Microbial Fuel Cell Based on Nitrogen-Fixing Rhizobium anhuiense Bacteria.

Rokas Žalnėravičius,Monika Vilkienė,Simonas Ramanavičius,Algimantas Paškevičius,Ieva Mockevičienė,Urtė Samukaitė-Bubnienė,Arūnas Ramanavičius

doi:10.3390/bios12020113

Abstract

In this study, the nitrogen-fixing, Gram-negative soil bacteria Rhizobium anhuiense was successfully utilized as the main biocatalyst in a bacteria-based microbial fuel cell (MFC) device. This research investigates the double-chambered, H-type R. anhuiense-based MFC that was operated in modified Norris medium (pH = 7) under ambient conditions using potassium ferricyanide as an electron acceptor in the cathodic compartment. The designed MFC exhibited an open-circuit voltage (OCV) of 635 mV and a power output of 1.07 mW m−2 with its maximum power registered at 245 mV. These values were further enhanced by re-feeding the anode bath with 25 mM glucose, which has been utilized herein as the main carbon source. This substrate addition led to better performance of the constructed MFC with a power output of 2.59 mW m−2 estimated at an operating voltage of 281 mV. The R. anhuiense-based MFC was further developed by improving the charge transfer through the bacterial cell membrane by applying 2-methyl-1,4-naphthoquinone (menadione, MD) as a soluble redox mediator. The MD-mediated MFC device showed better performance, resulting in a slightly higher OCV value of 683 mV and an almost five-fold increase in power density to 4.93 mW cm−2. The influence of different concentrations of MD on the viability of R. anhuiense bacteria was investigated by estimating the optical density at 600 nm (OD600) and comparing the obtained results with the control aliquot. The results show that lower concentrations of MD, ranging from 1 to 10 μM, can be successfully used in an anode compartment in which R. anhuiense bacteria cells remain viable and act as a main biocatalyst for MFC applications.

Highlights

In order to meet the growing demand for human food, the agriculture industry is intensifying production by new technologies, some of which involve the excessive use of nitrogen with other elemental fertilizers and alter chemical products
We have investigated the applicability of R. anhuiense bacteria as the main biocatalyst for constructing dual-chamber microbial fuel cells (MFCs)
We have shown that the nitrogen-fixing, Gram-negative bacterium R. anhuiense could be successfully utilized as a main biocatalyst in the anode compartment by using modified carbon felt anode in an H-type microbial fuel cell setup

Summary

Introduction

In order to meet the growing demand for human food, the agriculture industry is intensifying production by new technologies, some of which involve the excessive use of nitrogen with other elemental fertilizers and alter chemical products. Adding chemical nitrogen to agricultural systems has major benefits, there are numerous unpleasant environmental impacts. Some studies have revealed that the use of nitrogen in agriculture is one of the main triggers for coastal zone eutrophication processes [4]. This process leads to hypoxia in the coastal zone and other surface water bodies. Algae blooms are triggered by nitrogen (N) uptake from agricultural land [5,6]. Intensive agricultural systems emit reactive nitrogen-based gases, ammonia and various nitrogen oxides, which act as powerful greenhouse gases in the troposphere [7–9]

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Conclusion