Yeasts<\/strong>, like any living organism, carry in their DNA a set of innate responses that drive specific processes to meet their needs\u2014both as individual cells and as a population.<\/p>\n Their first mission is to colonize the environment they inhabit<\/strong>. That is why yeast will deploy every available resource to reach the highest possible population and outcompete other species. Producing new cells is a highly demanding process in terms of energy and nutrient requirements<\/strong>. <\/p>\n During the first hours, yeast prioritizes ATP generation from hexoses via the respiratory pathway<\/strong>, as it is far more efficient than fermentation. Carbon sources in grape must are abundant, so supply is not the limiting factor. <\/p>\n Regarding nitrogen needs, it has been demonstrated that yeast requires 150\u2013200 mg\/L of FAN<\/strong> (Free Amino Nitrogen) to reach adequate populations at Vmax. If grapes do not provide these initial levels, an early correction is required by adding organic or inorganic nitrogen compounds<\/strong>. Once established<\/strong> in the medium, yeast shifts its priority toward species survival<\/strong>. S. cerevisiae<\/em> has a complex sensor system that supports decision-making to ensure persistence as conditions change. After a few hours, it stops relying on respiration and switches to the fermentative pathway.<\/strong> <\/p>\n Because S. cerevisiae<\/em> is more firmly established and other yeast genera are highly sensitive to ethanol, those competing yeasts eventually disappear<\/strong>. This fermentation start is irreversible, and ethanol production will not stop until all sugar is consumed or the yeast dies. At LEV2050, everything we apply to our products and processes is based on scientific fundamentals, study, and experimentation.<\/strong> That\u2019s why we understand yeasts well\u2014what they need and when they need it. <\/p>\n Once fermentation has started, yeast rapidly consumes available FAN to build a high population.<\/strong> From that point on,<\/strong> supplying organic nitrogen sources becomes critical before yeast can no longer assimilate them<\/strong>. This limitation appears when oxygen is depleted and the first degrees of alcohol begin to develop. <\/p>\n Remember: amino acids enter the cell via symport transport coupled to H\u207a proton uptake.<\/strong> Eventually, as ethanol progressively weakens the membrane, proton influx becomes excessive. Yeast responds by closing controllable uptake pathways\u2014also preventing amino acid absorption. <\/p>\n For these reasons, it is essential<\/strong> to provide organic sources<\/strong> before reaching that point<\/strong>\u2014typically when density has dropped by 5\u201310 points.<\/strong> This organic nitrogen is stored in vacuoles as reserves that yeast will draw on as needed to renew protein structures. <\/p>\n Nitrogen needs at this stage are much lower than during multiplication: 10\u201315 mg\/L can be sufficient.<\/strong> This brings us to another key factor: the amino acid composition of organic nitrogen. <\/p>\n Yeast faces an increasingly toxic environment<\/strong>, so anything supporting survival is beneficial. Yeast can degrade amino acids to obtain elemental nitrogen and then synthesize new amino acids and, consequently, new proteins.<\/p>\n However, if yeast can directly incorporate amino acids that are used in protein structures, it saves the degradation-and-synthesis step. This relates to what we call auxotrophies<\/strong>\u2014and highlights the importance of knowing yeast preferences at this stage. <\/p>\n After more than 1,000 microvinifications and just as many aminograms<\/strong>, we gathered enough data to understand yeast nutritional needs at each stage. That science is what we embed into our nutrients.<\/strong> <\/p>\n<\/a>The mission of yeasts<\/h2>\n
<\/a>How does this process work? Here\u2019s the explanation: <\/h3>\n
Yeast nitrogen requirements<\/h4>\n
It is important to consider that yeast shows preferences for certain nitrogen sources. We know, for example, that ammonium is readily assimilated and that among amino acids, yeast prioritizes glutamate and glutamine. But that topic deserves its own dedicated discussion. <\/p>\n<\/a>Once yeast needs are covered :<\/h2>\n
<\/a>Fermentation onset<\/h3>\n
That is why it is so important\u2014preventively, before the onset of anoxic conditions<\/strong>\u2014that S. cerevisiae<\/em><\/strong> has sufficient selective<\/strong> or autotrophic reserves<\/strong> to remain viable until sugars are depleted. This is where the debate begins: different theories on when and how to feed yeast. <\/p>\n<\/a>When should yeast be fed?<\/h2>\n
<\/a>Supplying organic nitrogen sources<\/h3>\n
Amino acid composition of organic nitrogen:<\/h4>\n
<\/a>At LEV2050, we apply science to our nutrients<\/h2>\n