Quantification of Escherichia Coli via Analysis of β-glucuronidase Enzyme Concentrations
Concentration of Escherichia coli can be quantified based on a digestive enzyme produced by 97% of E. coli strains called β-glucuronidase (β-GUS). When in contact with a β-glucuronide (β-GLU) molecule, the enzyme cleaves the β-GLU segment off the molecule, leaving the remaining fragment untouched. The remaining fragment can serve as a marker for the presence of the enzyme and can be quantifiably calibrated to determine the concentration of the E. coli in each sample. For a colourimetric method approach, 4-nitrophenol-β-D-glucuronide (4-NβDg) can be used as a dye for the enzyme. The remainder of the molecule after enzymatic cleavage is a 4-nitrophenol, which is blue in colour. The change in colour can be quantified based on a calibration curve. For an electrochemical method approach, 4-NβDg can also be used because 4-nitrophenol gives a characteristic cyclic voltammogram on a potentiostat. The change in resistance of 4-nitrophenol can be determined and calibrated to show the concentration of the E. coli in each sample.
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