Greenhouse gases such as CO2 emitted by human society have caused global climate warming and ocean acidification. It is urgent to explore and implement ways and methods to reduce carbon emissions. Using microalgae to directly convert industrial source CO2 into biofuels has important strategic significance in the construction of a carbon-neutral energy system. But how can industrial microalgae efficiently fix CO2? The Single Cell Center of the Qingdao Institute of Bioenergy and Processes, Chinese Academy of Sciences and others found that as an industrial oil-producing microalgae, Nannochloropsis cells have at least three carbon concentrating mechanisms (CO2 Concentrating Mechanism, CCM) features in one. The revelation of this global CCM system structure blueprint lays the foundation for the design and transformation of "super carbon dioxide fixation modules" in industrial microalgae.
The current CO2 content in the earth's atmosphere is about 0.04%. In order to enrich such a low concentration of CO2 in the environment around Rubisco (ribulose-2-phosphate carboxyl oxidase) in the chloroplast to perform efficient photosynthesis, autotrophic organisms have evolved various CCM systems. Inorganic carbon molecules are actively supplied or recycled within cellular metabolic networks. Therefore, the CCM system contains the secret of discovering and transforming the carbon fixation capacity of microalgae cell factories.
Nannochloropsis spp. is an industrial microalgae that can be cultivated on a large scale outdoors using seawater or fresh water. It has the advantages of fast growth, high oil content, and the synthesis of high-value unsaturated fatty acids such as EPA. Therefore, it has been It has become one of the main research systems for molecular breeding of industrial oil-producing microalgae, and also supports many demonstration projects for microalgae-scale carbon dioxide fixation at home and abroad.
Wei Li of the Single Cell Center collaborated with Mohamed El Hajjami of Ruhr University in Germany and others to comprehensively analyze the marine Nannochloropsis (N. ) gene groups and metabolic modules specifically activated under low-carbon conditions, thus revealing the global structural blueprint of the CCM system. The study found that in the carbon fixation system of Nannochloropsis cells, there are at least three characteristics of CCM, including biophysical CCM dominated by carbonic anhydrase and bicarbonate transporter, and CCM similar to the C4 photosynthetic carbon fixation pathway of higher plants. Biochemical CCM, and background CCM focusing on mitochondrial carbonic anhydrase and respiratory chain. Moreover, the specific mechanisms supporting these characteristics are quite significant and even surprising when compared with laboratory model eukaryotic microalgae such as Chlamydomonas reinhardtii (green algae) and Phaeodactylum tricornutum (diatoms). These discoveries at the genome-wide level lay the foundation for the systematic design and construction of "super carbon dioxide fixation modules" in industrial oil-producing microalgae.
The work was led by Xu Jian, a researcher at Qingdao Institute of Energy, and Ansgar Poetsch, a professor at Ruhr University in Germany, with help from Zhou Wenxu, a professor at Texas Tech University in the United States, and Hu Qiang, a researcher at the Institute of Hydrobiology, Chinese Academy of Sciences. This research was supported by the National Natural Science Foundation of China, the Chinese Academy of Sciences’ CO2 Key Deployment Project, and the Institute’s “One, Three, Five” Project.
