Direct interspecies electron transfer stimulated by coupling of modified anaerobic granular sludge with microbial electrolysis cell for biogas production enhancement

•Fe-AnGS was prepared by a biologically induced mineralization method.•The effect of Fe-AnGS on performance and microbial community was studied.•Genes abundance for carbon dioxide reduction pathway increased by 29.40-43.54 %.•Inoculation of Fe-AnGS in MEC with glucose improved TMPCE by 11.83–29.30 %.•Fe-AnGS inoculation was an efficient strategy to establish and enhance DIET pathway.