Inhibitory Effect Of Sulfur-containing Flavors On Gram-negative Pathogenic Bacteria And Regulation Of Virulence Genes

With the development of instrumental analysis technology,more and more sulfur-containing flavors are detected in food.For example,there are more than 160 kinds of sulfur compounds in beef.The sulfur-containing spices have been accepted and valued by people because of their rich aroma,low threshold,safe and strong characteristic.Two kinds of flavors(sulfides and isothiocyanates)were selected and their antibacterial activities against two common gram-negative bacteria including Vibrio parahaemolyticus and Salmonella were investigated.And further investigated the effect of structure.The minimum inhibitory concentration(MIC)was determinated by broth dilution method,and the growth curve was obtained basing on OD600nm values.Vibrio parahaemolyticus tdh gene,is considered to be one of the most important virulence factors.TDH can quickly dissolve red blood cells,that is,Kanagawa phenomenon.It has hemolytic activity,enterotoxin activity and so on.The effects of sulfur-containing flavors on gene expression of major virulence gene tdh of V.parahaemolyticus were also studied by real-time PCR methods.Provided a theoretical basis for the application of sulfur-containing flavors.The results showed that when adjusted nine kinds of isothiocyanate flavors’concentration to 0.04 mol/L,Benzyl isothiocyanate(BZITC),3-Methylthiopropyl isothiocyanate(MTPITC),Phenethyl isothiocyanate(PEITC),Butyl isothiocyanate(BUITC)and 4-Pentenyl isothiocyanate(PTITC)have significant inhibitory effects against two tested bacteria(p<0.05).BZITC showed the strongest inhibitory effect with the MIC values of 9.54μmol/L and 2.44 mmol/L for V.parahaemolyticus and Salmonella,respectively.Methyl propyl disulfide(MPDS),Diallyl disulfide(DADS),Diallyl sulfide(DAS)and so on have significant inhibitory effects against two tested bacteria(p<0.05).DADS showed the strongest inhibitory effect.The MIC of DADS were 4.88 mmol/L and 19.5 mmol/L for Vibrio parahaemolyticus and Salmonella respectively.DADS inhibited tdh gene expression in a dose-dependent manner.In summary,BZITC and DADS have a good effect against two gram-negative pathogens.The presence of benzene group of isothiocyanates flavors has a certain impact on the antibacterial effect,and the presence of disulfide flavors and the allyl group maby enhance the antibacterial activities.These results suggest BZITC and DADS could be potentially applied as food preservaties.