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2020

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11

Biosynthetic pathways for developing nylon monomers in China


On October 20, when interviewing Professor Li Aitao, School of Life Sciences of Hubei University and State Key Laboratory of Biological Catalysis and Enzyme engineering jointly built by Hubei Province and Ministry of Education, the reporter learned that Li Aitao's research team had made a major breakthrough in the field of nylon monomer preparation, breaking the limit of environmental pollution caused by high pollution and energy consumption caused by existing industrial synthetic nylon monomer, and finding new methods for nylon monomer preparation.

Researchers have designed a novel artificial biosynthesis pathway for nylon monomers by designing a microbial community catalytic system. According to Li Aitao, the artificial biosynthesis system adopts the catalytic strategy of modularization and microbial flora, which divides eight enzymes in the whole biosynthesis pathway into three modules and expresses them in three kinds of Escherichia coli, thus obtaining three modular cell catalysts. Then, using the "plug and play" assembly strategy, three kinds of cells were combined to construct the Escherichia coli microbiome catalytic system, which ultimately realized the efficient biotransformation of cyclohexane or cyclohexanol to adipic acid. This research achievement provides a new approach for the synthesis of nylon monomers with its significant advantages of high efficiency and green color.

Nylon 66 is synthesized by condensation of adipic acid and adipic amine, and adipic acid is the main monomer. In traditional industry, its synthesis mainly relies on a multi-step chemical oxidation process with high pollution and high energy consumption. Li Aitao introduced that this process requires the use of a large amount of corrosive nitric acid, while generating a large amount of harmful greenhouse gases such as NO and N2O, causing many environmental problems, such as global warming and ozone holes, Therefore, it seriously restricts the development of the nylon 66 industry.

To address the above challenges, Li Aitao's team has designed an artificial biosynthesis system based on their previous accumulation in biocatalysis, which can catalyze the synthesis of cyclohexane to nylon 66 monomer adipic acid. Li Aitao further introduced, "This process can undergo catalytic reactions under mild conditions (room temperature, atmospheric pressure, and aqueous phase), using self-sufficient coenzyme autocirculation, without the need for any expensive exogenous coenzyme, with low cost. At the same time, the reaction process does not accumulate any intermediate products, has high selectivity, single product, and simple subsequent separation and purification

"In addition, a variety of naphthenic hydrocarbons or naphthenic alcohols (C5-C8) can be different by using the rationally designed Escherichia coli microbiome as a catalyst α,ω- The synthesis of dicarboxylic acids fully demonstrates the universality of this method. Finally, the whole biotransformation reaction was amplified in the fermentation tank, and the amplification of adipic acid products was successfully achieved. This artificial biosynthesis system is to achieve large-scale biological synthesis α,ω- Dicarboxylic acids have laid an important foundation Li Aitao said.

Nylon, as a widely used synthetic fiber, is widely used in many important fields related to the national economy and people's livelihood. Next, Li Aitao's research team will further improve enzyme catalytic efficiency, maintain consistent catalytic performance of 8 enzymes, break the bottleneck of rate limiting enzymes, and design and modify enzyme molecules to mutate the enzyme, endowing it with higher catalytic performance, thereby improving the efficiency of the entire artificial biosynthesis of nylon monomers.