Effect of Lactiplantibacillus mudanjiangensis strain isolated from post-fermented tea on dermal health

The effects of Lactiplantibacillus mudanjiangensis IYO1739 and Lactiplantibacillus plantarum IYO1653, isolated from Japanese post-fermented tea, and their type strains on skin cells were evaluated. The normal human epidermal keratinocyte (NHEK) cells were treated with each strain, and after 2 h, the cells were washed and the number of adhered bacteria was measured. L. mudanjiangensis showed high adhesion, while L. plantarum strains showed little adhesion. After washing, the cells were cultured in bacteria-free medium for an additional 4 h and 24 h, and the expression levels of genes related to maintaining skin health were evaluated. Cells treated with L. mudanjiangensis showed increased expression of hyaluronan synthases (HAS1 and HAS3), sphingomyelinases involved in ceramide synthesis (SGMS1 and SGMS2), sphingomyelin phosphodiesterase 1 (SMPD1), involucrin, and transglutaminase 1 (TGM1) genes. These effects were weak or absent in L. plantarum strains. In addition, the IYO1739 strain of L. mudanjiangensis was more effective than the type strain DSM28402T. Furthermore, IYO1739 grew faster in MRS broth than DSM28402T, and showed particularly good growth at 37 °C. In addition, the expression of skin-related genes was enhanced by even heat-killed bacteria. These results suggest that L. mudanjiangensis strains, especially IYO1739, are beneficial for maintaining healthy skin.