The Influence Of Environmental Factors On The Production Of Tyramine From Enterococcus Faecium

Biogenic amine is a kind of low molecular nitrogenous organic compound,which inevitably existes in food, especially for food fermentation, The proper amount of biogenic amines is beneficial to the physiological function of the human body. However, excessive intake will be toxic to the human body, with people's concern about food safety and safety awareness improving, more and more researches on biogenic amines are also studied. The change of environmental factors can affect the yield of biogenic amines.In order to reduce the production of biogenic amines, we take a enterococcus faecium high yield of tyramine isolated from Chinese Yellow Wine Qu as experimental materials, Effects of different environmental factors on the formation of biogenic amines from the phenotype to genotype was studied,expected to provide a basis for the reduction of biogenic amines in food.we studies effects of different environmental factors on the growth and yield of tyramine, determined by UV spectrophotometry and HPLC liquid chromatography.Then Preparation of crude enzyme liquid by ultrasonic fragmentation method, The effects of sugar content, temperature, pH, alcohol content and 5-PLP on enzyme activity were studied,Finally, through the fluorescence quantitative PCR technology research on environmental factors on the expression of tyrosine decarboxylase gene mRNA was studied.The results showed that the different amount of glucose and tyramine had little effect on the cell growth. However, the higher the concentration of glucose, the greater the change of the yield in the later stage of stable stage. Tyrosine promote the production of the tyramine as a precursor.Temperature increased, the density of bacteria and the content of tyramine would increase. Acidic condition was not conducive to the cell growth, but biogenic amine production gradually increased with time, The alcohol content has a certain inhibitory effect on cell growth and the production of tyramine.Biogenic amine is mainly composed by decarboxylation of amino acid, Therefore this thesis focuses on the effects of environmental factors on the activity of tyrosine decarboxylase experiment, The experiment showed that the amount of sugar added in 15g/L?at 40??5-PLP in 0.4g/Lwhen the enzyme activity was highest. Under acidic condition, the enzyme activity was higher, and the excess alcohol had inhibitory effect on the enzyme activity.Experiments showed that environmental factors significantly influence the expression level of tyrosine decarboxylase gene.The lower the temperature, the lower the expression of tdcA. The expression of genes in acid condition showed increasing trend with time. The greater the amount of tyrosine, the more expression of the gene, alcohol has an inhibitory effect on the expression level of genes. The effect of glucose on the expression of the gene is not very obvious, but the expression level was higher at 10g/L, and the effect was more significant in the late fermentation stage.