Bioresource Technology 98 (2007) 1183–1190 0960-8524/$ - see front matter  2006 Elsevier Ltd. All rights reserved. doi:10.1016/j.biortech.2006.05.009 Microbial hydrogen production with Bacillus coagulans IIT-BT S1 isolated from anaerobic sewage sludge Shireen Meher Kotay, Debabrata Das ¤ Fermentation Technology Laboratory, Department of Biotechnology, Indian Institute of Technology, Kharagpur 721 302, India Received 5 January 2006; received in revised form 11 May 2006; accepted 11 May 2006 Available online 23 June 2006 Abstract Bacillus coagulans strain IIT-BT S1 isolated from anaerobically digested activated sewage sludge was investigated for its ability to pro- duce H 2 from glucose-based medium under the inXuence of diVerent environmental parameters. At mid-exponential phase of cell growth, H 2 production initiated and reached maximum production rate in the stationary phase. The maximal H 2 yield (2.28 mol H 2 /mol glucose) was recorded at an initial glucose concentration of 2% (w/v), pH 6.5, temperature 37 °C, inoculum volume of 10% (v/v) and inoculum age of 14 h. Cell growth rate and rate of hydrogen production decreased when glucose concentration was elevated above 2% w/v, indicating substrate inhibition. The ability of the organism to utilize various carbon sources for H 2 fermentation was also determined.  2006 Elsevier Ltd. All rights reserved. Keywords: Bacillus coagulans; Fermentation; H 2 yield; Microbial hydrogen production; Process optimization 1. Introduction A future without reliance on fossil fuels for energy is widely touted. Global attention is towards reducing air pollution, greenhouse gas emissions, caused by combustion of fossil fuels and simultaneously discovering a sustainable future fuel. In this scenario, hydrogen is considered to be an ideal energy alternative for the future. Compared with conventional H 2 generation process (chemical and electro- chemical), biological H 2 production using fermentative, photosynthetic bacteria, or algae is an environmentally benign and less energy intensive process (Das and Veziro- glu, 2001; Levin et al., 2004). Microbial H 2 production is an attractive process for supplying a signiWcant share of the H 2 required for the near future. Furthermore, renewable biomass can be used as substrates for biological H 2 pro- duction facilitating both bioremediation and energy recov- ery. The feasibility of fermentative H 2 production from organic wastes or wastewaters has been widely demon- strated by various laboratories (Cai and Liu, 2005; Kim et al., 2004; Lay et al., 1999; Lin and Lay, 2005; Shu-Yii et al., 2006). Galore microbial species, belonging to the genera Enter- obacter, Bacillus, and Clostridium are reported to produce hydrogen (Nandi and Sengupta, 1998). Apart from pure cultures, various mixed micro-Xora and co-cultures have also been explored for hydrogen production from carbohy- drates (Das and Veziroglu, 2001; Haruhiko et al., 1998; Nandi and Sengupta, 1998). Nevertheless, the quest for ideal microbe(s) for microbial H 2 production has thrust the researchers to screen various sources. Sewage sludge has been reported to be the most proven and potent source of H 2 producers. B. coagulans, a gram positive, motile, acid-tolerant and heat-resistant facultative anaerobic bacterium is notori- ously known to spoil acidic foods. Bacillus coagulans and its close relatives are ideal biocatalysts for fermentation of lignocellulosic biomass to fuels and chemicals. Further these bacteria are metabolically versatile, grow in minimum mineral salts, utilize a wide range of carbon compounds as carbon and energy source. However very brief study has been reported on Bacillus sp. for H 2 fermentation. * Corresponding author. Tel.: +91 3222 278053/283758; fax: +91 3222 255303. E-mail address: ddas@hijli.iitkgp.ernet.in (D. Das).