Effect of cations on the activity of NADP+-dependent glutamate dehydrogenase in Acinetobacter calcoaceticus IMV B-7241, Rhodococcus erythropolis IMV Ac-5017 and Nocardia vaccinii IMV B-7405 grown on industrial waste.

Introduction. It is studied the activity of NADP+-dependent glutamate dehydrogenase in the presence of mono- and divalent cations (potential activators of this key enzyme of surface-active aminolipids biosynthesis) in A. calcoaceticus IMV B-7241, R. erythropolis IMV Ac-5017 and N. vaccinii IMV B-7405 during cultivation on waste of biodiesel production and sunflower oil waste. Materials and methods. Cultivation of strains was performed in liquid mineral media using as substrates: refined and waste (after frying potato) sunflower oil, refined glycerol and waste of biodiesel production. NADP+-dependent (EC 1.4.1.4) glutamate dehydrogenase activity in cell-free extracts was analyzed for glutamate formation during oxidation of NADPH at 340 nm. Monovalent (Na+, K+) and divalent (Mg2+, Ca2+, Zn2+) cations in the form of salts of NaCl, KCl, MgSO4 x 7H2O, CaCl2 and ZnSO4 x 7H2O were added to the reaction mixture, as well as into the medium for strains cultivation. Results and discussion. Calcium cations were found to be activators of NADP+-dependent glutamate dehydrogenase activity in R. erythropolis IMV Ac-5017 and N. vaccinii IMV B-7405 grown on refined and waste sunflower oil: in the presence of 1-5 mmol Ca2+ in the mixture, the activity of the enzyme increased 1.3-2 times compared with that without these cations. The increase in the concentration of CaCl2 to 0.2-0.4 g/l in oil-containing medium of strains IMV Ac-5017 and IMV B-7405 cultivation was accompanied by an increase in NADP+-dependent glutamate dehydrogenase activity by 1.3-1.5 times compared with that on basic medium. When additional quantity of CaCl2 (0.1-0.2 g/l) was introduced into the medium with purified glycerol for the cultivation of A. calcoaceticus IMV B-7241, an increase in NADP+-dependent glutamate dehydrogenase activity was observed by almost 2.5-3 times compared with those for strain IMV B-7241 on the basic medium. There was no impact of activating cations magnesium, zinc, potassium and sodium on NADP+-dependent glutamate dehydrogenase activity of all strains grown on oil-containing substrates and glycerol of different degrees of purification. Conclusion. The results demonstrate the possibility to increase activity of key enzymes of the biosynthesis of the desired product: the composition of the medium should be modified by changing the content of enzymes' activators. [ABSTRACT FROM AUTHOR]