• Journal of Microbiology and Biotechnology
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• v.33 no.5
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• pp.687-697
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• 2023

Identification of novel, electricity-producing bacteria has garnered remarkable interest because of the various applications of electricigens in microbial fuel cell and bioelectrochemical systems. Shewanella marisflavi BBL25, an electricity-generating microorganism, uses various carbon sources and shows broader sugar utilization than the better-known S. oneidensis MR-1. To determine the sugar-utilizing genes and electricity production and transfer system in S. marisflavi BBL25, we performed an in-depth analysis using whole-genome sequencing. We identified various genes associated with carbon source utilization and the electron transfer system, similar to those of S. oneidensis MR-1. In addition, we identified genes related to hydrogen production systems in S. marisflavi BBL25, which were different from those in S. oneidensis MR-1. When we cultured S. marisflavi BBL25 under anaerobic conditions, the strain produced 427.58 ± 5.85 µl of biohydrogen from pyruvate and 877.43 ± 28.53 µl from xylose. As S. oneidensis MR-1 could not utilize glucose well, we introduced the glk gene from S. marisflavi BBL25 into S. oneidensis MR-1, resulting in a 117.35% increase in growth and a 17.64% increase in glucose consumption. The results of S. marisflavi BBL25 genome sequencing aided in the understanding of sugar utilization, electron transfer systems, and hydrogen production systems in other Shewanella species.

• Journal of Korean Society of Environmental Engineers
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• v.37 no.12
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• pp.682-688
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• 2015

Effect of electrode spacing on the performance of microbial electrolysis cells(MECs) for treating sewage sludge was investigated through lab scale experiment. The reactors were equipped with two pairs of electrodes that have a different electrode spacing (16, 32 mm). Shorter electrode distance improved the overall performance of MEC system. With the 16 mm of electrode distance, the current density was $3.04{\sim}3.74A/m^3$ and methane production was $0.616{\sim}0.804Nm^3/m^3$, which were higher than those obtained with 32 mm of electrode spacing ($1.50{\sim}1.82A/m^3$, $0.529{\sim}0.664Nm^3/m^3$). The COD removal was in the range of 34~40%, and the VSS reduction ranged 32~38%. As the current production increased, VSS reduction and methane production were increased possibly due to the improved bioelectrochemical performance of the system. Methane production was more affected by current density than VSS reduction. These results imply that the reducing the electrode spacing can enhance the methane production and recovery from sewage sludge with the decreased internal resistance, however, it was not able to improve VSS reduction of sewage sludge.

• Journal of the Korea Organic Resources Recycling Association
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• v.29 no.2
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• pp.31-38
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• 2021

The aim of this study is to evaluate the possibility of treating slaughterhouse by-products using microbial electrolysis cells (MECs). The diluted pig liver was fed to MEC reactors with the influent COD concentrations of 772, 1,222, and 1,431 mg/L, and the applied voltage were 0.3, 0.6, and 0.9 V. The highest methane production of 5.9 mL was obtained at the influent COD concentration of 1,431 mg/L and applied voltage of 0.9 V. In all tested conditions, COD removal rate was increased as the influent COD concentration increased with average removal rate of 62.3~81.1%. The maximum methane yield of 129~229 mL/g COD was obtained, which is approximately 80% of theoretical maximum value. It might be due to the bioelectrochemical reaction greatly increased the biodegradability of pig liver. Future research is required to improve the methane yield and digestibility through optimizing the reactor design and operating conditions.