Group I Group II P. Serum 1. Autoclave Q. Luria broth 2. Membrane filtration R. Polypropylene tubes 3. UV irradiation S. Biological safety cabinets 4. Gamma irradiation 5. Dry heat
Matching Sterilization Methods for Lab Items
This question requires matching laboratory items and equipment (Group I) with their most appropriate sterilization methods (Group II).
Detailed Match Analysis
- P. Serum: Biological serums are often temperature-sensitive. Therefore, Membrane filtration ($2$) is the preferred method as it removes microbes by physical separation without heat, preserving the serum's composition.
- Q. Luria broth: This is a standard microbiological culture medium. Autoclave ($1$) sterilization, using pressurized steam, is the most common and effective method for sterilizing liquid media like Luria broth, ensuring complete microbial inactivation.
- R. Polypropylene tubes: Polypropylene is a type of plastic commonly used for labware. While some plastics can be autoclaved, Gamma irradiation ($4$) is a widely used method for sterilizing pre-packaged plastic items, including medical-grade polypropylene tubes, due to its high penetration power and effectiveness.
- S. Biological safety cabinets: These cabinets require surface decontamination. UV irradiation ($3$) is frequently employed to irradiate the internal surfaces and air within biological safety cabinets when they are not in operation, helping to reduce microbial load.
Conclusion: Correct Pairings
Based on the suitability of each method:
- P matches with $2$ (Membrane filtration)
- Q matches with $1$ (Autoclave)
- R matches with $4$ (Gamma irradiation)
- S matches with $3$ (UV irradiation)
The correct combination is P-2, Q-1, R-4, S-3.
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$.
