For growing mycelium for spawn production
and/or fruiting many types of grain can be used; rice, rye, milo,
wheat, rye grass seed. One spawn recipe uses bran and perlite as
a base. Again, many types of bran are acceptable. Rye grain is
one the most preferred grains for spawn production because it does
not tend to cake together as easily as does rice or wheat berries.
It is also one of the least expensive grains and is quite suitable
to mycelial growth. Rice tends to form solid cakes when sterilized.
These "patties" are excellent as fruiting tests for many
varieties of mushrooms. Caking can be avoided to some degree by
the addition of gypsum (calcium sulfate) (1-4 grams per 1/2-3/4
cup of grain) to the rice prior to sterilization. Another method
used to avoid caking is to precook the grain, mix in the gypsum
and then sterilize the blend.
The optimum moisture content for spawn grain is between 49-54%
(not counting the water in the uncooked grain). For example,
with rye grain use 1 cup of grain plus 3/4 cup of water (236
ml/cup) are placed into a one-quart jar. The lids are loosely
placed on the jars and the filled jars are sterilized at 15 psi
in a pressure cooker for 45-120 minutes. It is important when
using standard Mason jar lids to invert the inner dome so that
the lid does not seal when the jars cool. Sealed lids cause the
inhalation of ambient contaminants upon opening.
Calcium carbonate (chalk) can be added as buffer in the amount
of one to three grams per jar, but its use is optional. Stamets
recommends the addition of 1% (w/w) of a 1:4 chalk/gypsum combination.
That is one gram of the chalk/gypsum to one hundred grams dry
grain. When using these calcium buffers the volume of water should
be increased by 10%. Stamets also advises soaking the grain for
12-24 hours prior to heat sterilization. This initial wetting
will germinate heat resistant endospores. 4-10 hours soaking
should be adequate. With healthy grain, the seeds will begin
to sprout in 12-24 hours.
After the jars of grain have been sterilized, they are allowed
to cool. They can then be inoculated with pieces of mycelium
overgrown agar or with portions of sterile grain or sterile sawdust
grown spawn. Immediately after inoculation, the jars are shaken
to spread the mycelium throughout the grain. The jars are then
stored in the appropriate environment (humidity, temperature)
with the lids loose, to permit the exchange of gases. After 5-6
days, if growth seems slow or restricted to certain areas of
the jars, the jars are again shaken to disperse the cells. Sometimes
a third shake after 5 more days is required to ensure a saturated
growth. Once the grain is saturated with pure mycelium it is
ready to be used as inoculum for more grain, compost or sawdust
medium, or it can be cased to induce fruiting.
Casing: The term casing refers to a non-nutritive soil-like
layer which is put on top of a mycelium saturated grain or compost
media. The casing layer helps to induce fruit formation, support
the developing mushrooms and increase the fruiting yields. The
casing also provides the moisture essential to the developing
mushroom, and helps to maintain the appropriate humidity. A typical
casing recipe is: 1 part peat 1 part vermiculite 1 part lime
(calcium carbonate) This mixture is moistened to 70% water content
and is then applied to the beds or jars to a depth of 1-2 inches.
The casing is kept moist by light spraying, as needed; taking
care that water does not soak into the mycelium below. We will
discuss fruiting further in a later column.
Next: Growing Mushrooms on Compost
|
