Microbial biomass in a microbial fuel cell (MFC) was determined at varied external resistances and temperatures, and the current generations were correlated with biomass concentration. MFC operation with wastewater generated the highest current of 0.23 mA at 300 Omega compared with 100 Omega (0.22 mA) and 1000 Omega (0.18 mA). The microbial biomass (0.091 mg-protein/cm(2)) on the anode with 100 Omega was higher than the other resistances. With growth media, current and biomass density were increased due to high strength electrolyte and nutrient. The MFCs with higher current generation contained a more amount of biomass on an anode electrode. The highest biomass growth rate with growth media was 1.307 x 10(-4) mg-protein/hr.cm(2) at 30 degrees C (with 300 Omega), which was about 2 times higher than with wastewater. In linear regression, current generation is expected to increase by about 3 times as the biomass is doubled on the anode electrode. (C) 2016 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.