How to Get the Most Out of Agar for Culture Media

Bacteriological agar forms the basis of many culture media. Using it correctly improves the reproducibility and recovery of microorganisms. For this reason, we would like to offer some simple tips to help you make the most of this product.

First, choose the right quality. Purchase bacteriological or microbiological grade agar, considering its gel strength. For applications requiring greater precision, such as cell culture or clinical diagnosis, check the technical data sheet and perform isolated tests before using it on a large scale.

Adjust the product’s concentration according to the desired firmness and technique (spreading, pouring, etc.).

For preparation and thermal management, completely dissolve the agar in the indicated volume of water or medium. Allow it to cool to 45–50 °C before adding heat-sensitive components, such as antibiotics, blood, or substrates, to prevent degradation or denaturation.

Pour plates in a clean area to avoid contamination. Allow the plates to dry slightly with the lid tilted before storing to prevent condensation.

Adjust and check the pH of the medium before sterilizing it. Use distilled or deionized water to prevent ions from altering the gel or the solubility of compounds.

Store solid media in airtight bags or boxes at 4 °C to prevent drying and contamination. Do not reuse used plates.

Finally, record the preparation and storage conditions to facilitate troubleshooting and traceability.

Following these steps will optimize the firmness, transparency, and support capacity of the agar, thereby improving isolation, quantification, and reproducibility in your cultures.