High‐pressure—temperature bioreactor for studying pressure—temperature relationships in bacterial growth and productivity

Thermophilic organisms offer many potential advantages for biotechnological processes; however, realization of the promise of thermophiles will require extensive research on bacterial thermophily and high‐temperature cultivation systems. This article describes a novel bioreactor suitable for precise studies of microbial growth and productivity at temperatures up to 260°C and pressures up to 350 bar. The apparatus is versatile and corrosion resistant, and enables direct sampling of both liquids and gases from a transparent culture vessel without altering the reaction conditions. Gas recirculation through the culture can be controlled through the action of a magnetically driven pump. Initial studies in this bioreactor of Methanococcus jannaschii , an extremely thermophilic methanogen isolated from a deep‐sea hydrothermal vent, revealed that increasing the pressure from 7.8 to 100 bar accelerated the production of methane and cellular protein by this archaebacterium at 90°C, and raised the maximum temperature allowing growth from 90 to 92°C. Further increases in pressure had little effect on the growth rate at 90°C.