Selection of bacteria for use in microbial fuel cells by electric current

Abstract

Bacteria enriched under various electricity currents, were selected for tested in mediator-less microbial fuel cell. Total of 72 electricity enriched bacteria were isolated from three sources including, 28 isolates from sediment of pond in front of Physic I building, Chulalongkorn University, 40 and 4 isolates from sub-sediment from Koh Larn, Chonburi and soil from Phu Rua, Loei, respectively. Ferric reduction activity of all isolates under anaerobic condition was also characterized. Preliminary experiment found that acrylic model was not suitable for operating mediator-less MFC. Glass I and Glass II models were later designed and constructed for sterile system that suitable for microbiological aseptic techniques. Pure culture of 40 isolates of electricity enriched bacteria from Koh Larn were determined the ability of their self-mediate electron transfer in Glass I model. It can be concluded that ferric reduction activity has more impact than electricity current that used for selection and enrichment on the electricity generation of isolates in mediator-less MFC. In Glass I model, 12 isolates of Gram’s negative, ferric reducing, swarming bacteria from Koh Larn gave high current density ~11-13 mA m-2. After tested in Glass II, the highest of 18.57 mA m-2 and 0.62 mW m-2 for current density and power density, respectively were generated by KL22. These indicated that the increase of current density and power density more than those of Glass I, 67 % and 179%, respectively. As the results, anaerobic condition in anodic compartment enhanced electron transfer to anode electrode led to the increasing of electricity output. KL22 was identified as Proteus vulgaris by using 16S rDNA analysis and rapid identification kit API 20E. Proteus vulgaris can biocatalyse successfully in mediator-less MFC system from this study is firstly reported. Further improvements by optimizing the physical and chemical parameters of microbial fuel cells for the sustainable alternative energy in the future are required.