One very generic recipe, to offer up one that is used as an example in a guide book I have on shimeji cultivation, calls for 20g corn cob, 50g rice bran, 20g wheat bran, and 10g dried tofu lees per 850ml bottle (all figures represent dry weights), with the remaining 400 grams sawdust. This is just one approach though. Cottonseed hulls, for instance, have good water retention, and might be especially useful in a region with a dry climate or could be added seasonally during drier seasons. Soybean hulls are also useful for increasing yields, but they are easy food for many other molds and bacteria, so you don’t want to add too much. They also inflate considerably when water is added, so the total amount should be kept small if used.
Here I am just briefly going over a small fraction of the calculations that go into making a substrate, and many other nutrition supplements are possible, depending on the local agro-waste streams and the cost-point. As I have said elsewhere, farms shouldn’t get too caught up in some idea of perfection that they pay more than a substrate component is worth; perfect is what gets the job done and is simplest and cheapest to get your hands on.
Shimeji substrate runs around 66~70% water content at filling.

Sterilization and Spawning
In Japan the standard sterilization process uses a pressurized autoclave reaching max temperatures of 118 degrees Celsius, which they hold for thirty minutes before the cool down starts. These cycles are typically four hours. However, non-pressurized autoclaves operating at under .5 bars of pressure and maximum temperatures of 108~110 degrees Celsius running on a longer eight-hour cycle can also be used to sterilize substrate. It is very important however, that substrate be sterile, not just pasteurized, and that a farm upholds extremely high hygiene standards.
The industry standard in Japan is for a double-sided autoclave, the back end of which opens into a cooling room with reverse laminar flow that is connected to or part of the inoculation room. Hygiene standards fort the inoculation room should be well known, but they include changing in to full-body clean room suits, covering of hair, disposable latex gloves, and sometimes include facial masks as well. Prior to entry, workers use a lint roller over their bodies and go through an air shower. In Japan, some clean rooms can be at the hygienic standards of a surgery ward in a major hospital.

Incubation
As I mentioned above, shimeji have an 80~100-day incubation cycle. Incubation temperature settings range from 21~23 degrees Celsius. As I have written before, in the initial phases, up to the first month, is when you see the highest levels of metabolic activity. While the spawn is colonizing the substrate, the mycelia generate a lot of excess heat. That is why it is fairly standard in Japan to run incubation at the lower range during that time period, which for shimeji would be around 21 degrees Celsius for the first month. Afterwards, you can allow the thermometer to go up a little.
It is also important to make sure that there is good air flow in the incubation room, with fans circulating the air (small fans, not huge industrial fans). When you have a room with almost 8 meters to the ceiling and two pallet-high stacks of tightly packed bottles, it is easy to get dead spots even with proper HVAC systems with HEPA filtration. These dead spots can both overheat and/or have excessive CO2 concentrations. Over all, for shimeji incubation, the CO2 concentration can be as high as 4500 ppm, but it should never exceed 5000 ppm for even a short period of time. Humidity should be maintained at 65%.

Pinning and Fruiting
After fungal scraping, the bottles of shimeji substrate should be moved to a pinning and fruiting room. The ideal temperature range is 14~15 degrees Celsius. One thing about shimeji is the extremely high humidity in the fruiting room, as close to 100% saturation as a farm can maintain. CO2 saturation should remain under 2000 ppm during this period of time. Japanese farms have LED light systems built around the shelving, and a 12-hour light cycles with 15~30 minutes exposure to light at a time. Blue LED lighting has shown the best performance. A proper lighting cycle is important for pinning formation and maximizing yields. Light intensities should be between 500~1000 lux. Pinning to harvest typically requires between 20~22 days.

Wrapping up
This is a very cursory view of shimeji cultivation, but I have touched on the standard settings and given a generalized overview of the cultivation process in this article. I would like to emphasize that readers should not take this advice as universal. Shimeji are a high-performing variety, but there are plenty of components, some small, some big, that I cannot go into with a short primer like this. What is more, when growing shimeji via filter bag systems, the parameters of best practice will likely display some significant differences between Japan’s bottle system growing methods. Before beginning commercial cultivation of shimeji, I would definitely recommend contacting our parent company SALAI International Japan. Each farm is different, so getting the best performance generally requires personalized consultations.