Lactococcus lactis is used as a starter for fermented milk,particularly in traditional cheese products.In this study,the anti-Listeria monocytogenes(Lm)activity of 32 coast-isolated Lc.lactis strains was compared to t...Lactococcus lactis is used as a starter for fermented milk,particularly in traditional cheese products.In this study,the anti-Listeria monocytogenes(Lm)activity of 32 coast-isolated Lc.lactis strains was compared to that of the typical nisin A-producing strain NBRC 12007 using the overlay plate assay,to identify a novel Lc.lactis starter with beneficial properties.The 10 isolates exhibited anti-Lm activity greater than that of NBRC 12007.Among them,the isolate Nagasaki-SU6 was selected based on its anti-Lm and cow-and soymilk fermentation activity.Cow-and soymilk were inoculated with 7 log CFU/mL Lm,with or without fermentation using NBRC 12007 and Nagasaki-SU6 at 37◦C for 48 h.The fermentation and anti-Lm activities of Nagasaki-SU6 were significantly greater than those of NBRC 12007.In the case of soymilk fermented with Nagasaki-SU6,the Lm viable count decreased by 2.8 log CFU/mL The fermented samples were inoculated with Lm and stored at 10◦C for 14 d.In Nagasaki-SU6 fermented samples,Lm growth was suppressed both in fermented cow milk and reduced in soymilk.Whole genome sequencing revealed the presence of nisin Z and sucrose PTS pathway genes in Nagasaki-SU6.However,the type and number of drug resistance and virulence genes in Nagasaki-SU6 did not differ from those in the type strain and NBRC 12007.These results suggest that Nagasaki-SU6 can be used as a desirable starter not only in cow milk but also in plant-based milk alternatives.展开更多
文摘Lactococcus lactis is used as a starter for fermented milk,particularly in traditional cheese products.In this study,the anti-Listeria monocytogenes(Lm)activity of 32 coast-isolated Lc.lactis strains was compared to that of the typical nisin A-producing strain NBRC 12007 using the overlay plate assay,to identify a novel Lc.lactis starter with beneficial properties.The 10 isolates exhibited anti-Lm activity greater than that of NBRC 12007.Among them,the isolate Nagasaki-SU6 was selected based on its anti-Lm and cow-and soymilk fermentation activity.Cow-and soymilk were inoculated with 7 log CFU/mL Lm,with or without fermentation using NBRC 12007 and Nagasaki-SU6 at 37◦C for 48 h.The fermentation and anti-Lm activities of Nagasaki-SU6 were significantly greater than those of NBRC 12007.In the case of soymilk fermented with Nagasaki-SU6,the Lm viable count decreased by 2.8 log CFU/mL The fermented samples were inoculated with Lm and stored at 10◦C for 14 d.In Nagasaki-SU6 fermented samples,Lm growth was suppressed both in fermented cow milk and reduced in soymilk.Whole genome sequencing revealed the presence of nisin Z and sucrose PTS pathway genes in Nagasaki-SU6.However,the type and number of drug resistance and virulence genes in Nagasaki-SU6 did not differ from those in the type strain and NBRC 12007.These results suggest that Nagasaki-SU6 can be used as a desirable starter not only in cow milk but also in plant-based milk alternatives.
