In the article “Melatonin and Derived L-Tryptophan Metabolites Produced During Alcoholic Fermentation by Different Wine Yeast Strains,” Fernández-Cruz et al. (2017) considered the pathway of melatonin in wine yeasts of Saccharomyces and non-Saccharomyces strains. The study aimed to:
- Investigate whether the strains under examination can produce indolic compounds derived from L-tryptophan (L-TRP);
- Choose the strain that synthesizes the highest amount of various bioactive components;
- Determine when and how the bioactive components are formed during fermentation (Fernández-Cruz et al., 2017).
The investigators utilized Ultra-High-Performance Liquid Chromatography (UHPLC) and High-Resolution Mass Spectrometry (HRMS). They selected seven commercial strains of wine yeast, including five S. cerevisiae (Saccharomyces) and two non-Saccharomyces. The strains were then prepared and put under fermentation conditions to observe their synthesis of bioactive compounds. The data obtained during the UHPLC and HRMS of the strains was tested by one-way ANOVA analysis to establish the significance of the differences between the production of indolic compounds.
In total, eight compounds derived from L-TRP and L-TRP itself were assessed during fermentation. The compounds include 5-hydroxytryptophan (5-HTRP), serotonin (SERO), N-acetylserotonin (NACSERO), melatonin (MEL), 3-indolyl acetic acid (3-IAA), tryptamine (TRYPT), tryptophol (TOL), and L-Tryptophan ethyl ester (L-TRP EE) (Fernández-Cruz et al., 2017). Most importantly, MEL was seen during fermentation in five strains, two of which were non-Saccharomyces.
The occurrence of MEL was periodical and scattered, as it appeared and disappeared during the seven days. However, MEL’s synthesis was tied to the end of the exponential growth phase, when most of the L-TRP was gone. Also, the authors identified L-TRP EE as a new compound, establishing its close relation to MEL based on their identical exact mass. However, all strains were able to synthesize this compound in some capacity.
To conclude, the scholars found apparent differences in the metabolism of Saccharomyces and two non-Saccharomyces wine yeast strains. All strains produced different indolic compounds from L-TRP under the conditions of alcoholic fermentation, and MEL synthesis was not tied to Saccharomyces or non-Saccharomyces. The occurrence of MEL in non-Saccharomyces yeast and the identification of L-TRP EE during fermentation is especially novel and can become the foundation of further research.
Reference
Fernández-Cruz, E., Álvarez-Fernández, M. A., Valero, E., Troncoso, A. M., & García-Parrilla, M. C. (2017). Melatonin and derived L-tryptophan metabolites produced during alcoholic fermentation by different wine yeast strains. Food Chemistry, 217, 431-437. Web.