Max Torrellas, Emilia Matallana and Agustín Aranda

This doctoral thesis, directed by Emilia Matallana and Agustín Aranda, compares various strains of non-Saccharomyces yeasts and analyzes their potential to constitute useful inocula for the industry. Part of the results of the thesis have been published in the journal Food Microbiology. The thesis was defended on October 2, 2020.

The main objective of the thesis, titled “Biochemical characterization of non-Saccharomyces wine yeasts and technological adaptation of their industrial production as active dry yeast” was to characterize the behavior of non-conventional wine yeasts and the optimization of their preparation as active dry yeast (ADL), the way in which they are used as inocula in the industry. For this, eight yeast strains from the non-commercial collection of the company Lallemand Inc and that do not belong to the Saccharomyces genus were analyzed. These unconventional yeasts are appreciated as they allow the production of wines with complex aromatic profiles and a lower alcohol level. Under the conditions of obtaining LSA, these strains showed very different biochemical profiles and response capacity to oxidative stress. The use of antioxidant agents of natural origin, as well as the technological adaptation of the biomass production process to the requirements of each species, have allowed the improvement of LSA production. The LSA obtained in this research was used in mixed fermentations with natural grape must and in biomass production optimization trials on a bioreactor scale. The wines obtained were analyzed to determine the effect of the presence of these yeasts on conventional chemical parameters and the production of volatile compounds. Non-Saccharomyces yeasts have a clear effect on the organoleptic profile of wines, without this being negatively affected by the different treatments applied during the propagation of the biomass.

Max Torrellas' doctoral thesis has been developed in the Industrial Yeast Biotechnology group of the I²SysBio under the supervision of Emilia Matallana (professor of Biochemistry and Molecular Biology of the University of Valencia) and Agustín Aranda (Senior Scientist of the CSIC). During the development of the thesis, Max Torrellas has been the beneficiary of a contract from the Research Personnel Training program and carried out a research stay at the Università degli Studi della Basilicata (Potenza). The panel was made up of Roberto Pérez Torrado (IATA Institute of Agrochemistry and Food Technology, CSIC), Mª Jesús Torija Martínez (Rovira i Virgili University) and Jordi Tronchoni (International University of Valencia), who rated the thesis as outstanding.