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104 THE STOCK CULTURE LIBRARY
Culture slants are like "back-ups" in the computer
industry. Since every mushroom strain is
certain to die out, one is forced to return to the
stock library for genetically younger copies.
Good mushroom strains are hard to come by,
compared to the number of poor performers isolated
from nature. Hence, the Culture Library,
a.k.a. the Strain Bank, is the pivotal center of
any mushroom cultivation enterprise.
Preserving the
Culture Library
One culture in a standard 100 x 15 mm. petri
dish can inoculate 50-100 test tube slants measuring
100 x 20 mm. After incubation for 1-4
weeks, or until a luxurious mycelium has been
established, the test tube cultures are placed
into cold storage. I seal the gap between the
screw cap and the glass tube with a commercially
available elastic, wax-like film. (Those
test tube slants not sealed with this film are
prone to contaminate with molds after several
months of cold storage.) Culture banks inAsia
commonly preserve cultures in straight test
tubes whose ends are stuffed with a hydrophobic
cotton or gauze. The gauze is sometimes
covered with plastic film and secured tightly
with a rubber band. Other libraries offer cultures
in test tubes fitted with a press-on plastic
lid especially designed for gas exchange. The
need for gas exchange is minimal—provided
the culture's growth is slowed down by timely
placement into cold storage. Culture slants
stored at room temperature have a maximum
life of 6-12 months whereas cultures kept under
refrigeration survive for 5 years or more.
Multiple back-ups of each strain are strongly
recommended as there is a natural attrition over
time.
Ipreferto seal test-tube slants in plastic zip-lock
bags .Thme to four bags, each containing 4 slants,
Figure 83. Stock Cultures, in quadruplicate, sealed
in a plastic bag, stored in a cedar box, and refrigerated
for years at 35° F. (1-2° C.) until needed.
are then stored in at least two locations remote
from the main laboratory. This additional safety
precaution prevents events like fires, electrical failure,
misguided law enforcement officials, or other
naturni disasters from destroying your most valuable
asset—The Culture Library.
Household refrigerators, especially modern
ones, suffice. Those refrigerators having the
greatest mass, with thermostatic controls limiting
variation in temperature, are best for
culture storage. With temperature variation,
condensation occurs within the culture tubes,
spreading a contaminant, should it be present,
throughout the culture. Therefore, limiting temperature
fluctuation to 2-3° F. (1°C.) is crucial
for long term culture preservation. Furthermore,
when mushroom cultures freeze and
thaw repeatedly, they die.
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