In the Netherlands, University of Groningen scientists think they have figured out why some yeast cells produce ethanol: yeast cells produce ethanol as a ‘safety valve’ to prevent overload when their metabolic operation reaches a critical level. The new theory, which was published in Nature Metabolism on 7 January, could have far-reaching implications, as it also explains why cancer cells waste energy by producing lactate, known as the Warburg effect.
Cells use nutrients like glucose to make new cells. But sometimes, some of these nutrients are wasted. For example, the yeast Saccharomyces cerevisiae, which is used to produce beer, breaks glucose down into ethanol rather than carbon dioxide.
By adding thermodynamics to a model with around 1,000 chemical reactions and combining it with experimental data, researchers were able to determine the Gibbs energy dissipation rate as a function of glucose uptake. At first, the Gibbs energy dissipation increases with increasing rates of glucose consumption, but then a plateau is reached—and at that point, ethanol production starts.