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Growing Mushrooms at Home

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Interior surfaces such as the walls, counter-tops, shelving, etc. should not be able to support mold growth. Wood and sheet rock should be avoided. The floors should be painted several times or overlaid with a chemically resistant, cleanable mat. When using a paint, use a non-mildewing enamel. (Caution: Do not use paint containing fungicides, particular any containing tributyl tin oxide, an extremely dangerous toxin to both humans and mushrooms.) Counter-tops can be made of stainless, steel or a hardened laboratory grade formica The shelves storing the incubating bags should be wire meshed, and not solid, so that the heat generated from incubation is dissipated. Petri dish cultures can be stored on solid shelves.

5) Walls and ceiling well insulated. Ambience of temperature is critical for maintaining a laboratory. Temperature fluctuation causes two problems. When temperatures within the lab radically change from day to night, condensation forms within the spawn containers and on the upper, inside of the petri dishes. These water droplets will carry otherwise-dormant contaminants down to the rich media. Bacteria particularly love condensation surfaces When a laboratory is run at 50% relative humidity and 75° F. (24° C.) condensation should dissipate within 24 hours after autoclaving. The other problem caused by temperature fluctuation is that the outer walls of the laboratory, especially those made of concrete, sweat. I had one small home laboratory that grew an enormous colony of white mold on a painted, white cinder block wall. The whole laboratory contaminated despite my best efforts. Only when I washed the wall did I find the source. If your only option is a laboratory with an outside facing cinder block wall, make sure the pores have been sealed with a thick coat of paint and permanently place an electric, baseboard heating unit facing the wall to eliminate the possibility of condensation.

6) Lights covered with dust-proof covers. Fluorescent lights should be covered with lens coverings. Uncovered lights ionize particulates which will collect as dust layers on oppositely charged surfaces. Over time, a habitat for contaminants builds. Ionizers are similar in their effect and are greatly over-rated. (See Consumer Reports, Oct. 1992.)

7) Remote vacuum cleaning system. Since constant cleaning must occur throughout the inoculation process, having the ability to quickly pick up spilled grain and sawdust greatly enhances the ease of inoculation. When inoculations are done quickly, the likelihood of airborne fall-out (primarily from the cultivator) is minimized. Brooms should never be used in the laboratory. Wet/dry remote vacuums run the risk of clogging and then breeding contaminants. Therefore, a "dry" remote vacuum system is recommended.

Good Clean Room Habits: Helpful Suggestions for Minimizing Contamination in thz Laboratory

1) No shoes in the laboratory The lab is strictly a "shoes-off ' environment. Disposable booties are often used over socks. No outer clothing that has been exposed to the outside air should be worn into the laboratory.

2) Wear newly laundered clothes anil/or a laboratory coat . Once your clothes have come into contact with contaminants, these contaminants will become airborne within the laboratory. Two primary sources of contamination are people's pets and their car seats. Once the laboratory personnel come in contact with contamination sources, their usefulness in the laboratory has been jeopardized

3) Wash hands frequently with antibacterial soap and isopropanol. Personnel should thoroughly wash their hands before enten lg the laboratory and, with frequency, every 1/2 hour during the course of inoculations. Isopropanol ("rubbing") alcohol is used for wiping countertops, hands, and topically sterilizing tools. Other disinfectants are available from the hospital supply industry.

4) Frequently mop floors with a 10% bleach solution. The lab floors should be mopped at least once a week, and directly after each major run. Two buckets are used: one for bleach and one for rinsing the dirt-laden mop. Mop heads should be frequently replaced.

5) Do not conduct inoculations when you are sick with a cold, the flu, or other contagious illnesses. I know of cases where cultivators have inadvertently cultivated Staphylococcus bacteria and re-infected themselves and others. Face masks should be worn if you have no opl 'on but to work when you are side

6) Do not speak, exhale, or sing while conducting inoculations. Your breath is laden with bacteria that thrive in the same media designed for the mushroom mycelium. If you have a telephone in your laboratory, be aware that it often becomes a redistribution point for contamination.

