ABSTRACT
An iron reducing enrichment was obtained from sulfate reducing sludge and was evaluated on the capability of reducing Fe3+ coupled to acetate oxidation in a microbial fuel cell (MFC). Three molar ratios for acetate/Fe3+ were evaluated (2/16, 3.4/27 and 6.9/55 mM). The percentages of Fe3+ reduction were in a range of 80-90, 60-70 and 40-50% for the MFCs at closed circuit for the molar ratios of 2/16, 3.4/27 and 6.9/55 mM, respectively. Acetate consumption was in a range of 80-90% in all cases. The results obtained at closed circuit for current density were: 11.37 mA/m2, 4.5 mA/m2 and 7.37 mA/m2 for the molar ratios of 2/16, 3.4/27 and 6.9/55 mM, respectively. Some microorganisms that were isolated and identified in the MFCs were Azospira oryzae, Cupriavidus metallidurans CH34, Enterobacter bugandensis 247BMC, Citrobacter freundii ATCC8090 and Citrobacter murliniae CDC2970-59, these bacteria have been reported as exoelectrogens in MFC and in MFC involving metals removal but not all of them have been reported to utilize acetate as preferred substrate. The results demonstrate that the isolates can utilize acetate as the sole source of carbon and suggest that Fe3+ reduction was carried out by a combination of different mechanisms (direct contact and redox mediators) utilized by the bacteria identified in the MFC. Storage of the energy generated from the 2/16 mM MFC system arranged in a series of three demonstrated that it is possible to utilize the energy to charge a battery.
Subject(s)
Bacteria/classification , Bioelectric Energy Sources/microbiology , Iron/chemistry , Sequence Analysis, RNA/methods , Acetates/metabolism , Bacteria/genetics , Bacteria/isolation & purification , Biodegradation, Environmental , DNA, Bacterial/genetics , DNA, Ribosomal/genetics , Oxidation-Reduction , Polymorphism, Restriction Fragment Length , RNA, Ribosomal, 16S/genetics , Sewage/microbiologyABSTRACT
OBJECTIVE: an innovative non-thermal plasma (NTP) system constituted by a radiofrequency (RF) power generator directly coupled to a treatment probe is described and characterized. This system is intended to be applied as a medical device for therapeutic treatments. METHODS: electrical characterization of the radiofrequency power generator supplying the treatment probe was performed. Meanwhile, generated NTP was optically analyzed. Obtained data were studied to establish the safety profile of plasma application on heat sensitive matter. RESULTS: the NTP system was validated through bacterial deactivation trials, as well as, of being capable of deactivating carcinogenic cells. Besides promoting and accelerating wound closure in vivo performed in mice, demonstrating faster healing than that done with conventional treatments. CONCLUSION: the NTP system's characterization is an essential stage to determine the adequate application of the generated plasma over organic media. The therapeutic benefits of the NTP system were proved by the development of in vivo experiences involving laboratory mice. SIGNIFICANCE: the generated NTP interacts with surrounding air particles producing reactive oxygen and nitrogen species, which, exhibit bactericidal and antiseptic effects due to their strong biochemical reactivity; functioning like critical mediators in animal physiology and promoting wound healing processes. These properties make the NTP system a feasible technology intended for therapeutic treatments.
