Tiramine Production by Lactic Acid Bacteria from Tucuman Wines Detected by a New Colorimetric Method
Silvana Cecilia Ledesma, María Cristina Rubio,
and Pedro Adrián Aredes Fernández*
*Facultad de Bioquímica, Química y Farmacia – Universidad
Nacional de Tucumán – CONICET, Ayacucho 471, San Miguel de
Tucumán/Tucumán/4000, Argentina (pedroaredes@conicet.gov.ar)
Biogenic amines (BA) are low molecular weight metabolites produced during vinification, primarily by lactic acid bacteria (LAB), that affect human health and the quality of the final product. Tyramine can produce hypertension by releasing the vasoconstrictor noradrenaline. Thirty bacterial isolates from the 2013 vintage in Tucuman-Argentina were screened to detect the tyrosine decarboxylase enzyme (TDC) in agar medium using Maijala procedures. Six isolates positive for TDC were grown in commercial decarboxylating Moeller broth at 28°C. The supernatants obtained after 96 hr incubation were assayed for tyramine quantification using a rapid, inexpensive, and simple new colorimetric method. This method was validated using a high-performance liquid chromatography technique for tyramine quantification through recovery of added tyramine. The gene coding for the enzyme TDC was detected in the selected bacteria by PCR. The TDC-positive isolates were identified by amplification, and sequencing of the 16S DNA ribosomal gene and typification was performed by RAPD. The new method shows a linear relationship (correlation coefficient = 0.9959) between the color intensity at 450 nm and tyramine concentration in the range 0 to100 mg/L. Six positive isolates with the TDC gene were detected. These isolates were identified as Lactobacillus paracasei and through RAPD were identified as four different strains (AT38, AT45, RA39, and RA49). The supernatants obtained from decarboxilating culture broth showed tyramine at different concentrations. The higher concentration of the amine was found in the supernatant obtained from L. paracasei AT38 (40.45 mg/L). These results evidence the presence of L. paracasei strains in Tucuman wines with a functional TDC gene. Additionally, an inexpensive and rapid method for tyramine quantification in culture medium was developed.
Funding Support: CONICET
