Studies On The Inhibitory Effcct Of Allium Sativum Extracts Against Bacillus Cereus

Bacillus cereus is a common food-borne pathogenic microorganism and it could survivein terrible environment due to its spore. Garlic is a familiar seasoning in everyday life and itpossesses not only a good nutritional value but also antibacterial or bactericidal effect. In thispaper, we selected Bacillus cereus isolated from fermented bean curd as our research material,the growth characteristics of different Bacillus cereus strains as well as the inhibitory effect ofgarlic extracts on Bacillus cereus and its mechanism were studied systematically, which laidthe foundation for further applications.The primary models of Bacillus cereus grown in nutritional broth at37℃wereestablished. Using MMF model, Richards model and MMF model respectively to describe thegrowth change pattern of NO.1strains, NO.4strains and standard strain, the results showedthat the correlation coefficient （r2） of the three growth curves is above0.97, the fitting effectof NO.1strains was the best, all strains cultured for8hours stabilized basically; Bacilluscereus did not produce or produce very few spores within8hours, vegetative cellstransformed into spores in large quantities after12hours, under the same culture conditions,No.1strains and No.4strains were faster than standard strains in producing spores, in thesame time, the spores number order of the different strains: No.1strains> No.4strains>standard strains.By measuring the diameter of inhibition zone, the inhibitory effects of Allium Sativumextracts and Capsicum extracts on Bacillus cereus were discussed. All the tested strains weresensitive to aqueous extracts, ethanol exacts and acidic aqueous extracts from Allium sativum,the inhibitory effects enhanced in turn; Capsicum ethanol extracts also had inhibitory effecton Bacillus cereus, however, the inhibitory effect was weaker than that of Allium sativum.The volatile components in the garlic oil sample were determined by GC-MS. Theresults showed that17volatile substances were identified, including11sulfur compounds, thecontent of antibacterial substances, such as Allicin and Allitride, is about80%. Theantimicrobial activity of garlic essential oil against Bacillus cereus and its mechanism werealso studied. It was found that stock solution or diluted1000times with95%ethanol couldinhibit growth of three Bacillus cereus strains completely, the garlic essential oil with theconcentration of10^-4could controlled Bacillus cereus strains effectively and made them at orbelow10³cfu/mL. Using TEM to detect Bacillus cereus treated by garlic essential oil, it found that cells appeared distorted and deformed, membrane was melting like, the inner and theouter membrane were separated, some cells collapsed, garlic essential oil might change thepermeability of the cell membrane, thus affected the normal growth even caused death ofBacillus cereus.