Aim: To identify metabolites of alpha-ketoglutarate (alpha-KG) in Lactobacillus sanfranciscensis and Lactobacillus reuteri in modified MRS and sourdough. Methods and Results: Lactobacillus sanfranciscensis and L. reuteri were grown with additional alpha-KG in mMRS and in wheat sourdough. In mMRS, alpha-KG was used as an electron acceptor and converted to 2-hydroxyglutarate (2-OHG) by both organisms. Production of 2-OHG was identified by high performance liquid chromatography (HPLC) and confirmed by gas chromatography (GC). Crude cell extracts of L. sanfranciscensis and L. reuteri grown with or without alpha-KG exhibited OHG dehydrogenase activity of 6 center dot 3 +/- 0 center dot 3, 2 center dot 3 +/- 0 center dot 9, 1 center dot 2 +/- 0 center dot 2, and 1 center dot 1 +/-0 center dot 1 mmol l-1 NADH (min x mg protein)-1, respectively. The presence of phenylalanine and citrate in addition to alpha-KG partially redirected the use of alpha-KG from electron acceptor to amino group acceptor. In wheat sourdoughs, alpha-KG was predominantly used as electron acceptor and converted to 2-OHG. Conclusions: Lactobacillus sanfranciscensis and L. reuteri utilize alpha-KG as electron acceptor. Alternative use of alpha-KG as amino group acceptor occurs in the presence of abundant amino donors and citrate. Significance and Impact of the Study: The use of alpha-KG as electron acceptor in heterofermentative lactobacilli impacts the formation of flavour volatiles through the transamination pathway.