“Nanoengineered Optobioelectronics with Biomaterials and Bioinspired Assemblies”
This project has brought together eight research groups from two institutions in Israel (Technion and HU Jerusalem) and two in Germany (RU Bochum and Max Planck Institute CEC in Mülheim) with complementary expertise to design, construct, characterize and test novel photobioelectrochemical (PBEC) and photobiofuel cells (PBFC). For this endeavor genetically engineered photosynthetic reaction centers and hydrogenases were modified and integrated with electrodes to obtain functional systems. These bioinspired systems are harvesting (sun) light and convert it into electrical power or store it in fuels. Based on the great expertise of the researchers in the different laboratories most of the original goals of the proposal could be realized. The various results described in the report have been published in almost 60 scientific publications, many with authors from 2 or more collaborating institutions. For exchange of ideas, discussion of results and future strategies, and bringing together the participating researchers four workshops have been organized between 2014 and 2018, two in Israel and two in Germany. Furthermore, a large number of visits were scheduled to perform joint experiments in the laboratories of DIP partners. The young researchers profited strongly from the exchange with foreign scientists and the interdisciplinary work performed in other laboratories. In several cases the DIP has also been a stepping stone for future collaborations between the Israeli and German partners on related and new projects which is seen from recent publications and ongoing work plans (e.g. on aptamer-based conjugates (Happe/Willner) and the further characterization of Chlorella ohadii (Nechushtai/Lubitz).
Particular highlights of the multifaceted DIP project are:
(i) The understanding of native and genetically or chemically modified hydrogenases catalyzing hydrogen generation and usage has been strongly advanced during this project (Happe/Lubitz). This is important for the employment of such systems as catalysts in biofuel cells and (bio)electrolyzers.
(ii) It could be shown that embedding hydrogenases in low-potential (viologen) redox hydrogels safeguards the enzyme from oxygen and high potentials. At the same time, it serves as immobilization matrix and helps to wire the hydrogenase to an electrode (Schuhmann/Lubitz/Happe). Several electrodes have been fabricated using [NiFe]- and [FeFe]-hydrogenases from different organisms in the course of the DIP.
(iii) The first polymer-based dual gas diffusion H2/air biofuel cell was realized by coupling a redox polymer protected hydrogenase bioanode with a O2-reducing bilirubin oxidase biocathode yielding benchmark performances (Schuhmann/Lubitz).
(iv) Several photobioelectrodes have been tested using Photosystems I and II. By using an optically transparent (inverse opal ITO) electrode high photocurrent densities were obtained. The wiring of the photosystems was established via Os-complex modified redox polymers (Schuhmann/Rögner).
(v) An innovative bioelectrochemical electrode was assembled early in the DIP using a Pt-nanocluster-PS I-Os polymer-glucose oxidase system that generated a photocurrent upon illumination at the ITO electrode (Willner/Nechushtai/Schuhmann).
(vi) Recently, a full semiartificial Z-scheme assembly was realized by combining a redox polymer/PS II photoanode with a PS I/hydrogenase biocathode. The highly optimized system enabled an efficient electron transfer leading via the hydrogenase layer to evolution of H2 (Rögner/Schuhmann).
(vii) A new form of BPEC was presented (Adir/Schuster/Schuhmann) using living cyanobacterial cells in the anodic chamber. The cell produces photocurrent or hydrogen by respiration or photosynthesis.
(viii) The cross-section of light absorption could be increased by adding a light harvesting antenna to PS II forming a supercomplex interacting with the electrode; this construct significantly increases the photon-to-electron conversion efficiency (Adir/Rögner/Schuhmann).
(ix) The structural and functional characterization of the photodamage-resistant green alga Chlorella ohadii, which is highly interesting for light-driven devices has been successfully started by obtaining a cryo-EM structure of PS I supplemented by a spectroscopic analysis (Nechushtai/Adir and Lubitz/Rögner/Nowaczyk). Future work on PS II from C. ohadii is planned.