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Re: Aquatic Plants Digest V4 #1389
In regard to the question; " Do yeasts reproduce in reactors?"
There are many species of yeasts in existence. Some of them are domesticated
and most are wild species. Yeasts are plantlike and yet do not contain
chlorophyll and are classified as being single celled and often occurring in
colonies. The common domesticated yeast that we use in the reactors has
several strains. There is a bakers yeast that can be bought in the stores as
a "dry yeast" that comes in either foil packages or can be bought in small
glass jars as a larger bulk. In addition, this type can also be bought in a
semimoist cake in the dairy section of many food stores. Another variety is
often referred to as brewers yeast and is available through biological houses
and places that sell brewing supplies for the hobbyist as well. The yeasts
are lacking in chlorophyll and as we know them, derive their energy from
converting sugars into carbon dioxide and alcohol (this is the part of the
metabolism that we are most interested in since it is the Carbon Dioxide that
we need) Other complicated metabolic reactions are involved also. I have
used both forms in "yeast fermentation driven reactors".
When the alcohol in the mixture as a result of sugar fermentation reaches a
certain level, the yeast is inhibited in its activity and is either killed or
goes into a dormant state. The fermentation slows down as this level is
reached and eventually stops.
Yeast cells commonly produce quite rapidly in a matter of minutes at the
temperatures of our fishrooms if they are provided with sufficient energy
substrate (sugars and a proper aqueous solution at the proper pH-Hence the
common "yeast reactor recipe"). If you watch, them on a watermount slide
under the microscope, they grow new yeast cells out of their sides (called
budding) right under your very eyes. Therefore, they will produce new
billions in a culture overnight. You can sometimes see new yeast cells
growing out of a new bud before it has broken from the old parent cell.
Shaking an old and still active culture of yeasts and pouring a small amount
of it into a new culture will seed it with many-many-many cells which are
still active and you can continue this ad infinitum
When the alcohol in an old culture along with other products has accumulated
to a certain level, the culture will stop producing alcohol because the
culture has been poisoned by the toxicity of its own metabolic wastes and the
cells have been killed or gone into a dormant state. Because of the
foregoing, the culture stops producing carbon dioxide and must be renewed by
diluting these products with water (if it is diluted, adding new sugar etc.
will add new energy substrate which is usually necessary) or starting over
The commonly domesticated species of yeast has the scientific name
Saccharomyces cervissae (I hope I have the spelling correct here). This is
the same species which has a variety or varieties that commonly infests the
reproductive tract or mouth of some humans.
Elmer L Morehouse
PS-I am sure that this transmission will stimulate further discussion.