title: Metabolic pathway of α-ketoglutarate in Lactobacillus sanfranciscensis and Lactobacillus reuteri during sourdough fermentation.
abstract: OBJECTIVE
  To identify metabolites of α-ketoglutarate (α-KG) in Lactobacillus sanfranciscensis and Lactobacillus reuteri in modified MRS and sourdough.
  
  
  RESULTS
  Lactobacillus sanfranciscensis and L. reuteri were grown with additional α-KG in mMRS and in wheat sourdough. In mMRS, α-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 α-KG exhibited OHG dehydrogenase activity of 6.3 ± 0.3, 2.3 ± 0.9, 1.2 ± 0.2, and 1.1 ± 0.1 mmol l(-1) NADH (min x mg protein)(-1), respectively. The presence of phenylalanine and citrate in addition to α-KG partially redirected the use of α-KG from electron acceptor to amino group acceptor. In wheat sourdoughs, α-KG was predominantly used as electron acceptor and converted to 2-OHG.
  
  
  CONCLUSIONS
  Lactobacillus sanfranciscensis and L. reuteri utilize α-KG as electron acceptor. Alternative use of α-KG as amino group acceptor occurs in the presence of abundant amino donors and citrate.
  
  
  CONCLUSIONS
  The use of α-KG as electron acceptor in heterofermentative lactobacilli impacts the formation of flavour volatiles through the transamination pathway.
authors.affiliation: Department of Agricultural, Food and Nutritional Science, University of Alberta, Edmonton, AB, Canada.
authors.forename: C
authors.initials: C
authors.lastname: Zhang
authors.forename: M G
authors.initials: MG
authors.lastname: Gänzle
mesh_terms: D001939:Bread; D005285:Fermentation; D005977:Glutarates / Q000378:metabolism; D007656:Ketoglutaric Acids / Q000378:metabolism*; D007778:Lactobacillus / Q000254:growth & development / Q000378:metabolism*; D052200:Limosilactobacillus reuteri / Q000254:growth & development / Q000378:metabolism*; D014908:Triticum
chemical_list: D005977:Glutarates; D007656:Ketoglutaric Acids; C019417:alpha-hydroxyglutarate