_____ is the process of removing all microorganisms from a fluid stream, excluding viruses, to produce a sterile fluid.

• A. Aseptic filtration
• B. Microfiltration
• C. Sterilizing filtration
• D. Ultrafiltration

Answer: (C)

Sterilizing filtration is the process designed to render a liquid sterile by removing all viable microorganisms, producing a fluid that is free of life forms like bacteria and fungi. It typically uses very fine membrane pores (around 0.22 μm) that trap microbial cells, so the product can be sterilized by filtration alone. The caveat is that viruses are smaller and can pass through these filters, which is why this method is described as removing most microorganisms except viruses. That’s what makes it the best match for producing a sterile fluid by filtration.

Aseptic filtration refers to maintaining aseptic conditions during filtration and is not inherently the method to achieve sterility via the filtration step itself. Microfiltration can remove bacteria and some larger particulates but not all microorganisms or viruses. Ultrafiltration targets macromolecules and is not used to achieve sterility of a fluid.