[A new hydrogen-producing strain and its characterization of hydrogen production]

An anaerobic, thermophilic, hydrogen-producing strain T42 was obtained from a hot spring of South Mountain District, Tibet. Cells are Gram-positive, mobile rod-shaped. Spores were not observed. Temperature range for growth is 32 degrees C to 69 degrees C (optimum temperature, 60 degrees C - 62 degrees C), and pH range for growth is 5.0 to 8.8 (optimum pH, 7.0 - 7.5). The generation time is around 30 min. Organic nitrogen sourc is required for growth. Strain T42 utilizes a wide range of carbohydrates, including starch, dextrin, sucrose, cellobiose, fructose, maltose, ribose, glycogen and galactose. Acetate, ethanol, H2 and CO2 are the end products of glucose fermentation. The (G + C) content of strain T42 is 31.2 mol%. Phylogenetic analysis based on the 16S rDNA sequence similarity indicates that strain T42 is the closest relative to Thermobrachium celere and Caloramator indicus. Biological characteristics and phylogenetic analysis of the 16S rDNA gene indicate the new strain belongs to the genus Thermobrachium. Strain T42 produces H2 from glucose at maximal level when growing at 62 degrees C and initial pH 7.2, the hydrogen yields and maximal hydrogen production rate are 1.06 mol H2/mol glucose and 24.0 mmol H2/gDW/h, respectively. Strain T42 also produced H2 by fermentating from a variety of carbohydrates. 20 mmol/L Magnesium and 2 mmol/L iron increase the hydrogen production content by 20% and 23.3%, respectively, but nickel has no effect on the hydrogen production. In the co-culture of strain T42 and methane-producing strain M. thermautotrophicus Z245, hydrogen pressure is dramatically decreased, meanwhile deduced H2 production and the consumption of glucose are increased markedly by 2.8 fold and 1 fold, and the ratio of acetate/ethanol is enhanced froml to 1.7.