Production of citric acid in continuous culture

Work has been carried out on the production of citric acid by Aspergillus foetidus in single‐stage continuous culture, operated under nitrogen‐limiting conditions at dilution rates between 0.04 to 0.21 hr−1. Citric acid concentration increased rapidly as the dilution rate decreased and appears to be critically dependent on the pH in the culture vessel and the nitrogen concentration in the feed. A mathematical model based on a distinction between basic cells, which require nitrogen but do not produce citric acid, and stroage cells, which accumulate carbon and simultaneously produce citric acid, is proposed.