Résumé
γ-Aminobutyric acid (GABA) is a major inhibitory neurotransmitter in central nervous system, and its application in drugs and functional foods has attracted great attention. To enhance production of y-aminobutyric acid, Lactobacillus rhamnosus YS9, a strain isolated from Chinese traditional fermented food pickled vegetable, was grown under submerged fermentation. Its cultivation conditions were investigated. When culture pH condition was adjusted to the optimal pH of glutamate decarboxylase activity, culture of Lb. rhamnosus YS9 in medium supplemented with 200 mM of monosodium glutamate and 200 µM of pyridoxal phosphate (PLP), produced 187 mM of GABA.
Sujets)
Fermentation , Glutamate decarboxylase/analyse , Glutamate decarboxylase/isolement et purification , Microbiologie industrielle , Lacticaseibacillus rhamnosus/enzymologie , Lacticaseibacillus rhamnosus/isolement et purification , Activation enzymatique , Échantillons Alimentaires , Méthodes , MéthodesRésumé
In this paper, a colorimetric method with high sensitivity, reproducibility and low cost for determining glutamate decarboxylase (GAD) activity was developed based on Berthelot reaction. The optimum substrate system is 0.2 mol/L MacIlvaine buffer pH4.7, containing 0.1 mmol/L pyridoxal phosphate (PLP) and 10 mmol/L L-monosodium glutamate (L-MSG). The reaction mixture consisted of 200 ?L substrate solution and 1～100 ?L enzyme preparation from lactic acid bacteria and was incubated at 30℃. The enzymatic reaction was terminated by immersion in ice-water and addition of 200 ?L 0.2 mol/L sodium borate buffer, pH9.0, then 1 mL 6% phenol solution and 400 ?L sodium hypochloride were added. Color development was carried out in boiling water for 10 min then immediately put in ice-water bath for 20 min. The optical density is read at 630 nm. ?-aminobutyric acid (GABA) produced was calculated using the standard curve. Applications of the method in GAD studies were discussed.