Microbial community analysis of mixed anaerobic microflora in suspended sludge of ASBR producing hydrogen from palm oil mill effluent Marzieh Badiei a , Jamaliah Md Jahim a,b, *, Nurina Anuar a , Siti Rozaimah Sheikh Abdullah a , Lim Swee Su b , Mohd Aidil Kamaruzzaman a a Department of Chemical & Process Engineering, Faculty of Engineering & Built Environment, Universiti Kebangsaan Malaysia, 43600 Bangi, Selangor, Malaysia b Fuel Cell Institute, Universiti Kebangsaan Malaysia, 43600 Bangi, Selangor, Malaysia article info Article history: Received 5 August 2011 Received in revised form 9 November 2011 Accepted 13 November 2011 Available online 10 December 2011 Keywords: Biohydrogen Palm oil mill effluent (POME) Microbial community Anaerobic sequencing batch reactor (ASBR) abstract This study investigated the microbial community of an anaerobic sequencing batch reactor (ASBR) operating at mesophilic temperature under varying hydraulic retention times (HRTs) for evaluating optimal hydrogen production conditions, using palm oil mill effluent (POME) as substrate. POME sludge enriched by heat treatment with hydrogen-producing bacteria was used as inoculum and acclimated with the POME. The microbial commu- nity was determined by first isolating cultivable bacteria at each operating HRT and then using polymerase chain reaction (PCR). The PCR products were sequenced and sequence identification was performed using the BLAST algorithm and Genbank database. The findings revealed that about 50% of the isolates present were members of the genus Streptococcus, about 30% were Lactobacillus species and around 20% were identified as species of genus Clostridium. Scanning electron microscopy (SEM) analysis also confirmed the presence of spherical and rod-shaped microbial morphologies in the sludge samples of bioreactor during prolonged cultivation. Copyright ª 2011, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved. 1. Introduction Hydrogen has been introduced as an ideal and promising renewable carrier of energy to replace fossil fuels. When it is produced biologically, hydrogen is considered as a potential biofuel that does not cause CO 2 emission [1]. Biohydrogen production through dark fermentation has been used to study different groups of pure cultures of known species of hydrogen-producing bacteria [2e4]. Also, varieties of mixed microflora, particularly indigenous microorganisms obtained from natural sources, have been examined for their hydrogen- producing potential using different types of carbohydrate- based substrates ranging from simple sugars to complicated wastewaters [5]. Mixed microbial communities are able to survive on non-sterile substrates and have revealed higher hydrogen yield because they are highly resistant to unfavor- able environmental conditions and so are more practical than pure cultures for development of commercial sustainable biohydrogen production processes. On the other hand, earlier studies [6,7] have reported that operating conditions such as * Corresponding author. Department of Chemical & Process Engineering, Faculty of Engineering & Built Environment, Universiti Kebangsaan Malaysia, 43600 Bangi, Selangor, Malaysia. E-mail address: jamal@vlsi.eng.ukm.my (J.M. Jahim). Available online at www.sciencedirect.com journal homepage: www.elsevier.com/locate/he international journal of hydrogen energy 37 (2012) 3169 e3176 0360-3199/$ e see front matter Copyright ª 2011, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved. doi:10.1016/j.ijhydene.2011.11.063