Isolation,Screening,Characterization And Safety Evaluation Of Enterococcus From Soy Sauce Mash

Enterococcus is a common lactic acid bacteria in fermented foods,and some of them can be used as potential starter culture.Soy sauce mash contains rich Enterococcus,which has not been well exploited and used.In view of this,we isolated and screened Enterococcus in soy sauce mash,and systematically studied their characteristics and safety,aiming to fully dig out Enterococcu resources,and to provide scientific theoretical basis for the development and utilization of soy sauce brewing starter.Enterococcus were isolated and identified from soy sauce mash by the agar plate method.Then their biological properties including growth curve,salt tolerance,acid resistance,acid producing,and antibacterial activity were investigated.Based on properties data,the strains with excellent comprehensive performance were screened.Meanwhile,PCR detection of virulence genes,amino acid decarboxylase test,indoles test,hemolysis test and drug resistance test were used to evaluate the safety of these strains.The main results are as follows:(1)Forty-three strains of Enterococcus were identified by hydrogen catalase test,gram staining,16 S r RNA sequence information comparison and phylogenetic tree.It contains forty strains of Enterococcus faecium and three strains of Enterococcus lactis.(2)The biological properties of forty-three Enterococcus strains identified from soy sauce mash were studied.The results showed that this strains grew to a stable phase within 12 h,and had good salt resistance,acid resistance and acid production ability.In addition,some strains inhibited the growth of Staphylococcus aureus.Among forty-three strains,E3,E15 and E39 exhibited the excellent comprehensive properties.(3)The safety of strains E3,E15 and E39 was evaluated.These strains displayed negative results on the tests of virulence factors,indole production and hemolysis activity.They were sensitive to several common antibiotics.The safety evaluation showed that the three strains were relatively safe.The characteristics and safety evaluation show that Enterococcus lactis E39 has excellent performance on the potential starter in soy sauce brewing.