In Europe, the major raw material for yeast extract is primary grown high protein yeast (strains of Saccharomyces cerevisiae), which is grown on molasses based media. In the United Kingdom and in the United States, yeast extracts are also manufactured from debittered brewers yeasts (strains of Saccharomyces cerevisiae or Saccharomyces uvarum). Other raw materials in use are yeasts such as Kluyveromyces fragilis (fermented on whey) or Candida utilis (grown on high carbohydrate waste-products of the timber industry or on ethanol).

Yeast Extract is the water-soluble portion of autolyzed yeast. The autolysis is carefully controlled to preserve naturally occurring B-complex vitamins. Yeast Extract is prepared and standardized for bacteriological use and cell cultures, and is an excellent stimulator of bacterial growth. Yeast Extract is generally employed in the

concentration of 0.3% - 0.5%. Yeast Extract is typically prepared by growing baker’s yeast, Saccharomyces spp., in a carbohydrate-rich plant medium. The yeast is harvested, washed, and resuspended in water, where it undergoes autolysis, i.e., self-digestion using the yeast’s enzymes. Yeast Extract is the total soluble portion

of this autolytic action. The autolytic activity is stopped by a heating step. The resulting Yeast Extract is filtered clear and dried into a powder by spray drying.

With best regards

In some cases it is possible to replace YE with other nitrogen, vitamin and amino acid sources, which have defined composition, e.g. Yeast Nitrogen Base (Difco, Sigma, Invitrogen).

Thank you very much Tobias, I recommend this article about the ability of yeast extract in promotes cell growth. With best regards

http://www.hindawi.com/journals/er/2011/179819/

Minor element composition of yeast extract

http://jb.asm.org/content/84/4/869.full.pdf

Interesting patent. Method for the preparation of a yeast extract

http://www.google.com/patents/US5288509

Hello.

BD has some information. (http://www.bd.com/ds/technicalCenter/misc/br_3_2547.pdf)

Not an answer but another question. Does anyone have a link to the macronutrient content of YE?

In my case, the major concern as to the composition of YE is the total nitrogen, as I want to use it as one index for evaluating microbial growth. As some one provided the link above for the YE from Neogen, their yeast contains 9-12% in total nitrogen, and on the website of Sigma-Aldrich, there is one YE, which is claimed to have 11% in total nitrogen. Hope this would help you a little.

This is interesting because a little while ago I was developing a defined medium. I was wondering why the species I was growing in the particular media wasn't responding to thiamine pyrophosphate the way I thought it would. If yeast extract rich in Thiamine pyrophosphate (vitamin B1) then it would make more sense to me? I knew yeast extract provides nitrogen, amino acids, and carbon as well as some vitamins, but wasn't aware they were complex B.

How to escape YE for cultivation yeasts?

Is there any cheap solution instead of YE for cultivation YE? as in YPD medium we mostly use high amount of YE which in other sense is costly. Is there any solution to tackle the problem.

Not an answer, another question - has anybody looked at the organic and inorganic phosphate content of typical yeast extract? Of course there must be RNA and DNA, but how much might be intact vs. degraded?

I did just find a partial answer, for anyone interested: "Yeast extract was estimated to be 40% organic carbon, 5% potassium, 0.2% chloride, and 0.13% magnesium based on literature ... it was experimentally determined to be 10% nitrogen, 0.8% ammonia, 1.8% phosphorus, and 1% phosphate and to contribute 0.81 mg COD per mg yeast extract." DOI: 10.1039/C7EW00304H (Paper) Environ. Sci.: Water Res. Technol., 2017, 3, 1120-1131 (Research not done in a connection that would have occurred to me!)

Somewhat related, putting this here just so it's out there - the following paper includes the amino acid composition of casamino acids, as predicted from the protein sequence and (partially) verified experimentally.

Time-resolved amino acid uptake of Clostridium difficile 630Δerm and concomitant fermentation product and toxin formation

• Meina Neumann-Schaal
• Julia Danielle Hofmann
• Sabine Eva Will
• Dietmar Schomburg

BMC Microbiology201515:281

https://doi.org/10.1186/s12866-015-0614-2

Can yeast extract be an electron donor for bacterial cells?

Does anyone have this publication to share: Yeast extract: production, properties and components by R. Sommer?

Cheers

How do you then include yeast extract in a stoichiometric equation?

Yeast extract is a complex and widely used hydrolysate of yeasts. It provides nitrogenous compounds, carbon, sulfur, trace nutrients, vitamin B complex and other important growth factors, which are essential for the growth of diverse microorganisms. There are two different types of yeast extracts - the hyrolyzed yeast extract, also called yeast peptone, and the autolyzed yeast. The hyrolyzed yeast extract is produced by digestion of exogeneous enzymes or acid to hydrolyze the proteins. A yeast autolysate or yeast autolysate extract is made by fermentation of yeast to a concentration level where the yeast dies and the cells walls break. The proteases from the yeast itself start the digestion of the proteins and split them into peptides and amino acids. The insoluble portion is removed.

For more information about yeast extract I can recommend you following literature:

• Yeast Phisiology and Biotechnology (2000) Graeme M. Walker, published by John Wiley&Sons,
• Yeast Technology (1991) Gerald Reed and Tilak W. Nagodawithana, published by Van Nostrand Renhold

Kind regards

Azadeh Farzaneh short answer = probably not.

In my experience, when I grow my bacteria anaerobically with up to 2 g/L yeast extract in the media, it does not provide any growth unless I also add an electron donor. But some of these comments suggest there is around 40% organic carbon with some of that being sugars, so maybe other bacteria that I haven't worked with could use something there.

Hello Angel,

Thanks for bringing this question on the definition of a yeast extract. There are many answers that are really relevant and provide good insights. A general description of YE composition is a "complex mixture of nitrogen source (incl. amino acids, peptides), nucleic acids, carbohydrates, vitamins and trace elements.

I also want to emphasize there are many type of yeast extracts with diverse composition depending upon the yeast strain used, the yeast fermentation process and finally the lysis and DSP.

Please reach out to me for more precise information if needed.

Thanks!