Abstract
Wastewater treatment coupled with electricity recovery in microbial fuel cell (MFC) prefer mixed anaerobic sludge as inoculum in anodic chamber than pure stain of electroactive bacteria (EAB), due to robustness and syntrophic association. Genetic modification is difficult to adopt for mixed sludge microbes for enhancing power production of MFC. Hence, we demonstrated use of eco-friendly plant secondary metabolites (PSM) with sub-lethal concentrations to enhance the rate of extracellular electron transfer between EAB and anode and validated it in both bench-scale as well as pilot-scale MFCs. The PSMs contain tannin, saponin and essential oils, which are having electron shuttling properties and their addition to microbes can cause alteration in cell morphology, electroactive behaviour and shifting in microbial population dynamics depending upon concentrations and types of PSM used. Improvement of 2.1-times and 3.8-times in power densities was observed in two different MFCs inoculated with Eucalyptus-extract pre-treated mixed anaerobic sludge and pure culture of Pseudomonas aeruginosa, respectively, as compared to respective control MFCs operated without adding Eucalyptus-extract to inoculum. When Eucalyptus-extract-dose was spiked to anodic chamber (125 l) of pilot-scale MFC, treating septage, the current production was dramatically improved. Thus, PSM-dosing to inoculum holds exciting promise for increasing electricity production of field-scale MFCs.
Highlights
Wastewater treatment coupled with electricity recovery in microbial fuel cell (MFC) prefer mixed anaerobic sludge as inoculum in anodic chamber than pure stain of electroactive bacteria (EAB), due to robustness and syntrophic association
Cisplatin was applied on Shewanella oneidensis MR-1 to boost electricity generation in M FC11; cisplatin can act as an electron shuttle that depicted in cyclic voltammetry (CV) p lot[13,14]
Results from these preliminary investigation confirmed that Plant water extracts (PWE)-plant secondary metabolites (PSM) can act as an electron shuttle, form tannin-protein complex with bacterial cell, cause alteration in bacterial cell morphology such as cluster formation, chain and spheroplast development depending on the source of plant species and these properties all together played key role for facilitating electron transfer (EET) (Figs. 1a–e, 2a–c)
Summary
Wastewater treatment coupled with electricity recovery in microbial fuel cell (MFC) prefer mixed anaerobic sludge as inoculum in anodic chamber than pure stain of electroactive bacteria (EAB), due to robustness and syntrophic association. PSM-dosing to inoculum holds exciting promise for increasing electricity production of field-scale MFCs. Microbial fuel cell (MFC) generate electricity when electroactive microorganisms (EAM) respire at anode by extracellular electron transfer (EET) coupled with the oxidation of organic c arbon[1]. Cisplatin was applied on Shewanella oneidensis MR-1 to boost electricity generation in M FC11; cisplatin can act as an electron shuttle that depicted in cyclic voltammetry (CV) p lot[13,14] Though these physiochemical and biological approaches successfully improved electricity in bench-top MFCs, these are uncertain for application in full-scale MFCs, either due to high cost and not being as an eco-friendly[6]. For the first time in this research it is demonstrated that microbial cell stress associated with exposure to PSM causes alteration in cell morphology, form tannin-protein complex, and enhances EET This PSM-based strategy to enhance electricity production in small laboratory scale-MFC was further validated in pilot-scale MFC treating septage
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