What pH ranges are used in industrial scale fermentation?
Fermentation pH will differ a great deal depending on the bacteria or fungi being used and the process. But it is not uncommon to have a relatively narrow range of pH as a target. Remember pH is the -log[H+] so the pH scale is not linear. Also some fermentation reaction involve very expensive pharmaceuticals or intermediates, a single fermentation batch may have a value in the hundreds of thousands of dollars so keeping +/- 0.3 range in pH is trivial.