The microbial population of wineries producing award winning wines from Priorat D.O.C. (Spain) were studied during a Ph.D investigation with the Rovira I Virgili University (Biotecnología Enológica de la Facultad de Enología de Tarragona - Spain). The main goal of this study was to select Saccharomyces cerevisiae yeasts that help shape the distinct Carignan & Grenache grapes from this terroir. The yeast Lalvin Clos is the result of this selection. The name refers to the enclosed area typical where the grapes are cultivated, that is typical of this appellation. A unique terroir & a unique yeast. The Priorat D.O.C. in the province of Tarragona (Spain) is a particularly unique area. The land is surrounded by steep hills and the grapes are planted on 100-700 m slopes. The unusual terroir is made out of a type of dark brown slate called ‘llicorella’. It is believed that this terroir gives the Priorat wines their characteristic minerality. The yeast population of this appellation was studied for 3 consecutive years in wineries where no starter cultures were ever used. The Lalvin Clos was found during this study to respect the varietals typicity and tolerate the fermentation difficult conditions of those wines, such as high alcohol, low nutrient availability and the ability to ferment over a wide temperature range. It has also been showed to be MLF friendly. It has been trialed successfully in varietals such as Grenache, Carignan, Syrah, Cabernet Sauvignon, Merlot and Tempranillo, resulting in wines respecting the varietal characters of each area, with complexity, minerality, and a good balance between structure and mouthfeel. Technical data sheet .