KILLER YEASTS AND ALCOHOLIC BEVERAGES.

Mariano García-Garibay*, Lorena Gómez-Ruiz*, Alma E. Cruz-Guerrero*, Patricia Lappe ∇, Miguel Ulloa ∇

*Departamento de Biotecnología, Universidad Autónoma Metropolitana, Iztaplapa, México D.F. México ∇Laboratorio de Micología, Instituto de Biología, Universidad Nacional Autónoma de México, México D.F., México. E-mail: [email protected]

Keywords: killer yeasts, alcoholic beverages, pulque, wine.

Killer yeasts are able to produce a toxic protein killer strains and it had a remarkable ethanol which is lethal for sensitivity yeast strains. The killer tolerance, suggesting that this strain could be used effect of these toxins is due to they damage the for alcohol production. integrity of cell membranes, producing an inhibition of the active transport of several nutrients and other This Saccharomyces cerevisiae var. chevalieri strain effects. Killer yeasts are usually tolerant to the toxin was used for the elaboration of wine. The strain was that they produce. not killer but it displayed a wide tolerance when it was challenged to yeasts strains producers of killer The killer effect plays an important role in the toxins from K1 to K9. It resulted also highly tolerant ecology of the natural communities of yeasts, and to alcohol, SO 2, and high concentrations of glucose. also has great relevance in industrial yeast It grew well in a range of pH from 3 to 6.5, and processes, such as the production of alcoholic temperature from 26 to 41ºC. This yeast was used beverages. In any yeasts community the killer for the production of red wine (Cabernet Sauvignon), strains can inhibit the growth of sensitive strains, comparing the resulted product with a commercial and important implications have been observed in wine elaborated under the same conditions with the many beverages such as beer, wine, rum, pulque, usual (control) yeast. S. cerevisiae var. chevalieri cachaça, etc. Wild killer yeasts have been identified displayed faster fermentation rate in wine most, and as inhibitory to strains used as starters in the produced more alcohol than the control yeast. The production of alcoholic beverages; but, on the other resulted wines were sensory evaluated by a trained hand, the isolation, characterization and application panel, and the attributes were very similar for both of killer or killer-resistant strains has interesting products. A profile of volatile metabolites was biotechnological applications. obtained by MS-GLC: no significant differences were found in aroma compounds. It was concluded In our research group, we performed a study to that this strain of S. cerevisiae var. chevalieri know the incidence of killer strains in sugar cane isolated from pulque, demonstrated to be excellent molasses 1. We found that there was at least one wine yeast, resistant to killer toxins. killer strain in every sample that we analyzed. These strains eventually could inhibit industrial starters used in the production of rum or alcohol. We did not 1Bonilla-Salinas M., Lappe P., Ulloa M., García- find previous reports of killer strains of the species Garibay M., Gómez-Ruiz L. 1995. Isolation and Schizosaccharomyces pombe , but in our study we Identification of Killer Yeasts from Sugar Cane found some killer strains of this species. Molasses. Letters in Applied Microbiology 21(2), 115-116. In a similar study performed in agave sap (aguamiel) and pulque 2, a total of 16 strains belonging to six 2Estrada-Godina A.R., Cruz-Guerrero A.E., Lappe species were isolated from both products. One P., Ulloa M., García-Garibay M., Gómez-Ruiz L. strain of Saccharomyces cerevisiae (chevalieri ) 2001. Isolation and identification of killer yeasts from isolated from pulque which did not show killer Agave sap (aguamiel) and pulque. World Journal of activity was, on the other hand, resistant to other Microbiology & Biotechnology 17(6), 557-560.