Question

Which sterilization method is suitable for heat-sensitive media and is commonly used in the pharmaceutical industry?

• A. Autoclaving
• B. Membrane filtration
• C. Pasteurization
• D. Dry heat sterilization

Hint:

• Heat-based sterilization (autoclaving, dry heat) is effective but damages heat-sensitive materials.
• Filter sterilization (using membrane filters) physically removes microbes without heat, suitable for heat-labile liquids and gases.
• Other non-heat methods: Radiation sterilization (gamma rays, electron beams), chemical sterilization (e.g., ethylene oxide gas).
• Pasteurization reduces microbial load but is not sterilization.

Answer 1

The Correct Option is B

Sterilization is the process of eliminating all forms of microbial life, including bacteria, viruses, fungi, and spores.

• (a) Autoclaving (Steam Sterilization): Uses high-pressure saturated steam at high temperatures (e.g., 121°C for 15-20 minutes). It is very effective but not suitable for heat-sensitive (heat-labile) materials as the high temperature can degrade them.
• (b) Membrane Filtration (Filter Sterilization): This method physically removes microorganisms from liquids or gases by passing them through a filter with pore sizes small enough to retain the microbes (e.g., 0.22 µm pores for bacterial removal). It does not involve heat and is therefore ideal for sterilizing heat-sensitive solutions like pharmaceuticals (e.g., protein solutions, vaccines, some vitamin solutions) and culture media components that would be damaged by heat.
• (c) Pasteurization: A heat treatment process (e.g., 63°C for 30 min or 72°C for 15 sec) that kills most pathogenic microorganisms and reduces the number of spoilage organisms in liquids like milk and fruit juices. It is not sterilization, as some thermoduric organisms and spores may survive.
• (d) Dry Heat Sterilization: Uses high temperatures in a dry oven (e.g., 160-180°C for 1-2 hours). Suitable for heat-stable materials like glassware and metal instruments, but not for heat-sensitive liquids or media.

For heat-sensitive media, especially in the pharmaceutical industry where product integrity is critical, membrane filtration is the common method of sterilization. \[ \boxed{\text{Membrane filtration}} \]