Exploring the effect of bisphenol S on sludge hydrolysis and mechanism of the interaction between bisphenol S and α-Amylase through spectrophotometric methods.

Sewage sludge, as a very significant sources of BPS (up to 523mg/kg dw) introduction into the environment, must be handled properly. Therefore, it is important to access BPS removal and its effect on sludge treatment with the biological treatment. However, it is unclear for its effect on the hydrolysis of sludge. In this research, impact of BPS on sludge hydrolysis by α-Amylase is studied from the respect of component of soluble organic matter in sludge using three-dimensional fluorescence spectra. Enzyme activity assay suggests that sludge hydrolysis is inhibited due to the denaturation of α-Amylase with BPS exposure. In order to illuminate the interaction mechanism between BPS and α-Amylase, UV-vis, steady-state fluorescence, circular dichroism, synchronous fluorescence, light scattering spectra, enzyme activity assay and molecule docking techniques are applied. Results show that BPS interacts with α-Amylase by hydrophobic bond in the activity region of α-Amylase. This interaction not only causes an unfolding skeleton structure of α-Amylase and a less hydrophobic microenvironment of tyrosine and tryptophan residues, but also leads to a specific fluorophore quenching involving static and dynamic type. This work provides direct evidence about enzyme toxicity of BPS and establishes a new strategy to investigate the interaction between protein and BPS at a molecular level, which is helpful for clarifying the bioactivities of BPS.