The Selection And Application Of Electrochemically Active Microorganisms From Marine Sediments

A marine microbial fuel cell (MFC) was constructed using natural seawater and sediments which reached a maximum current density of 0.07 A/m2. Electrical current could be harvested from marine sediments by embedding the anode that enriched electrochemically active microorganisms. An anaerobic microorganism was isolated from the anode surface of marine MFC using separation and purification methods. It can be inferred from molecular biology that the pure strain was a kind of sulphate reducing bacteria (SRB) and was most closely related to the strain Desulfovibrio.The graphite electrode surface polarized at anode potential by chronoamperometry in the electrochemical reactor serve as anode of MFC. The current density on graphite electrode surface polarized at the different anode potential can be generated. At +0.0 V, the current increased after ca. 1 day up to a maximum current intensity of 0.33±0.01 A/m2. The results demonstrate that the SRB as biocatalyst could oxidize sodium lactate and generate electricity. To find new electrochemically active microorganisms and understand the bacterial anodic electron transfer mechanism, the electrochemical activity of the SRB strain on polarized and non-polarized graphite electrode was investigated using a series of electrochemical methods, scanning electron microscopy and the determination of the growth curve. The SRB played important role in enhancing the extracellular electron transfer in the absence of electrochemical ?mediators. An almost fully developed biofilm was observed on polarized graphite surface by scanning electron microscopy. The SRB biofilm growth on polarized electrode surface showed significant improvement in electrochemical activity. The results indicated the established SRB biofilm helped to enhance the extracellular electron transfer from the SRB to graphite electrode. Effect of microorganisms from marine sediments on the corrosion behaviors of carbon steel was studied by comparing the corrosion behaviors of the carbon steel without and with linked graphite electrode from marine sediments in natural seawater. It can be found that the carbon steel linked graphite electrode from marine sediments can decrease the corrosion rate, and it is related to microorganisms from marine sediments. Meantime, effect of biofilm on the corrosion behaviors of carbon steel was studied by comparing the corrosion behaviors of the carbon steel immersed in natural and sterile seawater. In the early phase, biofilms can decrease the corrosion rate. It is correlated with synergistic action of a variety of aerobic microorganisms. In the later phase, it is marked by an increased rate of corrosion. It is related to the rapid growth of anaerobic microorganisms, such as SRB.