7) Remove trash and contaminated cultures daily. I do not have wastebaskets in my laboratory, forcing me to remove trash constantly and preventing a site for contamination.

8) If cloning a specimen, never bring sporiilatiiig mushrooms into the laboratory. Ideally, have a second, small, portable laminar flow hood specifically used for cloning. I use this same laminar flow hood as a "Micron Maid" to help kept airborne particulates at reduced levels in downstream environments. New petri dish cultures from clones should be wrapped wi th elastic film or tape to prevent the escape of molds, bacteria, and mites into the laboratory. If sporulathg molds are visible, isolate in a still-air environment.

9) Isolate cultures by placing petri dishes on "sticky mats". I came up with this innovation when fighting mites and trying to prevent cross-contamination. Sticky mats are also known as Decontamination Floor Pads. See Figure 60

10) Establish a daily and weekly regi men of activity. Daily anu weekly calendar schedules for managing the laboratory will help give continuity to the production stream. Since so many variables affect the outcome of mushroom cultivation, try to establish as many constants as possible.

11) Rotate spawn frequently. Do not let cultures and spawn over-incubate. Over-incubated Oyster cultures are especially a hazard to the lab's integrity. After 3-4 weeks, Oyster mushrooms will fruit within their containers, often forcing a path through the closures. If unnoticed, mushrooms will sporulate directly in the laboratory, threatening all the other cultures.

The laboratory's health can be measured by the collective vitality of hundreds of cultures, the lack of diseases, and the diversity of strains. Once filled to capacity with the mycelia of various species, the lab can be viewed as one thermodynamically active, biological engine The cultivator orchestrates the development of all these individuals, striving to synchronize development, en masse, to meet the needs of the growing rooms.

Success in mushroom cultivation is tantamount to not cultivating contaminants. Confounding success is that you, the caretaker cultivator, are resplendent with legions of microflora. Individuals vary substantially in their microbial fall-out. Smokers, pet owners, and even some persons are enden ically more contaminated than others. Once contamination is released into the laboratory, spores soon find suitable niches, from which a hundred-fold more contaminants will spring forth at the earliest opportunity. As this cycle starts, all means must be enacted to prevent outright mayhem. Contamination outbreaks resemble dominos falling, and is soon overwhelming to all but the most prepared. The only recourse is the mandatory shutting down of the entire laboratory—the removal of all incubating cultures, and the necessary return to stock cultures. After purging the lab of virtually everything, a strong solution of bleach is used for repetitive cleaning in short sequence. Three days in row of repetitive cleaning is usually sufficient. Clearly, prevention is a far better policy than dealing with contaminants after the fact.

No matter how well the laboratory is de signed the cultivator and hL/her helpers ultimately hold the key to success or failure. Each individual can differ substantially in their potential threat to a clean room. Here's a poignant example. At one t:me when contamination was on an upward spiral, I had eliminated all the vectors of contamination except one: the MCU's, mobile contamination units—which includes people and other mobile organisms. Determined to track down the source, I brought in an expensive airborne particulate meter, used commonly by the computer industry to judge the quality of clean rooms. This unit measured airborne contamination per cubic meter through a range of particle sizes, from .10 microns to >10 microns.

Several fascinating results were observed. One obvious measurement was that in a calm air room, 100 times more particulates were within one foot of the floor than were within a foot of the ceiling. Truly, the air is an invisible sea of contaminants What was most surprising was the contamination fall-out from each employee. Standing each employee in the airstream coming from the laminar flow bench, I recorded downwind particle counts The contamination source was immediately identified, an employee was generating nearly 20 times the contamination fall-out than anyone else. The dirty employee was summarily banned from the laboratory. Soon thereafter, the integrity of the laboratory was restored... The lesson learned— that humans carry their own universe of contaminants—and are the greatest threat to clean room integrity.

