Potential of molasses substrate for bioelectricity production in microbial fuel cell with the help of active microbial community

The present study investigated the potential of different concentrations of molasses wastewater to produce bioelectricity, reduction of chemical oxygen demand (COD) and functionally active microbial community in microbial fuel cells (MFCs). Five different MFC setups were compared in which three were fed with molasses (two at room and one at 35 degrees C temperature), while fourth and fifth were used as control reactors fed with distilled water and acetate, respectively. During first, second and third phases of the experiment; 1, 3 and 5 g L-1 molasses in distilled water were used as 500, 1000 and 1500 mg L-1 COD loading rate, respectively. Analysis of different parameters including pH, total dissolved solids (TDS) and electrical conductivity performed after 3 days interval due to 3 days hydraulic retention time, while COD, current, the voltage after 24 hours interval. The maximum voltage (1011 mV) and current (0.91 mA) were produced in MCF-3 when 5 g L-1 of molasses was used, while maximum power density 1570.68 mW L-1 was produced by MFC-1. The highest COD removal (95%) was found in MFC-3 at 500 mg L-1 influent COD, comparable with control MFC-5 with acetate which exhibited 97% COD removal at the same loading rate of acetate. High throughput DNA sequencing showed Clostridium sensu stricto abundance was higher among all other genera in all MFCs, ranges between 11 and 17 in MFCs with molasses, 18.3 in MFC with acetate and a lower value of 5.8 in control MFC without molasses. Romboutsia found higher in MFCs with molasses and acetate, might be responsible for higher electricity generation in these MFCs. Higher Shannon diversity and low abundance were found in MFC4 with distilled water while low diversity with higher abundance due to enrichment of certain genera under specific substrates was found in MFC 2 and 5 fed with molasses and acetate, respectively. It was concluded that MFC with molasses concentration 5 g L-1 showed more efficient power generation as compared to acetate, hence can be used to generate electricity while COD removal efficiency was almost the same with molasses and acetate.