Denisa Mateus, Susana Sousa, Cláudia Coimbra, Frank Rogerson, and João Simões *
*Biocant, Parque Tecnológico de Cantanhede, Núcleo 04, Lote 8, 3060-197, Portugal (joao.simoes@biocant.pt)

Non-Saccharomyces yeasts, naturally abundant during the first phase of spontaneous alcoholic fermentation, possess enormous potential to enhance organoleptic wine complexity. These yeasts are particularly relevant in the production of port wine, since fermentation is stopped prematurely through the process of must fortification. This work aimed to isolate, identify, characterize and select non-Saccharomyces yeasts with biotechnological potential, from populations present in spontaneous fermentations, to be subsequently used in the vinification of port wine. To accomplish this goal, populations of non-Saccharomyces yeasts were isolated from different spontaneous fermentations of port wine. Species and strains were identified by PCR analysis, with selected yeast stains from the most representative strain groups subjected to phenotypic screening for relevant enological conditions associated with stress factors in must. A total of 500 non-Saccharomyces yeasts were isolated from eight identified species: Hanseniaspora uvarum, Metschnikowia pulcherrima, Kluyveromyces thermotolerans, Issatchenkia orientalis, Torulaspora delbrueckii, Rhodotorula mucilaginosa, Issatchenkia occidentalis, and Hanseniaspora osmophila. Interestingly, the clonal characterization evidenced a wide diversity of strains within each species. Phenotypic screening revealed that strains within the same species showed different levels of tolerance to the tested stress factors. Nonetheless, the strains that showed more promissory attributes belonged to M. pulcherrima, K. thermotolerans, H. uvarum, and I. orientalis. Sixteen of these strains were inoculated individually or in consortium in must, dominating fermentation until fortification. Remarkably, the resulting wines had equal or better organoleptic properties then wines produced with commercially available strains.

Funding Support: Portugal 2020-(SI I&DT) programme. POCI-01-0247-FEDER-017736; Ângelo Coimbra, S.A.; Symington Group.; Biocant