Oligogalacturonic acids from citrus pectin: structural characterization and mechanistic insights into hydrophobic-antibacterial effect

Oligogalacturonic acid demonstrated potent antibacterial efficacy against foodborne pathogens. To obtain oligogalacturonic acids with favorable antibacterial activity, this study established a controlled enzymatic hydrolysis process for citrus peel pectin based on the characterization of three commercial pectinases. Different fractions of the pectin hydrolysates were then obtained via ethanol fractional precipitation. Results showed that the supernatant from 90% ethanol fractionation (F90%-s) exhibited the best antibacterial effects. ESI-MS analysis revealed that pectin hydrolysates with higher degradation degrees displayed better antibacterial activity. Interestingly, oligogalacturonic acid standards (DP ≤ 4) unexpectedly showed no antibacterial activity. FT-IR analysis suggested that hydrophobic groups might contribute to the antibacterial properties of the hydrolysates. It could disrupt cell membranes, leading to leakage of cellular contents and ultimately to bacterial death. These findings established theoretical foundation for developing citrus peel pectin-derived oligosaccharides as next-generation food preservatives, while guiding the value-added utilization and sustainable development of pectin-rich agro-industrial waste. Graphical abstract