Photobiological hydrogen-producing systems

Abstract

Hydrogen photoproduction by micro-organisms combines the photosynthetic properties of oxygenic and non-oxygenic microbes with the activity of H2-producing enzymes in nature: hydrogenases and nitrogenases. The overall efficiency of the process depends on the separate efficiencies of photosynthesis and enzymatic catalysis. This tutorial review discusses the biochemical pathways for H2 production in different organisms, barriers to be overcome, and possible suggestions for integrating photobiological H2 production with fermentative, anaerobic systems for a potentially more efficient process.

Induction of Photosynthetic Carbon Fixation in Anoxia Relies on Hydrogenase Activity and Proton-Gradient Regulation-Like1-Mediated Cyclic Electron Flow in Chlamydomonas reinhardtii

“…Although hydrogen metabolism in microalgae has been largely studied in the last 15 years in perspective of promising future renewable energy carriers (Melis et al, 2000;Kruse et al, 2005;Ghirardi et al, 2009), the physiological role of such an oxygen-sensitive enzyme linked to the photosynthetic pathway has been poorly considered. The 40-year-old proposal that H 2 evolution by hydrogenase is involved in induction of photosynthetic electron transfer after anoxic incubation (Kessler, 1973;Schreiber and Vidaver, 1974) has been only recently demonstrated in C. reinhardtii.…”

How oxygen attacks [FeFe] hydrogenases from photosynthetic organisms

“…Hydrogenases are able to catalyze both H 2 oxidation and H 2 evolution with minimal electrochemical overpotential (driving force) (4,7), comparable to the 2H ϩ /H 2 equilibrium established on platinum (5). The [FeFe] hydrogenases are of particular interest as they tend to be more biased toward H 2 evolution than [NiFe] hydrogenases (8). The active site of [FeFe] hydrogenases, a complex structure known as the ''H-cluster,'' consists of a binuclear Fe center (2Fe H ) linked to a [4Fe-4S] cluster (9).…”

“…Numerous publications report the chemical synthesis of analogues for the 2Fe H domain and even the entire H-cluster (10)-such is the interest displayed not only in understanding the enzymes, but also in finding cheap alternatives to Pt catalysts. However, [FeFe] hydrogenases are extremely prone to irreversible inactivation by O 2 , and this sensitivity is a key challenge for both the biotechnological and the synthetic chemistry approaches (8).…”

Genetic Engineering of Cyanobacteria to Enhance Biohydrogen Production from Sunlight and Water

“…Photobiological production of H 2 by cyanobacteria and eukaryotic microalgae that use H 2 O as the electron donor has the potential to produce renewable clean energy on a scale sufficient to meet much of the world energy demand (Ghirardi et al 2007(Ghirardi et al , 2009Sakurai and Masukawa 2007;Tamagnini et al 2007;Bothe et al 2010;Ghirardi and Mohanty 2010). In cyanobacteria, H 2 gas is generated by either hydrogenase or nitrogenase (Tamagnini et al 2002(Tamagnini et al , 2007.…”