Screening of peptides associated with adhesion and aggregation of Lactobacillus rhamnosus GG in vitro

Probiotics are viable microbes in food and feed supplements that are beneficial to the health of humans and animals. A direct peptide-bacteria binding assay for identification of Toll-like receptor 2 (TLR2)-derived peptides binding to a probiotic bacterium, Lactobacillus rhamnosus GG, was performed using an octameric-peptide library spot-synthesized on a cellulose membrane. Twenty-three peptides enhanced bacterial binding (>4-fold increase as compared to no-peptide control). High-density adhesion of L. rhamnosus was observed with 15 peptides synthesized on a glass surface, and six peptides also maintained adhesion at mild acidic condition of pH 5.5. Remarkably, one of the identified peptides, QRCVNLQA, induced aggregation of lactic acid bacteria and promoted bacteria-mucosa interaction. When the QRCVNLQA peptide was co-incubated with L. rhamnosus, it contributed to cellular aggregation and enhanced in vitro adherence to Caco-2 intestinal epithelial cells, leading to slight enhancement of MUC2 expression in Caco-2 cells. These results indicate that this peptide promotes adhesion and causes cellular aggregation of lactic acid bacteria as well as enhances their interaction with the host intestinal mucosa.