Principle of the enzyme-substrate method

Total coliforms produce beta-galactosidase, which decomposes the ONPG chromogenic substrate and turns the medium yellow. E. coli produces beta-glucuronidase, which decomposes the MUG fluorescent substrate and emits fluorescence under 366 nm ultraviolet light. The method detects total coliforms, thermotolerant (fecal) coliforms and E. coli in water. Colitech medium includes a matrix intended to suppress non-target reactions and reduce false-positive results.

The method is suitable for the drinking-water testing method referenced by GB/T 5750.12-2006. Used with colitech reagent and a quantitative detection tray, it tests a 100 mL water sample without dilution.

Detection range

• 51-well tray: 0–200 MPN/100 mL
• 97-well tray: 0–2419 MPN/100 mL