Liquid culture is an effective and simple way to inoculate substrate, and you can easily do it at home. Just be sure that everything remains sterile as even minor breaches in cleanliness may lead to contamination of the process.
Begin with clean mason jars or media bottles equipped with AirPort lids (or modified mason jars). Add a magnetic stirrer, and agitate the solution to break up mycelium and evenly disperse it throughout.
1. Water
Water is an inoffensive liquid that forms the mainstay of Earth’s hydrosphere and of most living organisms’ fluids. Composed of molecules with the chemical formula H2O (two small hydrogen atoms bonded very firmly to one large oxygen atom), water provides essential hydration.
Many liquid culture recipes utilize water as their base ingredient because it is both inexpensive and readily available – both at home and most stores. For optimal results, distilled or reverse-osmosis water should be used to avoid contamination from contaminants.
Water is combined with other ingredients in order to give mycelium the nutrients it requires for growth. Different sugars such as corn syrup, Karo light or honey work particularly well as carb sources for mycelium growth, while protein, lipids starches and minerals may be added for food value. Liquid cultures are most often made using sterilized mason jar lids with filter ports for air/gas exchange and injection ports designed specifically for inoculation (see below). Furthermore, magnetic stir bars may help facilitate mixing the media together.
2. Sugar
Sugar is an integral component of liquid culture for providing nutrients to mycelium growth and helping the strain adapt to new environments. There are various kinds of sugar available which may be suitable, such as honey, agave nectar, corn syrup (Karo) and soy peptone, that may all serve this purpose.
Before beginning, when creating a nutrient solution it’s crucial to use sterilize your tools and work space with isopropyl alcohol or cleaning wipes to avoid contamination of jars. This ensures the highest possible levels of cleanliness during production.
Once your jar is complete, use a sterile syringe, spore bottle or ampoule to add some mushroom mycelium to it. Please be patient as this process may take several days – once completed your liquid culture will be ready for further steps and may need daily stirring to promote growth and avoid clumping.
3. Nutrient Broth
Some people add sugar or other nutrients to the liquid culture solution in order to speed up colonization of their species of interest. You can find recipes online and experiment with ingredients until finding an effective combination for your specific species, such as Karo syrup with light malt extract (LME) or honey as a popular example. Once completed, this solution should be added to a mason jar equipped with self-healing injection ports (AirPort or grain spawn jars are ideal), before being sterilized at 15 psi for 25 minutes in your pressure cooker for sterilization purposes.
Nutrient broth or nutrient agar is one of the easiest culture media used in diagnostic labs, comprised primarily of peptone water and beef/yeast extract to provide microorganisms with organic nitrogen compounds, water-soluble vitamins, salts and other essential nutrients. If needed for fastidious organisms it can also be enhanced further with blood, serum, sugars or biological fluids for extra support. Please be aware this medium is highly hygroscopic so to protect itself against dehydration seal it to prevent dehydration!
4. Substrate
Substrates are materials on which chemical reactions take place, where enzymes interact to convert substrates to new molecules called products through catalysis. Enzymes are proteins which act as catalysts, speeding up biological reactions within cells.
Once a liquid culture jar has successfully produced mycelium, it can be used to inoculate your substrate bag with inoculum. Simply use a sterile syringe to extract mycelium-laden liquid from its self-healing injection port and transfer into your substrate bag for inoculation.
To create the highest-quality liquid culture, start with an organic grain substrate (such as rye, wheat or barley) soaked in water. Next, you can add other ingredients such as honey, agave nectar, karo syrup (corn syrup) and soy peptone as additional nutrient sources for mycelial growth. Finally yeast extract provides essential amino acids and nitrogen essential for fungal development; all this combined will allow faster colonization by fungi than traditional spores!