Thermophilic fermentative hydrogen production by the newly isolated Thermoanaerobacterium thermosaccharolyticum PSU-2

A thermophilic H-2-producing bacterial strain was isolated from a biohydrogen reactor fed with palm oil mill effluent (POME) and identified as Thermoanaerobacterium thermosaccharolyticum using 16S rRNA gene analysis. The isolated bacterium, designated as T thermosaccharolyticum PSU-2, showed a high yield and production rate of H-2. Temperature optimum, pH optimum and substrate utilization for H-2 production were investigated in batch conditions. All of tested substrate was utilized for H-2 production, while sucrose, xylose and starch were the preferred substrates. The strain produced H-2 within a wide range of pH (4.5-8) and temperature (45-7 degrees C), with the optimal temperature 60 degrees C and optimal initial pH about 6.25. Maximum of H-2 production rate was registered from hour 8 to hour 16 in late exponential phase. The H-2 production was drastically reduced in a prolonged fermentation (24 h) and stopped at pH 4.5 due to the accumulation of organic acids. The maximum H-2 production yield and rate at sucrose concentration of 20 gl(-1), pH 6.25 and temperature 60 degrees C were 2.53 mol H-2 mol(-1) hexose and 12.12 mmol H-2 l(-1) h(-1), respectively. Organic nitrogen amended medium improved the H-2 production with 68% compared to inorganic nitrogen amended medium. The strain performed ethanol-acetate type fermentation in inorganic nitrogen amended medium, while it performed butyrate-acetate type fermentation in organic nitrogen amended medium. (C) 2008 International Association for Hydrogen Energy. Published by Elsevier Ltd. All rights reserved.