Bioenergy generation processes are getting importance due to the utilization of fossil fuels which are exhaustible. The aim of the present study was to enhance the overall energy recovery from substrates through two-phase anaerobic dark fermentation process with obligate anaerobes, Clostridium acetobutylicum MTCC 11274 and Clostridium saccharoperbutylacetonicum DSM 14923. The two-phase (biohydrogen and biobutanol) batch process was carried out under mesophilic condition. Maximum cumulative hydrogen and butanol contents of 3.110 L L-1 (2.48 moL H-2 mol(-1) glucose) and 4.26 g L-1, respectively were obtained after anaerobic fermentation with C. saccharoperbutylacetonicum. This process resulted in a significant increase in energy recovery (75.50%) as compared to the single stage dark fermentation process. Starchy wastewater supplemented with distiller's dried grains with soluble (DDGS) was found to be a more potential feedstock than starchy wastewater alone for this process and a maximum cumulative hydrogen and butanol contents of 3.003 L L-1 and 4.17 g L-1 respectively were obtained with C. saccharoperbutylacetonicum. (C) 2017 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.