Diversity of N -acyl homoserine lactones in activated sludge detected by Fourier transform mass spectrometry

Quorum sensing is recently considered to play important roles in biological wastewater treatment processes. This study aimed to investigate diversity of N-acyl homoserine lactones (AHL) among biological wastewater treatment processes and their locations. We analyzed and quantified 10 AHL in activated sludge at wastewater treatment plants (WWTPs) by Fourier transform mass spectrometry (FTMS) and by bioassay on thin-layer chromatography (TLC). Sludge samples were taken at seven WWTPs in Japan and in Thailand, which were chosen to compare different process types including a pilot-scale membrane bioreactor process. Various AHL were detected in activated sludge, suggesting the presence of quorum sensing activity in many practical WWTPs. Detection of AHL by LC-FTMS was much more sensitive than by TLC bioassay, because TLC bioassay was implied to be affected by the presence of quorum quenching molecules in activated sludge. With LC-FTMS analysis, AHL, which has short straight chain in the acyl group, were more abundant. Especially, C4-HSL, C7-HSL, and C8-HSL were detected widely independent of locations and process types. AO processes had higher AHL productivity than other processes.