Killer Yeasts: Incidence in the Ecology of Spontaneous Fermentation

¹ Departamento de Agricultura, Universidad de La Rioja, Avda. de la Paz, 105, 26004 Logroño, La Rioja, Spain
² Centro de Investigación y Desarrollo Agrario de La Rioja, P.O. Box 433, 26080 Logroño, La Rioja, Spain

Email: ana-rosa.gutierrez{at}daa.unirioja.es

The occurrence of the killer character was studied in 1320 yeasts isolated from 12 wineries of the Rioja DOCa, Spain, at different stages of spontaneous fermentation, for both white and red wines. The objective of the study was to investigate the importance of the killer phenotype in vinification at different wineries. Killer, neutral, and sensitive strains were found among the Saccharomyces cerevisiae isolates, while the killer phenotype was absent from the non-Saccharomyces cerevisiae strains. The distribution of the killer character was linked to the production area (Rioja Alta, Rioja Baja, and Rioja Alavesa) and to the production technology used (vinification with destemming/crushing and carbonic maceration). The only killer strains found were in the Rioja Baja. In the carbonic maceration vinifications, almost 100% of the strains were sensitive. Monitoring of this killer character was carried out over five years at the winery of the Centre for Research and Agricultural Development of La Rioja with the following results: Saccharomyces cerevisiae strains with different phenotypes coexist at the different fermentative stages, and the dominant phenotype varies with the year. In addition, genetically identical strains were detected with different killer phenotypes, perhaps indicating that the killer character is of lower technological importance than has been previously supposed.

Key words: Killer, Saccharomyces cerevisiae, spontaneous fermentation, carbonic maceration