| description |
The anode potentials in microbial electrolysis cells (MECs) influence the energy availability for the microbial growth, the microbial community structure and also the reactor performance. However, the stimulus of set anode potentials (SAPs) on the performances of MECs fed with a high concentration of propionate have not been demonstrated. Here, we examined the impact of various SAPs (-0.25, 0, and 0.25 V vs. SHE) on the reactors performance, electrons flux to various sinks, and the microbial community structure in a double chamber MECs fed with propionate (36mM). Electron balances and microbial fingerprinting showed that SAPs modulate the electron fluxes between the electrical current and CH4 and also affected the microbial community structure of a propionate fed MECs. Electrical current (49-71%) and CH4 (22.9-41%) was the largest electron sinks regardless of the potentials tested. However, 0 V indicated that higher electron fluxes to the electrical current (71±5%) and lower fraction to CH4 (22.9±1.2%). In contrast, more negative SAP (-0.25 V) had a lower percentage of the electrical current and there was a greater fraction of electron loss to CH4 (41.1±2%). Furthermore, open circuit (O.C) reactors had significantly higher CH4 (73±4%) than the SAP-MECs. A complete degradation of propionate (36mM) with no accumulation of it intermediates was observed in all the tested SAPs. Analysis of 16S r RNA gene indicated that more negative SAP (-0.25 V) showed a highly diverse communities the other potentials tested. Interestingly, in all the anode of SAPs dominated by G. sulfurreducens followed by Smithella spp. and Syntrophobacter sulfatereducens. While, the suspensions were predominated by the classic propionate fermenters namely S. sulfatereducens, Smithella spp. and Methanobacterium formicicum. Overall, these results provide new insights on the influence of SAPs of MECs fed with a high concentration of propionate. |