Treatment of triclosan through enhanced microbial biodegradation.

Triclosan (TCS) is extensively used in healthcare and personal care products as an antibacterial agent. Due to the persistent and toxic nature of TCS, it is not completely degraded in the biological wastewater treatment process. In this research work, identification of TCS degrading bacteria from municipal wastewater sludge and applying the same as bioaugmentation treatment for wastewater have been reported. Based on the 16S rRNA analysis of wastewater sludge, it was found that Providencia rettgeri MB-IIT strain was active and able to grow in higher TCS concentration. The identified bacterial strain was able to use TCS as carbon and energy source for its growth. The biodegradation experiment was optimized for the operational parameters viz. pH (5-10), inoculum size (1-5% (v/v)) and different initial concentration (2, 5, and 10 mg/L) of TCS. During the TCS degradation process, manganese peroxidase (MnP) and laccase (LAC) enzyme activity and specific growth rate of P. rettgeri strain were maximum at pH=7% and 2% (v/v) inoculum size, resulting in 98% of TCS removal efficiency. A total of six intermediate products were identified from the Liquid chromatography-high-resolution mass spectrometry (LC-HRMS) analysis, and the two mechanisms responsible for the degradation of TCS have been elucidated. The study highlights that P. rettgeri MB-IIT strain could be advantageously used to degrade triclosan present in the wastewater.

Balakrishnan P ，Mohan S 《-》

Effect of Pleurotus ostreatus and Trametes versicolor on triclosan biodegradation and activity of laccase and manganese peroxidase enzymes.

Triclosan (TCS) is an extensively used antibacterial agent which has been frequently detected in different environmental compartments. Because of TCS inhibition effect on vast majority of bacterial species, it is important to explore fungal species and their involved enzymes in TCS biodegradation. The aim of this study was to compare the potential of two white rot fungi Pleurotus ostreatus and Trametes versicolor for TCS biodegradation through the whole cell culture of fungi in an aqueous culture medium. Additionally, the changes in ligninolytic enzyme activities and possible correlations and contributions of degradative enzymes during TCS biodegradation process were monitored. This study was carried out using a factorial experiment with a completely randomized design in three replications. factorial design in The experimental factors included: two white rot fungi Pleurotus ostreatus and Trametes versicolor and uninoculated controls which were subjected to five levels of TCS concentrations (0, 5, 10, 20, 30 and 50 μg mL-1) to assess ligninolytic enzymatic activity during biodegradation of TCS. Samples were harvested periodically at three time intervals (4, 7 and 10 days). An AB SCIEX 3200 QTRAP LC-MS/MS system was used in order to analyze the biodegradation of TCS in liquid medium. Results suggested that the two white rot fungi responded differently when exposed to the different concentrations of TCS. In general, P. ostreatus exhibited more potential and ligninolytic enzymatic activity compared to T. versicolor. LC-MS/MS analyses also showed that P. ostreatus degraded TCS with higher efficiency compared to T. versicolor. In addition, almost all P. ostreatus biodegradation activity was completed within the first day of sampling. Contrasting, less efficient degradation was observed by T. versicolor, reaching around 88% of TCS biodegradation at concentration of 20 μg mL-1after 10 days. At higher TCS concentrations (≥30 μg mL-1), the growth of T. versicolor severely inhibited and led to a drop in enzymatic activity and biodegradation. Furthermore, laccase and manganese peroxidase (MnP) were determined as more involved enzymes which significantly correlated to TCS biodegradation by T. versicolor and P. ostreatus, respectively. P. ostreatus might be considered as efficient fungus in biodegradation of high amount of TCS in environmental matrices. The results of the present study might provide insights for future investigations on potential of fungi for applications in bioaugmentation-based strategies to remove TCS from wastewater and activated sludge.

Maadani Mallak A ，Lakzian A ，Khodaverdi E ，Haghnia GH ，Mahmoudi S ... -  《-》

Fate and effects of triclosan in activated sludge.

Federle TW ，Kaiser SK ，Nuck BA 《ENVIRONMENTAL TOXICOLOGY AND CHEMISTRY》

Biological treatment of triclosan using a novel strain of Enterobacter cloacae and introducing naphthalene dioxygenase as an effective enzyme.

In recent years, triclosan (TCS) has been widely used as an antibacterial agent in personal care products due to the spread of the Coronavirus. TSC is an emerging contaminant, and due to its stability and toxicity, it cannot be completely degraded through traditional wastewater treatment methods. In this study, a novel strain of Enterobacter cloacae was isolated and identified that can grow in high TCS concentrations. Also, we introduced naphthalene dioxygenase as an effective enzyme in TCS biodegradation, and its role during the removal process was investigated along with the laccase enzyme. The change of cell surface hydrophobicity during TCS removal revealed that a glycolipid biosurfactant called rhamnolipid was involved in TCS removal, leading to enhanced biodegradation of TCS. The independent variables, such as initial TCS concentration, pH, removal duration, and temperature, were optimized using the response surface method (RSM). As a result, the maximum TCS removal (97%) was detected at a pH value of 7 and a temperature of 32 °C after 9 days and 12 h of treatment. Gas chromatography-mass spectrometry (GC/MS) analysis showed five intermediate products and a newly proposed pathway for TCS degradation. Finally, the phytotoxicity experiment conducted on Cucumis sativus and Lens culinaris seeds demonstrated an increase in germination power and growth of stems and roots in comparison to untreated water. These results indicate that the final treated water was less toxic.

Ghafouri M ，Pourjafar F ，Ghobadi Nejad Z ，Yaghmaei S ... -  《-》

Measurement of triclosan in wastewater treatment systems.

McAvoy DC ，Schatowitz B ，Jacob M ，Hauk A ，Eckhoff WS ... -  《ENVIRONMENTAL TOXICOLOGY AND CHEMISTRY》