Quorum Sensing Inhibitory and Anti-Biofilm Activity of Essential Oils and Their in vivo Efficacy in Food Systems

The present study investigated the effect of the essential oils of Cuminium cymium, Murraya koenigii, Curcuma longa, Zingiber officinale, Myristica fragrans (mace and nutmeg), Trigonella foenum graceum, and Elettaria cardamomum on AHL-mediated quorum sensing and biofilm formation. Inhibition of quorum sensing (QS) regulated phenotypes by the essential oils at subinhibitory concentrations was investigated using the biosensor bacteria Chromobacterium violaceum (C. violaceum 12472 and C. violaceum CV026) and Pseudomonas aeruginosa PA01. Sub-MIC of essential oils was screened for inhibition of quorum-sensing regulated pigment production, motility and biofilm formation in the biosensors. The essential oil of M. koenigii showed the most promising QS inhibitory and anti-biofilm activity at a concentration of 0.02% v/v and hence was used for further studies. Anti-biofilm activity against food spoilage Pseudomonas species was studied by crystal-violet MTP method and fluorescence microscopy. The essential oil of M. koenigii at sub-MICs inhibited biofilm formation in the pseudomonads by inhibiting cell attachment, reducing metabolic activity and EPS production, and preventing biofilm maturation. Further, it was capable of delaying spoilage by psychrotrophic P. psychrophila PSPF19 in refrigerated milk. The major components present in M. koenigii essential oil were caryophyllene, caryophyllene oxide, cinnamaldehyde, α-, and β-phellandrene and eugenol. Application of M. koenigii essential oil and its constituents based on the quorum-sensing inhibitory and anti-biofilm activity would be a novel intervention strategy to enhance shelf life and food safety.