Liberating photoinhibition through nongenetic drainage of electrons from photosynthesis

• Published in: Natural sciences (Weinheim) Vol. 1; no. 2
• Main Authors: Wang, Wangyin, Li, Dingyi, Cao, Xupeng, Xue, Song, Li, Can
• Format: Journal Article
• Language: English
• Published: Providence John Wiley & Sons, Inc 01.10.2021; Wiley-VCH
• Subjects: Algae; Aquatic microorganisms; Chemical activity; Chemical synthesis; Chloroplasts; Cyanobacteria; Drainage; Drainage channels; Efficiency; Electron transfer; Electrons; Energy; Light; Metabolism; Microalgae; Oxidation; Photoinhibition; Photosynthesis; Photosystem II; Redox reactions; Saturation; Shuttles; Water
• ISSN: 2698-6248; 2698-6248
• DOI: 10.1002/ntls.20210038

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. Illustration of liberating photoinhibition through drainage of excess photosynthetic electrons. Photosynthetic electron flow is drained by electron acceptors via an extracellular electron transfer pathway to output excess energy generated from high light flux. The unblocked drainage of electron liberates photoinhibition of photosystems which conduct photochemical reaction on the thylakoid membrane of the chloroplast. The extracted reducing powers including electrons and protons were applied to in situ hydrogenations of two artificial reactants to value‐added products across the NADPH oxidase export sites. LHC, light harvesting complex; PQ, plastoquinone; PC, plastocyanin; ROS, reactive oxygen species; Fd, ferredoxin; FNR, ferredoxin: NADPH reductase; CBB cycle, Calvin‐Benson‐Bassham cycle; TP, transporter protein; eA, electron acceptor; eD, electron donor.