Studies on the aerobic utilization of synthesis gas (syngas) by wild type and recombinant strains of Ralstonia eutropha H16

The biotechnical platform strain Ralstonia eutropha H16 was genetically engineered to express a cox subcluster of the carboxydotrophic Oligotropha carboxidovorans OM5, including (i) the structural genes coxM, ‐S and ‐L, coding for an aerobic carbon monoxide dehydrogenase (CODH) and (ii) the genes coxD, ‐E, ‐F and ‐G, essential for the maturation of CODH. The cox (Oc) genes expressed under control of the CO (2)‐inducible promoter P(L) enabled R. eutropha to oxidize CO to CO (2) for the use as carbon source, as demonstrated by (13) CO experiments, but the recombinant strains remained dependent on H(2) as external energy supply. Therefore, a synthetic metabolism, which could be described as ‘carboxyhydrogenotrophic’, was established in R. eutropha. With this extension of the bacterium's substrate range, growth in CO‐, H(2)‐ and CO (2)‐containing artificial synthesis gas atmosphere was enhanced, and poly(3‐hydroxybutyrate) synthesis was increased by more than 20%.