Fig. 2

Safety assessment for Tetragenococcus halophilus EFEL7002. a Detection of genes related to biogenic amine production. Lane M, 1 kb DNA marker; lane 1, negative control with no template DNA; lane 2, positive control for the genes hdc (encoding histidine decarboxylase, 440 bp), and tyrdc (encoding tyrosine decarboxylase, 1100 bp) from Limosilactobacillus reuteri ATCC 23272 and Enterococcus faecalis KCCM 11729, respectively; and lane 3, EFEL7002. The 16S rRNA gene (1530 bp) was also amplified. The gel image was cropped because the gel contained samples that are not discussed in this study. b Thin layer chromatography detection of biogenic amines produced by T. halophilus EFEL7002. Biogenic amine standards of 5, 12.5, 25, and 50 μg/mL were prepared for the following: phenylethylamine, tyramine, spermine, histamine, spermidine, cadaverine, tryptamine, and putrescine. c Hemolytic activity of T. halophilus EFEL7002 was measured in brain heart infusion broth supplemented with 7% horse blood. Right, EFEL7002 strain; left, the positive control, Listeria monocytogenes, showing a clear zone around the cell drop. Abbreviations: PHE, phenylethylamine; TY, tyramine; SM, spermine; HI, histamine; SD, spermidine; CA, cadaverine; TRP, tryptamine; and PU, putrescine