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Influence of metal ions and organic carbons on denitrification activity of the halotolerant bacterium, Paracoccus pantotrophus P16 a strain from shrimp pond
Pintathong, P.; Richardson, D.J.; Spiro, S. & Choorit, W.
Abstract
The effect of metal ions, ferric ion (Fe3+) and
molybdenum ion (Mo6+) on the denitrification process of
Paracoccus pantotrophus P16 grown under saline
conditions was investigated. Results revealed that the
dosages of added Fe3+ and Mo6+ significantly accelerated
nitrate utilization and nitrite accumulation. Enzymatic
studies revealed that the membrane-bound nitrate
reductase and the periplasmic nitrite reductase had
activities of 998 ± 28 and 373 ± 18 nmol (mg protein)-1
min-1, respectively after growing Paracoccus
pantotrophus P16 in medium supplemented with 1.5 μM
Fe3+. If provided with 1.5 μM Fe3+ and 2.4 μM Mo6+, the
membrane-bound nitrate reductase activity increased to 6,223 ± 502 nmol (mg protein)-1 min-1 and the
periplasmic nitrite reductase was 344 ± 20 nmol (mg
protein)-1 min-1. The results indicated that an addition of
Fe3+ and Mo6+ led to an overstimulation of nitrate
reductase activity as compared with nitrite reductase
activity. When glucose was supplied, the minimal ratio
of carbon per nitrate (C/N) was 2.31 mg C/mg NO3
--N
with denitrification yield of 0.45 g NO3
--N/g C. Addition
of ethanol instead of glucose, the minimal ratio of C/N
was 1.15 mg C/mg NO3
--N with denitrification yield of
1.08 g NO3
--N/g C.
Keywords
metal ions, nitrate reductase, nitrite accumulation, nitrite reductase, Paracoccus pantotrophus
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