The major role of sodium bicarbonate in culture media is:
Sodium bicarbonate central role in mammalian physiology reproducing blood acid base homeostasis via carbonic acid bicarbonate buffer pair handling volatile acid carbon dioxide produced by cellular respiration ten thousand times more than fixed acids lactate. Enzyme carbonic anhydrase family zinc metalloenzymes CA I II IX highly efficient catalyzing hydration CO2 plus H2O ↔ H2CO3 ↔ HCO3- plus H+ turnover near diffusion limit 10^6 per second enabling rapid equilibration. In culture when glucose metabolized via glycolysis to lactate plus proton, proton combines with bicarbonate producing carbonic
Ref: Freshney bicarbonate buffering carbonic acid pH Henderson-Hasselbalch; Lodish MBoC carbamoyl phosphate pyrimidine bicarbonate carbon source.