In animal cell culture, which of the following is commonly used as a shear protectorant to reduce interfacial damage during aeration and agitation?

Introduction:
Shear and interfacial stresses from bubbles and agitation can damage fragile animal cells. Shear protectants mitigate cell adsorption at gas–liquid interfaces and cushion membranes during collisions, thereby improving viability and productivity in bioreactors.

Given Data / Assumptions:

• Cells are shear-sensitive and lack rigid walls.
• Bioreactors may use sparging and mechanical agitation.
• Additives can protect cells by modifying interfaces and medium properties.

Concept / Approach:
Serum contains proteins (e.g., albumin) that preferentially occupy interfaces, reducing direct cell contact with bubbles and impeller-generated eddies. This lowers interfacial tension effects and dampens mechanical damage. Other specialized protectants include poloxamers (e.g., Pluronic F-68), but among the listed options, serum is the well-established choice.

Step-by-Step Solution:
Step 1: Identify agents known to shield cells at interfaces (proteins, certain surfactants, poloxamers).Step 2: Recognize serum proteins adsorb at interfaces first, protecting cells.Step 3: Compare with other listed compounds and select the established shear protectant.

Verification / Alternative check:
Culture media formulations historically included fetal bovine serum to enhance robustness under agitation; serum-free processes often replace it with Pluronic F-68 for similar protection.

Why Other Options Are Wrong:

• Silicone oil: Used as antifoam; not a standard cellular shear protectant and can hinder downstream processing.
• Glucose: Carbon source; no interfacial protection role.
• Glutamic acid: Amino acid/nutrient, not a shear protectant.
• Polysorbate 20: A surfactant used in formulations, but not the conventional choice for bioreactor shear protection of cells.

Common Pitfalls:
Assuming any surfactant or antifoam equals a shear protectant; process additives must be biocompatible and downstream-compatible.

Final Answer:
Serum