[saquiwej]

I am sorry that you find my post difficult to read. I am not sure, whether you are hinting at my English, or rather to the incorrect use of some technical terms. I tried to be as clear as possible. I have never been very good at punctuation, so, a comma might be missing here and there.
Bacteria produce some phytase, for sure, which contributes to dephytinisation, the same as the endogenous phytase. What I am saying is only that in case of enzyme-rich cereals, such as wheat and rye, which are principally used for bread-making, the role of bacterial phytase is minimal. The reason people are using sourdough, or bakers yeast, for that matter, is not to break down phytates present in the dough, but to make it swell and more palatable. The phytates would break down even if there were not a single microorganism in the dough.
My other point was that people make great efforts to dephytinise pig feed, but no one really cares what people eat. I am trying to work out a simple method to dephytinise grains at home. A fool-proof acid buffer (pH 5 - pH 6) would be a great asset to achieve this end.

[Borek]

Wall of text - you are not splitting your text into paragraphs, which makes reading challenging. Other than that it is OK for me.

Safe (in terms of consumption/food stuff) pH 5-6 buffer would be one based on the citric acid and its sodium salts.

[Babcock_Hall]

Good idea about citrate.  It will buffer well in a broad region of pH values.

[saquiwej]

Thanks for the suggestions. I see now that I’ll have to do a bit of experimentation myself. It seems that there is no ready for use recipe for an acid buffer to be used with foods. For my experiments I will need a reliable pH meter with a precision of ±0.5 pH. Could anyone suggest a brand? I am thinking to pay up to 30€. Is it true that a pH meter needs to be calibrated before each measuring?

[Borek]

Is it true that a pH meter needs to be calibrated before each measuring?

Perhaps not literally before "each", it should be enough to check the calibration once per each series of measurements, or once daily, but it definitely requires calibration if you want reliable results.