X-Gal/IPTG Premix contains X-Gal (20 mg/ml) and IPTG (16 mg/ml) in a non-toxic solvent and is filtered through a 0.22 μm membrane. It is convenient to detect the positive colonies using the principle of α-complement. With no need of weighing and mixing before use, it is convenient and time-saving for high throughout screening. The volume of 50 μl is sufficient for one plate (Φ 90 mm).