Large scale cultivation of Hydrogenobacter thermophilus on hydrogen

The thermophilic hydrogen-oxidizing eubacterium, Hydrogenobacter thermophilus was grown with a semi-continuous gas feed in a 150 l fermentor, on different ratios of H 2 , O 2 (air) and CO 2 and on media of variable mineral salts composition. The best gas ratio during the exponential phase was approximately 0.5 :1.0 :0.03 atm of H 2 :air :CO 2 . Cell densities were increased by increasing the concentration of ammonium and phosphate in the medium. The maximum cell density obtained under the most favourable conditions was 2.62 g wet wt l -1 , corresponding to an absorption of 1.6 at 600 nm. The maximum specific growth rate (μ) was 0.44 h -1 .