APPENDIX III

Mushroom Cultivation Room Design

The first attempts at growing mushrooms indoors were in caves in France late in the 18th century. They provided ar ideal environment for the Button Mushroom (probably Agaricus brunnescens): constant, cool temperature and high humidity. To this day, cave culture for the button mushroom is still widely practiced. One of the largest mushroom farms in the world utilizes an extensive network of caves in Butler County, Pennsylvania. Cave culture has one major drawback for gourmet mushroom production: darkness.

The Button mushroom does not require, nor is it sensitive to light. In contrast, all the mushrooms described in this book are phototropic. This major difference—the need for light—presents a financial obstacle to the retrofitting of Button mushroom farms into gourmet mushroom production facilities. Many gourmet mushroom farms must build customized growing rooms. But, in many cases, other types of structures can be retrofitted for commercial production. Here are some examples:

Gi-ow Room Layout c

Grow Room v

Substrate

Grow Room VI

Grow Room III

Transfer Hallway

Inoculatioi \ Roon*

Grow Room IV

Sorting, \ Packaging, Prcchiil

Steam Room

Refrigeration Room

Figure 388. Floor plan of standard growing room complex, processing areas to be housed under one roof.

airplane hangers army barracks basements cargo containers caves greenhouses mines potato bunkers Quonset huts slaughter houses airplane shells barns bomb shelters car washes dairies hog farms missile silos poultry sheds ship hulls train cars train & highway tunnels warehouses volcano (lava) tubes

In general, custom designed growing rooms will perform better than structures which have been engineered for other purposes. However, with wise modifications, any of the above structures can be made into intensive growing chambers.

Whereas the laboratory is maintained at a constant temperature and humidity, the grow-

This configuration allows for 6 growing rooms and ing room's environment is fluctuated during the development of the mushroom crop. These changes in environment are specific, and sometimes must be radical, to trigger the switch-over to mushroom formation and development. A whole new set of skills is demanded of the growing room manager which are distinctly not needed by the laboratory technician. The ability of the manager to implement these changes is directly affected by the design of the growing rooms. Here are some of the design criteria that must be satisfied for creating a functioning growing room.

1) Shape The general shape of a growing room should be rectangular. I have never seen a square or circular growing room function well. The growing room should be at least twice as

The growing room 471

MOUTH OF KUSHROuH-CAVE NE Alt PAJtIS
BOTTOM Oi' »HAJil MÜKHKOOM-CAVB

Figure 389. Caves were first use J as growing chambers in France circa 1868. (Reprinted from Robinson's Mush room Culture (1885)). See also Figure 12.

long as it is wide. This configuration allows for air to be distributed down a central duct-work. The rectangular shape is naturally process-oriented: permitting the flow-through of substrate materials and fresh mushrooms. Rectangular rooms are simply easier to manage

2) Interior walls The inside skin of a growing room must be built of water/mold resistant materials. Fiberglass, polycarbonate, acrylic, glass, galvanized metals can all be used for intenorizing a growing room The material of choice, by most professional cultivators, is called FRP for Fiberglass Reinforced Plastic. This high temperature extruded fiberglass material has a smoothed finish, and its pliability makes installation simple. Furthermore, FRP will not be degraded by mold fungi, does not out gas toxic fumes, and is tolerant to mosi cleaning agents. Wood or metal surfaces can be painted with a mold/rust resistant glazing. Hammerite™, Exterior Varathane ™, or ma rine base enamel paints have been used in the past with moderate success. Cultivators should check with local ordinances so that the materials used in their growing rooms fully comply with food production and building code standards.

For those with limited budgets, the cheapest material is polyethylene plastic sheeting used by the greenhouse industry. This material usually survives no more than two or three years under the conditions used for growing mushrooms. I have attached greenhouse sheeting using galvanized staples over lengths of thick plastic tape.

