During sterilization of a fermentation medium in a given bioreactor,
Vheating = 12.56,
Vcooling = 7.48 and the total value of
V required for the whole sterilization process is
52, where V is the design criteria.
Q.54 What is the value of Vholding?
- (A) 31.96
- (B) 42.32
- (C) 52.43
- (D) 61.18
Bioreactor Sterilization: Vholding Calculation (31.96)
Fermentation media sterilization in bioreactors follows a three-phase process: heating, holding, and cooling. Given Vheating = 12.56, Vcooling = 7.48, and total V = 52, the holding phase completes the sterilization design criteria.
✅ Correct Answer
(A) 31.96
Vholding = Total V – Vheating – Vcooling = 52 – 12.56 – 7.48 = 31.96
Sterilization Design Formula
The total design criterion V represents the cumulative lethality across all phases:
**Vtotal = Vheating + Vholding + Vcooling**
Where V quantifies the sterilization effectiveness (del factor) integrated over time at varying temperatures during steam sterilization at 121°C. The holding phase contributes the majority of lethality as temperature stabilizes.
Step-by-Step Calculation
Vholding = 52 - 12.56 - 7.48
= 52 - 20.04
= 31.96
This confirms option (A) as mathematically precise for the given values.
Option Analysis
| Option | Value | Explanation |
|---|---|---|
| (A) | 31.96 | Correct: 52 – (12.56 + 7.48) = 31.96 matches exact arithmetic |
| (B) | 42.32 | Incorrect: Possibly total V misinterpreted as holding alone |
| (C) | 52.43 | Incorrect: Exceeds total V (52), logically impossible |
| (D) | 61.18 | Incorrect: Far exceeds total V, calculation error |
Process Significance
🔥 Heating Phase (12.56)
Ramps temperature from ambient to 121°C, contributing partial lethality.
⏱️ Holding Phase (31.96)
Maintains 121°C for maximum microbial kill (typically 20-30 min).
❄️ Cooling Phase (7.48)
Safely reduces temperature while preserving residual lethality.
