Achieving high electrogenic output from microbial fuel cell by chloroform-biotin pretreatment of wetland soil inoculum

Abstract

Bioelectricity generation by microbial fuel cell (MFC) is governed by the electrogenic microbes, whereas presence of non-electrogenic microbes, mainly the methanogens hamper its performance. Chloroform is known to suppress methanogens while its effect on electrogenic microbes is not well documented. In this study, a novel biotin-chloroform combination was used for pretreatment of the inoculum to neutralize any negative effect of chloroform and promote the growth of electrogenic bacteria by using biotin, a vitamin. The aim is to enhance power generation by MFC through pretreatment of wetland soil inoculum with acid (MFC-A), chloroform (MFC-Ch), and biotin-chloroform combination [MFC-(Ch+B)], while nontreated inoculum (MFC-NT) served as control. The novel biotin-chloroform pretreatment in MFC-(Ch+B) exhibited a distinctively superior performance, yielding high power density (5.79 W/m3), which was about 81% higher than that of control, MFC-NT (3.2 W/m3), 37% higher than that of MFC-A (4.23 W/m3) and 21% higher than that of MFC-Ch (4.8 W/m3). With pretreatment inoculum, COD removal in MFCs was, however, reduced, which can be attributed to the partial elimination of microbial communities. Coulombic efficiency was much higher in response to pretreated inoculum, particularly in MFC-(Ch+B). Estimation of the specific methanogenic activity in the MFC anodes indicated less methane production on pretreatment of inoculum with acid (0.102 mLCH4/gVSS.d), chloroform (0.096 mLCH4/gVSS.d) and Ch+B (0.095 mLCH4/gVSS.d) treatment compared to that of control (0.226 mLCH4/gVSS.d). This further implies that while chloroform suppresses methanogens, biotin supplement is majorly boosting electrogenic activity rather than affecting methanogenic activity in the MFC anode.