Question

In Citric acid production, batch fermentation is used.

(a) True

(b) False

I had been asked this question during an interview.

This intriguing question comes from Comparison of Batch and Continuous Culture in Industrial Processes in section Microbial Growth Kinetics of Bioprocess Engineering

Answer 1

Right choice is (b) False

Best explanation: Citric acid (citrate) is widely used as a flavour enhancer, a preservative in manufactured foods and an antioxidant. It is produced as an intermediate of the Krebs cycle under aerobic conditions. Citric acid is mass produced by continuous fermenter systems from cultures of the fungus Aspergillus niger. Carbohydrates are continuously introduced into the fermenter in order to maintain the citric acid production. Iron (Fe^2+ ions) is excluded from the mixture in order to slow the further conversion of citric acid within the Krebs cycle. As citric acid accumulates it is extracted as part of the medium that is being continuously withdrawn from the fermenter.