The use of mitochondrial mutants in hybridization of industrial yeast strains

Summary

A hybrid betweenSaccharomyces diastaticus, an industrial yeast strain of theSaccharomyces cerevisiae group, andSaccharomyces (Zygosaccharomyces) rouxii, an osmotolerant species, was constructed by protoplast fusion and characterized. The hybrid was similar to theS. diastaticus parent in its fermentation and sugar utilization patterns, but was tolerant of sugar concentrations that were higher than those permitting growth of theS. diastaticus parent. In addition, the DNA from the hybrid showed a much higher degree of reassociation with the DNA from theS. diastaticus parent than with that of theS. rouxii strain. The hybrid sporulated and produced viable spores, after being maintained in culture for a number of generations, and yielded clones which also sporulated and were therefore homothallic. The segregants from several asci formed by these hybrids were tested for their ability to increase the volume of a simulated bread dough and of a sweet dough, containing additional sucrose, and some of them had a much greater dough-raising capacity than either the original hybrid or a commercial baker's yeast, grown under similar conditions.