The calibration parameters (linear range and sensitivity) from
calibrations with OECD synthetic wastewater were used to characterize
biosensors (Fig. 2). The linear range of a biosensor is defined
as the substrate range that gives a signal directly proportional to
Fig. 2. The calibration curve for A. hydrophila and P. fluorescens biosensors.
the substrate concentration [21]. The linear ranges for A. Hydrophila
and P. Fluorescens biosensors were up to 45 mg l−1 and 40 mg l−1
BOD7, respectively. The sensitivity is defined as the signal change
at the definite concentration of the substrate and it is measured by
the slope of the calibration curve [21]. Sensitivities of A. Hydrophila
and P. Fluorescens biosensors were 0.019 (1/(BOD7, mg l−1)) and
0.023 (1/(BOD7, mg l−1)), respectively. The lower level of detection
was 5 mg l−1 BOD7. Relative standard deviation of calibration
points at different BOD7 values varied from 2.0 to 13.7% (n = 6) for A.
Hydrophila biosensor and from 5.5 to 13.5% (n = 6) for P. Fluorescens
biosensor.