In bioreactors, I maintain a low pH via combination of cell metabolism and base addition. In shake flask, base addition is not possible, and I've been looking for a suitable, biologically compatible buffer system for a pH between 3 and 4. Most biological buffers are designed for much higher pH ranges.
I've tried sodium citrate/citric acid, but my cells grow poorly and lyse.
Any suggestions? I plan to try a glycine-HCl system, but I'm not too confident about it, the HCl doesn't sound cell-culture friendly.
As an alternative to adding a buffer, you might try using urea rather than ammonium salts as the nitrogen source. This simple replacement strongly decreases acidification of yeast cultures in defined media and, in most yeast strains, has little impact on growth rates.
Hi there,
I think this paper should help :
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC123831/
As an alternative to adding a buffer, you might try using urea rather than ammonium salts as the nitrogen source. This simple replacement strongly decreases acidification of yeast cultures in defined media and, in most yeast strains, has little impact on growth rates.
I have had very good results with 25-50 mM citrate buffer. Urea as nitrogen source is a good option too.
You may want to check answers given to a related question at this forum: «What is the best buffer for pH 3,5?»: https://www.researchgate.net/post/What_is_the_best_buffer_for_pH_3_5
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