At the Biotechnical Faculty of the University of Ljubljana, Department of Biology, the final conference and Management Committee meeting of the COST Action CA 19116 PLANTMETALS was held from September 17 to 20, 2024. Dr. Irena Budić-Leto participated as a member of the Action’s Management Committee. At the gathering, we presented preliminary research results related to the metabolism of certain non-Saccharomyces yeast isolates and the concentration of metal ions and antioxidant activity in the wine of the Maraština grape variety.
This study examined the impact of indigenous non-Saccharomyces yeasts on wine aroma through monoculture and sequential fermentations with Saccharomyces cerevisiae. The primary metabolites and volatile profiles of Maraština wine were modified solely by the tested yeasts, as the research was conducted on sterilized must of the Maraština variety.
This is the first comprehensive study on the yeast strains Metschnikowia chrysoperlae, M. sinensis/shanxiensis, Hypopichia pseudoburtonii, and Starmerella apicola in wine technology research. In monoculture, fermentations with the M. pulcherrima isolate resulted in the lowest ethanol concentration and higher total terpene concentrations. Pichia kluyveri produced a high level of thiols and esters, while Hanseniaspora guilliermondii increased the total concentration of C13-norisoprenoids.
Seven sequential fermentations revealed interactions between indigenous non-Saccharomyces yeasts and commercial S. cerevisiae yeast. P. kluyveri – S. cerevisiae fermentations had the most distinctive volatile profiles compared to controls, especially in C13-norisoprenoid and ester concentrations. M. pulcherrima in sequential fermentation reduced the production of volatile phenols. The isolates did not affect wine color and produced lower polyphenol concentrations thanS. cerevisiae. These results highlight different volatile profiles under the same winemaking conditions, emphasizing the biochemical role of each isolate in fermentation. This study represents a first step in understanding the positive roles of non-Saccharomyces yeasts in winemaking.
A targeted metabolomic UHPLC-MS/MS approach was used to investigate the influence of H. uvarum, H. guilliermondii, L. thermotolerans, M. pulcherrima, and P. kluyveri isolates, as well as two yeast species not previously studied in wine-M. chrysoperlae and M. sinensis/shanxiensis-on the metabolism of aromatic amino acids during monoculture and sequential fermentations with S. cerevisiae. The results were compared with fermentations using commercially available strains of M. pulcherrima, L. thermotolerans, and S. cerevisiae.
The results demonstrate the impact of individual yeast strains in different fermentations. These findings will enhance the understanding of tryptophan, phenylalanine, and tyrosine metabolism, through which indigenous non-Saccharomyces yeast contribute to the aroma of wine.
“Autochthonous non-Saccharomyces extra-cellular metabolism of tryptophan, tyrosine, and phenylalanine,” authored by Ana Boban, Urska Vrhovsek, Andrea Anesi, Vesna Milanović, and Irena Budić-Leto.
Our poster, which showcased the results on aromatic amino acids and their derivatives in samples of must and experimental wine of the Maraština variety, was awarded the best poster presentation at OpenGPB 2024. The indigenous yeasts isolated and identified in this project exhibit diverse metabolism that can contribute to the formation of the secondary aroma of wine. Particularly notable are the species Metschnikowia sinensis/shanxiensis and Hanseniaspora guilliermondii.
PhD studentAna Boban had a short oral presentation titled “Impact of Autochthonous Non-Saccharomyces Yeasts on Wine Aroma Complexity”, co-authored by Ana Boban, Urska Vrhovsek, Silvia Carlin, Vesna Milanović, Jasenka Gajdoš Kljusurić, and Irena Budić-Leto.
The presentation showcased the initial results of the aromatic profile of Maraština wine, produced using different autochthonous non-Saccharomyces yeasts in sequential fermentation with Saccharomyces yeast.
The results indicate the positive influence of certain genera and strains of yeasts on increasing the concentration of volatile metabolites in the wine’s aroma.
The paper explores the impact of autochthonous microbiota on the phenolic composition of Maraština wine, as discussed in the journal Food Research International (Q1, IF=8.1). Employing a metataxonomic approach,we investigated the microbiota during spontaneous alcoholic fermentation, identifying and molecularly characterizing 95 distinct taxa at the species or genus level. Additionally, we established and validated an HPLC-UV/VIS method for identifying and quantifying 21 phenolic compounds. Through in-depth bioinformatics analysis, correlations with specific phenolic compounds in the wine were founded.
We participated in the Reconnect science with the blue society (Blue-connect) project as part of the Europeans Night of Researchers, which took place on Semptember 29, 2023 at Prokurative in Split. We presented the research we are conducting as part of the WINE AROMAS project with the aim of popularizing science. We also showed different yeast strains and clarify role of microorganisms in alcholic fermentation closer to the interested public.
We participated at annual meeting of COST Action Plantmetals CA 19116 co-located with 1st JointInternational Conference of Biochemistry of Trace Elements & 21st International Conference of Heavy Metals in Wuppertal, Germany from Sep 5 to Sep 9, 2023 with a poster presentation of the study in collaboration with scientists from the Ruđer Bošković Institute:
Budić-Leto, Irena; Boban, Ana; Smokrović, Kristina; Maltar-Strmečki, Nadica: Antioxidant activity and metal micronutrient content of Croatian wines determined by electron spin resonance spectroscopy
We have published the results of enological and enzymatic characterization of different species of non-Saccharomyces yeasts, isolated and identified at the molecular level in this project which we have stored in the Institute’s collection. This work is a continuation of the previous research on the microbiota present in the Maraština variety that we published in the journal Food Research International (2022). We achieved part of the project goals with this two publications in the aims of elucidation of the specific mechanism of non-Saccharomyces yeasts in the formation of the primary and secondary wine aroma of variety Maraština.
More details about the results can be found at the link, and free access by the journal publisher has been enabled since August 11 until October 3, 2023.
We’re sharing with you the atmosphere from this year’s Researchers’ Night. 
