Section 4: Bioprocess Engineering and Process Biotechnology
Media Sterilization and Stoichiometry
Subtopic: Thermal Sterilization & Stoichiometry
Question Statement:
The overall stoichiometry for an aerobic cell growth is
3C6H12O6 + 2.5NH3 + O2 1.5CaHbOcNd + 3CO2 + 5H2O
What is the elemental composition formula of the biomass?
Options:
(A) C9H18.2O5N1.667
(B) C9H22.33O6N1.667
(C) C10H18.2O5N1.667
(D) C10H22.33O6N1.667
Official Answer Key:
D
Step-by-Step Solution & Explanation
### **Official Solution & Concept Analysis (GATE BT 2022 Q.16)**
**1. Governing Concept**:
- **Topic**: Bioprocess Stoichiometry & Macroscopic Elemental Balances
- In aerobic microbial cell growth, the general macroscopic elemental balance is:
$\text{C}_w\text{H}_x\text{O}_y\text{N}_z + a\text{O}_2 + b\text{NH}_3 \rightarrow c\text{CH}_\alpha\text{O}_\beta\text{N}_\delta + d\text{CO}_2 + e\text{H}_2\text{O}$
- Conservation of available electrons (degree of reduction balance):
$\gamma_s - 4a = c \gamma_b$
where $\gamma_s$ is the degree of reduction of substrate and $\gamma_b$ is that of biomass.
**2. Option Analysis**:
- **Option (A) is INCORRECT**: Violates elemental mass conservation.
- **Option (B) is INCORRECT**: Electron balance violated.
- **Option (C) is INCORRECT**: Nitrogen balance violated.
- **Option (D) is CORRECT**: Satisfies all elemental (C, H, O, N) and available electron balances.
**3. Final Answer**:
- **Correct Choice**: **D**
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