Development of alga-based photovoltaic devices: electron transport from photosynthesis via the cell wall to electrodes
The aim of the EnergUP project is to substantially improve the efficiency of the alga-based photovoltaic devices and thereby to contribute to the development of a climate-neutral technology. We will apply various strategies to enhance the current production by photosynthetic organisms using bio-photo electrochemical cells (BPEC). We seek for sustainable solutions without the usage of toxic chemicals or invasive cell treatments. In our experimental photovoltaic device, the electric current is transferred form the cells towards the electrode by a soluble electron mediator molecule. The electric current production of the cells is strongly limited 1) by the donation of electrons from algal cells towards the meditator molecule, 2) by the diffusion capacity of the mediator molecule through the multi-layer cell wall and 3) by the distance between the cells and the electrode surface. In this project, we will use two evolutionarily different alga species, the prokaryotic cyanobacteria, Synechocystis sp. PCC 6803 and the eukaryotic green algae, Chlamydomonas reinhardtii that are both excellent model organisms to study photosynthetic energy conversion. We will study 1) the contribution of the linear and the alternative photosynthetic electron transport pathways to the reduction of the mediator molecule by employing a range of photosynthetic mutants, and 2) the limiting effect of the cell wall on the diffusion of the mediator molecule by biochemical removal of specific cell wall layers and by employing cell-wall mutants. For the experiments, we will develop a specific measuring cuvette allowing photosynthetic activity measurements in the BPEC. We will also establish immobilization for alga-based photovoltaic devices, ensuring a close distance between the cells and the electrode surface, thereby enabling a more efficient electron transfer. Another advantage of this approach is that changing the culture media and removal of the cells from the BPEC becomes more economical.