In addition to HPLC analysis of D/L-lactic acid, D- and L-lactic
acid isomers were individually quantified for selected experiments
using an enzymatic assay based on conversion of lactate to
pyruvate by D-lactate dehydrogenase and L-lactate dehydrogenase,
respectively (D-/L-lactic acid kit Catalog# K-DLATE, Megazyme
International Ireland Limited, Bray, Co. Wicklow, Ireland).
The NADH produced by the reaction was measured spectrophotometrically
at 340 nm with a Cary 300 Bio UVeVisible Spectrophotometer
(Agilent Technologies (formerly Varian), Santa Clara,
CA, USA).