Cometabolic biodegradation of chlorinated ethenes with methanotrophs in anaerobic/aerobic simulated aquifer

Aim: This study explores anaerobic/aerobic biodegradation efficiencies of aerobic cometabolism with methanotrophs when contaminants trichloroethylene (TCE) and cis-1,2-dichloroethylene (cDCE) are present individually or in tandem. Methodology: Batch tests and an anaerobic/aerobic column system were used to simulate saturated, contaminated aquifers. A brown glass bottle with an effective volume of 44 m l-1 was prepared for the batch test. An integrated one-dimensional sequential anaerobic/aerobic column system was used to simulate the accumulative intermediates such as TCE, cDCE and VC caused by incomplete degradation of PCE during the upgradient anaerobic stage in the saturated aquifer. In the downgradient aquifer, aerobic cometabolism was employed to degrade the intermediates. Methanotrophs in the aerobic aquifer were inoculated to degrade the by-products of incomplete degradation of PCE by aerobic cometabolism. Results: In the batch test, biodegradation of TCE was significantly inhibited by cDCE. However, biodegradation of cDCE was not significantly inhibited by TCE. In the simulated aquifer test, aerobic cometabolism completely degraded intermediates (TCE, cDCE, and VC) produced by incomplete anaerobic degradation of tetrachloroethylene (PCE). The results showed that methane, a by-product of anaerobic reductive dechorination of PCE, was used as a primary substrate for aerobic degradation, at a utilization rate of almost 100%. Interpretation: Biodegradation of TCE was significantly inhibited by cDCE. Bioremediation should have sufficient oxygen and methane at aerobic stage to ensure that chlorinated ethenes fully mineralize.

Biodegradation of Indanthrene Blue RS dye in immobilized continuous upflow packed bed bioreactor using corncob biochar

The current study describes the aerobic biodegradation of Indanthrene Blue RS dye by a microbial consortium immobilized on corn-cob biochar in a continuous up-flow packed bed bioreactor. The adsorption experiments were performed without microbes to monitor the adsorption effects on initial dye decolorization efficiency. The batch experiments were carried out to estimate the process parameters, and the optimal values of pH, temperature, and inoculum volume were identified as 10.0, 30 °C, and 3.0 × 106 CFU mL−1, respectively. During the continuous operation, the effect of flow rate, initial substrate concentration, inlet loading rate of Indanthrene Blue RS on the elimination capacity, and its removal efficiency in the bioreactor was studied. The continuous up-flow packed bed bioreactor was performed at different flow rates (0.25 to 1.25 L h−1) under the optimal parameters. The maximum removal efficiency of 90% was observed, with the loading rate varying between 100 and 300 mg L−1 day−1. The up-flow packed bed bioreactor used for this study was extremely useful in eliminating Indanthrene Blue RS dye using both the biosorption and biodegradation process. Therefore, it is a potential treatment strategy for detoxifying textile wastewater containing anthraquinone-based dyes.

Novel clades of soil biphenyl degraders revealed by integrating isotope probing, multi-omics, and single-cell analyses

Most microorganisms in the biosphere remain uncultured and poorly characterized. Although the surge in genome sequences has enabled insights into the genetic and metabolic properties of uncultured microorganisms, their physiology and ecological roles cannot be determined without direct probing of their activities in natural habitats. Here we employed an experimental framework coupling genome reconstruction and activity assays to characterize the largely uncultured microorganisms responsible for aerobic biodegradation of biphenyl as a proxy for a large class of environmental pollutants, polychlorinated biphenyls. We used 13C-labeled biphenyl in contaminated soils and traced the flow of pollutant-derived carbon into active cells using single-cell analyses and protein–stable isotope probing. The detection of 13C-enriched proteins linked biphenyl biodegradation to the uncultured Alphaproteobacteria clade UBA11222, which we found to host a distinctive biphenyl dioxygenase gene widely retrieved from contaminated environments. The same approach indicated the capacity of Azoarcus species to oxidize biphenyl and suggested similar metabolic abilities for species of Rugosibacter. Biphenyl oxidation would thus represent formerly unrecognized ecological functions of both genera. The quantitative role of these microorganisms in pollutant degradation was resolved using single-cell-based uptake measurements. Our strategy advances our understanding of microbially mediated biodegradation processes and has general application potential for elucidating the ecological roles of uncultured microorganisms in their natural habitats.