Bio-hydrogen production enhancement by co-cultivating Rhodopseudomonas palustris WP3-5 and Anabaena sp. CH3 Siang Chen Wu a , Pi Fen Lu a , Yu Chien Lin a , Pei Chung Chen b , Chi Mei Lee a, * a Department of Environmental Engineering, National Chung Hsing University, 250 Kuo Kuang Rd., Taichung 402, Taiwan, ROC b Institute of Biomedical Nutrition, Hung Kuang University, 34 Chung Chie Rd., Taichung 433, Taiwan, ROC article info Article history: Received 14 July 2011 Received in revised form 30 September 2011 Accepted 5 October 2011 Available online 12 November 2011 Keywords: Biohydrogen Co-cultivation Rhodopseudomonas palustris Anabaena Nitrogenase abstract Photobiological H 2 production is a promising method for renewable energy development. An innovative system that co-cultivating Rhodopseudomonas palustris WP3-5 and Anabaena sp. CH3 was carried out to estimate the effect of co-cultivation on H 2 production enhancement. H 2 production prolongation and enhancement were observed due to the light and metabolic compatibility of these two strains. Co-culture system served by acetate and fructose as carbon source can accumulate H 2 in 140.8 mL, almost double than the sum of individuals. Moreover, the enhancement of H 2 production was significantly affected by the mixed ratio of two strains. The mixed ratio (WP3-5:CH3) of 1:2 showed a highest H 2 production rate in 44.8 mL-H 2 /L-culture/h, and both 2:1 and 1:2 exhibited a relatively high substrate conversion efficiency during the latest period of cultivation, whereas the mixed ratio of 1:1 and 3:1 only revealed a prolongation in H 2 production due to metabolic compatibility of two strains. Copyright ª 2011, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved. 1. Introduction Hydrogen (H 2 ) is a potentially renewable energy as an alterna- tive to fossil fuels because of its high energy content and clean combustion product [1]. Development of H 2 can mitigate both present energy crisis and greenhouse effect. In tradition, H 2 can be produced in a variety of ways, including by thermal cracking of light oil, electrolysis from water, and steam reforming of natural gas. However, some traditional methods still depend on fossil fuels as source. Recently, H 2 produced by photosynthetic microorganisms is an attracted method due to a high purity of H 2 but less energy intensive and environmental pollution [2]. Photobiological processes to produce H 2 specifically contain the following three types (i) water photolysis by oxygenic photo- synthetic bacteria through bidirectional hydrogenase, (ii) nitrogen fixation by heterocyst cells of filamentous cyanobac- teria, (iii) nitrogen fixation by non-oxygenic photosynthetic bacteria [3e5]. Each process has been widely studied in diverse procedures, trying to maximize the efficiency of H 2 production. In those photobiological H 2 producing processes, anaerobic photo-fermentation under nitrogen-deficiency condition is the most promising way based on the flexible applicability of those photosynthetic bacteria. H 2 produced under this condition is mainly attributed to the key enzyme, Nitrogenase, for nitrogen fixing according to following reactions: N 2 þ 8e  þ 8H þ þ 16ATP/2NH 3 þ H 2 þ 16ADP þ 16Pi ðwith N 2 Þ ð1Þ 2H þ þ 2e  þ 4ATP/H 2 þ 4ADP þ 4Pi ðwithout N 2 Þ (2) * Corresponding author. Tel.: þ886 4 22850024; fax: þ886 4 22862587. E-mail addresses: siangchen.wu@gmail.com (S.C. Wu), jelly740515@hotmail.com (P.F. Lu), freeair030@freeair.com.tw (Y.C. Lin), chenpc@sunrise.hk.edu.tw (P.C. Chen), cmlee@nchu.edu.tw (C.M. Lee). Available online at www.sciencedirect.com journal homepage: www.elsevier.com/locate/he international journal of hydrogen energy 37 (2012) 2231 e2238 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.2011.10.066