Abstract
The most important microorganisms contaminating milk, such as staphylococci, exert their influence by producing toxins and biogenic amines (BA). The purpose of this study was to evaluate the influence of cell-free supernatants (CFS) related to the probiotic strains of Lactococcus lactis and Bifidobacterium bifidum on the expression of BA-producing genes, histamine decarboxylase, and tyramine decarboxylase in staphylococci isolated from milk. Staphylococci isolates of cow raw milk were identified and isolated using standard methods. Samples containing these strains were analyzed by HPLC for BA production. Bacteria with target genes were treated with L. lactis and B. bifidum CFS, and the expression of target genes was measured by Real time PCR. Generally, 60 strains of Staphylococcus were isolated, and 90% of strains had HDC and TDC genes in genome. The levels of BAs were significantly higher on the second and third days after sampling compared with the first day (p <0.02). The analysis RT-PCR indicated that the under expression of target genes was statistically significant (P<0.05). This study showed that the use of probiotic bacteria can reduce the production of these amines and increase the quality of milk through reducing the expression of tyramine and histamine producing genes.
Keywords:
histamine; milk; probiotic; Staphylococcus; tyramine
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