Inhibition of biofilm formation of Pseudomonas aeruginosa by an acylated homoserine lactones-containing culture extract

•Pseudomonas aeruginosa had a short-term growth in the presence of AHL-CCE.•Addition of AHL-CCE caused an increase in protease activity.•AHL-CCE had no effect on lipase activity.•Biofilm formation was inhibited by addition of AHL-CCE.

The objective of this study was to examine the effect of an acylated homoserine lactones-containing culture extract (AHL-CCE) on bacterial growth, enzyme activity and biofilm formation of Pseudomonas aeruginosa. Chicken breast muscle broth in which P. aeruginosa had been grown for 24 h at 20 °C was extracted with acidified ethyl acetate, the solvent was evaporated and the residue was dissolved in water and heated at 100 °C for 15 min. Thin-layer chromatography combined with Agrobacterium tumefaciens KYC55-based bioassays indicated the presence of C4-, C6-, C8- and C12-homoserine lactones in the extract. The addition of AHL-CCE to a culture of P. aeruginosa caused the bacteria to reach their highest count after 36 h whereas cultures without the extract required 72 h to reach their peak counts, but the maximum cell count was higher for the extract-free culture. No biofilm was detected when P. aeruginosa was cultured in chicken broth at 10 °C when the extract was present. Addition of extract reduced proteolysis of actin, troponin-T and tropomyosin by P. aeruginosa, but had no effect on lipase activity. Therefore, AHL-CCE can be used to reduce the bacterial growth time and inhibit biofilm formation; thus, benefiting food safety and quality.