Liberating photoinhibition through nongenetic drainage of electrons from photosynthesis

Abstract

Light is the prerequisite for photosynthesis. However, excess light flux higher than the light-saturation point gives rise to photoinhibition or photodamage. To efficiently utilize the excess energy under the light saturation is a long-standing issue of photosynthesis. Herein, we found an electron drainage channel using artificial redox shuttle as a nongenetic tool to direct excessive electron transfer from chloroplast of microalgae (Chlorella pyrenoidosa) to extracellular redox reactions. Guiding the excess electrons to the outside cell enhanced water oxidation activity of photosystem II by 2.6-fold and increased the light saturation point by 7.1-fold. Intrinsic quantum yield and electron transfer rate of photosystems (PSII and PSI) were also in response to an increased light flux, due to the liberation of the initial photoinhibition. The electrons drained from photosynthesis served as the reducing equivalents for extracellular synthesis of chemicals. This work sheds light on the nature of photosynthetic electron transportation and distribution in a light-saturated state of microalgae through a nongenetic drainage of electron for extracellular chemical synthesis. Key points: An electron drainage channel was developed using artificial redox mediator to liberate the photoinhibition of microalgal photosynthesis. Guiding the excess photosynthetic electrons to the outside cell enhanced water oxidation activity of photosystem II and increased the light saturation point. Electrons from photosynthesis with the reducing power can be used for extracellular synthesis of chemicals.