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When dealing with Shiitake liquid culture it is advised to first inoculate a grain substrate, like a bag, after which to transfer the spawn to saw dust. It seems to me, that the big advantage of using liquid culture is the possibility to inoculate via syringe, which will lessen the possibility of contamination. However, if you end up opening the grain bag anyway and transferring to saw dust, it kind of defeats this purpose.

Would it be possible to have a two layer bag, where the top layer is grain and the bottom is saw dust?

So you inoculate the grain and after colonization it will transfer to the bottom layer of saw dust, without having to ever open the bag?

Is this done?

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Yes, this is a widely used technique for growing some varieties. You can buy pre-made and sterilized preparations readily online. I have not seen such kits with sawdust as the substrate, but that is likely because the value of varieties you would grow in sawdust would not be worth the cost of the prepared bag itself. I believe the bags in the link are designed to simplify the growing of a much higher value and less available (or less legal) species. Another thought I have is that the ratio of grain spawn to substrate in the store bought bag is very high - likely to help mitigate less than sterile technique. Production growers of Shitake can get away with a much lower spawn/substrate ratio, at a significant cost savings.

Depending on what you are looking to accomplish - high volume vs home experimentation - I see no reason this couldn't work for you. You prepare bags with a layer of rye berries or other suitable grain on the bottom and sawdust on the top.

You will want to make sure you're grains are properly cooked and hydrated and that the sawdust you put in is at the correct water content as you set them up.

You will also want to modify your planned growing technique just a touch. Once the grain is fully colonized - I do not know how long Shitake will take to colonize - you'll want to shake the bag to distribute the berries throughout the sawdust. This will speed up colonization dramatically over just depending on mycelial migration across the interface between grain and sawdust.

Some potential concerns that come to mind, in no particular order are:

  1. Supplemented vs un-supplemented sawdust. Depending on the speed with which the grain is colonized, supplemented sawdust could be at risk for contamination if it takes too long. The species commonly grown in the commercially available bags grow very fast.
  2. I would still want to inoculate the bags under "sterile" conditions of a still-air box or at least a trash bag that you've sprayed inside with lysol or something like that.
  3. I'm not sure at what point you'll need to cut openings for fresh air exchange. That depends on what species you are growing. I would guess you'd only do that after you have shaken the bag and the sawdust/grain mix has fully colonized once again.
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  • Thank you for your informative answer. I plan on growing oysters and shiitake and possibly some medicinal mushrooms. With liquid inoculation compared to grain to grain result in time loss or would the colonization happen just as quickly? I am not sure why anybody would provide this commercial substrate mix though. The "less legal" varieties only require grain afaik? Or maybe its for something else. As for air, I will be using bags with micro filters, so there will be some air exchange. – user1721135 Jan 23 '20 at 20:28
  • using liquid culture (LC) can result in some rapid colonization COMPARED TO using agar. But you must be confident your LC is clean before going to grain. A grain to grain transfer is only possible once you have colonized grain. It would be faster to expand grains via grain to grain than via LC, but you aren't expanding grain. You are basically creating the initial grain spawn, which would mix directly with substrate that is already inside the bag - so you don't have an opportunity or need to use grain to grain transfer. – That Idiot Jan 23 '20 at 21:07
  • Please keep us posted. I don't really know if this is a practical endeavor, or that I'd ever go about it this way, but I'll admit that there is something appealing about the fire and forget potential and I'd like to hear what happens. – That Idiot Jan 23 '20 at 21:10
  • Sounds pretty good. I can multiply LC easily, injecting a big, sterile jar with a purchased LC right? So I basically get to eliminate the need for a lab, since everything only ever sees the inside of a syringe or bag until fruiting, colonize faster, not worry about grain spawn etc. I only see upsides now. – user1721135 Jan 24 '20 at 12:12
  • yes, in theory. LC can be hit or miss. People either love it or hate it. It is more difficult to see contamination in LC. Follow one of the recipes online for preparation. I've always used the powdered nutrient from fungi perfecti and had good luck. Then if you have time once your LC is growing well, it would be a good idea to test it on a single bag. Then if that doesn't contaminate you can be fairly certain that the culture is clean. I've had bad batches that ruined multiple 5lb bags of grain spawn at once. I won't be so careless in the future. – That Idiot Jan 24 '20 at 12:51

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