α-Ketoglutarate biosynthesis in wild and industrial strains ofLactococcus lactis

Abstract

Aims: This study was carried out to explore the ability of wild and industrial strains of Lactococcus lactis to produce α‐ketoglutarate (α‐KG), which is essential during the conversion of amino acids to flavour compounds. Methods and Results: Two pathways in α‐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 α‐KG or Glu via GDH was confirmed. However, L. lactis strains were not able to biosynthesize α‐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.

Comparison of volatile compounds produced by wild Lactococcus lactis in miniature Chihuahua-type cheeses

“…These strains have been previously identified with GDH activity. Two out of three strains (MH05 and RQ07) with GDH-NADP activities and one strain with GDH-NAD activity (Gutiérrez-Méndez et al 2008a). However, other strains similarly confirmed with GDH activities and also used in this work did not produce unusual patterns or large abundance of volatile compounds.…”

Formation of volatile compounds, peptidolysis and carbohydrate fermentation by mesophilic lactobacilli and streptoccocci cultures in a cheese extract

“…On the contrary, S. thermophilus 2 alone was not able to increase the concentration of pyruvate in the extract when reinoculated. Conversely, α-ketoglutaric acid is a less ubiquitous intermediate compound, as it participates in fewer metabolic pathways than pyruvate does; it is involved mainly in production via GDH activity on glutamate and consumption in transamination reactions (Gutiérrez-Méndez et al 2008;Tanous et al 2005;Yvon 2006). The increase in the concentration of α-ketoglutaric acid during incubation in St extracts is in agreement with the high levels of GDH activity of S. thermophilus 2 (Peralta et al 2016).…”

“…The selection of LAB that possess key enzymatic activities (AT and GDH) and their use in mixed cultures with complementary enzymatic profiles have been proposed as an approach to increase flavour in cheese (Gutiérrez-Méndez et al 2008;Smit et al 2009). In particular, interest has been paid to elucidate whether cooperation between strains showing either high GDH or AT activities was possible.…”

On-line monitoring of food fermentation processes using electronic noses and electronic tongues: A review

“…This classification of strains based on the production of volatile compounds was in conformity with the classification obtained with the repetitive extragenic palindromic polymerase chain reaction (REP-PCR) molecular method. Gutiérrez-Méndez et al [17] used a metal oxide semiconductors based e-nose to screen the aroma generation of Another interesting contribution deals with tea fermentation. During black tea manufacturing, tea leaves pass through a fermentation in which the grassy smell is transformed into a floral smell.…”