Dual substrate sensor platform for rapid detection and differentiation of coliforms

In the present work, we modified and improved the previously developed sensor platform (based on screen-printed carbon electrode) for rapid detection and quantification of coliforms. The second substrate (L-alanyl-p-nitroanilide) was included in the sensor platform, which produced the second cathodic voltammetric peak at the new potential (-113 mV) in the defined potential range (-600 to 400 mV). The 10⁶ CFU/mL of 5 different groups of coliforms in 3 h of incubation produced electrochemical signals equal to 960 μA, 970 μA, 988 μA, 950 μA, 956 μA and 920 μA respectively. After 3 h of incubation the two strains of Gram-positive bacteria with concentration of 10⁶ CFU/mL produced voltammetric signals equal to --80 μA and- 200 μA (due to high /-150 μA/ capacitive/background current) respectively. No voltammetric peak occurred with Gram-positive bacteria at the potential equal to -113 mV. The voltammetric signals produced at the new potential range were specific for coliforms.