Question

The citric acid production in the shallow tank method at standardized conditions is completed in ‐‐‐‐‐‐ days.

• A. 2‐3
• B. 5‐6
• C. 7‐10
• D. 11‐15

Hint:

Surface fermentation is the older "low-tech" method. It takes longer ($7-10$ days) but requires less energy for aeration compared to submerged fermentation.

Answer 1

The Correct Option is C

Step 1: Understanding the Question:
Citric acid is produced industrially using the fungus Aspergillus niger. The question refers to the "Shallow Tank" or "Surface Fermentation" method and asks for the typical duration of the process.

Step 2: Detailed Explanation:

• Shallow Tank Method: In this process, the sugar medium (molasses) is placed in large, shallow trays ($5$ to $20$ cm deep). The fungal spores are blown onto the surface.

• Fermentation Kinetics: Because the fungus grows as a mat on the surface and oxygen must diffuse through the liquid, the reaction is slower than the submerged method.

• Duration: Under standardized industrial conditions, the fungus takes about $2$ to $3$ days to form a complete mat, and then several more days to convert the sugar into citric acid. The total cycle typically takes 7 to 10 days for maximum yield.

• Comparison: The submerged (deep tank) method is much faster, usually taking $3$ to $5$ days, due to higher oxygen transfer through aeration and agitation.

Step 3: Final Answer:
The surface/shallow tank method for citric acid takes 7-10 days.