Beer Fermentation Tanks: Difference between revisions
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===Do the microbes that are present interact with each other?=== | ===Do the microbes that are present interact with each other?=== | ||
S. pastorianus naturally ferments for a longer time than ale yeasts which calls for the necessity of careful sanitization of the vat and area as to avoid contamination by wild microbes. Due to the presence of only a single population of yeast, microbe interaction is limited to how the yeast within the population grow. One very important trait of yeast for brewers is that at certain conditions, yeast flocculates. The conditions are ideally when the sugars within the wort have been converted to ethanol and available energy sources are low. Flocculation is the aggregation of yeast cells into clumps that sediment in the environment. With S. pastorianus, these clumps sink to the bottom of the tank, hence the name bottom-fermenting yeast. In brewing yeast, this is an asexual aggregation where the yeast prepares for dormancy by producing glycogen: the microbe’s preparation at the end of the stationary phase caused by starvation. In S. pastorianus, flocculation is controlled by a lectin-mediated mechanism and requires Ca+. Lectin is recognized by mannan receptors on yeast cells, and so the presence of mannose blocks this mechanism. Unlike with ale yeasts, flocculation of S. pastorianus, is not affected by the pH of the environment. [http://www.pubmedcentral.nih.gov/picrender.fcgi?artid=167332&blobtype=pdf (3)] | |||
===Do the microbes change their environment?=== | ===Do the microbes change their environment?=== | ||
Revision as of 22:17, 26 August 2008
Description of Niche
Where located?
Physical Conditions?
What are the conditions in your niche? Temperature, pressure, pH, moisture, etc.
Influence by Adjacent Communities (if any)
Is your niche close to another niche or influenced by another community of organisms?
Conditions under which the environment changes
Do any of the physical conditions change? Are there chemicals, other organisms, nutrients, etc. that might change the community of your niche.
Who lives there?
Ale Fermenting Yeast
Which microbes are present?
You may refer to organisms by genus or by genus and species, depending upon how detailed the your information might be. If there is already a microbewiki page describing that organism, make a link to it.
Are there any other non-microbes present?
Plants? Animals? Fungi? etc.
Do the microbes that are present interact with each other?
Describe any negative (competition) or positive (symbiosis) behavior
Do the microbes change their environment?
Do they alter pH, attach to surfaces, secrete anything, etc. etc.
Do the microbes carry out any metabolism that affects their environment?
Do they ferment sugars to produce acid, break down large molecules, fix nitrogen, etc. etc.
Lager Fermenting Yeast
Which microbes are present?
Ideally during the fermentation step in beer brewing, the only microbe present is the specific strain of yeast that the brewer uses. The most common yeast used for brewing lager is Saccharomyces pastorianus (also called Saccharomyces carlsbergensis) (1). These are cold, bottom fermenting yeast (as opposed to the top fermenting yeast for ales). They ferment in a temperature range of 7-15°C (45-59°F) (2). Because of the lower range they ferment at a slower rate, resulting in less foam and thus when the yeast flocculates, it settles to the bottom of the tank.
Are there any other non-microbes present?
There are no non-microbes living in a beer fermentation vat (preferably).
Do the microbes that are present interact with each other?
S. pastorianus naturally ferments for a longer time than ale yeasts which calls for the necessity of careful sanitization of the vat and area as to avoid contamination by wild microbes. Due to the presence of only a single population of yeast, microbe interaction is limited to how the yeast within the population grow. One very important trait of yeast for brewers is that at certain conditions, yeast flocculates. The conditions are ideally when the sugars within the wort have been converted to ethanol and available energy sources are low. Flocculation is the aggregation of yeast cells into clumps that sediment in the environment. With S. pastorianus, these clumps sink to the bottom of the tank, hence the name bottom-fermenting yeast. In brewing yeast, this is an asexual aggregation where the yeast prepares for dormancy by producing glycogen: the microbe’s preparation at the end of the stationary phase caused by starvation. In S. pastorianus, flocculation is controlled by a lectin-mediated mechanism and requires Ca+. Lectin is recognized by mannan receptors on yeast cells, and so the presence of mannose blocks this mechanism. Unlike with ale yeasts, flocculation of S. pastorianus, is not affected by the pH of the environment. (3)
Do the microbes change their environment?
Do they alter pH, attach to surfaces, secrete anything, etc. etc.
Do the microbes carry out any metabolism that affects their environment?
Do they ferment sugars to produce acid, break down large molecules, fix nitrogen, etc. etc.
Current Research
Enter summaries of the most recent research. You may find it more appropriate to include this as a subsection under several of your other sections rather than separately here at the end. You should include at least FOUR topics of research and summarize each in terms of the question being asked, the results so far, and the topics for future study. (more will be expected from larger groups than from smaller groups)
References
1. “Saccharomyces pastorianus”. Wikipedia. 7 August 2008.
5. “Diacetyl”. Wikipedia. 16 August 2008.
6. “Laagering FAQs”. Midwest: Homebrewing & Winemaking Supplies. 2005
Edited by Daniel Stromwall, Andrea Lin, and Chrissta Maracle; students of Rachel Larsen
