temperature and pH of culture media

Temperature:
Temperature affects culture media pH by compounding small fluctuations in pH values. Increasing the temperature of culture media favors a dissociation of hydrogen ions, leading to an acidification of the medium and a decrease in the pH value. Although drastic temperature changes are required to make drastic pH changes, it’s important to consider that temperature is one of the variable reasons that your culture medium currently is in the pH range you have and why there will always be small fluctuations.

Temperature also affects the pH result observed through pH testing using a pH electrode probe. Changes in temperature affect the Nernst Equation slope used by the pH electrodes. It can also affect the isothermal point of the pH probe, the intersection of calibration lines at differing temperatures. The error is further exaggerated when the buffer solutions and the medium to read are at widely differing temperatures. Changes to the Nernst Equation slope can be resolved by using a pH probe with automatic temperature compensation (ATC) capabilities or by measuring the temperature of the media solution and adjusting the slope accordingly. While many pH probes have combined temperature and pH reading electrodes, they can have a sluggish response, further adding ambiguity to your final pH value as ambient air conditions shift proton dissociation to a more basic pH value.