An embedded portable biosensor system for bacterial concentration detection
Résumé
Microbial screening is a primary concern for many products. Traditional techniques based on standard
plate count (SPC) are accurate, but time consuming. Furthermore, they require a laboratory environment
and qualified personnel. The impedance technique (IT) looking for changes in the electrical characteristics
of the sample under test (SUT) induced by bacterial metabolism represents an interesting alternative to
SPC since it is faster (3–12 h vs. 24–72 h for SPC) and can be easily implemented in automatic form.
With this approach, the essential parameter is the time for bacteria concentration to reach a critical
threshold value (about 107 cfu mL−1) capable of inducing significant variations in the SUT impedance,
measured by applying a 100 mV peak-to-peak 200 Hz sinusoidal test signal at time intervals of 5 min.
The results of this work show good correlation between data obtained with the SPC approach and with
impedance measurements lasting only 3 h, in the case of highly contaminated samples (106 cfu mL−1).
Furthermore, this work introduces a portable system for impedance measurements composed of an
incubation chamber containing the SUT, a thermoregulation board to control the target temperature and
an impedance measurement board. The mix of cheap electronics and fast detection time provides a useful
tool for microbial screening in industrial and commercial environments.
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