Identification and Characterization of Antiyeast Organic Acids Produced by Lactiplantibacillus plantarum 3121M0s Derived from Mongolian Traditional Fermented Milk, Airag

Lactic acid bacteria are beneficial for food biopreservation by inhibiting not only bacteria but also fungi. However, reports on the control of fungi, especially yeasts, by lactic acid bacteria are limited. In this study, strain 3121M0s derived from Mongolian traditional fermented milk, airag, was selected with relatively high antiyeast activity among 236 strains, and identified as <i>Lactiplantibacillus plantarum</i>. The activity was exhibited under acidic conditions and remained stable after heating. It was also highly resistant to catalase and proteases, indicating that the primary antiyeast substances of 3121M0s were neither H₂O₂ nor peptides. Then, organic acids (lactic acid, acetic acid, 4-hydroxyphenyllactic acid, 4-hydroxybenzoic acid, and 3-phenyllactic acid) were detected and quantified in the ethyl acetate extract of the 3121M0s culture supernatant. Among them, only acetic acid showed antiyeast activity on its own, and the activity was enhanced by lactic acid or 3-phenyllactic acid. Compared to the type strain of <i>L. plantarum</i>, the production of lactic acid from 3121M0s was almost equal, but acetic acid and 3-phenyllactic acid were about 1.5 times higher. These results suggest that strain 3121M0s would be useful as a biopreservative starter for fermented foods susceptible to yeast contamination due to being produced in open environments without final sterilization.