Untitled

Isolation, Purification, and Characterization of Nitrate Reductase from a Salt-Tolerant Rhodotorula glutinis Yeast Strain Grown in the Presence of Tungsten

“…Previously we have shown [16] that 1 mM W, being added to the medium containing nitrate and Mo, enhanced growth of the salt tolerant Rh. glutinis yeast strain and stimulated its nitrate reductase activity.…”

“…Cells were routinely grown at 28 30°C with orbital agitation (220 rpm) in 750 ml flasks in 100 150 ml of liq uid modified Rider's medium, pH 4.5 4.6, containing (g/liter): MgSO 4 ·7H 2 O, 0.5; NaCl, 0.1; CaCl 2 ·2H 2 O, 0.05; KH 2 PO 4 , 8.6; KNO 3 , 0.3; glycerol, 7.5; Na 2 WO 4 ·2H 2 O, 0.33, supplemented with microelements and vitamins as described earlier [16]. In the control experiments, Na 2 WO 4 ·2H 2 O was omitted and the medi um contained only trace amounts of Mo as impurities from the reagents used.…”

“…Cell extract was obtained by cell disruption in a French press at 100 150 atm as described previously [16]. The homogenate was centrifuged at 19,000g for 20 min at 4°C, and the supernatant (the cell free extract) was used for nitrate reductase purification.…”

“…Tungsten in the protein fractions was determined by the kinetic method designed in our laboratory [23].…”

“…Previously [16], we have shown that a salt tolerant Rhodotorula glutinis yeast strain, unlike many other microorganisms, including the salt sensitive Rh. glutinis strain, is able to grow in the presence of high (1 mM) equimolar concentrations of W and Mo.…”