Construction of a cDNA-based K1/K2IK28 Triple Killer Strain of Saccharomyces cerevisiae

Manfred J. Schmitt*, Gerhard Schernikau¹

Angewandte Molekularbiologie der Universität des Saarlandes, FR 13.3, Gebaude 2, 0-66041 Saarbrücken, Germany
¹Institut für Mikrobiologie end Weinforschung, Johannes Gutenberg-Universität Mainz, D-55099 Mainz, Germany

Article history:
Received September 10, 1997
Accepted November 24, 1997

Key words:
S. cerevisiae, killer toxin expression vectors, triple killers

Summary:
By transforming a natural, dsRNA-based K1 killer strain of the wine yeast Saccharomyces cerevisiae with two multi-copy (2µ) vectors carrying cDNA copies of the K₂ and K₂₈ preprotoxin/immunity genes, a triple killer strain has been constructed that (i) simultaneously secreted three different killer toxins [Kl, K2, K28], (ii) expressed functional toxin immunities, and (Hi) exhibited a strong and significantly broader killing spectrum than the single killer derivatives. Both plasmids were shown to be self-selective under conditions where the triple killer was cultivated in YEPD medium at pH - 4.7. It is proposed that recombinant K₁/K₂/K₂₈ triple killers should be able to predominate in mixed yeast cultures and therefore might be useful in industrial wine fermentations to prevent stuck fermentations and/or killer yeast contaminations.

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