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– 70 ∘ C ), with the optimal temperature 60 ∘ 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 g l - 1 , pH 6.25 and temperature 60 ∘ 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.