Enhancement of the Activity of a Lactobacilli-Aggregating Peptide by Freezing Treatment

Abstract

The effects of freezing treatments on the activity of the lactobacilli-aggregating peptide QRCVNLQA were studied. The aggregation activity of the peptide solution was enhanced by rapid deep freezing in liquid nitrogen followed by storage for at least 1 d below -10°C. The treated peptide strongly induced aggregation of suspended cells of Lactobacillus rhamnosus GG to give a clear supernatant after 1.5 h. An assay of the thiol group showed that the peptide was activated by oxidation of this group, probably through dimerization of the peptide molecules to form disulfide bonds. Addition of the freeze-oxidized peptide to a suspension of lactobacilli cells promoted the adhesion of the lactobacilli cells to a monolayer of Caco-2 intestinal epithelial cells.