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Isolation and Characterization of Functional Microorganism in Microbial Electrolysis Cell (MEC)

Author: SunDan
Tutor: WangAiJie
School: Harbin Institute of Technology
Course: Microbiology
Keywords: microbial electrolysis cell (MEC) serial dilution method minimum exoelectrogenic consortium the amorphous Fe(III) oxyhydroxide reduce medium Electrochemical activity
CLC: TQ116.2
Type: Master's thesis
Year: 2008
Downloads: 68
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Abstract

Microbial electrolysis cell (MEC) for H2 prodcution is a advaced technology to use small molecular organics to produce hydrogen by microbial way, which focus on the potential energy that still contained in the hydrogen manufacturing fermenting terminal products. However, till now, little information presents the remarkable bacteria that function in a microbial electrochemical assisted hydrogen production reactor, especially, their characterization and interaction.In this study, we established a new isolation way for anode functional microorganisms in Microbial electrolysis cell (MEC) system—serial dilution method. After serial dilution (10-1~10-9), the functional microorganisms in anode biofilm were inoculated into a Fe(III) reduce medium contained the amorphous Fe(III) oxyhydroxide, took reduce efficiency of Fe(III)-oxide as the estimate target to filtrate. The results showed that the microorganisms with ability to reduce Fe(III)-oxide existed under every dilutions, their lag phases is prolonged with the increasing dilutions, but the terminal ability to deoxidize Fe(III)-oxide was not affected by dilution. So we defined the functional microorganisms under the dilution 10-6 as“minimum exoelectrogenic consortium”. In this research we obtained“minimum exoelectrogenic consortium”—E23, which is isolated from the anode biofilm of a MEC system. The system is inoculated active sludge and run stead for three months. The research showed that E23 completely reduce 100 mmol amorphous Fe(III) oxyhydroxide using acetate as electron donors and form Fe3O4 after 6 days cultivation.When this“minimum exoelectrogenic consortium”was inoculated into a mediator-less MEC reactor fed with acetate as sole electron donor, it produced 417.5 mA/m2 of current density, which is higher than sewer sludge in the similar device. In a 15-day batch cycle, the total columbic efficiency of the“minimum exoelectrogenic consortium”—E23 could reach 22.4±2%. Meanwhile, microbial community analysis using denaturing gradient gel electrophoresis (DGGE) technology showed the right structure and composition of E23 is very important in the startup operation of MEC, and the optimization of the structure and composition of E23 inoculum can effectively shorten the lag phase. Meanwhile, a nonexoelectrogenic isolate, named WL-4 was isolated from the same double-chamber MEC, using the Hungate roll-tube technique. It could not use common electron donors (acetate, lactate, formate, propionate, butyrate, citrate, ethanol, cellobiose, glucose) to reduce Fe(III). Analysis of physiological-biochemical characterization and 16S rRNA gene sequence showed that strain WL-4 is a member of the genus Bacteroides. The MEC operation tests showed that strain WL-4 could not produce electricity if using acetate as electron donors. To further investigate the cooperation of different kinds of functional bacteria, enrichment of E23 and strain WL-4 were simultaneous inoculated in a MEC. In this test, the co-culture can reach a highter Ec.

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