Study On The Screening And Preservation Effects Of Quorum Sensing Inhibitors Of Pseudomonas Fluorescens In Refrigerated Turbot

Quorum sensing(QS)of spoilage organisms,mediated by signal molecule is involved in food spoilage.Interfering with the corruption expression of QS system to inhibit corruption factor,provides a new direction for food preservation.The Cortex moutan(CM)extract was screened out to be a quorum sensing inhibitor by Chromobacterium violaceum CV026 biosensor detecting system from 21 traditional Chinese medicines(TCM).We could identify monomer,which has anti-QS activity,by isolating and purifying CM extract.As a research object,Pseudomonas fluorescens,a Specific Spoilage Organism(SSO),was isolated from refrigerated putrid Turbot.Biofilm,proteinase,siderophore,swarming and swimming motivity,combined with GC-MS analyzing species of AHLs,were assessed to study on its ability of spoilage and QS inhibition activity.Then sub-MIC of CM extract was used to study its fresh-keeping effect on Turbot block as a preservative.Finally,recombination of CM extract and conventional antimicrobial agents was used to study its compound fresh-keeping effect on Turbot block,which was look forward to provide a new-type idea for aquatic preservation from the perspective of corruption bacterial quorum sensing inhibitors.Main conclusions were shown as follows:1.With Chromobacterium violaceum CV026 as a reporter strain,fourteen out of 21 TCM yielded QS inhibition activity and CM extract possessed the best inhibition activity.The separation and purification assays demonstrated that CM extract has maximum absorption peak at 273 nm,containing characteristic group such as hydroxyl,benzene ring,methyl-and oxygen heterocycle.CM extract was isolated out three main absorption peak by HPLC-MS,they were gallic acid,paeoniflorin and paeonol,respectively.Paeoniflorin did not have QS inhibition activity,while gallic acid and paeonol both possessed QS inhibition activity,and the QS inhibition activity of paeonol was greater than gallic acid at the same concentration.2.Pseudomonas fluorescens could produce two kinds of AHLs(C4-HSL and C8-HSL),meantime the content of C4-HSL,main signal molecule,was obviously higher than that of C8-HSL.CM extract could reduce significantly the production of C4-HSL and C8-HSL and inhibit significantly the spoilage activity of Pseudomonas fluorescens in a concentration-dependent manner.It displayed mainly that CM extract could prevent its biofilm formation,destroy the structure of biofilm,thin the surface of biofilm with gap,decrease its proteolytic activity(p<0.05),reduce effectively the diameter of migration of swarming and swimming(p<0.05).Therefore,CM extract could interfere with QS system of Pseudomonas fluorescens and reduce its corruption ability by reducing the production of signal molecule.The inhibitory activity may be caused by gallic acid and paeonol of CM extract.3.CM extract,as QSI,could improve the quality of Turbot sterile block inoculated by Pseudomonas fluorescens at the condition of no bacteriostasis.Total viable counts of Turbot block dealt with 1 mg/mL CM extract,were not different from the control sample.However,the freshness index of sensory evaluation,pH,TVB-N,TBA and K value were lower than control sample at same time.In addition,CM extract could have no influence on fish colour.To sum up,we could conclude CM extract could reduce fat oxidation,delay deterioration,improve the quality of muscles and extend shelf-life for 2-3 d.Therefore,CM extract could be applied in the preservation of cold Turbot as QS inhibitor.4.Total viable counts of Turbot block dealt with CM extract(QSI)and tea polyphenol(preservative),were lower than other samples.Sensory evaluation,pH,TVB-N,TBA and K value were also lower than other samples.In addition,recombination of CM extract and tea polyphenol could have no influence on fish colour.To sum up,we could conclude recombination of CM extract and tea polyphenol could delay deterioration,improve the quality of muscles and extend shelf-life than control sample about 9 d,than CM extract processing sample about 6-7 d,than tea polyphenol processing sample about 2-3 d.Therefore,recombination of QSI and bacteriostatic agent used in aquatic preservation has certain feasibility.