Purposesi To recapture as many mushrooms possible whichcan not be realized in controlled environment growing rooms.This building can solve a dilemma constantly confronting the growing room personnel: to maximize mushroom yield while not jeopardizing future crops as contaminants become more common as the cycle comes to completion.
By the third or fourth flush, yields are in a state of precipitous decline. Rather than discarding this mycelium, additional harvests can be realized, with minimum effort, if the substrate is placed outside during conducive weather conditions. In the temperate regions of the world, these favorable weather conditions span several months. During these moist months, Oyster and Shiitake mushrooms produce prolifically outdoors. I am continually amazed at the size of mushrooms that can be harvested outside from "spent" straw or sawdust that has been exported from the indoor growing rooms. Two types of buildings serve this purpose well.
Facilities: Either a hoop frame structure covered with "bug-out" or shade cloth or a coveret I building with walls constructed of the same, draping from the outer roof joists.
MaximumTemperature: Ambient MinimumTemperature: Ambient Humidity: Ambient, augmented to 85-100% by overhead sprinklers.
Light: Ambient. Indirect natural light coming from the sides is best. Insulation: None needed. Positive Pressurization: n/a Additional Comments: Two structures meet these needs well. The first is the simplest. By constructing a hoop type greenhouse and covering it with 70-80% shade or "bug-out" cloth, moisture can penetrate through to interior and air flow is naturally high. If the pore spacing is fine enough, as in the commercially available anti-bug screens ("bug-out"), then flies will be hindered from entry. If a metal roofed, open sided, hay-barn is used, then draping the this fabric from the outer frame to create fabric walls will accomplish a similar function. In either environment, a simple, overhead misting system activated by a timer or hand controls, will promote additional mushroom crops. Compared to the details needed for the controlled environment, high efficiency growing rooms, the construction of these types of rooms are self explanatory and open to modification.
ushroom cultivation is affected as much by psychological attitude as it is by scientific method. The synergistic relationship between the cultivator and his cultures becomes the overwhelming governing factor in determining laboratory integrity. Since contamination is often not evident for days, even weeks, after the mistake in technique has occurred, the cultivator must develop a super-sensi tive. prescient awareness. Practically speaking, this means that every time I enter the laboratory, I do so with a precautionary state of mind.
The laboratory is designed and built for the benefit of the mushroom mycelium The role of the cultivator is to launch the mycelium onto appropriate sterile substrates in the laboratory and then leave. The less non-essential time spent by humans in the laboratory, the better, since humans are often the greatest threat to the viability of the mushroom cultures. Growing mushrooms successfully is not just a random sequence of events scattered throughout the week. One's path through the facilities, growing rooms and laboratory, can have profound implications on the integrity of the entire operation.
The growing of mushroom mycelium in absence of competitors is in total contradiction to nature. In other words, the laboratory is an artificial environment, one designed to forestall the tide of contaminants seeking to colonize the same nutritious media that has been set out for the mushroom mycelium. This was a frightening state of affairs for most would-be cultivators until books like The Mushroom Cultivator by Stamets & Chilton (1983) and this one offered simple techniques for making sterile culture practical for mushroom cultivators. These volumes represent, historically, a critical step in the passing of the power of sterile tissue culture to the masses at large.
Before the advent of HEPA filters*, sterile culture work succeeded only by constantly battling legions of contaminants with toxic disinfectants, presenting real health hazards to the laboratory personnel. Now, the use of disinfectants is minimized because the air is constantly being re-filtered and cleaned. Once airborne contamination is eliminated, the other vectors of contamination become much easier to control. (Please consult Chapter 10 for the Six Vectors of Contamination.)