3) Doors As with the laboratory, the growing rooms should be protected from the outside by at least two doors. The first door from the outside leads into an operations room or hallway where the second door opens into the growing room. Doors should

Mushroom Green House
Figure 390. The first growing rooms resembled chicken houses. Reprinted from a 1929 USDA circular: The Mushroom Growing House.

be at least 4 ft. x 8 ft. Some farms have two 5 ft. x 10 ft. double-opening bay doors, or a 10 ft. x 10 ft. sliding door. These large doors allow the easy filling and emptying of the growing rooms. A small door is sometimes inner framed within one of the larger doors so the growing room environment is not jeopardized when only personnel need to enter. In any event, the doors should accommodate small forklifts or similar machinery which need access to the growing rooms. The doors should be made of a material that does not support the growth of molds. The bottom of the door is often fitted with a brush-skirt that discourages insects from entering. The door jams are usually gasketed to assure a tight seal when closed.

At the opposite end of the growing room, a similarly sized exit door should be installed. This door facilitates the emptying of the growing room after the cropping cycle has been completed. To bring aged substrate, which is often contaminated after the 4th or 5th flush, into the same corridor that leads to other growing rooms presents a significant cross-contamination vector.

Figure 391 & 392. Modified gothic framed buildings have several advantages. Simple and quick to build, the inside curvature of the walls eliminates condensation from dripping onto the crop The condensation adheres to the walls and streams to the Poor where it is re-evaporated or drained off. The peak roof allows for the removal of excess heat and/or the mixing of humidity and air prior to contact with the mushroom crop.

Figure 391 & 392. Modified gothic framed buildings have several advantages. Simple and quick to build, the inside curvature of the walls eliminates condensation from dripping onto the crop The condensation adheres to the walls and streams to the Poor where it is re-evaporated or drained off. The peak roof allows for the removal of excess heat and/or the mixing of humidity and air prior to contact with the mushroom crop.

Many farms employ pass-through curtains, usually made of clear, thick, over-lapping strips of plastic. These are especially useful in the sorting, packaging, and refrigeration rooms However, pass-through curtains do not afford a tight enough seal for protection of the growing rooms from other environments.

4) Structures insulated Environmental control systems will function far better in grow'ng rooms that are insulated than in those

Mushroom Growing House Design

Figure 393. Two mo~:fied gothic-shapsd greenhouses supplied by central air system-

that are not. Some strains of mushrooms are far more sensitive to temperature fluctuati n than others. In localities where temperature fluctuation is extreme, insulation is essential. Some cultivators partially earth-berm portions of their growing rooms for this purpose. When using insulation, make sure it is water-repellent and will not become a food source for mc'd:

5) Inside roof The inside roof should be curved or peaked for heat redistribution by the air circulation system. Furthermore, the slope of the inside roof should be angled so that condensation adheres to the sloped roof surface and is canied to the walls, and eventually spilling onto the floor. This allows for the re-evaporation from the floor back into air The height of a grow"1ng room should be at least 10 feet, preferably 216. At least 4 to 6 feet of free air space should be above the uppermost plateau of mushrooms.

Flat roofs encourage condensation, and a microclimate for contamination growth. If the cultivator has no choice but to work with a flat roof, I recommend the installment of lengths of 6-12 inch diameter drain-field p-pe, perforated every 2 feet with 1 inch holes, down the length of each growing room at the junction of the wall and the ceiling. By installing a "T" mid-span, and locating a downward flowing duct fan at the base of the "T", air will be drawn into the holes. This scheme will eliminate the dead-air pockets which form along the corner of the wall and ceiling After fine tuning entrainment of the air can be greatly improved. (Entrainment can be measured by a "smoke or steam" test and observing the swirling air patterns)

6) Floors Floors should be cement, painted with a US DA approved, dairy grade paint, and sloped to central drain Channel-like drains used in dairies work well, although they need not be wider than 6 inches. Before entering the drain field, a screened basket is fashioned out of metal

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