 
The budding yeast, Saccharomyces cerevisiae, has enjoyed a long and distinguished history in the fermentation industry. Owing to its efficiency in producing alcohol, S. cerevisiae is without question one of the world's most widely used commercial microorganisms. Yeasts have been designated as GRAS (Generally Regarded As Safe) substances by the U.S. FDA. By fermenting wine and beer, mankind's oldest domesticated organism made possible the world's first biotechnological processes. With the emergence of modern molecular genetics, S. cerevisiae has again been harnessed to shift the frontiers of mankind's newest revolution, genetic engineering. S. cerevisiae is at the forefront of many of these developments in modern biotechnology. As a result, its industrial importance has extended beyond that of traditional fermentation. The products of yeast biotechnologies influence many commercially-important sectors including food, beverage, biofuels, chemicals, industrial enzymes, pharmaceuticals, agriculture and the environment. Nevertheless, ethyl alcohol produced by yeast fermentation is likely to remain the foremost worldwide biotechnological commodity for the foreseeable future.
In the fermentation process yeast is used to convert grape juice into wine. Arginine, one of the most abundance amino acids in grape juice, is taken up by yeast as a nutrient and metabolized to produce urea. Urea then accumulates in the yeast cell until it reaches a critical concentration, at which point it is released into the wine. Urea spontaneously reacts with the alcohol in the wine to form Ethyl Carbamate. The chemical reaction between urea and ethanol is exponentially accelerated at elevated temperatures.
To a lesser extent citrulline, an amino acid, which is not incorporated into yeast protein, and is formed during arginine biosynthesis, can also serve as an Ethyl Carbamate precursor. Lactic acid bacteria can also be a source of citrulline under winemaking conditions. However, the key reaction for Ethyl Carbamate formation in wine is between urea and ethanol.
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