Most people reading this book will retrofit a bedroom or walk-in pantry in their home. Large scale, commercial operations will require a separate building. In either case, this chapter will describe the parameters necessary for designing and building a laboratory. If you are building a laboratory and pay strict attention to the concepts outlined herein, contamination will be
* HEPA = High Efficiency Particulate Air Filters eliminate particulates down to .3 microns with an efficiency rating of 99.99%. ULPA (Ultra-Particulate Air) filters screen out particles down to . 1 u m with 99.9999% efficiency minimized. Like a musical instrument, the laboratory must be fine tuned for best results. Once the lab is up and running, a sterile state of equilibrium will preside for a short time. Without proper maintenance, the lab, as we say "crashes". The laboratory personnel must constantly clean and stay clean while they work Since the laboratory personnel are the greatest threat to the lab's sterility, they must shoulder the responsibility for every failure.
The laboratory should be far removed from the growing rooms, preferably in a separate building. The air of the laboratory is always kept free of airborne particulates while the growing rooms' air becomes saturated with mushroom spores. The growing rooms are destined to contaminate. Even the spores of mushrooms should be viewed as potential contaminants threatening the laboratory. If both the laboratory and growing rooms are housed in the same building, contamination is much more likely. Since the activities within the laboratory and growing rooms are distinctly different, separate buildings are preferred. I know of several large mushroom farms which built their spawn laboratory in amidst their growing rooms. Their ability to generate pure culture spawn is constantly being jeopardized by the contaminants coming from the growing rooms. Every day, the laboratory manager faces a nightmarish barrage of contaminants.
A good flow pattern of raw materials through the laboratory, and of mature cultures out of the laboratory is essential. Farms with bad flow patterns must constantly wage war against seas of contaminants. The concepts are obvious. The positioning of the growing room exhaust fans should be oriented so as not to direct a "spore stream of contaminants" into the laboratory filtration system. Furthermore, the design of a mushroom farm's buildings should
Electrostatic Air Cleaner
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Laboratory Air Filtration System
Fan to be capable of delivering 1200 cfm at 4" water gauge static pressure.
Electronic Air Cleaner downstream from Refrigeration Coil would catch any growth from the Coil..
Pre-Filter is upstream from Refrigeration Coil.
Return From Lab Outside Air
Figure 386. Exteriorly located, air filtration system for the laboratory. This configuration allows the filtration, heating and cooling of incoming and recirculated air. The filters must be removed periodically for cleaning and/ or replacement.
take into account prevailing wind direction, sunlight exposure, shade, the positioning of the wetting or compost slabs, the location of the bulk substrate storage, and the overall flow patterns of raw materials and finished goods.
The major problem with having a laboratory within a home is the kitchen —a primary breeding ground for contamination. Rotting fruits, food spoiling in the refrigerator, and garbage containers represent a triple-barrelled threat to the laboratory's integrity with the air and the cultivator as carrier vectors, However, good sterile technique coupled with the use of HEPA filters, can make a home laboratory quite functional for the small and m;d-size cultivator. Most importantly, the cultivator must have a heightened awareness of his/her path through the sources of contamination before attempting sterile tissue culture. I prefer to do my laboratory work in the mornings after showering and putting on newly washed clothes. Once the lab work is completed, the packaging and growing rooms can be entered by the laboratory personnel. Otherwise, these areas should be strictly off-limits. In a mushroom facility, duties musl be clearly allocated to each person. If you are working alone, extra attention to detail is critical to prevent cross-contamination.
The design criteria for constructing a spawn laboratory is not complicated. A short description of my lab might help the reader understand why it works so well. My laboratory is housed in a 1440 sq. ft. building. A 15 HP boiler is located in its own room and generates steam for the 54 in. diameter, 10 ft. long, double door retort. The walls and ceilings are covered with FRP (Fiber Reinforced Plastic). The lights are
• Uminar Flow Hood
Figure 387. Floor plan of a mushroom spawn laboratory. Most of the substrate enters the clean room through the autoclave (mid-way left.) Spawn is exported from laboratory to the growing rooms. Spawn is rotated frequently out of the laboratory
Figure 387. Floor plan of a mushroom spawn laboratory. Most of the substrate enters the clean room through the autoclave (mid-way left.) Spawn is exported from laboratory to the growing rooms. Spawn is rotated frequently out of the laboratory covered with waterproof, dust-proof lenses. Plug-ins for the remote vacuum system are handy and well used. To enter, you must pass through three doors before reaching the clean room. In the clean room, a 2 ft. high by 12 ft. long home-made laminar flow bench gives me ample freedom of hand movement and surface area. (See Figure 72.) Fresh, outside air is serially filtered and positive-pressurizes the lab from overhead through a coarse pre-filter, an electrostatic, and finally a 24 x 24 HEPA filter. A return duct, recycling the room's air should be on the floor but, I admit, is not. By locating the return duct low in the laboratory, contaminants aie constantly being pushed to and skimmed off the floor. My laminar flow bench—with its massive surface area—recir culates the entire room once every 1.3 minutes. This is far more than what is minimally necessary.
