What is Agar?

Instructor: Jeremy Battista
Here we will look at what agar is, what it is used for, and generally why it is important. Agar resembles gelatin and in most cases is very similar to it.

What Is Agar?

Agar, which looks similar to Jello, is derived from red/purple algae. It utilizes two polysaccharides (sugars) called agarose and agaropectin found in the cell walls of certain algae. They can be extracted from the alage through boiling. Again, it looks similar to Jello and has a similar texture and feel to it, albeit a little bit slimier.

Where Is It Found?

The red algae that are used to produce the agar are from Pacific coastal regions of Asia and California. The specific algae are from the Gelidium and Gracilaria genera. Agar can essentially be found anywhere from kitchens to laboratories. We will go into greater detail next as to where and why it would be found in these places.

What Is It Used For?

Agar is commonly used in the laboratory to help feed and grow bacteria and other microorganisms. It acts as a culture that provides nutrients and a place for these items to grow, but since it is indigestible to the microorganisms, they cannot eat and destroy it. There are various types of agar, some of which include MacConkey Agar, Chocolate Agar, Tryptic Soy Agar, Triple Sugar Iron Agar, Hektoan Agar, and Mannitol Salt Agar.

Various strains of bacteria growing on agar plates
Bacteria growing on agar plates

Agar is also found in things like jelly, make-up, and clarifying agents for drinks. Agar can also be used a substitute for gelatin for those who are vegetarians and want to stay away from animal products.

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