Targeting the quorum sensing (QS) system of Hafnia alvei, this study aimed to screen for quorum sensing inhibitors (QSIs) that exhibit synergistic effects with penicillin G acylase (PGA). The QS quenching activity of PGA individually and in combination with chlorogenic acid (CGA), phenyl lactic acid (PLA), or epigallocatechin gallate (EGCG) were assessed using the agar plate diffusion method. By analyzing bacterial spoilage phenotypes and calculating the Jin Zhengjun Q value, QSIs exhibiting a synergistic effect with PGA were selected. The results demonstrated that PGA (2.4 mg/mL), CGA (2.0 mg/mL), PLA (0.6 mg/mL), and EGCG (1.5 mg/mL) degraded C₈-HSL by (50.05 ± 0.12)%, (15.08 ± 0.10)%, (10.01 ± 0.11)%, and (8.02 ± 0.14)%, respectively. PGA combined with CGA, compared with PLA and EGCG, showed a higher degradation rate of 60.00% for C₈-HSL. Additionally, the combined use of QSIs proved to be more effective in inhibiting bacterial spoilage phenotypes than individual treatments. The combination of PGA with CGA, relative to its combination with PLA or EGCG, more effectively inhibited violacein production, H. alvei biofilm, and swarming, with inhibition rates of (74.19 ± 0.15)%, (62.28 ± 2.21)%, and (54.10 ± 1.72)%, respectively. PGA combined with PLA showed the strongest inhibitory effect on exopolysaccharide production, with an inhibition rate of (37.87 ± 1.39)%. PGA combined with CGA had a synergistic inhibitory effect (Q > 1.15) on violacein production and swarming motility and an additive inhibitory effect (0.85 < Q < 1.15) on biofilm formation, exopolysaccharide production, and swimming motility. The combination of PGA with CGA, compared with its combination with PLA or EGCG, showed a stronger synergistic inhibitory effect on the QS of H. alvei. This study provides a theoretical foundation for the development of novel, green, and efficient QSIs.

In this study, lactic acid bacteria (LAB) capable of degrading N-acyl-homoserine lactones (AHLs) signal molecules from Aeromonas sobria were screened from traditional fermented foods and identified. The locations and types of LAB quorum quenching enzymes were explored. The salmon spoilage ability of LAB was evaluated by measuring total bacterial count, water-holding capacity, thiobarbituric acid (TBA) value and total volatile basic nitrogen (TVB-N) content. The results showed that a strain capable of degrading almost 100% of A. sobria-derived AHLs, named as YF-8, was obtained using the 96-well plate method combined with the Oxford cup method. It was identified as Pediococcus pentosaceus. The quorum quenching enzyme of strain YF-8 existed in the extracellular supernatant and had AHL degradation activity under both acidic and neutral conditions. It was preliminarily identified as AHLs-acyltransferase. The crude extract of YF-8quenching enzyme did not affect the growth of A. sobria at sub-inhibitory concentrations of 2.0, 4.0 and 6.0 mg/mL. In addition, the crude extract could maintain the total bacterial count, water-holding capacity, TBA value and TVB-N value of salmon infected with A. sobria during storage. The results of this study are expected to provide a theoretical basis for the screening of microbial quorum sensing quenchers and aquatic product biopreservatives.