5-Bromo-4-chloro-3-indolyl-β-D-glucuronide (X-GLUC) is a chromogenic substrate for β-glucuronidase.1,2 Upon cleavage by β-glucuronidase, an indigo pigment is released that can be used as a marker of β-glucuronidase activity. X-GLUC has been used for the detection of E. coli contamination in foodstuffs.
1.Frampton, E.W., Restaino, L., and Blaszko, N.Evaluation of the β-glucuronidase substrate 5-bromo-4-chloro-3-indolyl-β-D-glucuronide (X-GLUC) in a 24-hour direct plating method for Escherichia coliJ. Food Prot.51(5)402-404(1988) 2.Restaino, L., Frampton, E.W., and Lyon, R.H.Use of the chromogenic substrate 5-bromo-4-chloro-3-indolyl-B-D-glucuronide (X-GLUC) for enumerating Escherichia coli in 24 H from ground beefJ. Food Prot.53(6)508-510(1990)