Here are a few key concepts in designing laboratory, whether the clean room is in the home or in its own building. If incorporated into the design of your facility, contamination vectors will be minimized. Following this list are helpful suggestions of behavior which, in combination, will give rise to an efficient, steady state clean room.
1) Positive Pressurize Laboratory. The laboratory should be continuously positive-pressurized with fresh air. The fresh, outside air is serially filtered, first through a^(j||se pre-fil-ter(30% efficient ai 1m), theifflua §|ctrostatic filter (95-99% efficient at \£/a|J finally a HEPA filter (99.99% efficient at .Tu). Blowers must be oroperly sized to overcome the cumulative static pressures of all the filters. In most cases, the combined static pressure approaches 1.25 inches. (1 inch of static pressure is the measure of resistance represented by the movement of water 1 inch, in a 1 inch diameter pipe.) Air velocity off the face of the final filter should be at least 200 feet per minute. For a 400 sq. ft. clean room, 2 ft. x 2 ft. x 6 in. filters should be employed. The construction of the intake air system should allow easy access to the filters so they can be periodically removed, cleaned, and replaced if necessary. (See Figure 386.) Fresh air exchange is essential to displace the carbon dioxide and other gases being generated by the mushroom mycelium during incubation. Should carbon dioxide levels escalate, the growth of contaminants becomes more likely. Sensitive cultivators can determine the quality of the laboratory immediately upon entering using their sense of smell.
2) Stand-alone laminar flow bench. A laminar flow bench constantly recirculates the air within the laboratory. The air entering the laboratory has been already filtered from the por"': /e pressurization system described in the previous paragraphs. By having two independent systems, the lifespan of the filter in the laminar flow bench is greatly extended. And, the clean room becomes easy to maintain. Furthermore, I am a strong believer in creating a laboratory that is characterized by turbulent air streams, with a high rate of impact through micron filters. Turbulent, filtered air in the laboratory is far more desirable than a still a r environment. The key idea: if airborne particles are introduced, they are kept airborne from turbulence. If kept airborne, particles are soon impacted into the micron filters. This reduces the stratification of contaminant populations in the laboratory, and of course, temperature variations. It is important to note that this concept is diametrically opposite to the "old school" concept that still-air in the laboratory is the ideal environment for handling pure cultures.
3) Double to triple door entries. There should be at least two doors, preferably three doors, separating the clean room from the outside environment. Double door entrhs are a standard in the industry. Doors with windows have obvious advantages in preventing accidents. Furthermore, the doors should be gasketed with dirt skirts. When the doors swing outwards as you exil the innermost clean room, the export of mature spawn or blocks is made easier. (I prefer to kick the doors open upon exiting as often times my hands are full.) As workers travel towards the clean room, ihey enter rooms hygienicly cleaner than the previous, and into increasingly, higher pressure zones Floor decontamination pads, otherwise known as "sticky mats" are usually placed before each doorway to remove debris from the feet.
With ultra-modern clean rooms, a double door anteroom, called a "Decontamination Chamber", utilizes the down-flow of HEPA filtered air over the worker who stands on a metal grate. The air is pushed from above and actively exhausted through the floor grate to the outside. The principle concept here is valid: the constant descensión of airborne particulates improves laboratory integrity. Another variation of this concept is the replacement of the solid inner doors with down-flowing air curtains. However, decontamination chambers and air curtains should be the last projects on a long list of other priorities for the financially conservative investor.
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