Choice of sterilization method — The suitable sterilization approach for a process stream depends primarily on which factors?

Introduction:
Selecting a sterilization method is a balance between microbial lethality and preservation of product quality. In bioprocessing, we choose between heat sterilization (autoclaving, SIP), filtration, chemical sterilants, or radiation based on material compatibility and process logistics. This question asks which factors drive that choice most directly.

Given Data / Assumptions:

• Additive or solution may be heat-labile or reactive.
• Process scale dictates equipment choice and feasible cycle times.
• Sterility assurance levels must be met reliably.

Concept / Approach:
The physicochemical properties of the additive (thermal stability, viscosity, particulate content, ability to be filtered) determine whether heat or filtration is suitable. Meanwhile, the volume and required feed rate influence whether a method is practical and economical (e.g., sterile filtration for large viscous volumes may be impractical; heat sterilization cycles scale differently). Thus, both the material nature and throughput needs are decisive.

Step-by-Step Solution:
Assess stability: heat-stable → use moist heat; heat-labile → use sterile filtration or chemical alternatives.Assess scale: large volumes at high flow may prefer SIP; small, sensitive additives may be 0.22 μm filtered.Combine constraints to choose the viable, validated method.

Verification / Alternative check:
Validation documents (F0 calculations for heat, bacterial retention for filters) explicitly incorporate material properties and process timing/volume, confirming both factors matter.

Why Other Options Are Wrong:

• (a) or (b) alone is incomplete.
• (d) and (e) ignore critical technical determinants; regulations guide validation but do not dictate physics.

Common Pitfalls:
Choosing filtration for protein solutions without viscosity/particulate considerations; ignoring hold-up and dead-leg issues in SIP at larger scales.

Final Answer:
Both (a) and (b)