S. cerevisiae (Saccharomyces cerevisiae) are single-celled fungi which multiply by budding or in some cases by division (fission). Yeast fermentations comprise the oldest and largest application of microbial technology. Yeast physiology can be either obligately aerobic or facultatively fermentative. There is no known obligately anaerobic yeast. In pharmacy and chemistry, a large number of substances (Vitamins and enzymes) are extracted from this organism. In addition, some medications are now produced by manipulated yeasts, for example vaccines against Hepatitis-B surface antigen are produced by S. cerevisiae utilizing recombinant technology. The metabolism of Glycine, Serine and Threonine in S. cerevisiae is of vital importance as they use L-Serine or L-Threonine as sole nitrogen source for its survival. L-Threonine is generally synthesized from [...]