Endoscope tube is sterilized by -

Glutaraldehyde is especially effective against the tubercle bacilli, fungi, and viruses. It is less toxic and irritant to eyes and skin than formaldehyde. it has no deleterious effects on the cement or lenses of instruments such as cystoscope and bronchoscpe. It can be safely used to treat corrugated rubber, anesthetic tubes, face masks, plastic endotracheal tubes, metal instruments, and polythene tubings REF:Ananthanarayan and Panicker's Textbook ofMicrobiology 8thEdition pg no:36