Photocatalytic inhibitory effect of immobilized TiO2 semiconductor on the growth of Escherichia coli studied by acoustic wave impedance analysis

The effect of immobilized TiO2 photocatalyst on the growth of Escherichia coli was investigated with acoustic wave impedance (AWI) analysis technique for the first time. The motional resistance variation (ΔR1) curves under different growth conditions were obtained and compared. By fitting ΔR1 versus time curves toward the impedance response model, three growth kinetic parameters (A, μm and λ) for different growth situations were gained. The results showed the lag time (λ) was prolonged, and the maximum specific growth rate (μm) and the asymptote (A) were decreased in the presence of UV light and TiO2 photocatalyst. In addition, the quantificational relationships between the growth parameters and TiO2 dosage were also investigated, which reflect the inhibitory effect of TiO2 under a certain light intensity on the growth of E. coli. The three kinetic growth parameters (A, μm and λ) obtained from the impedance response model are close to those obtained from the Gompertz popular growth model. These results showed that the AWI analysis technique adapts to study the effect of TiO2 photocatalyst on the growth of bacteria on the qualitative and quantificational level.