Effect of acid-pretreatment on hydrogen fermentation of food waste: Microbial community analysis by next generation sequencing Dong-Hoon Kim a , Sujin Jang a,b , Yeo-Myeong Yun c , Mo-Kwon Lee a , Chungman Moon a , Won-Seok Kang d , Seung-Shin Kwak d , Mi-Sun Kim a,b,* a Biomass and Waste Energy Laboratory, Korea Institute of Energy Research, 152 Gajeong-ro, Yuseong-gu, Daejeon 305-343, Republic of Korea b Division of Renewable Energy Engineering, University of Science and Technology, 217 Gajeong-ro, Yuseong-gu, Daejeon 305-350, Republic of Korea c Department of Civil and Environmental Engineering, KAIST, 373-1 Guseong-dong, Yuseong-gu, Daejeon 305-701, Republic of Korea d New Technology Research Team, Korea District Heating Corp. R&D Institute, 781 Yangjae-daero, Gangnam-gu, Seoul 135-220, Republic of Korea article info Article history: Received 30 May 2014 Received in revised form 30 July 2014 Accepted 2 August 2014 Available online 28 August 2014 Keywords: Hydrogen Food waste Acid pretreatment Next generation sequencing Lactic acid bacteria Substrate concentration abstract This work presents the effect of acid-pretreatment on H 2 fermentation of food waste with detailed microbial information by next generation sequencing. The pretreated food waste at pH 1.0e4.0 was cultivated under mesophilic conditions without external inoculum addition. From the food waste acid-pretreated at pH 1e3, H 2 yields in the range of 1.37 e1.74 mol H 2 /mol hexose added were achieved, attaining the highest value at pH 2. Clos- tridium sp. such as Clostridium acetobutylicum ATCC 824 and Clostridium perfringens occupied more than 70% of total number of sequences at pH 1e3. On the other hand, in the control (no pretreatment) and at pH 4, lactic acid bacteria such as Lactobacillus and Streptococcus were found to be the dominant genus (>90% of total number of sequences), resulting in a low H 2 yield. In addition, the effect of substrate concentration on H 2 fermentation was investigated, and the maximum H 2 productivity was estimated to be 27.2 L H 2 /L/d by Andrew's model. Copyright © 2014, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved. Introduction Hydrogen (H 2 ) is widely regarded as one of the most promising energy carriers since it produces only water when combusted, has a high energy capacity of 33 kWh/kg H 2 , and can be easily converted to electricity by fuel cells [1]. Currently, most H 2 is made by splitting natural gas, heavy oil, naphtha, and coal, which are all fossil fuels, under high temperature and pres- sure conditions [2]. However, it is necessary to use renewable * Corresponding author. Division of Renewable Energy Engineering, University of Science and Technology, 217 Gajeong-ro, Yuseong-gu, Daejeon 305-350, Republic of Korea. Tel.: þ82 42 860 3707; fax: þ82 42 860 3739. E-mail address: bmmskim@kier.re.kr (M.-S. Kim). Available online at www.sciencedirect.com ScienceDirect journal homepage: www.elsevier.com/locate/he international journal of hydrogen energy 39 (2014) 16302 e16309 http://dx.doi.org/10.1016/j.ijhydene.2014.08.004 0360-3199/Copyright © 2014, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.