The first time mushroom mycelium ' i transferred onto grain, that container of spawn is c ailed a Grain Master, or G1. The preferred containers for incubating Grain Masters are traditionally small glass jars or bottles, wi.h narrow mouths to limi; contan 'nant exposure. Since the Grain Master is used to generate 100 to 1000 times its mass, special attention is giiven to its purity. Otherwise, the slightest amount of contan ination is exponentially expanded with each step, not by a factor of 10, but by a factor of thousands! Molds have advantages over
Figure 106. Sterilization indicator test strips are placed into a few grain filled jars to test effectiveness of sterilization cycle. Note the letter "K" appears when sterilization has been achieved.
Figure 105. Giain-filied 1/2 gallon jars ready for loading into a commercial autoclave.
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mushrooms in that within two to four days every spore can send up hundreds of microscopic tree-like structures called conidiophores on whose branches are dozens more mold spores (SeeThe Mushroom Cultivator (1983) Chapter 13, pp. 233-317). Mushroom mycelium, on the other hand, typically expands as a linear exten sion of cells. In a jar holding thousands of kernels of grain, a single kernel of grain contaminated with a mold such as Penicillium surrounded by tens of thousands of kernels impregnated with pure mushroom mycelium makes that entire container of spawn useless for mushroom culture
A single 100 x 15 mm. petri dish culture can inoculate 4-20 cups of steri" ied grain. The traditional transfer method calls for cutting the must iroom mycelium into wedges or squares us-
ing a sterilized scalpel. Prior to this activity, the space where the transfers are to take place has been aseptically cleaned. The hopeful spawn maker has showered, washed, and adorned newly laundered clothes. Immediately prior to doing any set of inoculations, the cultivator washes his hands and then wipes them with 80% rubbing alcohol (isopropanol). If working in front of a laminar flow hood, the freshest, sterilized material is kept upstream with the mycelium directly downstream. The cultivator prioritizes items on the inoculation table by de gree and recetVness of sterility. The same attention to movement that was used to inoculate nutrient-filled petri dishes in Chapter 12 is similarly necessary for successful production of grain spawn. Attention to detail, being aware of ever/ minute movement, is again critical to success.
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