Tyramine poisoning is caused by consuming of food with high level of tyramine (TY). This biogenic amine is produced through the tyrosine decarboxylation by tyrosine decarboxylase (TDC) enzyme derived by Gram-positive bacteria in food, especially Lactic Acid Bacteria (LAB). Bacterial TDC is reported to be also able to decarboxylate phenylalanine to produce another biogenic amine, namely phenylethylamine (PEA). The aim of this work was to study the ability to accumulate tyramine in model systems by different LAB strains, possessing the tyrosine decarboxylase (tdcA) gene. Lactobacillus brevis LB42, Lactobacillus rhamnosus C1112, Lactobacillus paraplantarum DBT 1411, Lactobacillus fermentum RAF15800, Enterococcus faecalis EF37, Enterococcus faecalis ATCC 29212 and Streptococcus thermophilus 1TT45 were grown in standard broth (namely MRS for Lactobacillus, M17 for Streptococcus and BHI for Enterococcus) and in Bover-Cid broth medium, added or not with 0.1% (w/v) of tyrosine and incubated at 37°C for 144 hours. Their growth curve were measured by optical density (DO at 600 nm) while their ability to accumulate tyramine were detected by HPLC analysis. All the tested strains were able to produce high levels of tyramine in all the conditions, with the exception of L. paraplantarum DBT1411 and L. fermentum RAF15800, which could accumulate very small amounts of this biogenic amine only after 144 hours in broths added with 0.1% (w/v) of tyrosine. Tyramine concentration increased concomitantly with the cell number with a relatively small further rise during the stationary phase. For all the tested strains the maximum level of tyramine (more than 500 mg/L) was reached in poor acidified medium added with tyrosine, except for L. rhamnosus C1112 which accumulate this compound with the same kinetics in MRS and in Bover-Cid medium. Moreover, the results showed that E. faecalis EF37, S. thermophilus 1TT45 and L. rhamnosus C1112 could accumulate also 2-phenylethylamine. In particular, E. faecalis EF37 produced more than 400 mg/L and 200 mg/L of this amine even after 48 hours of incubation in BHI and in Bover Cid (added with 0.1% tyrosine), respectively. The presence of LAB tyrosine decarboxylase positive strains in fermented food can be dangerous and the health risks associated with tyramine (also known as “cheese reaction”) should be avoided by using pure starter cultures without TDC. In addition, a deeper knowledge of TDC diffusion among the LAB having a role during ripening and of the factor affecting tyramine production is fundamental to limit intoxication due to this amine.
In vitro tyramine accumulation by different strains of lactic acid bacteria
TORRIANI, Sandra;FELIS, Giovanna;
2013-01-01
Abstract
Tyramine poisoning is caused by consuming of food with high level of tyramine (TY). This biogenic amine is produced through the tyrosine decarboxylation by tyrosine decarboxylase (TDC) enzyme derived by Gram-positive bacteria in food, especially Lactic Acid Bacteria (LAB). Bacterial TDC is reported to be also able to decarboxylate phenylalanine to produce another biogenic amine, namely phenylethylamine (PEA). The aim of this work was to study the ability to accumulate tyramine in model systems by different LAB strains, possessing the tyrosine decarboxylase (tdcA) gene. Lactobacillus brevis LB42, Lactobacillus rhamnosus C1112, Lactobacillus paraplantarum DBT 1411, Lactobacillus fermentum RAF15800, Enterococcus faecalis EF37, Enterococcus faecalis ATCC 29212 and Streptococcus thermophilus 1TT45 were grown in standard broth (namely MRS for Lactobacillus, M17 for Streptococcus and BHI for Enterococcus) and in Bover-Cid broth medium, added or not with 0.1% (w/v) of tyrosine and incubated at 37°C for 144 hours. Their growth curve were measured by optical density (DO at 600 nm) while their ability to accumulate tyramine were detected by HPLC analysis. All the tested strains were able to produce high levels of tyramine in all the conditions, with the exception of L. paraplantarum DBT1411 and L. fermentum RAF15800, which could accumulate very small amounts of this biogenic amine only after 144 hours in broths added with 0.1% (w/v) of tyrosine. Tyramine concentration increased concomitantly with the cell number with a relatively small further rise during the stationary phase. For all the tested strains the maximum level of tyramine (more than 500 mg/L) was reached in poor acidified medium added with tyrosine, except for L. rhamnosus C1112 which accumulate this compound with the same kinetics in MRS and in Bover-Cid medium. Moreover, the results showed that E. faecalis EF37, S. thermophilus 1TT45 and L. rhamnosus C1112 could accumulate also 2-phenylethylamine. In particular, E. faecalis EF37 produced more than 400 mg/L and 200 mg/L of this amine even after 48 hours of incubation in BHI and in Bover Cid (added with 0.1% tyrosine), respectively. The presence of LAB tyrosine decarboxylase positive strains in fermented food can be dangerous and the health risks associated with tyramine (also known as “cheese reaction”) should be avoided by using pure starter cultures without TDC. In addition, a deeper knowledge of TDC diffusion among the LAB having a role during ripening and of the factor affecting tyramine production is fundamental to limit intoxication due to this amine.
I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
