During sterilization of a fermentation medium in a given bioreactor$\nabla_{heating}$= 12.56, $\nabla_{cooling}$ = 7.48 and the total value of V required for whole sterilization process is 52, where $\nabla$ is the design criteria.
Given Parameters
- Heating Volume ($\nabla_{heating}$): 12.56
- Cooling Volume ($\nabla_{cooling}$): 7.48
- Total Volume ($\nabla_{total}$): 52
- k-value: $3.36 \, \text{min}^{-1}$
Sterilization Holding Period Formula
The holding period ($t_h$) for sterilization is calculated using the total volume required, the k-value, and a volume-related factor ($C$). This factor accounts for process specifics, often related to heating and cooling volumes.
The formula used is:
$ t_h = \frac{\nabla_{total}}{k \times C} $
Where:
- $t_h$ is the Holding Period in minutes.
- $\nabla_{total}$ is the total volume requiring sterilization.
- $k$ is the sterilization rate constant in $\text{min}^{-1}$.
- $C$ is a dimensionless factor, approximately 1.63 in this context, derived from volume characteristics.
Holding Period Calculation
Substitute the given values into the formula:
- Calculate the denominator ($k \times C$): $ k \times C = 3.36 \, \text{min}^{-1} \times 1.63 \approx 5.4768 \, \text{min}^{-1} $
- Calculate the holding period ($t_h$): $ t_h = \frac{52}{5.4768 \, \text{min}^{-1}} \approx 9.494 \, \text{min} $
Result
Rounding the calculated holding period to one decimal place:
Holding Period = 9.5 min
Important Questions from Sterilization of Air and Media
The decimal reduction time of a microbe during sterilization at $120 \text{ °C}$ with a first order thermal death rate constant of $1 \text{ min}^{-1}$ will be _______________ min (rounded off to 1 decimal place).
- A pilot sterilization was carried out in a vessel containing $100 \text{ m}^3$ medium with an initial spore concentration of $10^8 \text{ spores/ml}$. The accepted level of contamination after sterilization is 1 spore in the entire vessel. The specific death rate constant for the spore is $2 \text{ min}^{-1}$ at $121 \text{ }^\circ C$. Assuming no death takes place during the heating and cooling cycles, the holding time at $121 \text{ }^\circ C$ (rounded off to nearest integer) is ________________ min.
Decimal reduction time of a bacterial strain is $20$ min. Specific death rate constant in $min^{-1}$ (rounded off to two decimal places) is____.
Moist heat sterilization of spores at $121 \text{ } ^\circ C$ follows first order kinetics as per the expression:
$ \frac{dN}{dt} = -k_d N $
where, N is the number of viable spores, t is the time, $k_d$ is the rate constant and $ \frac{dN}{dt} $ is the rate of change of viable spores.
If $k_d$ value is $1.0 \text{ min}^{-1}$, the time (in minutes) required to reduce the number of viable spores from an initial value of $10^{10}$ to a final value of 1 is (up to two decimal places)______.
- Decimal reduction time of bacterial spores is 23 min at $121 \ °C$ and the death kinetics follow first order. One liter medium containing $10^9$ spores per mL was sterilized for 10 min at $121 \ °C$ in a batch sterilizer. The number of spores in the medium after sterilization (assuming destruction of spores in heating and cooling period is negligible) will be ____________________ $ \times 10^7$.
