Sunlight‐Dependent Hydrogen Production by Photosensitizer/Hydrogenase Systems

Abstract

We report a sustainable in vitro system for enzyme-based photohydrogen production. The [FeFe]-hydrogenase HydA1 from Chlamydomonas reinhardtii was tested for photohydrogen production as a proton-reducing catalyst in combination with eight different photosensitizers. Using the organic dye 5-carboxyeosin as a photosensitizer and plant-type ferredoxin PetF as an electron mediator, HydA1 achieves the highest light-driven turnover number (TON ) yet reported for an enzyme-based in vitro system (2.9×10 mol(H ) mol(cat) ) and a maximum turnover frequency (TOF ) of 550 mol(H ) mol(HydA1) s . The system is fueled very effectively by ambient daylight and can be further simplified by using 5-carboxyeosin and HydA1 as a two-component photosensitizer/biocatalyst system without an additional redox mediator.

Direct visible light activation of a surface cysteine-engineered [NiFe]-hydrogenase by silver nanoclusters

“…One approach to motivate and inspire progress has been to use enzymes as the catalysts in model solar conversion devices and photocatalytic complexes. [1][2][3][4][5][6][7][8][9][10][11][12] Enzymes are valuable because evolution has taken them close to perfection -their suitability being gauged in terms of their high substrate specificities, high turnover rates, low overpotential requirements and use of abundant elements (e.g. Fe, Mn, Ni and Cu) instead of precious metals.…”

Artificial Light‐Harvesting Complexes Enable Rieske Oxygenase Catalyzed Hydroxylations in Non‐Photosynthetic cells

“…5(6)-Carboxyeosin (CE) was chosen first since it possesses excellent photosensitizer properties ( Figure S8) with an E Redox of À1.06 V, which is similar to the E Redox of proflavine. [22] Performing the photoenzymatic hydroxylation of 1 and 2 with 50 mm MES and 100 mm 5(6)-carboxyeosin (CE) at a cell density of 100 g WCW L À1 resulted in a smooth formation of the desired products 1 a (up to % 360 mm in 24 hours) and 2 a (up to % 200 mm in 24 hours) under illumination with white light. Nonetheless, the obtained concentrations of 1 a and 2 a always remained low ( 360 mm, Table 1).…”

“…We investigated EY, rose bengal (RB), and CE with EDTA, as well as with MOPS and MES as sacrificial electron donors that can be up taken by cells ( Table 2). [22,39,41,42] The electron donor can constitute an obstacle in this photobiocatalytic setup, [23] as EDTA may suffer, for example, from incompatibility with the RO due to its ability to sequester the Fe 3+ ion located in the active site of the oxygenase. However, we did not see any activity loss of NDO H295A and CDO M232A in dark reactions supplemented with EDTA ( Figure S13) nor any toxicity effects of MES/MOPS on the cells ( Figure S14).…”

Artifizielle Lichtsammelkomplexe ermöglichen Rieske‐Oxygenase‐ katalysierte Hydroxylierungen in nicht‐photosynthetischen Zellen

“…Um diese Herausforderung zu lçsen, werden derzeit viele alternative Ansätze in Betracht gezogen. [16][17][18] Neben der Verknüpfung der Photochemie mit Enzymen in vitro zur Cofaktor-Regeneration, [18][19][20][21][22][23][24] haben autotrophe und chemolithoautotrophe Organismen in jüngster Zeit Aufmerksamkeit erhalten, da sie dazu in der Lage sind, anorganische Verbindungen als Elektronendonoren zu nutzen. [25][26][27][28][29] Lichtgetriebene Ganzzellreaktionen in Cyanobakterien zeigen die gleichen Reaktionsgeschwindigkeiten wie E. coli.…”

“…Wir haben zunächst MES untersucht, da MES bereits zuvor erfolgreich als effizienter Elektronendonor eingesetzt wurde, [37] nicht toxisch ist und von E. coli-Zellen aufgenommen werden kann. [38,39] Dem hier verwendeten E. coli-Stamm fehlt ein natürliches Aufnahmesystem für Flavine, [40] deswegen entschieden wir uns für einen Photosensibilisator (PS), der leicht von Zellen aufgenommen werden kann [32] und ähnliche Redoxeigen- [22,39,41,42] Der Elektronendonor kann ein Hindernis in diesem photobiokatalytischen Ansatz darstellen, [23] da EDTA unter Umständen inkompatibel mit den ROs sein kann, da es das Fe 3+ -Ion, dass sich im aktiven Zentrum der Oxygenase befindet, potentiell binden kann. Wir konnten jedoch weder einen Aktivitätsverlust von NDO H295A und CDO M232A in Dunkelreaktionen mit EDTA (Abbildung S13), noch Toxizitätseffekte von MES/MOPS auf die Zellen feststellen (Abbildung S14).…”