Greets All/Richard
 
Richard - you asked about my suggestion that one replenish the sugar
in the spent yeast and aerate it and whether this would not just
increase alcohol prodution, and secondly as to whether the sludge is
still alive or if it has been killed by the brewing byproducts and
lack of food at the end of the brewing proccess.
 
Large breweries here, and I gather this is common around the world
reuse yeast for six or seven batches of beer, after which it gets a
bit sluggish - this is the stuff I suspect beekeepers get sold - and
which I suspect is nutritionally less useful than good vital yeast.
 
Between batches many breweries will aerate the yeast, acid wash it
and heat it, in a specific order to kill of bacteria (yeast is acid
resistant down to about pH1.8 - 2.0) and after this the yeast is
aerated and fed a bit of sugar - using the sugar as a carbon source
and oxygen it is able to replenish it's stores of various fats
including gamma linoleic and linolenic acid which are essential
stored products in young emerging bees which are about to synthesize
wax (Hepburn et al, 1990 ish - I can look this up if anybody needs
it exactly). The yeast is once again vital and can brew another batch
or two - and I suspect this yeast is ten times more valuable to a bee
than the spent stuff which has lipids that are about as useful to a
bee as cooking oil.
 
As far as the yeast dieing is concerned - yeast is difficult to kill.
The strain I work with can sit at the bottom of a flask for three
weeks at low pH, room temp, no sugar, no oxygen and still remain
vaguely alive.
 
The heating proccess - it is both to rid the slurry of alcohol, to
kill the yeast - but hopefully not damage the nutritious stuff.
(Interestingly some strains of yeast can produce alcohol even while
being aerated - the Crabtree effect - it would depend on the brewery
whether they had a strain which did this or not)
 
I don't know what
bees alcohol tolerance is, but suspect that lightly fermnted nectar
makes them a bit ratty and unreasonable as here on humid days when
certain upward cupping sweet flowers are open the bees can be quite
unreasonable, and on similar days when they aren't flowering, but
other things are the bees are fine.
 
Keep well
 
Garth
 
Garth Cambray           Camdini Apiaries
15 Park Road
Grahamstown             Apis mellifera capensis
6139 South Africa
 
Time = Honey