Agar consists of a mixture of agarose and agaropectin. Agarose, is a linear polymer, made up of the repeating monomeric unit of agarobiose. Agaropectin is a heterogeneous mixture of smaller molecules that occur in lesser amounts. Agar and the solidifying agents in solid growth media should be well chosen. Agar is available in a range of qualities dictated by the target application. Agar should be highly purified and ideal when high transparency and brightness is needed. For identification and differentiation we recommend using a purified or even highly purified agar. However, when isolating a single colony in most cases a standard quality will suffice. Typical solid
media has an agar concentration of 1.0 - 1.5%, to accommodate the requirements of different applications and growth habits of the target microorganisms.