New research project on microbial consortia of wine

Establishment of microbial consortia for the improvement of wine quality and stability

Reference PID2019-108722RCB-C33, Spanish Ministerio de Ciencia e Innovación. Leader reaserchers: Mª Jesús Torija & Gemma Beltran. 2020-2023.

During alcoholic fermentation (AF), yeasts can synthesize, from aromatic amino acids, compounds of special interest such as higher alcohols and esters, but also some bioactive compounds that can contribute to the quality and stability of wines, such as melatonin (MEL), serotonin or hydroxytyrosol (HT), among others (aromatic amino acid-derived compounds, AADC). This project aims to deepen the potential impact of these molecules on the sensory properties together with their possible antioxidant and antimicrobial effect on wine. 

In the previous projects (BIOACTIYEAST and SYNBIOFERM), we have improved our knowledge about the synthesis of these bioactive molecules (mainly MEL) by yeasts during AF. We could observe that MEL is synthesized by yeasts during the lag or early exponential phase, but there was a gap between intracellular production and secretion to the extracellular medium, during the exponential or stationary phase. Our results showed that during this period MEL is bound to some glycolytic enzymes, only in yeasts with high fermentative capacity. The interaction of MEL with these proteins suggested the presence of a glycolytic complex, and our hypothesis is that MEL can act as a positive or negative regulator of this complex to channel the flow to the fermentative metabolism.

 

Therefore, different yeasts (Saccharomyces and non-Saccharomyces (NS)) and different physiological conditions (fermentation vs. respiration) were used, as well as tdifferent yeast mutants, in order to decipher the metabolic role of MEL in yeasts. Likewise, our results also showed that the presence of MEL increased the proportion of NS at the end of fermentation. In addition, contrary to what we observed in individual fermentations, higher extracellular levels of MEL were detected when a mixed inoculum of Saccharomyces and NS was used, pinpointing towards an effect of the microbiota present during fermentation in the synthesis of AADC. 

 

For this reason, the main objective of this project is to exploit the great metabolic diversity of yeasts and lactic acid bacteria (LAB) to increase the concentration of these bioactive molecules in wines. Therefore, we will first select the strains with the highest AADC synthesis capacity, to be then used for the design of microbial consortia. In some cases, yeasts will be improved by non-GM techniques in order to maximize this AADC production. In the designed consortia, microbial, metabolic and molecular interactions will be evaluated during fermentation, using different inoculation strategies (inoculation ratios, with and without cell contact). These selected consortia will be tested on a laboratory scale to determine the optimal oenological conditions for increasing the production of AADC in wines. Finally, the impact of this higher concentration of AADC on wines will be analyzed in terms of organoleptic quality and stability (antioxidant and antimicrobial).