Agar

Substitute for gelatin, isinglass, etc. in making emulsions including photographic, gels in cosmetics, and as thickening agent in foods especially. confectionaries and dairy products; in meat canning; in production of medicinal encapsulations and ointments; as dental impression mold base; as corrosion inhibitor; sizing for silks and paper; in the dyeing and printing of fabrics and textiles; in adhesives. In nutrient media for bacterial cultures.
Agar is produced by some red algae species (Rhodophyceae), especially Gelidium and Gracilaria. Agar contains two polysaccharides - agarose (agaran) and agaropectin. Agarose consists mainly of D-galactose and the 3,6-anhydro form of L-galactose, with small amounts of D-xylose. Some of the D-galactose units are methylated at C-6. The polymer contains alternatingsegments of α(1~3) linked D-galactose units and β (1~4) linked 3,6-anhydro-L-galactose. The main chains of agaropectin are similar, but contain D-glucuronic acid and small amounts of other sugars, including sulphate esters. Agar is not attacked by microorganisms and its strong gel-forming properties make it an ideal matrix for microbial cultures.