Depending upon the species, three to six weeks pass before the bags are placed into the growing room Before moving in the blocks, the growing room has been aseptically cleaned. After washing with bleach, I tightly close up the room after for 24 hours and turn off all fans. The residual chlorine becomes a disinfecting gas permeating throughout the room, effectively killing flies and reducing mold contaminants. A day after chlorine treatment, fans are activated to displace any residual gas before filling. Additional measures prior to bleaching include replacing old air ducting with new, the changing of air filters, etc.
By spacing the bags at least 4-5 inches apart, the developing mushrooms mature without crowding. Sufficient air space around each block also limits mold growth. Galvanized, stainless steel and/or epoxy coated, wire mesh shelves are preferred over solid shelves. Wood shelves should not be used because they will eventually, no matter how well treated, become a site for mold growth. Farms which do use wood trays either chemically treat them with an anti-fungal preservative to retard mold growth or construct them from redwood or cedar. I know of no studies determining the transference of toxins from chemically treated trays into mushroom fruitbodies.
any wood decomposers can be grown on alternative I substrates such as cereal straws, corn stalks, sugar cane ba-| gasse, coffee pulp, banana fronds, seed hulls, and a wide variety of I | other agricultural waste products. Since sources for hardwood by-1 products are becoming scarce due to deforestation, alternative j substrates are in increasing demand by mushroom cultivators. How- j ever, not all wood decomposers adapt readily to these wood-free j i substrates. New mushroom strains that perform well on these alter- ; native substrates are being selectively developed. j
The more hearty and adaptive Pleurotus species are the best ex-I amples of mushrooms which have evolved on wood, but readily j j produce on agricultural waste products. When these materials are j supplemented with a high nitrogen additive (rice bran, for instance), simple pasteurization may not adequately treat the substrate, and sterilization is called for. (Without supplementation, pasteurization usually suffices.) Each cultivator must consider his unique circumstances— | juxtaposing the available substrate components, species, facilities, and market niches—in their overall system design.
Growing the Oyster Mushroom, Pleurotus ostreatus, on straw is less expensive than growing on sterilized sawdust. In contrast, Shiitake, Lentinula edodes, which barely produces on wheat straw is best grown on wood-based substrates.* When both straw and sawdust are difficult to acquire, alternative substrates are called for. Mini-trials are encouraged before substantial resource are dedicated to any commercial enterprise, encourage readers to formulate new blends of components which could lead to a breakthrough in gourmet and medicinal mushroom cultivation.
Here is a basic wood-free formula for the cultivation of wood-decomposing mushrooms. A nitrogen supplement, in this case rice bran, is added to boost yields. As discussed, the substrate must be heat-treated by any one of a number of methods to affect sufficient sterilization.
Alternative Fruiting Formulas
100 lbs. (45.5 kg.) ground com cobs, peanut shells, chopped roughage from sugar cane bagasse, tea leaves, coffee banana, saguaro cactus, straw, etc.
10 lbs. (4.6 kg.) rice Iran or approximately
2.5 lbs extracted soybean oil 4 lbs. (1.8 kg.) gypsum (calcium sulfate) 1 lb. (.45 kg.) calcium carbonate 100-140 lbs. (45-64 kg.) water or as requires The amount of calcium carbonate can be al tered to effectively raise pH, offsetting any inherent acidity. The components are mixed in dry form and wetted until a 70-75% moisture content is achieved. The mixture is loaded into bags and immediately heat-treated. Should the bags sit overnight, and not autoclaved, contaminants proliferate, making the mixture unsuitable for mushroom cultivation.
The methods described here for the cultivation of mushrooms indoors on straw can be extrapolated for cultivating mushrooms on chopped cornstalks, sugar cane bagasse, and many other agricultural waste products. In contrast to wood wastes, which should be sterilized, I believe most unsupplemented agricultural by-products are better pasteurized using steam or hot water baths. Pasteurization typically occurs between 140-180° F. (60-82° C.) at atmospheric pressure (1 psi). Sterilization is by definition, above the boiling point of water, >212° F. (100° C.), and above atmospheric pressure, i.e. >1 psi. A hybrid treatment, which I call atmospheric sterilization or "super pasteurization" calls for the exposure of substrates to prolonged, elevated temperatures exceeding 190° F. (88° C.) for at least 12 hours. (See Figure 137.) In any case, a carefully balanced aerobic environment must prevail throughout the incubation process or competitors will flourish.
Readily available, inexpensive, needing only a quick run through a shredder (and sometimes not even this), wheat straw is ideal for both the home and commercial cultivator. Straw is a "forgiving" substrate for the small to mid-size cultivator, accepting a limited number of contaminants and selectively favoring mushroom mycelium. Growing on straw is far less expensive than growing on sawdust. Many cottage growers enter the gourmet mushroom industry by first cultivating Oyster mushrooms on straw. Wheat, rye,
* Several patents have been awarded in the cult'vation of Shiitake on composted[ -,vood-free substrates. Although fruitful, wood-based substrates are still preferred by most Shiitake cultivators.
cultivating gourmet mushrooms 183
rice, oat and sorghum straws are the best. Hay, resplendent with abundant bunches of seed kernels, should not be used as the grain kernels tend to contaminate. However, limited numbers of grain kernels generally boost yields. Royse (1988) found that yields of Oyster mushrooms from wheat straw are enhanced by the addition of 20% alfalfa without increasing the risk of contair:nat;on. Alfalfa by itself is "too hot" to use because of its elevated nitrogen content. Straw supports all the gourmet Oyster mushrooms, including Pleurotus citrinopileatus. P. cystidiosus. P. djamor, P. eryngii- P. euosmus, P. ostreatus&ndP. pulmonarius. Other mushrooms, King Strophari i (Stropharia rugoso-annulata), Shaggy Manes (■Cop sinus comatus), the Paddy Straw (Volvariella volvacea), and Button (Agaricus spp.) mushrooms also thr-e on straw-based substrates, often benefiting from modest supple-
mentation. The specifics for cultivation of each of these species are discussed further on, in Chapter 21.
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