Optimized over-expression of [FeFe] hydrogenases with high specific activity in Clostridium acetobutylicum

It was previously shown that Clostridium acetobutylicum is capable to over-express various [FeFe] hydrogenases although the protein yield was low. In this study we report on doubling the yield of the clostridial hydrogenase by replacing the native gene hydA1Ca with a recombinant one via homologous recombination. The purified protein HydA1Ca shows an unexpected high specific activity (up to 2257 μmol H2 min−1 mg−1) for hydrogen evolution. Furthermore, the highly active green algal hydrogenase HydA1Cr from Chlamydomonas reinhardtii was heterologously expressed in C. acetobutylicum, and purified with increased yield (1 mg protein per liter of cells) and high activity (625 μmol H2 min−1 mg−1). EPR studies demonstrate intact H-clusters for homologously and heterologously expressed [FeFe] hydrogenases in the CO-inhibited oxidized redox state, and prove the high efficiency of the C. acetobutylicum expression system.