Monitoring of Escherichia coli concentrations at wastewater treatment plants (WWTPs) is important to ensure process performance and protect public health. However, conventional E. coli enumeration methods are complicated and time- and labor-consuming. Here, we report a novel simple and reliable method based on β-D-glucuronidase (GUS) activity assay to enumerate E. coli concentrations in wastewater (WW) samples. An aliquot (20 μL) of the medium with fluorogenic enzyme substrate for E. coli and 180 μL of a WW sample were added to one well of a 96-well microplate. The microplate was placed in a microplate reader at 37 °C. To this end, the fluorescence intensity of a fluorogenic enzyme substrate for E. coli was measured every 10 min over 3 h to determine GUS activity. The linear increase in the fluorescence intensity representing the GUS activities showed a positive correlation with E. coli concentrations in wastewater samples. However, the correlation equations were specific to WWTPs, which could be due to the difference in the E. coli population structures among WWTPs. We observed that the wastewater matrix is not a limitation to measure the GUS activity, and a WWTP-specific correlation equation can be used as a calibration curve to estimate the E. coli concentrations in the samples collected from that site. A comparison of the results with those of culture-dependent Colilert method proved that the current method is simple and useful for the enumeration of E. coli concentrations in wastewater samples reliably.
Bibliographical noteFunding Information:
This research was supported financially by JSPS KAKENHI [grant numbers 17K18894 and 19K21979 ], Gesuido Academic Incubation to Advanced (GAIA) Project of the Ministry of Land, Infrastructure, Transport and Tourism (MLIT) [grant number 2016-4 ], Northern Advancement Center for Science & Technology (NOASTEC) [grant number 2016-Startup-7 ], Toda Scholarship Foundation [grant number 2016-1 ], and JST-Mirai Program [grant number JPMJMI18DB ], Japan.
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- A microplate reader
- Escherichia coli
- Fluorogenic enzyme substrate
- Sewage wastewater
- Simple enumeration method
PubMed: MeSH publication types
- Journal Article