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Upcycling Carbon Dioxide Into Glucose and Fatty Acids

A new hybrid electro-biosystem can convert carbon dioxide into energy-rich long-chain compounds, presenting a step towards a renewable-electricity-driven manufacturing industry.

With the rising concentration of carbon dioxide in Earth’s atmosphere, upcycling carbon dioxide (CO2) into value-added products in a sustainable manner is a way we can deal with environmental issues. However, compared with easily available C1/C2 products, synthesising energy-rich long-chain compounds from CO2 efficiently and sustainably remains a challenge.

Published in Nature Catalysis, a joint research team led by Professor Xia Chuan from the University of Electronic Science and Technology of China, Professor Yu Tao from the Shenzhen Institute of Advanced Technology of the Chinese Academy of Sciences, and Professor Zeng Jie from the University of Science and Technology of China, has innovated a hybrid electro-biosystem that efficiently converts CO2 to glucose with a high yield.

By coupling spatially separate CO2 electrolysis with yeast fermentation, the system can convert CO2 to glucose or fatty acids with both high titer and high yield.

“Acetic acid is not only the main component of vinegar, but also one of the excellent biosynthetic carbon sources. It can be transformed into other substances in life, such as glucose. Acetic acid can be obtained by direct electrolysis of CO2, but with ultra-low efficiency. We thus propose a two-step strategy to convert CO2 into acetic acid, with CO2 as the intermediate,” explained Prof. Zeng.

Thus, using a Ni-N-C single-atom catalyst, the researchers first converted CO2 into CO, and then developed a grain-boundary-rich Cu (GB_Cu) catalyst for acetate production from electrochemical CO reduction.

As the acetate produced by conventional electrocatalytic devices is always mixed with electrolyte salts that cannot be directly used for biological fermentation, the researchers developed a porous solid electrolyte reactor equipment with thick anion exchange membranes for pure acetic acid solution separation and purification. The result is a continuous and stable production of ultrapure acetic acid.

The team then proceeded to genetically engineer Saccharomyces cerevisiae to enable microbe growth on pure acetic acid and the efficient release of glucose in vitro. These modifications yielded an average glucose titer of 1.81 ± 0.14 g·L >-1, which is equivalent to a high yield of 8.9 μmol per gram of yeast per hour.

The researchers also went on to demonstrate that their proposed biosystem can be easily extended to produce other products like fatty acids.

“This demonstration is a starting point for realising light-reaction-free artificial synthesis of important organic products from CO2,” said Prof. Yu. [APBN]

Source: Zheng et al. (2022). Upcycling CO2 into energy-rich long-chain compounds via electrochemical and metabolic engineering. Nature Catalysis, 1-9.