How to prepare the grain spawn for Mycelium (spore) culture inoculation at home? One of the first questions that arise before novice mushroom growers.
In this article, we will describe step-by-step preparing Oat grain Spawn, using the example of the simplest and most convenient oats grain spawn for mushroom growers.
Table of Contents
Why oats grain for mushroom spawn?
In our opinion, this is the best option when choosing from grain cereals. It is important to emphasize that oats must be unshelled (other names are unpolished, unpeeled). Such oats are used for medical purposes, for sprouting, decoctions, and tinctures.
When buying, pay attention to the fact that the grain is light, dense and clean. If the grain is small, then it is probably overdried. If the grain is dark or gray, then most likely it is affected by a fungus or mold. And of course, the grain should be dry with a neutral smell.
In terms of nutritional value, oats are not inferior to wheat and barley, are much more nutritious than hay-straw substrates and are easy to prepare. Its remarkable property is that it does not need to be cooked. Due to the structure of the grain itself, it perfectly absorbs moisture during soaking and retains it softening the dense core of the grain.
Preparing Oat grain Spawn Step By Step
Soaking Oats Grain
Soak 1 liter (not kilogram) of oats in cold water and mix thoroughly. There should be more water in volume so that it is not all absorbed after the oats swell. The dishes with soaked oats should be covered and put in a cool place (for example, in the refrigerator) for 24 hours.
This is done so that the spores of the competitive microflora (molds, bacteria) of their “dry”, dormant state pass into a vegetative state, come to life and begin their development. Water always contributes to this. After that, we immediately kill them by heat treatment, sterilization in a pressure cooker.
After a day, you may notice that the bulk of the grain has sunk to the bottom, and garbage, low-quality grains and husks are floating on top. They need to be collected and thrown away. Then drain the water.
Washing grains
Like all cereals, oats contain gluten. When soaked, this substance is released in the form of mucus. If at this stage the grain is not washed, then later it may stick together. Also, this protein compound will promote the development of acidic bacteria if they survive after sterilization. Therefore, in order to minimize these risks, we carefully wash the grain. To do this, we use an ordinary shower.
After this simple procedure, we put the colander at a slight angle for about 30-40 minutes in order to drain excess water from the glass. Once this happens, the grain is ready to be loaded into the cans.
Putting grains in inoculation jar
This is the important part. The jars in which the substrate will be colonized by mycelium is a sterile environment! No microorganisms other than fungal spores should penetrate there. All of them are spore competitors in the struggle for a nutrient substrate.
It is important to understand that the spores of many molds are constantly in the residential, airspace of our habitat. You have often noticed how Trichoderma green mold settles on food over time or how Aspergillus black mold appears in wet areas of the bathroom. Because mold is everywhere and always! 200 million years ago, she learned to survive in any conditions: in radiation, arctic ice, and open space. And she wants to live and feed on the substrate that you have prepared for the mycelium! For this reason, your jars should be like a fortress, into which only air molecules necessary for the development of mycelium can enter.
For this to work, the lids of the jars must fit tightly or twist. We use food, polypropylene containers with a volume of 0.35 – 0.5l. This is the optimal volume for colonization. In large jars, the mycelium can often stop growing just because the lower layers of the substrate are poorly supplied with air. Therefore, it is better to prepare many small jars than several large ones. If one gets mold, it will be one of many. These jars are light and handy. The lids close quite tightly. When you press lightly, you will hear a click, which means the cover has entered the groove.
In the lid with a red-hot awl, you need to make a hole with a diameter of 3 maximum 5 mm. Do not need it anymore. This hole serves as a jar through which air enters the jar. Also, thanks to him, during sterilization in a pressure cooker, the pressure is equalized and the jars do not burst (or the lids do not break).
An important element is a filter that is fixed on this hole. It must also be sealed. It is very convenient to use a tissue-based medical patch as a filter. We advise you to buy high-quality and moisture resistant.
lids are equipped with an inoculation jar. Its task is to ensure that the needle of the syringe does not leave an open hole during inoculation. The rubber cover, due to its properties, does an excellent job with this task. It just needs to be planted on the sealant in a pre-prepared hole of the desired diameter.
