电能辅助二氧化碳生物转化

Electro-assisted carbon dioxide biotransformation

CO_(2)排放带来全球性气候变化问题,为此世界各国纷纷采取了一系列减排固碳措施。我国于2020年提出“碳达峰,碳中和”发展目标,推进固碳技术发展迫在眉睫。受益于近年来合成生物学领域的迅猛发展,基于酶或微生物催化的CO_(2)生物转化研究在酶元件、途径和系统的人工设计改造等方面取得一系列重要进展,典型产物代表有燃料、氨基酸、淀粉、单细胞蛋白、生物塑料及其他多种生化产品。为此,CO_(2)也被认为是第三代生物原料。CO_(2)转化的关键在于外加能量活化CO_(2)分子,相比于光能、热能和化学能等,电能在成本投入和小型便捷方面优势突出,因此更受科学界和产业界青睐。CO_(2)生物转化利用电能分为两种方式,即生物直接利用电能固定CO_(2)和利用电能间接辅助CO_(2)生物转化[包括电催化CO_(2)还原、电再生辅因子(如NADH)、电解水制氢]。本文全面介绍了这两种方法在CO_(2)生物转化方面的研究进展,分析了可能的固碳机制,并讨论了不同方法的优点和缺点。此外,还提出了合成生物技术应对低效CO_(2)生物转化时的可能策略如挖掘高活性固碳酶、酶工程改造提高酶与电极之间的电子传递效率、代谢工程改造丰富固碳微生物的产物种类和提高固碳效率等,以期相关研究能真正走向实际应用,助力我国双碳目标的实现。

The increasing emission of CO_(2)has resulted in severe climate problems,prompting global actions to reduce CO_(2)emission or fix the atmospheric CO_(2).In 2020,China set targets for carbon peaking and carbon neutrality,making it an urgent need to develop carbon-fixation technologies.Attributed to the rapid emergence of synthetic biology in recent years,CO_(2)biotransformation through biochemical reactions catalyzed by enzymes and microbes has achieved a series of significant progress,in the design and engineering of enzymes,metabolic pathway,as well as the construction of in vitro/vivo systems.Many products,such as fuels,amino acids,starch,single-cell proteins,bio-based plastics,and other biocommodities,have been synthesized.Consequently,CO_(2)is considered as the resource for thirdgeneration biomanufacturing.The crucial step in CO_(2)biotransformation is the activation of CO_(2)molecules through the introduction of external energy.Compared to light,heat,and chemical energy,electrical energy is favored due to cost effectiveness,miniaturized apparatus,and convenience,attracting significant attention from both academia and industry.Electrical energy can be utilized in two ways for CO_(2)biotransformation.In one way,CO_(2)is electro-activated directly and biotransformed.In the other way,electrical energy facilitates the production of C1 intermediate such as formate,carbinol,CO,and the C1 intermediates are then transformed by coupled microorganisms or enzymes,or the production of reducing forces such as NADH and H2,which participate essentially in CO_(2)biotransformation.This review comprehensively introduces research advancements in both approaches,analyzes potential carbon-fixation mechanisms,and discusses the advantages and disadvantages of different methods.Furthermore,the review proposes potential synthetic biology strategies to address efficiency concerns in CO_(2)biotransformation,such as mining highly active carbon-fixing enzyme,enzyme engineering to improve the electron transfer efficiency between the enzyme and the electrode,metabolic engineering to enrich products of carbon-fixing microorganisms and improve the carbon-fixing efficiency,aiming to enable practical applications and the achievement of carbon neutrality goals.