Rapid detection and toxicity assessment of ochratoxin A by Photobacterium leiognathi in drinking water

This study was aimed to develop a rapid technique for detection of ochratoxin A (OTA) by Photobacterium leiognathi (P. leiognathi) based on its inhibition of luminescence on P. leiognathi. The freeze‐dried powder of P. leiognathi was incubated and grown aerobically in sterile liquid medium at 28 °C for 20 h. Optical cell density (OD) at wavelength of 610 nm was measured using UV spectrometer every 2 h. Different concentrations of standard OTA solution were used to measure its luminescence inhibition and calculate its half maximal inhibitory concentration (IC₅₀). Scanning electron microscopy (SEM), flow cytometry (FCM), sodium dodecyl sulphonate polyacrylamide gel electrophoresis (SDS‐PAGE), DNA extraction and gel electrophoresis were used to observe the performance of P. leiognathi under the treatment of OTA. A correlation (R² > 0.98) was obtained between the relative luminosity unit of P. leiognathi and OTA concentration in the range of 0.01–20 mg L⁻¹ with recoveries of 80.8–87.4%. The effects of OTA on P. leiognathi are time‐dependent, and the IC₅₀ value of 12.71 mg L⁻¹ at 30 min demonstrated its good sensitivity to OTA. The cells of P. leiognathi under 40 mg L⁻¹ OTA exposure for 30 mins showed morphological alterations, protein damage, apoptosis and necrosis. The aforementioned results indicate that biological assay is a promising and alternative method used for rapidly monitoring the sudden pollution of OTA in the early emergency warning of drinking water system.