If you use glass jars with metal screw caps, then the filter and inoculation jar are made in exactly the same way, but taking into account the material of the cap. Holes will have to be drilled.
Cover the lids with aluminum foil before placing the jars in the pressure cooker. This is done so that the filter does not get wet in the pressure cooker during sterilization. Of course, it will also get wet under the foil in a hot steam environment, but not as much as without it.
Using pressure cooker for grain spawn
A pressure cooker is necessary in order for the competitors of our spores to die under the influence of high temperature, namely the spores of molds, bacteria and other microscopic living creatures, which then will not allow the mycelium to develop. But isn’t it easier and cheaper to use an oven, for example? After all, it can be heated up to 600C.
And then a little digression into physics.
The thing is that at normal atmospheric pressure, water boils at 100C. There will be no higher temperature, then the water turns into steam. And even if you heat the oven to 600C, the water that is in the substrate will still boil at 100C. Accordingly, the temperature in the substrate will not rise above 100C. It will only get higher when all the water has boiled away. But we do not need a dry substrate. But isn’t 100C enough, you ask. Experience shows, unfortunately not. For the death of many microorganisms, temperatures above 100C are required. That’s why we use a pressure cooker.
The principle of operation of the pressure cooker is that in its closed space, due to the accumulation of hot steam, increased pressure is formed. At this pressure, water boils at a temperature of almost 120C. And this temperature of water and steam is enough to destroy all life in our substrate. And so we load our jars into the pressure cooker.
grain spawn sterilization
Plastic jars need to be placed on some kind of metal stand such as a kitchen (under the pan) and placed so that they do not come into contact with the walls of the pressure cooker.
Glass jars can simply be placed on a towel at the bottom. Then you can close the pressure cooker according to its design.
There are many types of pressure cookers, but they all operate on the same principle and have approximately the same functionality. It is important that all the details are in place.
The lid must close tightly and be fixed. To do this, be sure to have a rubber or silicone round gasket on it.
The kit should include a weight that is placed on the working valve to relieve excess pressure; without it, your pressure cooker turns into a regular pan.
And in general, the pressure cooker should be without damage and deformation. Before use, it is important to check the working valve, air must pass through it freely. Also on the cover there is a second, emergency valve, it works if the worker does not work for some reason. It is equipped with a spring and should also rise with your little effort.
It is important to understand that if these valves are closed and the hot steam does not find an outlet, then your pressure cooker turns into a bomb!
After you have checked the valves and secured the lid, put the pressure cooker on high heat to bring the water to a boil. When this happens, the steam will sizzle out through your service valve, lifting the weight. You need to adjust the fire on the stove so that the valve releases steam with short breaks, in small portions. Usually this requires a very small fire.
In this mode, the substrate is sterilized from 60 to 120 minutes. Since substrates come in different degrees of contamination, we recommend at least 90 minutes.
ready to inoculated with spore suspension
After this time, you should never open the pressure cooker immediately, this is dangerous! Hot steam under pressure inside. Also, we do not recommend cooling it in cold water. Firstly, it is just as dangerous, and secondly, with such emergency cooling, the pressure cooker intensively sucks in air from the outside through the working valve, and with it all the microorganisms. You need to let the pressure cooker cool down naturally. It usually takes 4 to 6 hours.
If you use plastic jars, then immediately after you take them out of the pressure cooker, you need to lightly squeeze the lids, they are released during the sterilization process.
There you have it, your substrate is ready to be inoculated with spore suspension!
Conclusion
It should be noted that there is an alternative way to sterilize the substrate. This is tyndallization. But this method is akin to a lottery, it may work, or it may not. Plus, it’s a long process. A pressure cooker, on the other hand, gives you a 99% guarantee that your substrate is truly sterile.
Also, some cultivators use antibiotics in the preparation of the substrate. The tablet preparation Levomycetin is crushed into powder and added to water at the stage of soaking or cooking.
In theory, the drug should kill microorganisms of the bacterial series. The method is considered working, but has its drawbacks. The action of chloramphenicol affects the rate of mycelium colonization of the substrate in direct proportion, the more the drug, the slower the mycelium grows. And whether levomycetin acts on mold spores is unknown.
