Torulaspora delbrueckii
David Horwitz

Torulaspora delbrueckii is a yeast related to Saccharomyces cerevisiae and used commercially to produce wheat beer. Yeast occur in nature on the surface of many plant foods. Barley has yeast on the surface of it's grain. Spontaneous fermentation of barley mixed with water probably produced the first beer. In fact, beer was being brewed in Babylonia by 6000 BCThere was a time when the activity of yeasts such as T. delbrueckii was mysterious and even superstitious. It has an outer cell wall, which gives the yeast structure and shape, and protects the important interior cell components. Yeast cells are actually very physically tolerant, but very sensitive to extreme pH, osmotic, temperature, pressure and chemical environments. The plasma membrane lies immediately interior to the cell wall. It is made of a lipid bilayer in which specialized proteins are interspersed. This membrane allows selective passage or transport of nutrients into, and fermentation by-products out of the cell. Brewer’s yeast contains up to 4 copies each of 16 chromosomes.  They very rarely recombine by mating with a separate brewing strain to create a crossbred strain or hybrid. Brewers yeast are extremely genetically stable in terms of sexual reproduction. They normally reproduce themselves by making exact duplicates of themselves.

Budding takes place when a mother cell gives birth to a daughter cell. There are no sons. Each new daughter cell is now capable of giving birth to another yeast cell, transforming them into mother cells as well. And so on... A yeast cell may give rise to many generations of daughters. Each time a mother cell gives birth, she develops a birth scar. When her cell wall has so many scars, she cannot reproduce and has trouble with passage of nutrients in and out of the cell. It is now time for her to pass on into yeast heaven. Below is a micrograph of a Saccharomyces cerevisiaecell budding, I couldn’t find a good picture of Torulaspora delbrueckii, Torulaspora delbrueckii is also commonly known as Weiss or weizen bier yeast, Saccharomyces delbruekii, or a mixture of this strain with a neutral strain of Saccharomyces cerevisiae. Torulaspora delbrueckii produces 4-Vinyl Guaiacol Decarboxylating Ferulic Acid (mainly from wheat) and this compound gives a spicy, clove like flavor to beer. The lower the fermentation temperature, the less phenolic flavor and the higher the temperature, the more of this compound is produced.

More about Torulaspora delbrueckii

Torulaspora delbrueckii has also been used in research involving Trehalase Activity and Trehalose content as a Freeze-tolerant Yeast.

There are two main sources from which it has been isolated and classified.

MAFF accession number

113811

Scientific name

Torulaspora delbrueckii (Lindner) Lindner

Source

sweet, jelly of bean

Source

Year of isolation

1984

Strain number

154-CA

MAFF accession number

113863

Scientific name

Torulaspora delbrueckii (Lindner) Lindner

Source

yeast, baking

Source

Year of isolation

1995/04

Strain number

NFRI-3863, CYL-5601

Here are some facts about beer yeast in general.

There are two main types of beer yeast .Saccharomyces cerevisiae is the top-fermenting type. Saccharomyces uvarum a.k.a. Saccharomyces carlsbergenisis is bottom fermenting.

ALE VS LAGER YEAST

LAGER
ALE
FERMENTS ON
  BOTTOM
 TOP
 FERMENTS GLYCERALDEHYDE
 YES
 NO
 FERMENTS MELIBIOSE
YES
NO
CAN METABOLIZE ETHANOL
NO
YES
 GROWTH AT 37 DEGREES C
NO
YES
 NORMAL FERMENTATION TEMP
 47-58 F
 60-70 F

Both are classified as Saccharomyces cerevisiae, but lager yests are still being called Saccharomyces uvarum or Saccharomyces carlsbergensis.

YEAST TAXONOMY

 GENUS

 SPECIES

 NAME

 SACCHAROMYCES

 CEREVISIAE

LATIN MEANING SUGAR-FUNGUS BEER

These are broken down into more specific categories based on fermentation temperature, flocculation (clumping together of yeast), ethanol production, alcohol tolerance, flavor of byproducts, degree of attenuation, specific gravity of media (beer), and more.

The ale strains tend to flocculate on the surface of the fermenting beer (top fermenting), they are generally mesophilic and some are psychrotolerent (13-24C). Lager yeast is psychrophilic (0-13C), and may be allowed to ferment for weeks to many months to give the beer smoothness. The final flavor of beer will depend a great deal on the strain of yeast and the temperature at which its fermented.

Wild yeast, yeast other than those normally used in lager and ale breweries, can be detected using selective media: -Copper Sulphate -LINS -Lysine Medium -YM + Actidione. Here are some examples: Torulaspora delbrueckii, Brettanomyces sp., Candida sp., Debaryomyces sp., Dekkera sp., Schizosaccharomyces pombe,

Hansenula sp., Kluveromyces marxianus, Pichia sp., Zygosaccharomyces sp., Saccharomyces sp.

More about brewing beer

Yeast needs to act quickly and in good health to prevent contamination by bacteria and other wild yeasts. The conditions a brewer has to take into account are

Temperature - too cold- activity lowers or stops; too hot- yeast will die or activity will be increased risk of bacterial contamination. yeast may produce off flavors: hydrogen sulfide (rotten eggs), acetaldehyde (grassy), solvent-like alcohols rather than, ethanol, butterscotch (diacetyl)

pH

most yeast enjoy 5 -5.5 (neutrophilic / slightly acidophilic) the byproducts of yeast reduce the pH to 4 -4.5

Nutrients: sugars, proteins, fats (oils): malnutrition = sluggish fermentation, mutation of yeast, poor sedimentation, off flavors and poor beer stability.

Mixing the beer media vigorously before closing the lid dissolves enough oxygen for the yeast to harness during respiration. Good initial Health (of yeast)(yeast need a head start) behavior varies with batch size, ingredients, temperature, contamination, type of wort used, amount of yeast used (mysterious yeast-bite), house flavors(at home-brewery), mixing yeast strains

Bacteria are helpful to yogurt, pickles, soy sauce…. not beer. They can pickle fermenting beer in as little as 24 hours. Lactobacillus is the most common invader, sours beer by producing lactic acid. Pediococcus is another nescience that loves wort and produces nasty off flavors. Acetobacter is less of a problem but is responsible for making vinegar out of the beer by producing acetic acid.

All of these factors help a brewer match the right yeast with the best environment and wort.

*Disclaimer - This report was written by a student participaring in a microbiology course at the Missouri University of Science and Technology. The accuracy of the contents of this report is not guaranteed and it is recommended that you seek additional sources of information to verify the contents.

 

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