Topic: Bt Toxin — From Bacterium to Insect Cell Death

Key Point 1 — pH Specificity: Lepidopteran midgut pH ≈ 10 (alkaline). Human stomach pH ≈ 1-2 (acidic). Protoxin does NOT dissolve in acidic environment → safe for humans.

Key Point 2 — Receptor Specificity: Human intestinal cells LACK the glycolipid receptor for Bt toxin. Even if toxin were hypothetically activated, it could not bind to human cells.

Key Point 3 — Biodegradability: Cry proteins are degraded by human digestive proteases and UV radiation, preventing environmental accumulation.