A detailed, illustrated technical review focuses on the definitive characteristics of yeasts and their commercial production. Topics include descriptions of: the asexual and sexual reproduction of yeasts; the 2 basic energy-yielding reactions of yeasts (anaerobic fermentation and aerobic oxidative respiration); and the characteristics of the different types of yeast, including active yeasts (used for fermentation and as sources of nutritional and flavor components) and inactive yeasts (non-fermentative "dried yeasts," used as nutritional, flavor, and bulking aids). The characteristics, use, and production of each of the active yeasts (Baker's yeasts, Brewer's yeasts, and yeasts for alcohol production) and inactive yeasts (dried Brewer's yeast and primary yeasts and yeast products) are individually discussed. Yeast derivatives also are covered.(wz)