Better catalysts for solar-driven hydrogen producing devices: isolation and characterisation of novel [FeFe]-hydrogenases from the bacterial consortium of a pilot plant producing biohydrogen from waste

Several studies are undergoing to exploit [FeFe]-hydrogenases as highly efficient catalysts to produce hydrogen gas from renewable sources and to couple these biocatalysts with solar driven energy production. In this perspective the isolation and characterisation of novel [FeFe]-hydrogenases from bacterial consortia selected on sludge and pilot reactors can provide optimised catalysts with extended applicative potential in solar-driven devices. Here results are presented on the isolation of hyperactive hydrogenases from the bacteria selected in a pilot plant efficiently producing biohydrogen (up to 50% of the total gas) from waste. The bacterial consortia was characterised and Clostridia strains (C. perfringens, C. beijerinckii and C. butyricum) were isolated that were excellent hydrogen producers. By genome and transcriptional analysis the novel genes responsible for the high hydrogen production activity of the isolated strains were identified. The most promising [FeFe]-hydrogenase enzymes were produced after gene cloning and recombinant heterologous expression in E.coli and characterized. Turnover frequencies of up to 1000 sec -1 were measured in the expressed hydrogenases, showing an enhanced activity (nearly double) compared to the well characterised model system of the [FeFe]-hydrogenase CaHydA from the bacterium Clostridium acetobutylicum recombinantly expressed in E. coli.