Screening And Characterization Of Phage P2 Resistant Lactobacillus Plantarum Strain

A virulent bacteriophage P2,previously isolated from a slow liquid fermentation using Lactobacillus plantarum,and its host Lactobacillus plantarum IMAU10120,were using as researching objects.Then,the spontaneous mutant anti-phage strain was screened out by secondary culture method.To find the differences between the mutant strain and wild strains,the probiotic characteristics,adsorption characteristics and fermentation characteristics were compared.The results were described below:(1)A spontaneously mutated bacterium,P2-resistant Lactobacillus plantarum,was screened.The bacterium exhibited complete resistance to phage P2 and stable inherity.Mitomycin C and UV induction indicated that the mutant strain could be considered as a non-lytic bacterium.(2)Using in vitro digestion experiments,the mutant strain was shown to exhibit resistance to bile salts,gastric acid and gastrointestinal juice.Microbial survival rates at pH 3.0 and 8.0 were c.90%.(3)The adsorption rate of phage P2 to both mutant and wild bacterial strains was greater than 97%,indicating that the adsorption receptor sites did not change.Moreover,there was no significant(P>0.05)effect on the host cell's physiological state with regards to phage adsorption capacity.The bacterial cell wall of mutant and wild bacterial strains were purified by glass bead mechanical method.Phage adsorption decreased significantly(P<0.05)after the host cell wall was treated with trichloroacetic acid or lysozyme indicating that the receptor sites may be associated with teichoic acid or teichoic acid-peptidoglycan polymers.(4)The fermentation time taken for soybean milk using either the wild or the mutant strain was about 19h.In addition,there were no significant(P>0.05)differences in the fermentation properties and sensory characteristics between the two fermentations.It would appear that the anti-phage strain could be used as a commercial starter culture.In this paper,a L.plantarum IMAU10120 mutant strain,was isolated from a phage-containing P2 fermentation.The mutant strain is effective against the infection of phage P2.Moreover,through probiotic and fermentation characteristics experiments,the domesticated mutant strain possesses the advantage of the commercial product of the sensitive strain,which increases the possibility of replacing the sensitive strain with the mutant strain.This experiment provides theoretical basis and data support for breeding anti-phage engineering bacteria,in order to reduce the threat of phage contamination in industrial production environment and increase the stability of related products.