Electron Leaks in Biophotovoltaics: A Multi-Disciplinary Perspective

Biophotovoltaics (BPV), which exploits the natural oxygenic photosystem for energy production, provides a sustainable solution to produce carbon neutral or negative energy from sunlight to meet the growing global energy demand. BPV integrates oxygenic photoautotrophic microorganisms in an electrochemical cell, and harvests the water-splitting derived photosynthetic electrons to an electrical circuit. Here e. g. electricity or H2, etc, can be produced, thus directly coupling sunlight and water to energy. Despite of the rapid development in the past decade, the system efficiency of BPV still needs magnitude-level improvement for practical applications. In this perspective paper, we aim to address the electron transfer pipeline in BPV starting from the water splitting by the living whole-cell catalysts to external electron sinks (i. e. mediator/anode) and eventually to the cathode, from multidisciplinary aspects. We calculated the electron leaks along the electron transfer pipeline to different metabolic electron sinks, and prospectively predicted an untapped potential for extracellular electron transfer rate. BPV could potentially reach an energy efficiency that is two orders of magnitude higher than its current status. An interdisciplinary research approach, that should combine systems and synthetic biology, bioprocess engineering and material science, among others, is proposed to broach the upper boundary of BPV technology. The photosynthetic electrons leak to several metabolic electron sinks before reaching the extracellular electron transfer pathway in Biophotovoltaics for energy production. This perspective paper, from the multi-disciplinary perspective, addresses those electron leaks on semi-quantitative level and proposes potential solutions to plug those leaks to enhance the light-to-energy efficiency of Biophotovoltaics. image