Potato dextrose agar



Potato dextrose agar (BAM Media M127 ) and potato dextrose broth are common microbiological growth media made from potato infusion and dextrose. Potato dextrose agar (abbreviated "PDA") is the most widely used medium for growing fungi and bacteria.

PDA has the capability to culture various bacteria and fungi found in the soil. This agar can be used with antibiotics or acid to inhibit bacterial/fungal growth. PDA is used in the food industry to test for fungi that can spoil food products. It is also used in the pharmaceutical industry to screen for potential antifungal agents in medications.

Potato dextrose agar is a versatile growing medium for bacteria and fungi (yeasts and molds). This agar is used for a broad range of fungi but there are other agars that are more selective for specific types of fungi. These agars include but are not limited to malt extract agar and sabouraud agar. Malt extract agar is more acidic than PDA and is commonly used to cultivate penicillium species. Sabouraud agar is also slightly acid with pH of 5.6-6.0 which is similar to PDA. It is most often used for the isolation of pathogenic fungi such as dermatophytes.

Typical composition

 * {| class=wikitable style="text-align:center;"

! value || ingredients & conditions (sliced washed unpeeled)
 * 1000 mL || water
 * (strained broth from 200 g of infused potato into the water above) || potatoes
 * (strained broth from 200 g of infused potato into the water above) || potatoes
 * (strained broth from 200 g of infused potato into the water above) || potatoes
 * 20 g || dextrose
 * 20 g || agar powder
 * 5.6±0.2 || final pH
 * 25°C || temperature
 * }
 * 5.6±0.2 || final pH
 * 25°C || temperature
 * }
 * }

Potato infusion can be made by boiling 200 g of sliced (washed but unpeeled) potatoes in ~ 1 L distilled water for 30 minutes and then decanting or straining the broth through cheesecloth. Distilled water is added such that the total volume of the suspension is 1 L. 20 g dextrose and 20 g agar powder is then added and the medium is sterilized by autoclaving at 15 psi for 15 minutes.

A similar growth medium, potato dextrose broth (abbreviated "PDB"), is formulated identically to PDA, omitting the agar. Common organisms that can be cultured on PDB are yeasts such as Candida albicans and Saccharomyces cerevisiae and molds such as Aspergillus niger.