Competition Between E. coli and Shewanella sp. for Electricity Generation in Air Cathode MFC in Presence of Methylene Blue as Artificial Mediator

摘要

Shewanella sp. and E. coli are two types of bacteria which transfer electron in MFC directly and indirectly with aid of an artificial mediator such as: methylene blue (MB). In this study, competition between these bacteria for electricity generation, in pure and binary culture conditions, was studied, considering the effect of MB concentration. For E. coli increasing the MB concentration in the anode chamber from zero to 10 and 25 mol m~(-3) could enhance the maximum power density from 12.15±1.24 to 22.65±6.59 and 46.14 ± 3-92 mW m~(-2), respectively. However, further increase of the concentration to 50 mol m~(-3) decreased the power density to 33.54 ±9.11 mW m~(-2). For Shewanella. sp. applying the same range of concentration increase as E. coli (0-50 mol m~(-3)), continuously, diminished the power density from 26.91 ±1.71 to 14.06 ±6.84, 12.56 ±0.90, and 3.01 ± 0.66 mW m~(-2). The binary culture of these bacteria had an intermediate trend between their pure cultures. These results represented that Shewanella sp. could donate electrons directly and presence of MB, even, lessened the power generation yield. On the contrary, for E. coli the rise of MB concentration to an optimum value facilitated the electron transfer.