Introduction

Yeast converts fermentable sugars into alcohol. Sugar levels, temperature, oxygen levels, pH, and nutrients in the yeast's environment all play an important role. Today, we investigate nutrition. Healthy yeast creates a higher yield and a faster ferment. So let's dive in deeper and find out what nutrients it needs in order to perform!

Why?

Why does yeast need nutrition? Doesn't it come fully functional? It does, but - just like you and me - yeast needs nutrients to keep going. And there is more. Yeast, in an oxygen-rich environment, so especially at the beginning of your fermentation cycle, multiplies. One yeast cell becomes two, then four, then eight, then sixteen, etc. Without additional nutrients, the available nutrition would have to be divided between more and more cells.

Nitrogen

Yeast Assimilable Nitrogen (YAN) is very important. During the first 72 hours of your fermentation, the yeast will absorb it. During the fermentation, YAN is used to synthesize proteins, amino acids, other building blocks, that are essential to the yeast and its ability to produce alcohol.

A lack of YAN leads to an increased production of glycerol at the cost of alcohol production. YAN deficiency can decrease total alcohol yield by up to 10%. Put differently, by adding enough nitrogen, the craft distiller can potentially increase his yield with 10%!

But there is more. A lack of YAN also results in less esters and acids being formed. If you are educated in Odin's Theory of Fermentation, you will immediately understand that this is bad for overall flavor development.

The optimal amount of nitrogen is 267 mg per liter. Amounts below 140 or above 400 mg per liter will result in non-optimal outcomes. The yeast may stall and stop producing alcohol all together.

To prevent such a situation from developing, add 0.6 grams of di-ammomium Phosphate (DAP) per liter.

Zinc sulphate

Zinc sulphate is another essential nutrient to yeast growth and performance. The yeast cells use it to grow. It is also a source of energy, via the production of NADH and NAD+. and it increases alcohol tolerance. Off the yeast, not of the consumer. ;)

Zinc improves the production of ethanol. Zinc ions help the yeast create vitamine B2, essential to yeast growth.

Zinc sulphate is absorbed during the first 48 to 96 hours of the fermentation. An ideal level is 0.4 mg per liter of fermentation. Values above 0.6 or below 0.1 mg per liter will result in the yeast stopping to function.

Add 0.0004 grams of zinc sulphate per liter.

Copper sulphate

Copper ions and zinc ions can react and form a superoxidedismutase. That word helps you win at Scrabble. It is also an enzyme that catches biradical oxygen atoms, that are toxic to the yeast, and turns them into O2, oxygen, which is exactly what it needs.

Copper ions help induce metallothioneïnesynthesis, which helps bind heavy metals, that would otherwise harm the yeast cell. It is also essential to the yeast's metabolism and growth.

Add 0.001 grams of copper sulphate per liter.

Procedure

Mash or otherwise mix substrate with water. Bring the mix to fermentation temperature. Add the above nutrients and mix them in. After that, add the yeast.

For more reading

Please see:

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3. Mendes-Ferreira, A., Barbosa, C., Lage, P. & Mendes-Faia, A. The impact of nitrogen on yeast fermentation and wine quality. Cienc. e Tec. Vitivinic. 26, 17–32 (2011).

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5. Albers, E., Larsson, C., Lidé N, G., Niklasson, C. & Gustafsson, L. Influence of the Nitrogen Source on Saccharomyces cerevisiae Anaerobic Growth and Product Formation. APPLIED AND ENVIRONMENTAL MICROBIOLOGY 62, (1996).

6. Mendes-Ferreira, A., Mendes-Faia, A. & Leao, C. Growth and fermentation patterns of Saccharomyces cerevisiae under different ammonium concentrations and its implications in winemaking industry. J. Appl. Microbiol. 97, 540–545 (2004).

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9. Renger, R. S., Hateren, S. H. van & Luyben, K. C. A. M. THE FORMATION OF ESTERS AND HIGHER ALCOHOLS DURING BREWERY FERMENTATION; THE EFFECT OF CARBON DIOXIDE PRESSURE. J. Inst. Brew. 98, 509–513 (1992).

10. Zhao, X.-Q. & Bai, F. Zinc and yeast stress tolerance: Micronutrient plays a big role. J. Biotechnol. 158, 176–183 (2012).

11. Zhao, X. Q. et al. Impact of zinc supplementation on the improvement of ethanol tolerance and yield of self-flocculating yeast in continuous ethanol fermentation. J. Biotechnol. 139, 55–60 (2009).

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13. De Nicola, R., Hall, N., Melville, S. G. & Walker, G. M. Influence of Zinc on Distiller’s Yeast: Cellular Accumulation of Zinc and Impact on Spirit Congeners. J. Inst. Brew 115, (2009).

14. De Nicola, R. & Walker, G. M. Zinc Interactions with Brewing Yeast: Impact on Fermentation Performance. J. Am. Soc. Brew. Chem. 69, 214–219 (2011).

15. Šillerová, S. et al. Preparation of Zinc Enriched Yeast (Saccharomyces Cerevisiae) By Cultivation With Different Zinc Salts. J. Microbiol. Biotechnol. Food Sci. 2019, 689–695 (2019).

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18. Walker, G. M., De Nicola, R., Anthony, S. & Learmonth, R. Yeast-metal interactions: impact on brewing and distilling fermentations.

Yeast Cell Division Caused Nutrient Deprivation ...

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