This study was conducted to optimize microbial electrolysis cells (MECs) + anaerobic digestion (AD) using integrated Taguchi method and response surface methodology (RSM). The MECSs were applied to enhance the efficiency of AD using food waste as substrate. Using Taguchi method and RSM, the optimum conditions of the MEC + AD were applied voltage (1.2 V), substrate (2.4 g COD/L) and ratio of reactor volume and electrode area (0.33 m3/m2), respectively. The results of the modified Gompertz and dual-pool 1st order showed that the maximum methane yield, maximum methane production rate, and rate constant for rapidly degradable substrate were 1.2, 1.3 and 1.5 fold higher than those of the AD, respectively. Microbial communities analyses indicated that acetoclastic methanogens were initially floating in MEC + AD reactor, but they became attached onto electrodes over time. (C) 2018 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.