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Toxicity assessment of water is of great important to the safety of human health and to social security because of more and more toxic compounds that are spilled into the aquatic environment. Therefore, the development of fast and reliable toxicity assessment methods is of great interest and attracts much attention. In this study, by using the electrochemical activity of Shewanella oneidensis MR-1 cells as the toxicity indicator, 3,5-dichlorophenol (DCP) as the model toxic compound, a new biosensor for water toxicity assessment was developed. Strikingly, the presence of DCP in the water significantly inhibited the maximum current output of the S. oneidensis MR-1 in a three-electrode system and also retarded the current evolution by the cells. Under the optimized conditions, the maximum current output of the biosensor was proportional to the concentration of DCP up to 30 mg/L. The half maximal inhibitory concentration of DCP determined by this biosensor is about 14.5 mg/L. Furthermore, simultaneous monitoring of the retarded time (Δ t) for current generation allowed the identification of another biosensor signal in response to DCP which could be employed to verify the electrochemical result by dual confirmation. Thus, the present study has provided a reliable and promising approach for water quality assessment and risk warning of water toxicity. [ABSTRACT FROM AUTHOR]

Toxicity assessment of water is of great important to the safety of human health and to social security because of more and more toxic compounds that are spilled into the aquatic environment. Therefore, the development of fast and reliable toxicity assessment methods is of great interest and attracts much attention. In this study, by using the electrochemical activity of Shewanella oneidensis MR-1 cells as the toxicity indicator, 3,5-dichlorophenol (DCP) as the model toxic compound, a new biosensor for water toxicity assessment was developed. Strikingly, the presence of DCP in the water significantly inhibited the maximum current output of the S. oneidensis MR-1 in a three-electrode system and also retarded the current evolution by the cells. Under the optimized conditions, the maximum current output of the biosensor was proportional to the concentration of DCP up to 30 mg/L. The half maximal inhibitory concentration of DCP determined by this biosensor is about 14.5 mg/L. Furthermore, simultaneous monitoring of the retarded time (Δ t) for current generation allowed the identification of another biosensor signal in response to DCP which could be employed to verify the electrochemical result by dual confirmation. Thus, the present study has provided a reliable and promising approach for water quality assessment and risk warning of water toxicity. [ABSTRACT FROM AUTHOR]

A novel whole-cell electrochemical sensor was developed and applied for sensitive amperometric detection of riboflavin. In this work, a whole-cell based riboflavin redox cycling system was characterized, in which electroactive bacteria Shewanella oneidensis MR-1 was employed as the biocatalyst to regenerate the reduced riboflavin after the electrode oxidation. This redox cycling system efficiently enhanced the electrochemical response of riboflavin and enabled a stable current output at poised electrode potential. Thus, a sensitive amperometric biosensing system for riboflavin detection was developed by integrating this whole-cell redox cycling system with the conventional riboflavin electrochemical sensor. Remarkably, this riboflavin biosensor exhibited high sensitivity (LOD = 0.85 ± 0.09 nM, S/N = 3), excellent selectivity and stability. Additionally, reliable analysis of real samples (food and pharmaceutical samples) by this biosensor was achieved. This work provided sensitive and practical tool for riboflavin detection, and demonstrated that the integration of electroactive bacteria and using its outwards electron transfer for redox cycling would be a powerful and promising strategy to improve the performance of electrochemical sensing system. [ABSTRACT FROM AUTHOR]

Although microbial fuel cells (MFCs) is considered as one of the most promising technology for renewable energy harvesting, low power output still accounts one of the bottlenecks and limits its further development. In this work, it is found that Cu 2+ (0.1 μg L −1 –0.1 mg L −1 ) or Cd 2+ (0.1 μg L −1 –1 mg L −1 ) significantly improve the electricity generation in MFCs. The maximum power output achieved with trace level of Cu 2+ (∼6 nM) or Cd 2+ (∼5 nM) is 1.3 times and 1.6 times higher than that of the control, respectively. Further analysis verifies that addition of Cu 2+ or Cd 2+ effectively improves riboflavin production and bacteria attachment on the electrode, which enhances bacterial extracellular electron transfer (EET) in MFCs. These results unveil the mechanism for power output enhancement by Cu 2+ or Cd 2+ addition, and suggest that metal ion addition should be a promising strategy to enhance EET as well as power generation of MFCs. [ABSTRACT FROM AUTHOR]