Enhanced production of polyhydroxybutyrate from syngas by using nanoscaled cellulose particles with a syngas-converting enzyme complex immobilized on Ralstonia eutropha

Synthetic gas (syngas) produced from pyrolysis or a blast furnace is a mixture of different ratio of H₂, CO, N₂, CH₄, CO₂ and other carbon-containing gas. CO₂ and H₂ are the key sources for Ralstonia eutropha, which uses CO₂ to produce polyhydroxybutyrate (PHB) with a H₂ uptake system. For the efficient conversion of syngas to accessible carbon source, nanoscaled cellulose particles with an enzyme complex consisting of carbon monoxide dehydrogenase (CooS), carbon monoxide binding unit (CooA) and carbonic anhydrase (CA) were assembled by minimized scaffoldin (mCbpA). In addition to this assembly, mCbpA-BspA (MB) established to bridge the nanoparticle assembly and R. eutropha was used to provide higher enzyme stability and activity. The highest PHB accumulation after 72 h of fermentation was 14.2 g/L in a closed serum bottle that contained the enzyme assembly immobilized on R. eutropha. This catalytic assembly may be a new potential conversion tool to produce biodegradable PHB from syngas.