Hello,
I am trying to perform nitrate assay using UV-VIS Spectrophotometry at 220 nm, for synthetic wastewater inoculated with an isolated bacterial species. My control consists of autoclaved synthetic wastewater and the sample consists of the synthetic wastewater inoculated with bacteria. I calculated the % of nitrate reduction in the sample from the 0 hour reading of the control for 24 and 96 hours. However, after 96 hours the nitrate concentration in the sample increased from that present in the control.
Kindly provide with any possible explanation for this.
If your synthetic wastewater mimics real sewage, it should contain ammonia, which bacteria oxidize over time to release nitrate. In the absence of any further information this seems like the most likely explanation.
This is due to the bacterial action in the system. If ammonia present in the sample then Nitrifying bacteria (include ammonia-oxidizing bacteria (AOB) and nitrite-oxidizing bacteria (NOB), convert the most reduced form of Nitrogen, Ammonia, into its most oxidized form, nitrate. Many species of nitrifying bacteria have complex internal membrane systems that are the location for key enzymes in nitrification.
This is an interesting article too
https://www.technologynetworks.com/immunology/news/secret-to-bacterial-nitrate-production-finally-revealed-350967
Because nitrifying Nitrosmomonas and Nitrobacter bacteria continuously convert ammonium to nitrate if you want to stop this add a drops of chloroform to your samples to kill these bacteria
I think that the increase in nitrate concentration is due to the oxidation of ammonia by bacteria.
The increase in nitrate concentration may be due to the transformation of ammonia and nitrite into nitrate caused by the nitrite-oxidizing bacteria that are present in your samples.
From 24 hours to 96 hours…what is the percentage increase?
After 96 hours what is the percentage increase?
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