LARGE-SCALE CULTIVATION OF HYDROGENOBACTER-THERMOPHILUS ON HYDROGEN

The thermophilic hydrogen-oxidizing eubacterium, Hydrogenobacter therm ophilus was grown with a semi-continuous gas feed in a 150 1 fermenter , on different ratios of H-2, O-2 (air) and CO2 and on media of variab le mineral salts composition. The best gas ratio during the exponentia l phase was approximately 0.5:1.0:0.03 arm of H-2:air:CO2. Cell densit ies were increased by increasing the concentration of ammonium and pho sphate in the medium. The maximum cell density obtained under the most favourable conditions was 2.62 g wet wt l(-1), corresponding to an ab sorption of 1.6 at 600 nm, The maximum specific growth rate (mu) was 0 .44 h(-1).