Team:CHINA-FAFU/Description

Description

"Human activity is solely responsible for the rise in temperature."

In August, the UN-led Intergovernmental Panel on Climate Change (IPCC) released the core findings of the Working Group I report of its Sixth Assessment Report, Climate Change 2021: The Natural Science Basis: There is broad scientific consensus that human activities are causing the planet's warming and that the global climate system is undergoing rapid and widespread changes, some of which are irreversible. Since the late 19th century, there have been significant changes in all five of Earth's major circles. Although, the climate has always been changing from ancient times to the present, the warming in recent decades or centuries is unprecedented in the past millions of years and longer. Moreover, modern global warming is rapid. From the 50 years between 1850 and 1900 to the present, the Earth has warmed by about 1°C. In particular, the rate of warming in the last 50 years exceeds the rate of warming in any 50-year period on Earth in the last 2,000 years. Such warming has occurred in every region of the globe.

In the past year, humanity has made unprecedented efforts to cope with extreme climate anomalies. 2020 is one of the hottest years in recorded weather history. The U.S. National Environmental Protection Agency (EPA) released its latest climate report in May of this year, stating clearly that global warming is threatening people's health, safety and housing, making life more difficult. Flooding is becoming more common along the U.S. coast, especially in cities along the Atlantic and Gulf coasts, where flooding is five times more frequent than in the 1950s. The report also makes clear that global heat is now occurring three times more frequently than in the 1960s; Arctic sea ice is shrinking, with its minimum area of coverage getting smaller each summer; and ocean temperatures are also reaching record highs in 2020, with ocean waters continuing to acidify. As EPA Administrator Michael Regan has stated, "Fighting climate change is not an optional matter; it's critical in EPA's view." "We will move forward with a sense of urgency because we know the danger is coming. "

A dramatic global green and low-carbon transition is taking shape

In the face of unprecedented environmental problems of, in order to have a better living environment in the future, mankind has started to save itself. "To limit the increase in global average temperature to less than 2°C from the pre-industrial period and to strive to limit the temperature increase to less than 1.5°C." This is the long-term goal of the Paris Agreement. To achieve this temperature control goal, more than 20 countries around the world have declared their intention to become carbon neutral.

Carbon neutrality, also known as net zero emissions, refers to the balancing of greenhouse gas (GHG) emissions (mainly carbon dioxide) from human activities with those absorbed by nature, with the aim of maintaining a relative balance of GHG concentrations in the atmosphere and no further changes in temperature rise.

In the global effort to achieve the ambitious goal of carbon neutrality, we have to mention the technologies used for carbon neutrality: CO₂ capture, utilization and storage (CCUS), bioenergy with carbon capture and storage (BECCS) and direct air carbon capture and storage (DACCS). CCUS refers to the process of separating CO₂ from industrial processes, energy use or the atmosphere and using it directly or injecting it into the ground to achieve permanent CO₂ reduction (Fig.1). It differs from the previously proposed CCS by the addition of "Utilization". In addition, BECCS is the process of capturing, utilizing, or storage of CO₂ from biomass combustion or conversion, while DACCS is the process of capturing CO₂ directly from the atmosphere and utilizing or storing it.

Fig.1 Diagram of CCUS technology and main types
CCUS Annual Report on Carbon dioxide Capture(2021)

In China, for example, the achievement of the carbon neutrality goal requires China to establish a zero-carbon energy system based on non-fossil energy sources, decoupling economic development from carbon emissions[1].As an important part of China's technology portfolio to achieve carbon neutrality, CCUS technology is not only the only technology option for low-carbon utilization of fossil energy in China and the main technology means to maintain the flexibility of the power system, but also a feasible technology solution for hard-to-reduce emission industries such as steel and cement. In addition, CCUS and new energy coupled with negative emission technologies are the technical guarantee to offset the unmitigated carbon emissions and achieve the carbon neutrality target.

Fig.2 CCUS
CCUS Annual Report on Carbon dioxide Capture(2021)

An important component of the carbon neutral CCUS technology: BECCS

Biomass energy carbon capture and storage (BECCS) technology, an important component of CCUS technology, is the fourth largest contributor, accounting for 15% of cumulative emission reductions, according to the International Energy Agency (IEA) Sustainable Development Scenario, which aims to achieve net zero emissions globally by 2070. In the IEA Sustainable Development Scenario, CCUS grows in importance over time, and its role can be broadly divided into three phases: Phase I (until 2030) focuses on carbon capture in existing power plants and projects; Phase II (2030-2050) will see a rapid increase in the deployment of BECCS in addition to CCUS deployment, accounting for 15% of the total. The third phase (2050-2070) will see carbon capture increase by 85% over the previous phase, with 45% coming from BECCS and 15% from DAC.

