ABSTRACT
Chemoautotrophic “Knallgas” bacteria can utilize H2/CO2 for growth under aerobic conditions, and have great potential to directly produce liquid fuels from CO2 and/or syngas [1,2]. Ralstonia eutropha (R. eutropha), the model bacterium of this class, can grow to very high cell densities (>200 g/L) [3]. Under nutrient limitation, R. eutropha directs most of its carbon flux to the synthesis of polyhydroxybutyrate (PHB), a biopolymeric compound stored in granules. Under autotrophic growth conditions with H2/ CO2, R. eutropha has been reported to synthesize 61 g/L of PHB (representing ~70% of total cell weight) in 40 h [4]. With random mutagenesis and relatively simple engineering, PHB and related polyhydroxyalkanoate polymers have been produced in R. eutropha on industrial scales [3].
