Development of new strains for the food industry

This review examines the desired characteristics and possibilities of genetic manipulation of industrial yeasts. Brewing, wine, and distillers' yeasts are characterized by good utilization of sugar, alcohol tolerance and production, flavor and aroma, flocculation, fermentation rate, cropping ratio, ability to utilize trisaccharides, dextrines and starch, rapid onset of fermentation, nonfoaming fermentation, and low H2S production. The characteristics required for a good bakers' yeast include high potential glycolytic activity, ability to adapt rapidly to changing substrates, high invertase activity, high potential maltose fermentation rate and in terms of dough fermentation, storage ability, and osmotic resistance to salts and sugars. In all of these cases, the major desirable factors are under genetic control and hence are potentially subject to improvement by genetic manipulation. However, this control is thought to be governed by several, in most cases, unidentified genes. So, although most genetic techniques developed for laboratory yeasts are potentially applicable to the study and improvement of the properties of industrial yeast strains, traits such as homothallism, aberration in mating behavior, polyploidy, aneuploidy, poor sporulation and poor spore viability, etc., make conventional hybridization and isolation of single clones more difficult.