Last week we prepared our first batch of oyster mushrooms that we will grow out inside the farm building in the coming weeks. This crash course in small-scale oyster mushroom production is something we have been planning and waiting for this since mid January and we have devised a plan to produce edible fungi for the restaurants. To begin this process, our first move was to prepare a growing medium for the fungi to grow out from its ‘seed’ form known as spawn. Spawn is a small piece of material that the fungi can live in like wood, grains, agar that contain some of the fungi already growing in it. When dropped into a proper growing situation the spawn will continue to grow outward until it colonizes all nearby food sources. For this process we use grain spawn cultivated by @mississippimushrooms, a local mushroom producer in NE mpls who has been helping us along since the initial planning of our project. Grain spawn is a good route to go with because all the nutrition the plant had placed into its grain to support the seed’s growth is now being used to support the fungi instead. Spawn growth from grain spawn can be rapid as the well fed fungal mycelium, which can be thought of like a plant’s roots, are energetic and proliferate quickly in the growing media.
In order to properly prepare the growing media, in our case straw, we must first clean it before introducing the spawn. The basic premise here is that the straw contains some ‘good’ bacteria and some ‘bad’ bacteria (air-quotes to suggest relativity in these terms). In order to provide an ideal habitat for the fungi we must decrease the numbers of ‘bad’ bacteria while leaving some lof the ‘good’ ones. This can be done by using a process first described chemist and biologist @louispasteur during the 1800’s later named pasteurization. In this process the straw soaked in water is heated up to 55°C/135°F in a 55 gallon drum and maintained here for about half an hour. This water is hot but not boiling and in it specific microbes are being weeded out by this heat. Mainly these are the types of organisms that compete directly with the oyster mushroom by eating the same food source. With these organisms’ populations reduced other forms of beneficial bacteria continue to grow and by sheer numbers suppress the oyster’s competitor bacteria and make way for the fungi to grow.
After being pasteurized the straw is placed out on a tarp to cool before mixing in the spawn and a several cups of the mineral Gypsum (CaSO4·2H2O for anyone interested). This compound is not entirely necessary but does a lot of good by providing calcium to help proper fruiting formation for the mushrooms while simultaneously buffering the pH drop that occurs in any wet straw after about a week which can be hard on the oysters. It also adds small micro-pore space in densely packed growing media which is vital for growing spawn that needs a lot of oxygen all over its body all of the time. Once the batch is totally mixed up we fill food grade, recycled 5 gallon buckets from Gigi’s Cafe to incubate them while they grow out and colonize all the straw.
Next steps include finishing up renovations on the old meat locker turned mushroom fruiting room. We are working all this week to get that space prepped and ready to host our first batch of mushrooms. We’re super excited to see how we do on our first go at cultivating mushrooms, doing workshops and branching out with different mushroom projects as we go. Stay tuned for more updates on the roll-out of this project over the next several weeks.
Thanks for reading!
PS) Osiris and I and going to be having a workshop next Tuesday (8/5) introducing science basics of mycology and demoing the process I just described above. Think of it as a working conversation about mycology. This event is free but we will accept donations used to help pay staff for their time and contribute to procuring supplies for future classes. More info at https://www.facebook.com/TinyDinerUrbanFarm/photos/a.618958204821372.1073741830.602326506484542/775890712461453/?type=1&theater
More information below:
Fungal biology: http://urbanfarmsista.com/mushroom/
Pasteurization process: http://www.oystermushrooms.net/chap2.pdf