[Enhanced Removal of Herbicide 2,4-dichlorophenoxyacetic Acid and Simultaneous Power Generation in Microbial Fuel Cells].

This study investigated the effects of a widely used herbicide 2,4-dichlorophenoxyacetic acid on power generation, pollutants removal from microbial fuel cells (MFCs) and microbial community changes, and also explored anode pre-aeration for enhanced 2,4-D removal and power generation. The results showed that when 2,4-D was inputted to the anode chamber of MFCs which was previously enriched with acetate sodium as the fuel, the voltage output and power density declined and the internal resistance increased apparently. The maximum power density declined to 0.057 W·m-2 in the presence of 300 mg·L-1 2,4-D comparing to 0.151 W·m-2 obtained with acetate alone (850 mg·L-1), and the internal resistance increased from 524 Ω to 1230 Ω correspondingly. To accelerate 2,4-D removal rate and reduce its inhibition to anode exoelectrogens, 6h pre-aeration was applied to the anode chamber. Fast removal of 2,4-D was achieved during aeration period and simultaneous high maximum voltage output (0.42-0.47 V) was obtained. Anode microbial community changed after 2,4-D addition and several 2,4-D degrading bacteria and 2,4-D tolerant exoelectrogen were enriched. MFCs could be used for 2,4-D removal and simultaneous power generation through anode pre-aeration.

Characterization of late gene expression factor LEF-10 from Bombyx mori nucleopolyhedrovirus.

The LEF-10 expression factor from the Bombyx mori nuclear polyhedrosis virus (BmNPV) does not have significant homology with other late expression factors and is thought to be a transcriptional cofactor. To investigate the function of LEF-10, a Red recombination system was used to knock out the lef-10 gene from the BmNPV genome and a lef-10 gene knockout virus (ko-Bacmid) was constructed. The lef-10 gene was repaired back to the viral genome using a Bac-to-Bac system to create the repaired virus (re-Bacmid). When ko-Bacmid was transfected into BmN cells, the detected titer of progeny virus in the medium was zero, whereas the titer of the progeny re-Bacmid remained at a level similar to that of the wild type virus (wt-Bacmid). The viral DNA replication, transcription and expression of viral early, late and very late genes after ko-Bacmid transfection into BmN cells were evaluated. The quantitative polymerase chain reaction showed that the ko-Bacmid viral genome replication level remained low and that the ko-Bacmid viral gene transcription level was significantly lower than those of wt-Bacmid and re-Bacmid. No expression of the early gene lef-3 was detected. These results suggest that the lef-10 gene has significant effects on DNA replication of the viral genome and BmNPV gene transcription at each phase and deletion of the lef-10 gene affects the level of expression of the viral early gene directly.

Comparative investigation on microbial community and electricity generation in aerobic and anaerobic enriched MFCs.

This study compared the difference in microbial community and power generation capacity of air-cathode MFCs enriched under anode aerobic and anaerobic conditions. Results showed that MFCs successfully started with continuous air inputting to anode chamber. The aerobic enriched MFC produced comparable and even more electricity with the fuels of acetate, glucose and ethanol compared to the anaerobic MFC when returning to anaerobic condition. The two MFCs showed a slightly different microbial community for anode biofilms (a similarity of 77%), but a highly similar microbial community (a similarity of 97%) for anolyte microbes. The anode biofilm of aerobic enriched MFC showed the presence of some specific bacteria closely related to Clostridium sticklandii, Leucobacter komagatae and Microbacterium laevaniformans. The anaerobic enriched MFC found the presence of a large number of yeast Trichosporon sp. This research demonstrates that it is possible to enrich oxygen-tolerant anode respiring bacteria through purposely aeration in anode chamber.