Acidified 0.5x Potato Dextrose Agar (APDA)

Disclaimer

This protocol is provided for research and educational purposes only. Ensure that all procedures are conducted by trained personnel following relevant safety and ethical guidelines. The authors and publishers are not responsible for any injuries, damages, or legal consequences resulting from the use of this protocol.

Abstract

Acidified 0.5x Potato Dextrose Agar (APDA) is a specialized culture medium used in microbiology for the selective cultivation of fungi, particularly in environments where lower pH is required to inhibit bacterial growth. This medium contains a reduced concentration of nutrients compared to standard PDA, making it useful for specific fungal isolations and studies.

APDA is not ideal for cultivating bacteria, fungi that prefer neutral pH environments, or nutrient-demanding fungi. It should also be avoided in situations where accurate quantification of fungal growth, enzyme activity studies, or broad-spectrum fungal isolation is required.

Before start

Ensure that all materials and equipment are available, clean, and sterilized. Prepare the lactic acid solution and ensure that the autoclave is set up and ready for use.

Steps

Prepare the Medium:

In a 1-liter Erlenmeyer flask with a stir bar, dissolve the following components in 1 liter of distilled water (dH2O):

10g of potato dextrose broth.
18g of agar. Stir the mixture thoroughly until all components are fully dissolved.

Sterilize:

Autoclave the solution at 121°C for 20minutes using the liquid cycle to sterilize the medium.

After autoclaving, remove the flask from the autoclave and place it on a magnetic stirrer.

Stir the medium for approximately 1 minute until the solution is homogeneous.

Acidification:

Add 1mL of 85% lactic acid to the medium.* Stir the medium again for approximately 1 minute to ensure the lactic acid is evenly distributed.

Place the flask in a room temperature water bath and stir continuously until the temperature of the medium cools to between 55°C and 40°C .

Pour into Petri Dishes:

Work aseptically to pour the cooled medium into sterile Petri dishes.* Allow the medium to solidify at room temperature before storing or using.