After hydrogenation of the 300 µl sample and magnetic field cycle, the hyperpolarized reaction mixture was collected in a syringe containing 150 µl of acidic buffer solution (HEPES 144 mM, pH 5.5) to produce a 450 µl solution with physiological osmolarity (290 ± 2 mOsm) and optimal pH (7.6 ± 0.2) for the enzyme activity. 200 µl of the hyperpolarized reaction mixture was injected into a 5 mm NMR tube via syringe through PTFE tubing (1.6 mm O.D., 0.8 mm I.D.) in the high field NMR magnet. The NMR tube contained 200 µl of culture media at 310 K.