Question

What is denitrification of nitrate reactions?

Answer 1

In the process of denitrification nitrate (NO3−) is reduced and ultimately produces molecular nitrogen ($N_2$) through a series of intermediate gaseous oxide products and this process is done by microbes. Facultative anaerobic bacteria perform denitrification by reducing oxidized nitrogen in response to the oxidation of an electron donor for example organic matter, it is a kind of respiration by bacteria.

Complete answer:
Denitrification is defined as the process that converts nitrate to nitrogen gas and during this process bioavailable nitrogen is removed and it returns to the atmosphere. Dinitrogen gas ($N_2$) is the final outcome of denitrification, but other intermediate gases which contain nitrogen also exist. These intermediate gases, including the laughing gas ($N_2O$), are considered greenhouse gasses because they react with ozone and contribute to pollution.

Denitrification is an anaerobic process unlike nitrification which is an aerobic process. Denitrification occurs mostly in soil sediments and anoxic zones in lakes and oceans. Similar to organic processes , denitrification is administered by a various group of prokaryotes, and there's recent evidence that some eukaryotes also are capable of denitrification. Some denitrifying bacteria include species within the genera Bacillus , Paracoccus , and Pseudomonas. Denitrifiers are chemoorganotrophs and thus must even be furnished with some sort of organic carbon.

Denitrification is a vital process because it removes fixed nitrogen (i.e., nitrate) from the ecosystem and returns it to the atmosphere in a biologically inert form ($N_2$). This is an important process particularly in agriculture where the loss of nitrates in fertilizer is detrimental for the crop. In wastewater treatment denitrification plays very important role by removing unwanted nitrates from the wastewater effluent, thereby reducing the probabilities that the water discharged from the treatment plants will cause undesirable consequences (e.g., algal bloom).

Note:
When an organism dies or excretes waste in the environment then the nitrogen present in its tissues is a type of organic nitrogen for example amino acids, DNA etc. Now various microorganisms like fungi and prokaryotes decompose the tissue and release inorganic nitrogen back to the ecosystem as ammonia within the method mentioned as ammonification. The ammonia which is released then becomes available for uptake by plants and other microorganisms for growth.