Low Cost Sensor for E. Coli/ Colliform Detection in Water

Fabrication of Low Cost Optical Detection Systemfluorescence.
For E. coli 0157 Based OnThe sensor uses an LED light source shining on a
4-Methyl Umbelliferyl- ß -D-Galactoside--photodetector. When the colorimetric reaction has
ß-Galactosidase Reaction.taken place, light shines through a beaker containing
Joseph Michael D. Racho, Erba V. Del Rosario, Karlenthe sample, and onto a light-sensitive meter. A clear
C. Dawal,tube of water or other clear solution is the BLANK
Dan R. Laurente, and Raymond J. Sucgang*1,and has zero absorbance. A fraction of the incident
In cooperation with thelight that is blocked by the sample, can be used for
Chemists' & Educators' Support for thequantitative determination of the bacterial population
Advancement of Relevant Science Education, Inc.,in the water. The E. coli population is related to the
CESARSED, Inc.absorbance reading, following Beer's law. The amount
1R.J. Sucgang Center for Research in the Naturalof incident and transmitted light is expressed in foot
Sciencescandle units, by a LX 104 light meter. The sensor
Napti, Batan, Aklanshows outstanding response over the range of 0.8
Keywords: Sensor, Optical detection, E.colix107 to 1.35 x108 CFUs E. coli concentration. The
This paper reports the fabrication of a handheld,bacterial numbers in each test solution has been
simple to use sensor which detects contamination byconfirmed using standard plate count method.
deadly strains of E coli in drinking water. E. coli 0157,Excellent sensitivity and linearity (R2=0.984) has been
predominately 0157:H7, has been implicated as theachieved using the sensor, working with 6 replicate
causative organism of hemolytic uremic syndromemeasurements per particular concentration. The
and hemorrhagic colitis. The sensor works based onspecificity of the sensing system to E. coli, was
irreversible color changes that occur subsequent totested by spiking other bacterial strains, (
hydrolysis of a chromogenic substrate by aStaphyloccus aureus) during the 4th to 6th
ß-galactosidase enzyme of E.coli. The recognitiondetermination. The sensor is highly selective and
material, 4-methyl umbelliferyl- ß -D-galactosidespecific in its responses to E. coli. The cost of the
has two components: a fluorescent dye and asensor is very low in contrast to the cost of
"quencher" which is sensitive to cleavage byacquiring a laboratory spectrophotometer.
ß-galactosidase. In the absence of E.coli, theThis work demonstrated that assembly of a
quencher binds to the dye and preventssensitive, portable, low cost devices from an ordinary
fluorescence, while the interaction oflight meter, an LED light source, and traditional
ß-galactosidase with the quencher results to thebiochemical chromogenic reagents for the detection
dissociation of the complexand quantization of bacterial populations is practical.
,7-hydroxy-4-methylcoumarin, giving off a blue