Production of melatonin and its isomers by Saccharomyces and non Saccharomyces yeasts

Melatonin may represent a bioactive component in Mediterranean diet because of its occurrence in some traditional plant foods and beverages. In order to ascertain a possible role of yeasts as melatonin-producers during winemaking, different strains were investigated in oenological conditions. Saccharomyces cerevisiae EC1118, IOC18-2007 and UMY255, Torulaspora delbrueckii CBS 1146, UMY196 and UMY336, and Zygosaccharomyces bailii ATCC 36947 were inoculated in YNB broth, white musts (Chardonnay, Moscato Bianco) and red musts (Croatina, Merlot), added or not with the precursor (tryptophan), and monitored during the fermentation. Both supernatant and cellular content were submitted to UPLC-MS analysis. All strains did not produce significant amount of melatonin without tryptophan enrichment of the medium. After supplementation with the precursor, only Z. bailii ATCC 36947 and T. delbrueckii CBS 1146 synthesized melatonin (37 and 30 ng/109CFU, respectively) after 48 h. However, five melatonin isomers were detected with different retention times. In all the samples, the isomer RT 2.61 was the most abundant and, in general, its concentration increased in tryptophan-enriched medium, reaching the highest levels in Z. bailii ATCC 36947 and T. delbrueckii CBS 1146 (439 and 1127 ng/109CFU, respectively) and S cerevisiae UMY255 (557 ng/109CFU). Therefore, the capacity to synthesize melatonin and its isomers seems to be a strain specific phenomenon.