Enhancing Cyanobacterial Photosynthetic Carbon Fixation via Quenching Reactive Oxygen Species by Intracellular Gold Nanoparticles

Abstract

Reactive oxygen species (ROS) play an important role in sensing the redox pressure involved in the electron transfer chains of photosynthesis. However, due to variation in light, ROS accumulation originated from the excess electrons on the acceptor side of photosystem I gives rise to critical inhibition of photosynthetic carbon fixation. How to regulate the extent to which ROS decrease stimulates energy and metabolic fluxes beyond nature must be known to improve CO 2 fixation. Herein, we report a strategy to deliver biocompatible gold nanoparticles into cyanobacterium Synechocystis sp. PCC 6803 to dispatch the photosynthetic electron hub for improving CO 2 fixation. Biomass of the cyanobacteria increases to 1.6 times with intracellular Au nanoparticles. The enzyme-like gold nanoparticles quench 30% ROS from flavodiiron proteins Flv and increase 21% apparent oxygen evolution, boosting the enzymatic activity of glyceraldehyde 3-phosphate dehydrogenase by an increase of 40% under high light stress. In comparison, gold nanoparticles have no obvious effect on the photosynthetic carbon fixation of the Flv-deficient strain because of severe photoinhibition of photosystems. This intracellular biohybrid strategy for intervention and modulation of complex photosynthetic electron transfer provides new insight into energy conversion and CO 2 fixation of photosynthesis.

Revisiting Solar Energy Flow in Nanomaterial-Microorganism Hybrid Systems

“…Therefore, the E CB of candidate nanomaterials should be tuned to levels that not only satisfy the thermodynamic potential required to drive the target redox reactions, but also overcome the energy loss likely occur during subsequent energy transport, meaning it exceeds the sum of the thermodynamic potential and the potential reduction during transport. , Moreover, the spectral range that can be captured by semiconductor nanomaterials should be broadened to cover a wider range of solar radiation. While heterojunctions demonstrated superior solar-capture capabilities, rationally selecting and combining heterojunction candidates are expected to further expand the overall solar-spectrum available for harvesting, a biomimetic strategy following the accessory pigments in photosynthesis. ,− Additionally, it is crucial to take into account the biosafety profiles of nanomaterials, particularly in terms of reactive oxygen species (ROS) generation under high-intensity light irradiation, because excessive ROS is detrimental to the living microbial cells. − Therefore, nanomaterials with low ROS generation under strong light irradiation, or even with ROS-scavenging capabilities, are highly desirable for the construction of hybrid systems. , Overall, these standards can be established through the synthesis of a large number of materials and subsequent screening against desired properties. This would involve creating a comprehensive database, gathering experimental data on a variety of nanomaterials and the range of reactions they can facilitate, which can then be utilized for predictive modeling and optimization of NMHS performance.…”