Biotreatment efficiency, degradation mechanism and bacterial community structure in an immobilized cell bioreactor treating triclosan-rich wastewater

Unveiling microbial degradation of triclosan: Degradation mechanism, pathways, and catalyzing clean energy

Emerging organic contaminants present in the environment can be biodegraded in anodic biofilms of microbial fuel cells (MFCs). However, there is a notable gap existing in deducing the degradation mechanism, intermediate products, and the microbial communities involved in degradation of broad-spectrum antibiotic such as triclosan (TCS). Herein, the possible degradation of TCS is explored using TCS acclimatized biofilms in MFCs. 95% of 5 mgL-1 TCS are been biodegraded within 84 h with a chemical oxygen demand (COD) reduction of 62% in an acclimatized-MFC (A-MFC). The degradation of TCS resulted in 8 intermediate products including 2,4 -dichlorophenol which gets further mineralized within the system. Concurrently, the 16S rRNA V3-V4 sequencing revealed that there is a large shift in microbial communities after TCS acclimatization and MFC operation. Moreover, 30 dominant bacterial species (relative intensity >1%) are identified in the biofilm in which Sulfuricurvum kujiense, Halomonas phosphatis, Proteiniphilum acetatigens, and Azoarcus indigens significantly contribute to dihydroxylation, ring cleavage and dechlorination of TCS. Additionally, the MFC was able to produce 818 ± 20 mV voltage output with a maximum power density of 766.44 mWm-2. The antibacterial activity tests revealed that the biotoxicity of TCS drastically reduced in the MFC effluent, signifying the non-toxic nature of the degraded products. Hence, this work provides a proof-of-concept strategy for sustainable mitigation of TCS in wastewaters with enhanced bioelectricity generation.

Interpreting the degradation mechanism of triclosan in microbial fuel cell by combining analysis microbiome community and degradation pathway

Microbes play a dominant role for the transformation of organic contaminants in the environment, while a significant gap exists in understanding the degradation mechanism and the function of different species. Herein, the possible bio-degradation of triclosan in microbial fuel cell was explored, with the investigation of degradation kinetics, microbial community, and possible degradation products. 5 mg/L of triclosan could be degraded within 3 days, and an intermediate degradation product (2,4-dichlorophen) could be further degraded in system. 32 kinds of dominant bacteria (relative intensity >0.5%) were identified in the biofilm, and 10 possible degradation products were identified. By analyzing the possible involved bioreactions (including decarboxylation, dehalogenation, dioxygenation, hydrolysis, hydroxylation, and ring-cleavage) of the dominant bacteria and possible degradation pathway of triclosan based on the identified products, biodegradation mechanism and function of the bacteria involved in the degradation of triclosan was clarified simultaneously. This study provides useful information for further interpreting the degradation mechanism of organic pollutants in mixed flora by combining analysis microbiome community and degradation pathway.

Degradation of Triclosan in the Water Environment by Microorganisms: A Review

Triclosan (TCS), a kind of pharmaceuticals and personal care products (PPCPs), is widely used and has had a large production over years. It is an emerging pollutant in the water environment that has attracted global attention due to its toxic effects on organisms and aquatic ecosystems, and its concentrations in the water environment are expected to increase since the COVID-19 pandemic outbreak. Some researchers found that microbial degradation of TCS is an environmentally sustainable technique that results in the mineralization of large amounts of organic pollutants without toxic by-products. In this review, we focus on the fate of TCS in the water environment, the diversity of TCS-degrading microorganisms, biodegradation pathways and molecular mechanisms, in order to provide a reference for the efficient degradation of TCS and other PPCPs by microorganisms.