Shewanella baltica in a Microbial Fuel Cell for Sensing of Biological Oxygen Demand (BOD) of Wastewater

Abstract

Geobacter and Shewanella are the most characterized electroactive bacteria genera. Unlike genus Geobacter that is strictly anaerobic, Shewanella can grow under both oxic and anoxic environments and is capable of metabolizing a wider substrate range. In the present study, the use of strain Shewanella baltica 20 in MFC-based biosensor for BOD monitoring is reported. The S. baltica strain 20 was isolated from river sediment in Hungary. The bacterium could form a biofilm, oxidized glucose, and transferred electrons to produce current when they were enriched on the anode in an air cathode microbial fuel cell (MFC). The tested MFC system demonstrated linearity in the current response to glucose from 50 to 300 mg/L. The electrical efficiency was determined from the polarization curve using the method of Varying Circuit Resistance (VCR) with an external load probed from 10 Ω to 220 kΩ. The maximum power production was 1.2 mW/m2 at an external load of 40 kΩ. Studying the effect of external resistors on the MFC performance showed that the MFC reached higher saturation for 500 mg/L of glucose at lower resistances of 100 and 470 Ω, in comparison to 300 mg/L at 1000 Ω. The results show that the response of the MFC can potentially be tuned by adjusting the external load. Our preliminary study suggests that Shewanella baltica strain 20 may be used for online monitoring of BOD (biological oxygen demand) in wastewater.