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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.