In order to reduce the rapid breakdown of free L-glutamine and increase glutamine stability within cell culture media, L-alanyl-L-glutamine is often substituted. L-alanyl-L-glutamine is a dipeptide that is stable in cell culture medium over longer periods of time. The strong bonds within L-alanyl-L-glutamine stabilize the compound from degradation, while the L-glutamine itself is still readily accessible to the cells. Supplementing media with L-alanyl-L-glutamine can extend the shelf-life of the media at 2-8°C and significantly reduce the problems associated with the breakdown of glutamine into ammonia w