摘要
Using hard cheese made from yak milk as the research subject,we isolated and identified amine-producing strains through selective media,amino acid decarboxylase tests,high-performance liquid chromatography,and 16S rDNA analysis.Further,we investigated their biogenic amine production characteristics by altering pH,NaCl concentration,and free amino acid concentration.The results identified 10 amine-producing strains:6 Enterococcus durans strains,1 Enterococcus faecium strain,2 Lactococcus lactis strains,and 1 Leuconostoc mesenteroides strain.These strains produced tryptamine,phenethylamine,putrescine,cadaverine,and tyramine,with Enterococcus showing the highest amine production,reaching 1439 mg/L.The environmental conditions had varying effects on the strains.The amino acid concentration has the greatest impact on the amine production capacity of Enterococcus and Enterococcus faecium,followed by pH,with salt content having the least effect.The lowest amine production was observed at a pH of 6,while Enterococcus exhibited the highest amine production of 1773.74 mg/L at an amino acid concentration of 2 g/L.The biogenic amine content of Lactococcus lactis showed significant increases with rising salt and amino acid concentrations.Amino acid concentration significantly impacted the amine production ability of Leuconostoc mesenteroides,with biogenic amine content increasing significantly as amino acid concentration rose.However,high salt concentrations inhibited its growth and amine production ability.
基金
the National Natural Science Foundation of China for providing us with financial support(grant number:31860449).
