Purpose: To search the presence and expression of BA genes in bacteriocinogenic LAB, and to quantify this produced substances.
Methods: Eight Enterococcus and six Lactococcus previously isolated from raw goat milk and capable to produce bacteriocins were selected and submitted to PCR to identify genes for tyrosine (tdc), histidine (hdc) and ornithine (odc) decarboxylase. Their expression was identified using modified MRS (mMRS) agar containing the precursor amino-acids and a pH indicator. The production quantification was accessed by HPLC.
Results: None of the isolates carried the odc gene or produced putrescine. Seven Enterococcus and three Lactococcus were positive for tdc, and six Enterococcus and two Lactococcus were identified as tyramine producers using mMRS. Based on HPLC results, three Enterococcus produced high amounts of tyramine (maximum of 4.3 mg/kg) and only one Lactococcus produced 2.44 mg/kg of tyramine. However, one Enterococcus and one Lactococcus produced tyramine using mMRS, and both isolates did not present positive results for tdc. Only one Enterococcus carried the hdc gene, but did not produce histamine by mMRS or by HPLC.
Significance: The results demonstrated that bacteriocinogenic LAB strains are capable to produce virulence factors, such as BA. Also, Lactococcus isolates presented BA genes and were able to produced BA, even being usually considered as safe to be applied in foods. Finally, BA production should be quantified because only at high amounts can be a risk to human health.
Acknowledgments: CNPq, CAPES, FAPEMIG