Unprecedented exoelectrogenic activity in Parachlorella kessleri MACC-38: The interplay of photosynthetic electron transport and the oxidative pentose phosphate pathway

Exoelectrogenesis is the ability of living cells to export electrons. In photosynthetic organisms, exoelectrogenesis is of particular interest because it can be used for transduction of solar energy into electric current in biophotovoltaics or reducing power for biocatalysis. Previously, we identified and characterized the green microalga Parachlorella kessleri MACC-38 producing unprecedented current largely dependent on the photosynthetic electron transport chain (PETC). In this study, our comparative photosynthetic characterization demonstrates that chlororespiration is a crucial factor maintaining the PETC redox balance in MACC-38. Our data points that the oxidative pentose phosphate pathway (OPPP) is activated during exoelectrogenesis to meet the increased demand of reducing power. We hypothesize that chlororespitration prevents oversaturation of PETC during OPPP activation. These findings provide valuable insights into the fundamental mechanisms of exoelectrogenesis in green algae. By elucidating the complex interconnection between PETC, OPPP and exoelectrogenesis, our results pave the way towards improved bioelectrochemical and biocatalysis technologies.