Dioxane free. Commonly used inducer for beta-Galactosidase activity in many bacterial gene sequences controlled by the lac operon. IPTG and X-Gal are often used together to identify bacterial colonies containing recombinant plasmid DNA. Insoluble. Reaction Condition: Stocks: X-Gal 20 mg/ml in DMF; IPTG 20 mg/ml in water. Mix 4:1 (X-Gal/IPTG) for spreading onto agar plates prior to plating transformed bacteria.