RESPONSE OF PSEUDOMONAS-FLUORESCENS TO A CHANGE IN MEDIUM ACIDITY - THE EFFECTS OF PREGROWING CONDITIONS

The kinetic and stoichiometric parameters of P. fluorescens growth wer e determined in chemostat and batch cultures after an abrupt pH shift. In a continuous culture, a decrease in pH caused an increase in maint enance energy requirements m. However, no change in the growth yield Y -max was recorded. The response of P. fluorescens batch culture to a p H shift depended on the physiological state of the inoculum: cells pre grown in a chemostat culture at a low dilution rate D and then release d of limitation and supplied with glucose failed to grow after a pH sh ift from 7.0 to 4.8 - 5.5. In contrast, a rapidly growing batch cultur e was capable of growing upon a pH shift from 7 to 4. The observed beh avior of the cultures is explained by an increase in maintenance energ y requirements m after a pH shift; for growth continuation, the total catabolic activity q(resp) Should still exceed m, which was observed i n the batch but not in the continuous culture.