Protech PT-BL005 X-Gal Solution is a ready-to-use, stabilized, non-toxic solution. The X-Gal is a non-inducing chromogenic substrate of β-galactosidase that hydrolyzes X-Gal, resulting in the formation of an intense blue precipitate. The X-Gal solution is most frequently used in combination with IPTG for blue/white colony screening to distinguish recombinants (white) from non-recombinants (blue).