Determination of the isotope distribution in malate-14C with fumarase-negative lactic acid bacteria

No fumarase activity could be found in whole cells or in cell-free crude extracts from Leuconostoc mesenteroides or Lactobacillus curvatus. The degradation of l-malate-4-¹⁴C by these organisms yielded more than 95% of the label as ¹⁴CO₂. It is therefore recommended that these organisms, rather than Lactobacillus plantarum, should be used in the determination of isotope distribution in l-malate-¹⁴C, since L. plantarum exhibits a significant fumarase activity and thus randomizes malate prior to the decarboxylation of this substance by the malolactic enzyme.