Isotopomer analysis showing the mass fraction of isotopomers for selected proteinogenic amino acids [TBDMS based measurement] and D-lactate [MSTFA based measurement]. Standard abbreviations are used for amino acids in the figure. (A) Cultures grown with 5 g/L of [1,2-13C] glucose and (B) Cultures grown with 15 mM of [1,2-13C] acetate. "white bar" m0 – mass fraction without any labeled carbon; "grey bar" m1 – mass fraction with one labeled carbon; "black bar" m2 – mass fraction with two labeled carbon. (Note: natural 13C makes up about 1.1% of total carbon as measurement background).