Study On The Antibacterial Activity Of Garlic Juice To Bacillus Subtilis

The garlic is known as "natural broad-spectrum antibiotic",has strong bacteriostatic and bactericidal effect on the food spoilage and food pathogenic microorganisms,including Bacillus.They can cause food deterioration,food poisoning and some food-borne diseases.In this experiment,by crushing the whole garlic to get the juice,the antibacterial characterization to Bacillus subtilis——typical representative of Bacillus,was evaluated systemically;and the treatment temperature,pH and the processing time of garlic juice was optimized by response surface analysis; finally,garlic juice's inhibitory action at each stages of the spore was researched systemically.The study result are as following:(1) By the determination of the sulfur content of garlic in preservation periods,which showed that sulfur content was not obvious change with preservation in 4℃.Sulfur content was in the range of 0.198～0.215%.(2) The experiment of zone of inhibition showed the content of garlic juice in direct proportion to its antibacterial activity.The higher concentration of garlic juice,the larger zone of inhibition and the stronger antibacterial activity.By plate count and liquid assay method,confirmed garlic juice MIC is 0.4%,MBC is 1%.(3) 0.3%garlic juice could increase 12h of the lag phase,which showed that garlic juice obvious block germination of Bacillus subtilis.With the extension of treatment time,the garlic juice gradually decreased its antibacterial activity.When the concentration of garlic juice≥1%,the number of Bacillus subtilis did not increase reacted 16h,which showed that some Bacillus subtilis had been killed.The inhibitory effect at less than 16h was better than above 24h.(4) The antibacterial activity of garlic juice was highest at 35℃and gradually decreased at higher or lower 35℃.The antibacterial activity of garlic juice had not effect at 35℃.The results showed that heat treatment on garlic juice can decreased or eliminated the antibacterial activity,especially high temperature.Within treated garlic juice 24h,the antibacterial activity of garlic juice to Bacillus subtilis had not obviously change at 35℃.The optimum treatment time was 6h.After 6h,the antibacterial activity of garlic juice decreased,but slowly.When the pH was in the range of 3～8,the antibacterial activity of garlic juice to Bacillus subtilis had good effect at 35℃treated garlic juice 6h.The optimum pH was 6.5.When pH was 9.5,garlic juice was not effect.(5) The treatment conditions of garlic juice was optimized by response surface analysis.Through response surface model and ridge analysis,the result indicated that the optimum treatment conditions of garlic extract for inhibition of Bacillus subtilis was:temperature 35.1℃,time 7.2 h,pH 4.9.(6) Garlic juice had important influence function to sporulation of Bacillus subtilis.When the concentration of garlic juice and bacterial suspension respectively was 1%and 10~4 cfu/mL,the antibacterial time still exist at 48h.The higher concentration of garlic juice,the less spores;and the longer time of inhibited sporulation.The content change of dipicolinic acid(DPA) with sporulation indicated that growth of the DPA with treatment by garlic juice is later 12h than contrast.So,the influence of garlic juice to sporulation of Bacillus subtilis mainly delayed the process of sporulation.(7) The garlic juice had not obvious affect to germination of spore,within 2h of germination,2h of reaction time and 10%of the concentration of garlic juice.