Kinetic studies on citric acid production by Aspergillus niger. I. Phases of mycelium growth and product formation.

The physiology and growth kinetics of Aspergillus niger B-64-5 in shaken culture were studied, five successive phases of citric acid fermentation being distinguished. Growth was found to be diauxic, spore germination being followed by an exponential growth phase, then a period of growth disturbance, and last of all a phase of secondary growth, characterized by a constant coefficient of growth decline appeared. The citric acid production started in the phase of growth disturbance. The chief increase in citric acid concentration took place in the production phase, i.e. in the last fermentation phase.