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Abstract

Enzymatic carbon dioxide fixation is one of the most important metabolic
reactions as it allows the capture of inorganic carbon from the
atmosphere and its conversion into organic biomass. However, due to the
often unfavorable thermodynamics and the difficulties associated with
the utilization of CO2, a gaseous substrate that is found in
comparatively low concentrations in the atmosphere, such reactions
remain challenging for biotechnological applications. Nature has tackled
these problems by evolution of dedicated CO2-fixing enzymes, i.e.,
carboxylases, and embedding them in complex metabolic pathways.
Biotechnology employs such carboxylating and decarboxylating enzymes for
the carboxylation of aromatic and aliphatic substrates either by
embedding them into more complex reaction cascades or by shifting the
reaction equilibrium via reaction engineering. This review aims to
provide an overview of natural CO2-fixing enzymes and their mechanistic
similarities. We also discuss biocatalytic applications of carboxylases
and decarboxylases for the synthesis of valuable products and provide a
separate summary of strategies to improve the efficiency of such
processes. We briefly summarize natural CO2 fixation pathways, provide a
roadmap for the design and implementation of artificial carbon fixation
pathways, and highlight examples of biocatalytic cascades involving
carboxylases. Additionally, we suggest that biochemical utilization of
reduced CO2 derivates, such as formate or methanol, represents a
suitable alternative to direct use of CO2 and provide several examples.
Our discussion closes with a techno-economic perspective on enzymatic
CO2 fixation and its potential to reduce CO2 emissions.