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Yeast
From The Aquarium Wiki
Yeasts are microorganisms classified as Fungi. Over seven hundred species of yeasts have been described.
In the aquarium hobby the species of yeast often used is Saccharomyces cerevisiae, this yeast has been used in brewing and baking for thousands of years, and is also extremely important as a model organism in modern cell biology research. In the aquarium hobby we use this yeast to make CO2, to feed infusoria or to feed certain worm cultures like micro-worms. This item is widely available in the local shop and is usually very cheap.
It comes in a powder like form wrapped in silver paper lined packets to keep the yeast in a dormant state and it can last for a year in this way.
[edit] Making CO2
The yeast is simply added to sugar with warm dechlorinated water (around 20°C (68°F) ) to start the CO2 reaction. A by product of this reaction is that alcohol is produced and this eventually causes a pH shift which kills the yeast. So add Sodium bicarbonate to delay this shift and therefore produce CO2 for longer.
If you add a small amount of Marmite to the mixture then the yeast remains alive once the sugar is used up and you can restart the mixture by draining off the alcohol and adding more sugar and Sodium bicarbonate.
Companies have developed different strains of yeast which are more tolerant of the presence of the alcohol and one such strain is said to be Champagne yeast.
[edit] Links
- Saccharomyces cerevisiae
- Yeasts by Wikipedia
- DIY CO2 Injection: The Yeast Method
- How to make good long lasting CO2 from Yeast - A PowerPoint file. A free Powerpoint viewer or OpenOffice is required to view it.
