Question

In microbiological fermentation process, the most common cause of foaming is -

• A. Fats in the medium
• B. Proteins in the medium
• C. Carbohydrates in the medium
• D. High minerals in the medium

Hint:

Excessive foaming is dangerous in industrial fermentations because it can clog exhaust air filters, causing pressure buildup, contamination, and loss of valuable culture broth.
To manage this, chemical antifoams (such as silicones or vegetable oils) are added to destroy foam bubbles.

Answer 1

The Correct Option is B

Step 1: Understanding the Concept:
Industrial bioreactors (fermenters) use continuous agitation and aeration (sparging of air) to supply oxygen to microorganisms.
This vigorous mixing can lead to stable foam formation at the liquid-gas interface.

Step 2: Detailed Explanation:
The presence of proteins in the fermentation medium is the primary cause of foaming.
Proteins are amphiphilic molecules (containing both hydrophilic and hydrophobic amino acid side chains).
They behave as surface-active agents (surfactants) that migrate to the air-water interface of air bubbles.
The proteins denature and form a viscoelastic film around the bubbles, lowering surface tension and stabilizing them to form a thick, stable layer of foam.
Fats generally act as antifoaming agents by disrupting these protein films.

Step 3: Final Answer:
The most common cause of foaming is proteins in the medium, which corresponds to option (B).