Yes, yeast is used in the making of soy sauce, the dark-brown, salty liquid that was first produced in Japan to make soy beans more palatable. The old way of fermenting soy sauce is in two stages (note: not all soy sauce is made in this way): The soy beans are soaked, cooked, and mixed with roasted wheat. Then the fungus Aspergillus oryzae is added and kept aerobically active for up to forty hours. A paste forms and is put in a deep vat; the yeast Saccharomyces rouxii and lacto-bacilli are added—both preventing further growth of the A. oryzae. A month later, a liquid forms—with large concentrations of amino acids, simple sugars, and some vitamins—to produce what we call soy sauce.

Biologists have studied Saccharomyces cerevisiae, a yeast used by bakers and brewers, for many decades because it offers valuable clues to aid in the understanding of how more advanced organisms work. For example, humans and yeast share a number of similarities in their genetic makeup. The DNA present in certain regions of yeast contain stretches of DNA subunits that are nearly identical to those in human DNA. These similarities indicate that humans and yeast both have similar genes that play a critical role in cell function.

In 1996, an international consortium of scientists from the United States, Canada, Europe, and Japan completed the genome of S. cerevisiae—the first eukaryotic organism to be completely sequenced. They found that the genome is composed of about 12,156,677 base pairs and 6,275 genes, organized on sixteen chromosomes; only about 5,800 are believed to be true functional genes. With their rapid generation time, yeasts continue to be the organism of choice to provide significant insights into the functioning of eukaryotic systems (plus, it’s now known that yeast shares about 31 percent of its genome with that of humans). Thus, since the first sequencing, regular updates have been made to two main databases: the Saccharomyces Genome Database—a highly annotated and cross-referenced database for yeast researchers—and the Munich Information Center for Protein Sequences (MIPS).