Fig3 IEA Sustainable Development Scenario CCUS (IEA, 2020)

Technology Created by Nature: BECCS

The BECCS technology explains its principle biologically by taking advantage of the role played by photosynthetic organisms in CO₂ storage, especially photosynthetic microorganisms such as microalgae. CO₂ capture from biomass energy is an effective way to remove CO₂ from the atmosphere. Biomass energy is derived from biomass and not only is it a renewable energy source, it is also capable of acting as a carbon sink during the growth process. In industrial processes, the biomass that is burned or treated will re-emit CO₂ into the atmosphere, thereby achieving net zero or even negative CO₂ emissions.

Microalgae, an important component of BECCS, have a highly diverse microbiota that can photosynthesize through their own chloroplasts. In microalgae, light-dependent and light-independent reactions are synchronized to complete the CO₂ assimilation for photosynthesis. CO₂ is obtained from the growth environment converting inorganic carbon (C1) into organic carbon compounds and further producing various compounds such as: lipids, proteins, carbohydrates, and pigments. Microalgae are rich in these organic compounds and can be further industrialized into various products such as biodiesel, food, health products, cosmetics and feed.

Therefore, BECCS is proposed as a technology that can reverse emission trends and create a net negative global system. This means that there is a chance that carbon emissions will not only go to zero, but even create a positive result of negative carbon emissions.

Diatoms: the core "members" of BECCS

Diatoms are one of the most "successful" planktonic photosynthetic organisms in the ocean, fixing nearly 1/5 of the world's CO₂ through powerful photosynthesis, equivalent to the contribution of the entire tropical rainforest. As a typical single-celled oil-producing diatom in the ocean, Phaeodactylum tricornutum belong to the category of marine microorganisms. With its high photosynthetic efficiency, short growth cycle and high lipid content, it has become one of the most promising raw materials for biodiesel production, and while it does not compete with people for water (using seawater for cultivation), food and land, it can absorb and use N/ P and other nutrients that cause seawater eutrophication and greenhouse gases. Although there are so many advantages of using diatoms for biodiesel production, there are still problems of low biomass and high cost of diatom cultivation.

Phaeodactylum tricornutum & Ascorbic Acid & SynBio

In our team's project, we chose the single-celled oil-producing diatom P. tricornutum, which is common in the ocean, as the substrate material for our experiments. This material not only has excellent properties commonly found in diatoms, such as high oil content, but is also rich in fucoxanthin, which is a material with high environmental and economic potential.

Ascorbic acid (L-Ascorbic acid), also known as vitamin C, is a water-soluble vitamin that is directly involved in reactive oxygen species (ROS) reactions of singlet oxygen, superoxide radicals, and hydrogen peroxide, and thus has an important role in cellular resistance to oxidative stress. An important function of ascorbic acid in plant cells has been reported to be the protection of chloroplasts from oxidative damage.

Fucoxanthin is a fat-soluble carotenoid that is widely used for its anti-hypertensive, anti-inflammatory, and weight-loss properties. It has a promising future in medical and pharmaceutical fields, but its low content in microalgae makes it very expensive.

Inspired by the special effect of ascorbic acid on plant chloroplasts and the high oil content of the experimental substrate compared to other microalgae, our team decided to enhance the photosynthetic efficiency of P. tricornutum by adding ascorbic acid extracellularly as an entry point, and verified the results through several engineering iterations. After that, we performed real-time fluorescence PCR on key genes of Calvin-Benson Cycle, ascorbic acid metabolic pathway, lutein anabolic pathway, lipid anabolic pathway and nitrogen and phosphorus metabolic pathway, screened the genes according to their expression and synthesized the corresponding genes. After that, a second iteration of the project was carried out, in which the screened genes were constructed into the GFP-tagged expression vector of Pichia pastoris previously constructed by our team to verify whether some of the functions of the genes met our expectation. Finally, a third iteration of the project was performed, in which the genes that met our expectations were constructed into the P. tricornutumexpression vector and transferred into P. tricornutum by electroshock transformation. For the multiple engineered strains, physiological and biochemical parameters were measured, and a high quality strain with high oil production and high fucoxanthin content was selected to meet our project expectations. This expectation is consistent with the results of our public questionnaire conducted in human practice after modeling analysis.

Summary

In short, we designed an engineered algae strain with high oil production and high fucoxanthin content through the project. At the same time, the implementation of the project we came up with a method to promote microalgae biomass and oil production. This method is very easy and fast, focusing on low cost, and suitable for use in countries and regions where most GM foods are not yet legalized. In addition, one of our sponsors, Fujian Shenliu Group, showed very strong interest in our results and entered into a technical partnership with our team. Finally, our team conducted a site search for a suitable microalgae plant in China based on the project's cultivation program, which will provide some reference value for subsequent corporate development.

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