Science Buddies: "Ask an Expert"

I am thinking about making nutrient agar at home for my science fair project. In a book I read, it said that you could make nutrient agar by using unflavoured gelatin and beef bouillon cubes. Is it okay for the beef bouillon cubes to be beef flavour , or should it have real beef? Also, is it okay for the cubes to have seasoning in it (like rosemary, garlic) or should I filter that stuff out in some way? How would I do that? Thank you!

Hi,

Here are some Science Buddies resources on making nutrient agar plates and slants:

https://www.sciencebuddies.org/science- ... Agar.shtml

https://www.sciencebuddies.org/science- ... ntagar.pdf

https://www.sciencebuddies.org/mentorin ... =28&t=6033

https://www.sciencebuddies.org/science- ... plates.pdf

While you might be able to use unflavored gelatin in place of agar as a culture medium, be aware that they may not behave the same way in experiments. Gelatin is a protein ( a polymer of amino acids), agar is a polysaccharide (polymer of sugar molecules). If the bacteria you are growing eat protein(which is likely if they are eating beef bullion) they may digest the gelatin and turn your plates into liquid. That won’t happen with agar plates. For general info about agar see:

http://en.wikipedia.org/wiki/Agar

As to using beef bullion in place of beef broth, from what I can tell it should work. The beef bullion I recently bought from the grocery store have beef in the ingredient list and do not list herbs like garlic or rosemary in the ingredient list. I would be cautious about using bullion with these ingredients as many herbs and spices contain antibacterial compounds which might inhibit the growth of precisely the bacteria you are trying to encourage to grow. I could not advise how to remove these components if they are present, but I don’t think you should have any trouble buying bullion without them.

Good luck with your project!

Best regards,

Barrett L Tomlinson

Hi ,

This should be an interesting project.

Barrett has give you some excellent advice. If you cannot order the agar from one of the sources listed in the links, you can probably obtain it at a local Asian or gourmet grocery.

Donna Hardy