Isolation,Detection And Characterization Of A Lactic Acid Bacteria Phage In Dairy Plant Environment

At present,phage is considered to be the most important biological entity on earth,and one of the key roles of phage is to balance the number of bacteria in each shared environment.However,in the dairy fermentation industry,phage is the main cause of fermentation.Furthermore,due to the blind suspicion of raw milk without anti-detection,rotation of the operation of the species,yogurt fermentation process control and other factors ignored the root cause of the mining.Now the detection method of lactic acid bacteria in China is mainly dependent on the traditional microbial method;it takes time and requires the known host bacteria to be tested.Therefore,it is urgent to adopt a quicker and simpler detection method to improve the speed and accuracy of lactic acid bacteria phage detection.In this research,a strain of Streptococcus thermophilus phage(named ST)was isolated from the samples collected from the factory environment.The physiological characteristics of the phage were studied,and the rapid detection method of the phage was established.The following conclusions were obtained:The effects of sample environment,culture temperature,culture time,number of samples enriched and the sample size on the phage ST separation were studied.The optimum growth temperature,optimum culture time and optimum sampling method of phage ST were explored.The phage is more prone to the environment.The results showed that the optimum growth temperature of phage ST was 370 ℃,and the phage samples were collected by adding the phage samples directly for 72 h.Phage more likely exist in the fermentation tank sewer,yogurt sewer and yogurt valve array and other environmental of plant workshop.The PCR reaction system was as follows: 2×MasterMix 25 μL,2 μL upstream primer,2 μL downstream primer,1 μL of template DNA and 20 μL of dd H2O;PCR reaction condition was as follows: 94℃ was prepared by PCR.Degeneration of 3 min,94 ℃ denaturation 45 s,57 ℃ annealing 30 s,72 ℃ extension 1 min,final 72 ℃ extension 7 min,a total of 35 cycles,the method of detection limit is 104 PFU / mL.The biological characteristics of the isolated phage of Streptococcus thermophilus were investigated.The morphology of the phage was observed,and the specificity and primary growth curve of the phage were observed.The stability of the phage at different ethanol concentration,different temperature and different pH treatment also were tested.The results showed the phage was specific and could only infect one lactic acid bacteria.The incubation period was 0-45 min,the cleavage period was 45-75 min,the breeding period was slow and the breeding period was rapid.After the cleavage period,the number of phage was not increase.The phage in the use of lower temperature and low concentration of ethanol treatment showed a certain resistance,only the temperature reached 90 ℃,ethanol concentration of 100 %,the pH below 3;the phage will have a greater degree of inactivation.