When it comes to inoculating grain spawn, there are various options available. The speed at which your grain spawn colonizes can greatly impact its sterility and subsequent growth. Many growers prefer the simplicity of transferring a wedge of agar to grain, then using that grain to inoculate more bags. This method, known as Grain-to-Grain (G2G), is highly effective and is worth considering when working in clean room conditions with fully colonized grain. Another option is starting with liquid culture, where you can expand a single petri dish of colonized mycelium to multiple liquid culture jars by incubating them for 14 days. Lastly, there is the option of liquid inoculant, which involves using a blender to blend colonized agar with a nutrient-rich broth for instant liquid culture. This speeds up the homogenizing process and allows for immediate inoculation.
A solid grain to grain transfer with master grain spawn is one of the most advanced techniques when it comes to commercial mushroom growing (grain inoculated with agar or LC of a properly stored tissue cultured mushroom). This technique involves wiping down every crease of the grain bag with alcohol opening in front of the flow hood, each time you add myceliated grain into a sterile bag you must seal it immediately until all your work is finished. Vectors for contamination during G2G usually arise from clean room filters not being maintained and bags not being wiped down enough with 70 percent isopropyl alcohol.
Liquid culture recipes and procedures can go in so many different directions and yield a variety of results. The most important thing to remember when using liquid culture for inoculating sterile grain is to always add a magnetic stir pill first so you don’t forget after filling with water and nutrients. Once the jar is sterilized you cannot add the pill after. Sterilize your liquid culture solutions for at least 40 minutes to ensure the material is properly cleaned. Many other recipes recommend 20-30 minutes and this is clearly not enough time for most pressure cookers: All American, Presto Canner, even the 150 liter industrial autoclaves will not sterilize liquid culture in 20-30 minutes.
Once your media has cooled down, you add the agar wedge and turn on the magnetic stir plate to colonize for 2 weeks. After 2 weeks the quality control process begins by dropping liquid (2-3cc) onto an agar plate and waiting for clean white mycelium to form on the surface. It should not be a grey/milky ooze. The QCP (quality control plate) will show bad growth within 24-48 hours where mycelium will take about 3-5 days to appear depending on temperature. Around 75 degrees Fahrenheit will be best for incubating a QC plate, please note even clean mycelium will appear to look like bacteria for the first 2-3 days then it will turn white on day 4-5.
Until this point grain transfers and liquid culture were the standard for expanding grain spawn. Liquid Inoculant is arguably the most accelerated technique in the world for growing mushrooms in high volumes. The difference between liquid culture and liquid inoculant is the latter does not need any time to incubate and technically can be used instantly. The same process for sterilizing is key, 40 minutes at 15 PSI sterilization cycle.
The blender head of a commercial waring blender can be fixed onto a stainless steel mason jar lid with a 3/4 inch hole cut in the center of your lid (regular mouth works best). When you add an entire agar plate (or two) into the liquid inoculant jar and blend the entire jar, it becomes homogenized with culture and your ready to go! The benefit of blending agar into liquid inoculant is that it creates an instant culture ready to be used on the fly. When you work on a farm, the timeline to get anything ready for production is stressful enough. Trimming off weeks, this is by far the biggest bottle neck growers face.
Mushrooms grow so fast yet commercial farmers are always chasing their tails to stay ahead. Liquid inoculant can alleviate all the most common pitfalls endured when mushroom growers scale their business. As the industry becomes more competitive and supply exceeds demand efficiency will be apparent to survival in both the culinary and holistic market.