Liquid Culture

Liquid culture is a controversial method of inoculation in the mycological community.  This is because while liquid cultures can be a great asset when you need to expand inoculant or inoculate a large amount of spawn while avoiding the germination time associated with spores, liquid cultures are prone to contamination.  Any time you are preparing to inoculate a large batch of jars, you should always test the liquid culture on agar to ensure that it is free of contaminates.  Additionally, you should test a liquid culture on agar every 6 months that it has been stored.  Liquid cultures should always be started with living mycelium since no spore print is sterile.  Some people have had success with starting a liquid culture from spores, but conversations with these people have shown a rate of contamination over 50% when using only a few drops of spore solution.  There are several recipes for liquid cultures, and all can be prepared using a pot with a lid, or a pressure cooker.  Jars used for liquid culture should have lids that have a self healing injection port, and a permanently attached filter for gas exchange.  Jars should only be filled about half full with liquid culture medium so that the culture may be shaken to break up mycelium without getting the filter wet.  To avoid having to shake the jars, you can also place a piece of metal, such as a thick, bent back paper clip, inside the jar to use with a magnet glued to a computer fan.  Make sure the metal is magnetic!  This is essentially a home-brew magnetic stirrer.  When stirring is necessary, place the jar over the computer fan, turn the fan on, and as the magnet spins, so will the piece of metal inside the jar.

RECIPIES

Recipes may need to be scaled up or down based on the size jar you are using.  The jar size that the recipe is measured for will be in parenthesis.  These are just a few of the more common recipes available.

600ml water + 1g light malt dextrose powder (quart)
250ml water + 1tablespoon honey (clear honey, not the cloudy kind)(half pint)
100ml water + 4ml light karo (quarter pint)

PREPARATION

Step 1:  Mix your recipe of choice and fill your jars.  When tightening down the ring of the lid, leave the ring a little loose.  Cover the top quarter of the jar with foil.

Step 2:  Place jars in a pot with a lid, or a pressure cooker.  Make sure the jars are elevated off the bottom of the pot or pressure cooker so that they are not cracked by the heat of the burner.  If using a pressure cooker, heat at 15psi for 20 minutes.  Allow jars to cool inside the cooker over night.  If using a pot, add water so that the bottom 1/3 of the jars are submerged.  Bring the water to a low boil, then place the lid on the pot.  Heat for 1 hour.  Allow jars to cool inside the pot with the lid on over night.

Once cooled, remove the foil from the jars and inoculate via syringe, or use a still air box/glove box/flowhood to inoculate with an agar wedge.  Another method of inoculation is grain liquid culture.  This is a very effective method of inoculating a liquid culture while maintaining sterile conditions.  Simply take a colonized grain jar, inject a retrievable amount of water into it, shake the jar, then retrieve some of the now mycelium laden water to inoculate liquid cultures with.  The grain jar should be spawned immediately.