Construction of killer wine yeast strain

Area of Science:

• * Microbiology
• * Yeast Genetics
• * Fermentation Science

Background:

• * The killer phenotype in yeast is mediated by double-stranded RNA (dsRNA) plasmids.
• * Controlling spoilage yeasts is crucial for successful wine production.
• * Wine yeasts require specific traits for optimal performance in winemaking environments.

Purpose of the Study:

• * To engineer a wine yeast strain with the superkiller phenotype.
• * To evaluate the efficacy of the killer wine yeast against sensitive Saccharomyces cerevisiae strains.
• * To assess the killer activity under different pH conditions and in grape juice.

Main Methods:

• * Transfer of a dsRNA plasmid conferring the superkiller phenotype into wine yeast strains (Montrachet 522 and its derivative 694).
• * Utilization of cytoduction via protoplast fusion technique for plasmid transfer.
• * Growth assays comparing killer wine yeast with killer-sensitive strains in various media and pH levels.

Main Results:

• * The constructed killer wine yeast completely suppressed the growth of killer-sensitive Saccharomyces cerevisiae strains in yeast extract-peptone-glucose medium at pH 4.5.
• * The killer effect was reduced at a lower pH of 3.5.
• * Satisfactory inhibition of killer-sensitive cells was observed when the killer wine yeast was cultured in grape juice.

Conclusions:

• * Successful engineering of a wine yeast with a potent superkiller phenotype was achieved.
• * The killer wine yeast demonstrates effective control over sensitive yeast strains in conditions relevant to winemaking.
• * This engineered yeast holds promise for preventing spoilage and improving wine quality.