I am working on production of acid metabolites in E.coli in which I have to compare the effect of various bases like NaOH, KOH and Ammonia etc. Could anybody please suggest the concentration of ammonia for neutralization? Thanks in advance.
It mostly depends on the size of the reactor. We use very concentrated acids and bases for our smaller reactors, since we don't want a large volume increase. It would also depend on the minimum volume you can pump into the reactor.
Dear Mr. Mukesh: Ammonia solution used for neutralization is about 20% - 25 % and it also depends on the requirement of the organisms. In some process ammonical nitrogen concentration should not go beyond 550 - 600 ppm - so, ammonia solution is used accordingly but not only for pH adjustment but also as nitrogen source.
I usually use a 15% ammonia solucion. For a 1.5L E. Coli fermentation it requires around 50 ml to achieve a high cell density (above OD 120).
Thank you all for your valuable suggestions. I will be using 25% of ammonia for my experiments. Thanks again.
Dear Mukesh Shankar,
I use liquid Ammonia Solution (~ 37%), Sod. Carbonate (50% sterilized at 121 0C) for pH adjustment in normal protein adjustments.
Regards
V.Sreedhar
I used 25 % ammonia solution for pH-stat fed batch E.coli culture. The ammonia is also as a N-source which allows high cell density culture.
The ammonia concentration should be lower than 3 g/L in the culture medium because at higher concentrations it is toxic to E. coli. Do you use the ammonia solution to control pH or to supply Nitrogen too? Please consult 28. Riesenberg, D. (1990). Current opinion in Biotechnology. 2:380-384.
The ammonium concentration in the broth does not depends on the concentration of the solution used for pH-control, therefore it can be used any concentration of ammonia but at higher concentration your system might overshoots the ammonia titrant because of high concentration in the solution, typically 5% is ok.
If you use the protein medium (not mineral one) then pH typically is stable.
For E.coli fermentation the most important to control glucose concentration that should be below 2 g/l otherwise the glucose transforms into acetic acid that affects the pH and inhibits the cell growth. If you use just protein medium (Lauria medium) then whitout glucose the pH is stable and no risk of acetic acid releasing.
Is it required to sterilized ammonia solution.. by any method say filteration ?
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