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Metabolic pathway of α‐ketoglutarate in Lactobacillus sanfranciscensis and Lactobacillus reuteri during sourdough fermentation
Author(s) -
Zhang C.,
Gänzle M.G.
Publication year - 2010
Publication title -
journal of applied microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.889
H-Index - 156
eISSN - 1365-2672
pISSN - 1364-5072
DOI - 10.1111/j.1365-2672.2010.04753.x
Subject(s) - alpha ketoglutarate , lactobacillus reuteri , transamination , fermentation , biochemistry , lactobacillus , electron acceptor , biology , chemistry , food science , amino acid , enzyme
Aim: To identify metabolites of α‐ketoglutarate (α‐KG) in Lactobacillus sanfranciscensis and Lactobacillus reuteri in modified MRS and sourdough. Methods and 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. Significance and Impact of the Study: The use of α‐KG as electron acceptor in heterofermentative lactobacilli impacts the formation of flavour volatiles through the transamination pathway.