Metal-organic framework materials improve the carbon sequestration efficiency of photosynthesis

In natural photosynthesis, plants use sunlight, water, and carbon dioxide to synthesize biomass. However, the photosynthesis efficiency of plants is mainly limited by the quality of light and the capture and transport of carbon dioxide, which restricts the efficiency of photosynthesis into biomass. Recently, Academician Li Can and associate researcher Wang Wangyin of Dalian Institute of Chemical Physics, Chinese Academy of Sciences have made new progress in improving carbon sequestration by microalgae photosynthesis. The team found that the coupling mechanism of direct air capture of carbon dioxide and biochar concentration using metal-organic framework materials (MOFs) enhanced the carbon dioxide transfer from the environment to cells, and the carbon sequestration efficiency of microalgae photosynthesis increased from 5.1% to 9.8%. The results were published in Nature Communications.

Li Can’s research team increased the saturation point of light absorption, lifted photoinhibition, and introduced nanogold in photosynthetic cells by adding extracellular artificial electron shuttles in the early stage, and studied the limiting factors catalyzed by dark reaction carbonase. At present, how to capture concentrated carbon dioxide and efficiently transport it to Rubisco enzyme to improve the carbon sequestration reaction kinetics at atmospheric level carbon dioxide concentration is still a challenge in the field of plant photosynthesis.

Schematic diagram of improving efficiency. Photo courtesy of Dalian Chemical Properties

In this work, the researchers proposed a strategy of chemical and biological hybridization to self-assemble porous MOFs on the surface of photosynthetic microalgae to achieve direct air capture and bioconversion of carbon dioxide. It was found that the MOF material self-assembled on the surface of chlorella through electrostatic action, capturing and enriching carbon dioxide in the air in microalgae cells, increasing the affinity of microalgae photosynthetic oxygen release rate for carbon dioxide by 82%. Through enzyme kinetic experiments, the team found that the extracellular carbonic anhydrase secreted by chlorella hydrates the carbon dioxide captured by MOFs into bicarbonate, and the transporters on the biofilm transport the bicarbonate to the protein nucleus in the chloroplast, thereby increasing the carbon dioxide concentration around chlorella Rubisco enzyme. This effect induced an increase in the expression of Rubisco, a key enzyme for carbon sequestration, and accelerated the photosynthetic carbon sequestration rate of chlorella. The function of MOFs to capture carbon dioxide enables microalgae cells to strengthen the dark response while alleviating the inhibition of the photoreaction under photostress. The apparent conversion efficiency of light energy to biomass increased from 5.1% to 9.8%.

This strategy is a new attempt to improve natural photosynthesis with artificial methods. (Source: Sun Danning, China Science News)

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