Effect of Probiotic Fermentation on the Antibacterial Activity of Sea Buckthorn Trimorphic Polyphenols and its Application to Fresh Milk Preservation

Sea buckthorn, rich in polyphenols, serves as a potent natural antioxidant with antimicrobial properties. Through fermentation with the probiotic Lactobacillus plantarum Lp10211, the phenolic content of triterpenoid polyphenols in sea buckthorn juice is significantly enhanced. Plate assays demonstrated enhanced antimicrobial effects of fermented conjugated phenolics (FCP) against Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli), with FCP (5 mg/mL) exhibiting the strongest inhibition (E. coli: 3.9-cm zone). FCPs and unfermented CCPs showed minimum inhibitory concentrations (MICs) of 0.39 and 0.78 mg/mL, respectively, against E. coli. Mechanistically, CPs disrupt bacterial membranes by increasing permeability and hydrophobicity, inducing leakage of proteins, nucleic acids, and β-galactosidase, alongside conformational changes in membrane proteins. Fermentation consistently improved these bacteriostatic effects. In fresh milk preservation, FCPs delayed lactose degradation and acidity rise while suppressing bacterial growth at 4 °C. At 25 °C and 37 °C, FCPs dose-dependently reduced total bacterial counts. These findings highlight CPs, particularly FCPs, as promising natural preservatives against foodborne pathogens like E. coli and S. aureus, extending milk shelf life.

Graphical Abstract