초록
Anaerobic hydrogen producing mesophilic and thermophilic cultures were enriched and studied from an intermediate temperature (45 <SUP>o</SUP>C) hot spring sample. H<SUB>2</SUB> production yields at 37 <SUP>o</SUP>C and 55 <SUP>o</SUP>C were highest at the initial pH of 6.5 and 7.5, respectively. Optimum glucose, iron and nickel concentrations were 9 g/l, 25 mg/l and 25 mg/l both at 37 <SUP>o</SUP>C and 55 <SUP>o</SUP>C, respectively. The highest H<SUB>2</SUB> yields at 37 <SUP>o</SUP>C and 55 <SUP>o</SUP>C were 1.8 and 1.0 mol H<SUB>2</SUB>/mol glucose, respectively, with the optimal pH, glucose concentration and iron addition. Hydrogen production from glucose at 55 <SUP>o</SUP>C and 37 <SUP>o</SUP>C was associated with ethanol- and acetate-butyrate type fermentations, respectively. Bacterial composition was analyzed by 16S rRNA gene-targeted denaturing gradient gel electrophoresis (DGGE). Clostridium species dominated at both temperatures and the microbial diversity decreased with increasing temperature. At 55 <SUP>o</SUP>C, Clostridium ramosum was the dominant organism.