GATE BT 2017 • Q26
MCQ • 2 Marks
Section 4: Bioprocess Engineering and Process Biotechnology
Downstream processing (chromatography, filtration)
Subtopic: Fundamentals of Downstream processing (chromatography, filtration)
Question Statement:
Which of the following descriptions best represents the kinetics of protein precipitation during salting-out with ammonium sulfate (Cohn equation)?
Options:
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(A) Logarithm of protein solubility decreases linearly with increasing ionic strength
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(B) Protein solubility increases exponentially with ionic strength
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(C) Protein solubility is independent of salt concentration
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(D) Protein precipitates instantaneously in a hyperbolic curve
Step-by-Step Solution & Explanation
### **Step-by-Step Solution & Mathematical Derivation (GATE BT 2017 Q.26)**
**1. Governing Concept & Definition**:
- **Topic**: Downstream Processing & Cohn Equation for Protein Salting-Out
- The solubility of proteins during ammonium sulfate precipitation follows the Cohn equation:
$\log(S) = \beta - K_s I$
**2. Detailed Step-by-Step Calculation**:
- A semi-logarithmic plot of $\log S$ versus ionic strength $I$ produces a straight line with slope $-K_s$, corresponding to curve 1.
**3. Final Answer**:
- **Calculated Value**: **1**
- **Official GATE Accepted Range**: **1 to 1**
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