Abstract: In this study we conducted experiments to determine the minimal inhibitory concentration (MIC) and minimal bactericidal concentration (MBC) of hawthorn pectin oligosaccharides with different polymerization degrees, and to draw the growth curves of five test strains in order to explore the antibacterial activity of pectin oligosaccharides. The underlying mechanism was elucidated by evaluating the changes in cell morphology, cell membrane permeability and integrity. The results showed that pectin oligosaccharides with average polymerization degree of 3 had the strongest antibacterial effect, especially against Escherichia coli, Bacillus subtilis and Staphylococcus aureus, with MICs of 1.250, 0.625 and 0.625 g/L, respectively. The relative conductivity of bacterial cell suspensions increased with increasing addition of pectin oligosaccharides, accompanied by a simultaneous increase in nucleic acid and protein concentrations, implying that pectin oligosaccharides exerted antibacterial activity presumably by damaging the cell membrane permeability and integrity and consequently resulting in leakage of cell contents, thereby causing an adverse effect on the metabolic activity and consequently inhibiting bacterial growth. Therefore, hawthorn pectin oligosaccharides can be used as natural preservatives to inhibit the growth of spoilage bacteria and pathogens in foods and thus prolong their shelf life.

Key words: hawthorn pectin oligosaccharides, degree of polymerization, bacteriostasis, mechanism