Using Rye Grain For Mushroom Spawn
Making and Using Mushroom Grain Spawn
Using sterilised rye grain to make mushroom grain spawn is one of the basic steps mushroom growers need to get accustomed to and is a fairly easy process. This simple guide aims to talk you through the basic steps.
What is mushroom grain spawn?
Mushroom grain spawn, generally referred to as grain spawn, is one of the building blocks utilized in mushroom cultivation. As you might expect from the name, grain spawn a form of substrate which consists of sterilized grain, usually rye or wheat, which has been inoculated with live mushroom mycelium. Mycelium is what mushrooms grow from and can be thought of as both a form of ‘seed’ and also the roots of a mushroom.
Once live mycelium has been added to the sterilised grain it spreads and builds a network of fungal cells that colonizes all the grain, eventually resulting in the grain resembling a large white fungi-covered block. These grains, once colonised, act as a form of seed source for mushroom growth. The grain spawn provides the necessary nutrients for mycelium to develop and ultimately fruit into lovely edible or medicinal mushrooms.
What grain is best for grain spawn?
As with so many things in life, you’ll hear different growers singing the praises of different types of grain, based on their personal experience and the type of mushrooms they grow. However, it’s generally accepted that the gold standard is sterilised rye. Rye grain boasts excellent water absorption capability, provides optimal nutrient types and levels and is also compatibile with most mushroom species. In addition, rye is readily available, even in countries where it isn’t actually grown. Other types of grain can be used in the same way, such as wheat, barley, brown rice, millet, and sorghum, with each having their own supporters.
Using Rye Grain – Inoculation
By far and away the best way to make your own grain spawn is to buy pre-sterilised rye grain from suppliers such as ourselves, removing the need to buy equipment and learn how to sterilise and correctly hydrate grain. We sell sterilised rye grain, so for the purpose of this guide, we’re assuming you want to do next!
Inoculation
When we speak about inoculating grain we are referring to the process you might think of as ‘seeding’ the grain by adding an inoculate material in the form of live mycelium from a liquid culture syringe. Using liquid culture is generally the most common way of inoculating grain, and much safer than using spore syringes.
You will need:
A bag of sterilised rye grain
A liquid culture syringe containing live mycelium
70% isopropyl alcohol or sterile alcohol wipes
A flame source for needle sterilisation
Inoculation Steps:
Step One: It is always best to work in a sterile environment. If you have a laminar flow hood then you’re way ahead of the game, but their cost, size and infrequent use mean most growers will be using a form of ‘still air box’. A still air box is basically one of the large transparent storage boxes found in many stores, turned upside down (with the lid on) and arm holes cut into the sides. A still air box provides a space in which air can settle, reducing the chances of floating spores and bacteria from contaminating your mushroom growth. Clean the insides of the box with 70% alcohol, place the items you plan to use inside the box and then leave the air inside to settle for an hour or so. When you are ready to start work, try to reduce your movements (especially arms in and out of the box) to a minimum and clean the items inside the box with alcohol again.
Step Two: If you are using a liquid culture syringe for the first time, the needle will probably be in sealed sterile packing, in which case attach it to the syringe without touching the needle. Shake the syringe gently to distribute the mycelium well before injecting. Use an alcohol wipe to clean the surface of the injection port on your bag of sterilised rye, then ease the syringe needle into the bag and inject your liquid culture, moving the syringe as you do it, to help spread the liquid as widely as possible. The amount of liquid culture you should inject depends on many factors, such as the amount of rye in the bag, strength of liquid culture and the speed you want it to develop at, but as a general rule you might try 3ml – 5ml per Kg of rye. Many users will inject more, to make colonisation quicker, but injecting too much liquid has the potential to create contamination through excess liquid (over-hydrated grain is never a good thing). When you’re finished, it is a good idea to take a small strip of micropore tape and use it to cover the injection port. This helps prevent it getting knocked off and also adds a protective barrier.
Step Three: If you’re inoculating more than one bag, or if you’re using a previously used needle, hold the needle over a heat source until the needle is glowing red hot, to kill any potential contaminants prior to use. A fresh sterile wipe can be used to cool the needle – don’t stick a red-hot needle into the bag or injection port as it will leave a permanently open hole – a convenient entrance point for contaminants!
Using Rye Grain – Incubation
Once you have inoculated your rye grain with live mycelium, the next step is the least interesting and slowest – incubation. Your inoculated grain now needs to be stored in suitable conditions while the mycelium germinates and colonises the grain. This process can take several weeks and the grain needs to be left alone while it occurs. However, it is important to ensure the bags are kept in an optimal environment to ensure colonisation can proceed successfully.
Find a location where your grain can be left undisturbed, definitely out of direct sunlight, ideally in a dark or shady location. It is important that wherever you store it, your grain is kept at a steady temperature range typically, but depending on mushroom species, between 24-29°C to encourage optimal growth during incubation. Grain should maintain high humidity levels, around 90-95%, to prevent the grain from drying out, but assuming you are using sealed bags of sterilised grain this will manage itself.
Proper airflow should be ensured during the incubation process to prevent the build-up of carbon dioxide and to supply fresh oxygen to the grain. Again, bags which have built-in air filters will generally self-manage, but you need to ensure there is an open pathway between the air filter and the grain inside the bag – you don’t need to try to suck air in, just make sure it has a pathway it can follow.
Incubation time can vary depending on many factors including volume of liquid culture used, temperature, humidity, mushroom species and more, but in most cases you’ll see widespread colonisation after 10-14 days. Once the majority of the grain is colonised, you can use your hands to gently break up the now clumped-together colonised grain and mix it with uncolonised grain to speed up the process. You should normally only do this once.
When all the rye in your grain bag has been colonised, you’ll end up with what seems to be a solid white block. At this stage you could say the process is complete but it won’t hurt to leave the bag for another couple of days, just to ensure that the centre of the block which you can’t see is fully colonised.anted contaminants creeping in.
How to use colonised grain spawn
Once your rye grain has been fully colonised, it’s ready to be mixed with a bulk substrate, but that’s another topic. As a general guide you may find our product guide on using colonised grain spawn (really intended for users of the grain spawn we supply) useful and you’ll find it here: https://mushroomkits.co.uk/product-guides/using-grain-spawn-packs/