Approaching Study on the Relationship Between Saccharomyces cerevisiae Production of Tyrosol, Hydroxytyrosol, and Melatonin with Volatile Compounds in Fermented Must

Yeasts are feasible and effective bioreactors and, therefore, there is a great interest in their industrial employment for the production of a wide range of molecules. In this study, the production by Saccharomyces cerevisiae of bioactive compounds such as hydroxytyrosol (HT), tyrosol (TYR) and melatonin (MEL) vs. volatile compounds in fermented must was studied. The concentration of the bioactive compounds HT and MEL in fermented must employing different yeast strains revealed that the higher the concentrations, the lower the amount of volatile compounds determined. This inverse correlation was especially remarkable with respect to the production of higher alcohols, especially 2-phenylethanol (2-PE) and esters. Furthermore, the employment of a modified Aro4p(K229L)S. cerevisiae QA23 yeast strain which overproduces HT, gave rise to fermented must also higher in 2-PE and their corresponding esters but with an outstanding less presence of other important esters such as ethyl hexanoate and ethyl octanoate. Both premises could point out that S. cerevisiae might have different approaches to handling cell stress/toxicity due to their nitrogen metabolism. One detoxifying pathway could be through the production of higher alcohols and these in turn to esters and the other be more related to synthesizing antioxidant molecules such as MEL and HT.

Automated summary

Yeasts are feasible and effective bioreactors, making them highly valuable in industrial production. This study investigated the production of bioactive compounds by Saccharomyces cerevisiae in fermented must. It was found that higher concentrations of hydroxytyrosol (HT) and melatonin (MEL) led to lower amounts of volatile compounds, especially higher alcohols and esters. The use of a modified yeast strain with increased HT production also resulted in higher levels of 2-phenylethanol (2-PE) and esters, but decreased levels of other important esters like ethyl hexanoate and ethyl octanoate. These findings suggest that S. cerevisiae may have different mechanisms for handling cell stress/toxicity related to nitrogen metabolism.