Screening Of Anti-phage Lactobacillus Plantarum Strains And The Inactivation Condition Of Phage

Lactic acid bacteria are a class of probiotics widely used in the fermentation industry and play an important role in food production and human health.However,lactic acid bacteria are susceptible to bacteriophage in the fermentation process,resulting in slowing or even failure of fermentation,causing serious economic losses to the fermentation industry.Therefore,phage contamination is a huge threat to fermentation companies.In this paper,Lactobacillus plantarum phage P1 isolated from abnormal fermentation broth and its host strain Lactobacillus plantarum LP were used as research objects,and effective methods for controlling phage were explored from chemical fungicides and screening of spontaneous anti-phage mutants,and the mechanism of resistance was analyzed.Seven strains of spontaneously mutated anti-phage Lactobacillus plantarum strains were screened by secondary infection method,and two nonlysogenic strains with stable resistance were selected,and their growth status and acid production characteristics were not significantly different from those of sensitive strains.The transcriptome analysis of Lactobacillus plantarum LP and anti-phage mutants B4 and B7 showed that the synthesis of EPS in B4 cells increased,which may be the reason for the resistance of B4 to phage,the mechanism belongs to the inhibition of phage adsorption;In B7,the utilization of glucose is reduced,the energy released is reduced,and the synthesis ability of DNA and RNA is decreased.So the ATP and pyrimidine available to the phage in the host are reduced,the genetic material cannot be replicated,and the corresponding protein cannot be synthesized,which may be the cause of B7 resistance to phage,the mechanism belongs to the category of abortion infection systems.Comparing the effects of 16 different methods for preserving Lactobacillus plantarum phage P1,the results showed that dimethyl sulfoxide was used as a stabilizer,and the phage-enriched solution was not filtered,the phage maintained high activity at low temperature,it is suitable for general laboratory to save phage.The inactivation of phage at different concentrations was studied using ethanol,isopropanol,sodium hypochlorite and peracetic acid as phage killers.The results showed that 75%ethanol could completely inactivate the phage for 30 min;50%isopropanol required 50 min to completely inactivate the phage;the inactivation effect of sodium hypochlorite increased with increasing concentration,the phage P1 was completely inactivated with 400 ppm sodium hypochlorite for 10 min or 200 ppm sodium hypochlorite for 20 min.When peroxyacetic acid was used as the sterilizing agent,0.15%,0.25%and 045%peroxyacetic acid completely inactivated the phage within lOmin,and the inactivation effect was excellent.From the standpoint of inactivation and economic cost,peroxyacetic acid can be used as a killer for phage.In this paper,we screened the anti-phage strain of Lactobacillus plantarum and explored its resistance mechanism.At the same time,we studied the preservation method and inactivation method of phage P1,in order to lay the foundation for better use of phage,understanding phage resistance mechanisms,and developing effective phage control measures.