid, Butyric acid, Isobutyric acid and Isovaleric acid in the feces of the mice increased to varying degrees, after S. cerevisiae I4 treatment compared with the model group of drinking 3% DSS water without yeast treatment. Moreover, S. cerevisiae I4 treatment lifted the proportion of beneficial bacteria such as Muribaculaceae, Lactobacillaceae and Rikenellaceae in the intestinal tract of the mice, the abundance of harmful bacteria such as Staphylococcus aureus and Turicibacter was decreased. These results suggested that S. cerevisiae I4 could alleviate DSS induced colitis in mice by enhancing intestinal barrier function and regulating intestinal flora balance.

In our previous study, Lactiplantibacillus plantarum Y42 showed some potential probiotic functions and the ability to form biofilm. The aim of this study was to compare the similarities and differences in the probiotic and physiological traits of L. plantarum Y42 in the biofilm and planktonic states. L. plantarum Y42 in the biofilm state was proven to have higher survival after passing through mimic gastrointestinal fluid, as well as excellent adhesion properties on the HT-29 cell monolayers, than those in the planktonic state. The expression of tight junction proteins (TJ proteins) of HT-29 cell monolayers treated by L. plantarum Y42 in the planktonic state increased, while similar changes were not observed in the HT-29 cells treated by the strain in the biofilm state. Furthermore, Balb/c mice were orally administered L. plantarum Y42 in the biofilm and planktonic states, respectively. Compared to the planktonic state, the oral administration of L. plantarum Y42 in the biofilm state significantly boosted IgA levels and improved the immunity of the mice. High-throughput sequencing showed that the diversity and structure of the intestinal flora of the mice were changed after the oral administration of L. plantarum Y42, including the up-regulated relative abundance of Lactobacillus in the intestinal tract of the mice, with no difference between the biofilm and planktonic states. Moreover, oral administration of L. plantarum Y42 in biofilm and planktonic states reduced the release of proinflammatory factors, to a certain extent, in the serum of the mice. The similarities and differences in the probiotic and physiological properties of L. plantarum Y42 in the biofilm and planktonic states can be contributed to the reasonable application of the strain.

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