The desired pH was maintained by adding concentrated
feeding medium containing acetic acid (Mallinckrodt Baker
Inc., Phillipsburg, NJ). Once the pH reached 0.05 units higher
than the set-point, acetic acid medium was automatically
added. The feeding medium had a C/N ratio of 49/1, and it
contained 700 g/L acetic acid, 21.3 g/L NH4Cl, 4.8 g/L KH2PO4,
1.7 g/LNa2HPO4, 3.6 g/L MgSO4.7H2O, 1.8 g/L yeast extract,
1.8 g/L EDTA, and 178 ml/L spores stock solution. The growth
rate of the pH 7.0 culture became very low after 60 h of
fermentation, and it was stopped at the 72nd hour. All other
cultures were stopped at the same time