Anti-tyramine potential of Lactobacillus rhamnosus (LGG®) in cheese samples collected from Alexandria, Egypt

ABSTRACT Tyramine is generated by decarboxylation of tyrosine through tyrosine decarboxylase enzyme produced by bacteria in fermented food including different cheese types. In the current study, 27 cheese samples were collected from local markets in Alexandria, Egypt, and analyzed for the prevalence of tyramine-producing bacteria by PCR using degenerate primers (DEC5/DEC3). A probiotic, Lactobacillus rhamnosus LGG® was evaluated for its ability to inhibit tyramine production in these isolates by High-Performance Liquid Chromatography (HPLC) analysis. A total of 31 strains harbored tyrosine decarboxylase gene with the identification of novel tyramine-producing strains including Macrococcus caseolyticus, Bacillus vallismortis, Bacillus cereus, Staphylococcus sciuri, and Staphylococcus pasteuri. L. rhamnosus LGG® suppressed the growth of 81% of the studied tyraminogenic strains. It completely inhibited the tyramine production in B. vallismortis with a decline of 99.4% and 50% in tyramine production in S. saprophyticus, and S. pasteuri, respectively. These results indicated the promising application of L. rhamnosus to reduce tyramine production in cheese products, a goal that has been regarded as a challenge by manufacturers.