Dear,
I am preparing the PTM1 Trace elements for Pichia pastoris. I've known that biotin dissolves weakly in water, especially in low pH. In the PTM1 recipe, the biotin is 200 mg/L. This amount is the same with maximum solubility in water. In the other hand, we use Sulfuric acid; this acid makes the pH decrease.
I've tried once step by step according to the recipe, but the biotin could not dissolve completely.
So, how could you prepare the PTM1 solution? Please help me.
Thank you.
Best regards.
At 200 mg/L that's 1 mM, it should dissolve. Try warm water or 10 mM bicine buffer pH 8.3. Also, beware that it takes time. Leave it rocking at room temperature for at least 1 hour to let it dissolve.
Something I've done (but I've never properly validated, so take it with a grain of salt) is to prepare a very concentrated (10,000 X) biotin solution in dimethylformamide or DMSO. So far it has seemed to work; meaning, I've never found a problem doing it.
Hope it helps!
Dear Alejandro,
It sounds that I have a solution from you now. That's great. Thank you very much.
Could you tell me more about preparing biotin stock in dimethylformamide or DMSO? I would like to know about the buffer concentration.
There's not much to tell, I simply prepare it at 10,000 times the working concentration, so it depends on what your working concentration is. It dissolves readily in either DMF or DMSO (although my chemist friends have told me to stick with high quality DMF) and since the volume of solvent added to the culture is very small, I have always assumed that the solvent will have no effect on cell growth. That last part I have not verified rigurously, however, and I have no data on the stability of biotin in DMF, hence the "grain of salt" comment.
Dear Trung Nghia
For my suggestion, you can prepare biotin stock solution completely by dissolve in the water, then add a few drops of 5N NaOH or you can add more until the powder is completely solubilized. After that, adjust the volume with water and 0.22-micron filtrate.
Good luck
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