Industrial production of ammonia requires high temperature and pressure. But the natural fixation occurs in ambient environmental conditions.
I’d be interested to know the mechanisms employed (mediated by the enzyme) by the bacteria in achieving this?
BIOLOGICAL NITROGEN FIXATION
see links please
http://www.fao.org/wairdocs/ilri/x5546e/x5546e05.htm
https://www.nature.com/scitable/knowledge/library/biological-nitrogen-fixation-23570419
I suggest you to check literature about denitrification, biological nitrogen fixation anda ammonification. Enzymes involved are te key to understand this process in natural marine environments
Yes, i agree with Dr. Rosa that Enzymes involved are key to understand this process in natural marine environments. So, better check literature on nitrogen species conversion processes.
Best!
Dear Renjith,
The key enzyme responsible for fixing atmospheric N2 gas either in the marine or terrestrial (soil)/freshwater environment is Nitrogenase. This enzyme has been associated with most N2 fixing and chlorophyll bearing phototrophic microbes such cyanobacteria (e.g. Trichodesmium), bacteria and some archaea.
This wonder metalloenzyme (which contains Fe and Mo) has been estimated to have been present and active on earth 4 billion years ago. The enzyme is O2 sensitive owing to oxidisable metal content, however, is being utilised by N fixing unicellular microbes such as cyanobacteria successfully by allocating timing for O2 producing/energy creating photosynthesis process often proceeded by N2 fixation.
Solar energy captured through photosynthesis is the key to microbial N2 fixation, as you alluded industrial process of converting N2 + H2 to NH3 requires substantial amount of energy (450oC, 200 atmospheric pressure and the use of Fe3O4 as catalyst).
For the above reason, the enzyme process of fixing N2 is extremely energy taxing which utilises 16 ATP (+ 8 e- + 8 H+) for each N2 molecule to convert to 2 NH3 molecules (and one H2 molecule). Unlike the industrial reaction the enzyme reaction is slow but with steady process and large number of microbes, millions of tonnes of N can be fixed annually through this natural process (e.g. in the marine environment 100-190 million tonnes/year).
As you can see, since the enzyme requires Fe, scientists are excited to trigger phytoplankton activity (of which a large proportion is attributed to cyanobacteria) in the ocean to fix large amount of CO2 by introducing Fe artificially to mitigate the impacts on climate change.
Numerous literature had been published on biological N2 fixation in marine and terrestrial environment to date which you can easily access. Interestingly, NZ scientists have estimated, under clover-based ryegrass pasture system biological N2 fixation can be around 200 kg N/ha/year and excessive use of fertiliser-N can suppress biological-N fixation.
Kind regards
Selva
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