Fermentation Symposium—Part I Valuable Techniques in the Genetic Manipulation of Industrial Yeast Strains.
Russell, I. and Stewart, G.G.
Techniques such as mutation, classical
hybridization, spheroplast (protoplast) fusion, and liposome-mediated
transformation are being employed to effect genetic changes in brewing
yeast strains. Each technique offers advantages and disadvantages, and a
combination is often necessary to achieve the desired objective.
Treatment of polyploid brewing strains with the compound benomyl
permitted the recovery of industrial strains harboring recessive
auxotrophic markers indigenous to these strains. Hybridization was
employed primarily to construct strains suitable for use as partners in
spheroplast fusion with brewing strains. The method of “rare mating”
involving karyogamy defective (Kar) strains was employed to
produce hybrids between laboratory-constructed strains with killer
activity and industrial polyploid strains. In yeast transformation
experiments with DNA and RNA encapsulated in liposomes, the liposomes
(synthetic microcapsules, prepared by reverse-phase evaporation)
protected entrapped DNA from nuclease degradation and also interacted
strongly with yeast spheroplasts under conditions favoring somatic
fusion and transformation.
Keywords: Fusion, Hybridization,
Liposomes, Mutation, Rare mating, Transformation