Question

In the production of citric acid by Aspergillus niger, the accumulation of citric acid is primarily due to:

• A. Inhibition of the TCA cycle enzyme isocitrate dehydrogenase by Mn$^{2+}$ deficiency
• B. Increased expression of citrate synthase
• C. Enhanced glycolytic flux
• D. Addition of iron salts

Hint:

In biotechnological processes, metal ion deficiencies can alter key metabolic pathways, affecting product yields.

Answer 1

The Correct Option is A

The accumulation of citric acid during fermentation by Aspergillus niger is primarily caused by the inhibition of the TCA cycle enzyme isocitrate dehydrogenase due to a deficiency in manganese (Mn$^{2+}$). This leads to the diversion of intermediates towards citric acid production. The increased expression of citrate synthase, enhanced glycolytic flux, and addition of iron salts may also affect the process, but the primary cause is the disruption of the TCA cycle enzyme.