Isolation and characterization of a high H2-producing strain Klebsiella oxytoca HP1 from a hot spring

A hydrogen-producing bacterial strain was newly isolated from a hot spring and identified as Klebsiella oxytoca HP1 by 16S rRNA gene sequence analysis and detection by BioMerieux Vitek. Important parameters, including substrates, starting pH of culture, temperature and oxygen concentration for batch ferment hydrogen production, were investigated. Among different sugars, glucose and sucrose were the preferred substrates for hydrogen production. The optimal starting pH of culture was about 7.0. The activity was drastically reduced in a prolonged fermentation due to the accumulation of organic acids. Increasing temperatures (from 25 to 35 °C) improved the hydrogen production activity. K. oxytoca HP1 produced hydrogen under different concentrations (1-10%) of oxygen in the gas phase, indicating that it is highly resistant to oxygen inhibition. Under batch ferment conditions, the maximal hydrogen production activity, rate and yield were obtained as 9.6 mmol/g dw h, 87.5 ml/l h and 1.0 mol/mol glucose (conversion 16.7%), respectively. In continuous hydrogen production, the maximum activity, rate and yield were 15.2 mmol/g dw h, 350.0 ml/l h and 3.6 mol/mol sucrose (conversion 32.5%), respectively. These results indicate that K. oxytoca HP1 is an ideal hydrogen producer.