you can using different buffers and adding the medium components with measuring pH by pH meter in each case.

- Each has advantages and disadvantages.

- The best is to use a buffer that has a wide pH range. Thus, you can use the same buffer at different pH points. In addition, measure the pH after adding the components of the medium. If it changed after adding the components, you should increase the concentration of your buffer, i.e. use 0.2 M buffer rather than 0.1 M.

- Using buffers, you would study the effect of pH; the pH will usually stable along the incubation period. However, you need one buffer that is stable at a wide pH range. At the same pH point, different buffers may differently affect the bacteria due to different compositions in addition to pH.

- using NaOH and HCl to adjust the medium pH, you would study the effect of initial pH; the pH will usually be shifted during the incubation period by the action of metabolites. Thus, in this case, you should measure the final pH after incubation time-by pH meter.