Isopropyl thiogalactoside (IPTG) is a powerful inducer, which is not metabolized by bacteria and is very stable, so it is widely used in laboratories. IPTG is often used for induction β- Cloning experiment of galactosidase activity. It is often used in combination with X-Gal or Blue GaChemalbookl for blue and white screening of recombinant bacterial colonies, which can induce lac operon expression in E. coli. IPTG combines with lacI repressor protein and changes its conformation to play a role in preventing β- Inhibition of lacZ gene encoding galactosidase.