Ketoglutarate biosynthesis in wild and industrial strains of Lactococcus lactis

Aims:This study was carried out to explore the ability of wild and industrial strains of Lactococcus lactis to produce a-ketoglutarate (a-KG), which is essential during the conversion of amino acids to flavour compounds. Methods and Results:Two pathways in a-KG biosynthesis were explored in strains of L. lactis isolated from dairy products, vegetables and commercial dairy starter cultures. Half of the strains efficiently converted glutamine to glutamate (Glu) and grew in Glu-free medium. Strains did not present isocitrate dehydrogenase and aconitase activities. However, half of the strains presented glutamate dehydrogenase (GDH) activity. Conclusions:The ability of L. lactis to synthesize either a-KG or Glu via GDH was confirmed. However, L. lactis strains were not able to biosynthesize a-KG by the citrate-isocitrate pathway. NADP-GDH activity was mainly found in strains isolated from vegetables, whereas NAD-GDH activity was mainly found in strains isolated from dairy products. Significance and Importance of the Study:The origin of isolation highly influenced NAD or NADP-GDH activities. These enzymatic activities may be correlated to the flavour production capacity of the different strains.