Liquid Culture Recipe

Liquid culture (LC) is a sterile nutritional solution commonly used in mushroom cultivation and mycology to inoculate substrate with microbes. Preparation takes minimal effort and preparation is significantly faster than spore solution.

Begin by disinfecting your work surface and equipment with cleaning alcohol, then combine your Karo and peptone in a jar before stirring thoroughly.

Grain Broth

Grain broth is a nutrient-rich mixture designed to encourage mycelium growth prior to inoculating substrate (usually grains or compost) with mycelia for mushroom cultivation. Grain broth can also serve as a liquid culture as it’s easily inoculated into bags or jars with injection ports, or into pre-sterilised grain/agar bags – just make sure you place these inside a pressure cooker at 15 PSI for 90 minutes prior to adding any airborne contaminants!

A jar of mushroom liquid culture may last months if conditions remain consistent, but before using, it is prudent to test a small sample on an agar plate or piece of sterilised grain to ensure the mushrooms will grow without contamination. Any trace of mold could render the entire thing useless – to prevent this, always ensure your container seal is tight and regularly stir the liquid to prevent this happening.

Potato Broth

This recipe is ideal for anyone needing to produce large volumes of liquid culture in an efficient and quick manner. Simply combine all the ingredients in a large pot over medium heat and bring to a boil before simmering for around 10 minutes before straining out any solids that have settled to the bottom of the vessel.

Once the vegetables have been simmered for some time, add potatoes. Stir this mixture and continue cooking until all the potatoes have become coated with white starch coating that helps thicken the soup.

This classic recipe works wonderfully and produces a clear and transparent broth ideal for viewing mycelium growth. You can create this broth using any combination of water, carbon source (dextrose, honey, LME or light corn syrup), and nitrogen source (peptone or beef extract). Sterilization takes about 40 minutes in either an autoclave or pressure cooker.

Agar Broth

Nutrient broth is an easy liquid culture medium for growing nonfastidious microorganisms and maintaining stock cultures. This simple mixture consists of peptone, yeast extract and beef extract and serves as an effective growing medium.

It can also serve as the background for inoculations and metabolic tests (including the gelatinase test you will conduct in this lab later).

Prepare medium as described for agar plates, using a flask instead of a tube. Once mixed, heat to 100degC until all ingredients have dissolved (use a boiling water bath if possible) and pour into plastic dispensing bottles which have caps that cannot be tightened completely; sterilize as described above before labeling with date and type of medium used.

Nutrient Broth

Nutrient broth is a liquid medium designed for cultivating microorganisms with non-exacting nutritional needs. Peptone and yeast extract provide nitrogen compounds, vitamin B complex, amino acids and other essential components necessary for growth; while glucose supplies fermentable carbohydrates essential for bacterial proliferation. Finally, sodium chloride maintains its osmotic balance.

Standardized methods procedures recommend this medium for testing foods, dairy products, water and other materials. It is an inexpensive and straightforward solution.

Add 13g of nutrient broth powder to 1L of distilled water and combine thoroughly before sterilizing using autoclaving at 121oC for 15 minutes. You may further customize your broth with blood, serum or sugars to meet specific purposes. Nutrient broth makes an excellent inoculating substrate for early-stage mycelium growth as it provides rich food sources – providing different sources will make mycelium resilient and adaptable when transitioning onto research substrate.

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