Bioethanol production: your guide to yeast nutrition and health

Yeast is the star of the show in bioethanol production. A crucial ingredient in the dry grind fermentation process, yeast helps convert sugars into ethanol and carbon dioxide.  Saccharomyces cerevisiae—or brewer’s yeast— is most commonly used in the dry grind process thanks to its tolerance to high ethanol concentrations, efficient sugar metabolism and high ethanol productivity. But this comes with a unique set of challenges.

Yeast cells have a finite replicative lifespan that is affected by genetics and the environment, so ensuring the right conditions is vital for yeast growth—and improving overall ethanol yield. The process is made even more complex by the fact that yeast undergoes three growth phases during fermentation: the lag, exponential growth and stationary phases. By better understanding the nutritional and environmental needs of yeast during these different stages, we can unlock improved ethanol production efficiencies. So, to help you get started, we have put together a mini guide outlining the primary factors which affect growth below:

The right nutrition

Carbohydrates

Glucose is the main carbohydrate source for yeast in the dry grind process, but the long starch chains must be hydrolyzed to make the glucose readily available to the yeast.

Nitrogen

Nitrogen has several usable forms for yeast, including ammonium ions, urea, amino acids and small peptides. However, each source has different levels of relative availability which may dictate fermentation progress.

Nitrogen

Nitrogen has several usable forms for yeast, including ammonium ions, urea, amino acids and small peptides. However, each source has different levels of relative availability which may dictate fermentation progress.

Vitamins and minerals

Providing an adequate mix of vitamins and minerals can alleviate some of the negative stress effects of fermentation, such as high alcohol and temperature.  

Water and oxygen/sterols and unsaturated fatty acids

Water and oxygen are both factors that influence yeast cell growth – but if sterols and unsaturated fatty acids are present, oxygen isn’t as critical. Achieving a delicate balance of these four nutrients is therefore key.

Environment

A wide range of environmental factors can affect yeast health – and must be considered for optimal growth. For example, a pH of between 3.5 and 5, as well as a temperature of 28-34°C is acceptable, but additional factors like microbial contamination, osmotic and nutrient stresses would still require monitoring.

Healthy yeast

Understanding the nutrients and environmental needs of yeast is crucial for achieving the healthiest growing yeast and the most successful fermentations. Ultimately, the best results will come from growing and producing as many healthy yeast cells for as long as possible.

Interested in further insights on better fermentation? Download the full guide on yeast nutrition and health today.