Production of biohydrogen from sugars and lignocellulosic biomass using Thermoanaerobacter GHL 15 Hronn Brynjarsdottir, Sean M. Scully, Johann Orlygsson* Faculty of Natural Resource Science, University of Akureyri, Borgir, Norduslod, 600 Akureyri, Iceland article info Article history: Received 30 July 2013 Received in revised form 23 August 2013 Accepted 1 September 2013 Available online 3 October 2013 Keywords: Hydrogen Thermoanaerobacter Pretreatment Lignocellulose Hydrolysates abstract The effect of culture parameters on hydrogen production using strain GHL 15 in batch culture was investigated. The strain belongs to the genus Thermoanaerobacter with 98.9% similarity to Thermoanaerobacter yonseiensis and 98.5% to Thermoanaerobacter keratinophilus with a temperature optimum of 65e70  C and a pH optimum of 6e7. The strain metabolizes various pentoses, hexoses, and disaccharides to acetate, ethanol, hydrogen, and carbon dioxide. However substrate inhibition was observed above 10 mM glucose concentration. Maximum hydrogen yields on glucose were 3.1 mol H 2 mol 1 glucose at very low partial pressure of hydrogen. Hydrogen production from various lignocellulosic biomass hydro- lysates was investigated in batch culture. Various pretreatment methods were examined including acid, base, and enzymatic (Celluclast Ò and Novozyme 188) hydrolysis. Maximum hydrogen production (5.8e6.0 mmol H 2 g 1 dw) was observed from Whatman paper (cel- lulose) hydrolysates although less hydrogen was produced by hydrolysates from other examined lignocellulosic materials (maximally 4.83 mmol H 2 g 1 dw of grass hydrolysate). The hydrogen yields from all lignocellulosic hydrolysates were improved by acid and alkaline pretreatments, with maximum yields on grass, 7.6 mmol H 2 g 1 dw. Copyright ª 2013, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved. 1. Introduction Biohydrogen is an attractive alternative energy source due to its clean combustion and high energy density (2.75 times greater than that of hydrocarbons) with water being the only waste product [1,2]. At present, most hydrogen production is sourced from petroleum-derived hydrocarbon gases via steam reformation. The production of biohydrogen by anaerobic bacteria are well-known metabolic processes. Mesophilic and moderate thermophilic bacteria within genera of strict anaerobes such as Clostridium [3,4] and facultative anaerobes such as Citrobacter and Enterobacter [5,6] have been extensively studied. The hydrogen production yields of these bacteria are typically between 1 and 2 mol H 2 per mol hexose degraded or less than 50% of the theoretical maximum of 4 mol H 2 [7]. The main reason for lower than theoretical yields is due to the thermodynamic hindrance at lower temperatures related to H 2 extrusion from pathways involving ferredoxin or NAD(P)H become unfavourable [8,9]. Therefore, increased partial pressure of hydrogen results in the formation of reduced end products such as alcohols, volatile fatty acids, lactate, and alanine [10]. At high temperatures, the partial pressure of hydrogen has a lower influence on the thermo- dynamics of the pathways involved in H 2 production shifting the equilibrium away from reduced end products allowing * Corresponding author. Tel.: þ354 4608511; fax: þ354 4609889. E-mail address: jorlygs@unak.is (J. Orlygsson). Available online at www.sciencedirect.com journal homepage: www.elsevier.com/locate/he international journal of hydrogen energy 38 (2013) 14467 e14475 0360-3199/$ e see front matter Copyright ª 2013, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.ijhydene.2013.09.005