Sterile Minimum Essential Medium is a commonly used modification of the Basal Medium acc. to Eagle, having been developed in 1959 for culturing of HeLa cells. MEM contains high concentration of amino acids, which conform closely to the protein composition of human cells. Concentration of vitamins, and other essential nutrients, is enhanced, allowing longer cultivation periods between feedings. MEM is one of the most widely used cell culture media and can be used for a variety of suspension cell cultures and adherent cells. Generally, FBS is added to MEM basal media. ROTI ® Cell Eagle’s MEM / Earle’s CELLPURE ® ready-to-use, sterile, with stable glutamine, w/o pyruvate This modification of MEM contains stable glutamine and Earle’s salts, but no pyruvate. Stable glutamine is present as the dipeptide L-alanyl-L-glutamine. Due to its reinforced structure, this form of glutamine is not temperature sensitive, unlike normal L-glutamine, and therefore does not spontaneously decompose to toxic ammonia. Cells are able to break down this dipeptide bond and release L-glutamine as needed. Thus, the low ammonia concentration improves cell viability and growth. In addition, the concentration of L-glutamine is kept constant. Stable gluatmine has already been added to some cell culture media, but can also be purchased as a separate additive solution, the ROTI ® Cell Glutamine Solution.