Exploiting algal NADPH oxidase for biophotovoltaic energy

Abstract

SummaryPhotosynthetic microbes exhibit light‐dependent electron export across the cell membrane, which can generate electricity in biological photovoltaic (BPV) devices. How electrons are exported remains to be determined; the identification of mechanisms would help selection or generation of photosynthetic microbes capable of enhanced electrical output. We show that plasma membrane NADPH oxidase activity is a significant component of light‐dependent generation of electricity by the unicellular green alga Chlamydomonas reinhardtii. NADPH oxidases export electrons across the plasma membrane to form superoxide anion from oxygen. The C. reinhardtii mutant lacking the NADPH oxidase encoded by RBO1 is impaired in both extracellular superoxide anion production and current generation in a BPV device. Complementation with the wild‐type gene restores both capacities, demonstrating the role of the enzyme in electron export. Monitoring light‐dependent extracellular superoxide production with a colorimetric assay is shown to be an effective way of screening for electrogenic potential of candidate algal strains. The results show that algal NADPH oxidases are important for superoxide anion production and open avenues for optimizing the biological component of these devices.

Biophotovoltaics: oxygenic photosynthetic organisms in the world of bioelectrochemical systems

“…6,14,15,126,127 A wide variety of eukaryotic algae have now also been shown to respond positively to light in mediatorless BPVs. 15,[128][129][130] Increased power outputs have also been observed using BPV stacking approaches. 15,131 A microuidic-based BPV has recently demonstrated the highest recorded maximum power densities of 100 mW m À2 in the light (80 mW m À2 in the dark).…”

Tapping into cyanobacteria electron transfer for higher exoelectrogenic activity by imposing iron limited growth

“…1). 12,25 Nevertheless, biolms of photosynthetic microorganisms are capable of electricity generation with no addition of mediators (mediatorless), revealing direct electron transfer, 7 and potentially representing a more sustainable platform.…”

Overexpressing Ferredoxins in Chlamydomonas reinhardtii Increase Starch and Oil Yields and Enhance Electric Power Production in a Photo Microbial Fuel Cell

“…Another possibility is that the FDX transgenic lines accumulate more biomass, such as starch, which can be converted into cytosolic NADPH by the pentose phosphate pathway. In turn, electrons transfer to the extracellular space by NADPH oxidases encoded by RBO1 (respiratory burst oxidase) and RBO2 [ 10 ] (Anderson et al , 2015). Interestingly, the FDX5 transgenic line exhibited higher electric power density than the wild-type line and PETF transgenic lines, implying that FDX5 is a major electron carrier in Chlamydomonas in anaerobic conditions when FDX5 is induced and FDX5 is stabled [ 16 ].…”

“…The unicellular green alga Chlamydomonas reinhardtii has been used as a model organism for studying photosynthesis, starch metabolism and oil synthesis [ 7 , 8 , 9 ]. In addition, C. reinhardtii offers the potential to generate bioelectricity in a photo microbial fuel cell (PMFC), a device that is able to produce electrical energy using photo microorganisms under light [ 10 ]. Electrons produced by the microorganisms are transferred to the anode and flow to the cathode compartment via an external circuit [ 11 ].…”