D-Glutamine is primarily used in cell culture applications, especially in the production of biopharmaceuticals. It serves as a stable alternative to L-glutamine, which is prone to degradation in aqueous solutions. Due to its resistance to breakdown under standard storage and culture conditions, D-glutamine helps maintain consistent nitrogen and carbon supply in media, supporting cell growth and protein synthesis over extended periods. It is particularly valuable in large-scale mammalian cell cultures where medium stability and longevity are critical. Additionally, D-glutamine is used in research settings to study amino acid metabolism and transporter specificity, helping scientists understand chiral selectivity in cellular uptake mechanisms. Its inertness in most biological systems also makes it useful as a control in metabolic studies.