Protoplast fusion as a means of producing new industrial yeast strains.

The ability of the yeast Saccharomyces cerevisiae to produce ethanol and carbon dioxide from carbohydrates has been exploited by man for thousands of years. During its brief existence protoplast fusion has already become an invaluable tool for investigating the molecular genetics of yeast, as well as an important part of the arsenal of genetic manipulations available to develop new strains. In the case of industrial strains, a mating reaction is usually lacking. Protoplast fusion overcomes this barrier and allows for the genetic analysis of commercially valuable traits. A major block toward broader applicability of fusion is that hybrids becomes more unstable as the genetic backgrounds of the parents diverge. As greater progress in overcoming this problem is made, fusion, by itself and in conjunction with classical hybridization, will become increasingly important in the development of new strains. The incorporation of cytoplasmic elements into yeast protoplasts has the potential to vastly expand the array of biochemical reactions performed by yeasts, thereby increasing the importance of this microbe to mankind.