Natural carbon fixation and advances in synthetic engineering for redesigning and creating new fixation pathways

In Vivo Detection of Low Molecular Weight Platform Chemicals and Environmental Contaminants by Genetically Encoded Biosensors

“…Currently, the fixation of CO 2 through the Calvin-Benson-Bassham cycle mainly by autotrophs (e.g., plants, algae, cyanobacteria) and a few recently discovered natural carbon-fixation pathways in bacteria and archaea cannot balance the excessive anthropogenic CO 2 emission . Very recently, Gleizer et al.…”

“…coli) to produce all its biomass carbon from CO 2 via the Calvin-Benson-Bassham cycle, enabling autotrophic growth of an otherwise heterotrophic bacterium . Complementary, significant efforts have been made not only to transplant and improve natural carbon fixation but also to design artificial assimilation routes. , While many natural and de novo CO 2 fixation pathways depend on the same energy carriers such as ATP and (phosphorylated) nicotinamide cofactors, fixation products and pathway intermediates can be fairly distinct. , Besides the challenging implementation of synthetic pathways in microorganisms, biosensors might not have become available to sense associated small molecules. ,, This is also true for the CETCH (crotonyl-CoA/ethylmalonyl-CoA/hydroxybutyryl-CoA) cycle, assembled by Schwander and co-workers, for the fixation of two molecules CO 2 in vitro . Furthermore, many immediate CO 2 fixation products are quickly metabolized and do not accumulate in living (micro)­organisms, calling for qualitative and quantitative measurement tools that are highly sensitive to evaluate engineering efforts.…”

“…Biosensors have been developed and employed to match these requirements but have yet to be implemented to accelerate the optimization of (artificial) CO 2 assimilation pathways and to complement (indirect) performance assessments such as growth assays. , Hence, biosensor systems that have been developed for other purposes but are suitable to detect carbon fixation products and related molecules will be highlighted in the following. , …”

“…One industrially important CO 2 fixation product is formate (C 1 ; 46.03 g mol –1 ), for example. Since it can be produced (enzymatically) from multiple (renewable) sources and further converted into platform chemicals like formaldehyde and pyruvate, formate is of interest to different industries. , Mormino et al constructed a biosensor, discussed for biosensing formate, by fusing the Saccharomyces cerevisiae (S. cerevisiae) TF Haa1 and the DBD of BM3R1 from Bacillus megaterium.…”

“…Complementary to recent reviews highlighting advancements in natural and artificial carbon fixation pathways, ,, this review will focus on genetically encoded biosensor systems operating in living cells, suitable to detect immediate fixation products (e.g., formate and pyruvate) and their industrially relevant derivatives. Physicochemical biosensor designs employed in vitro were recently reviewed by others and are not included herein. , Furthermore, this condensed review will feature devices for the biosensing of (inorganic) contaminants that directly relate to anthropogenic activities, including, but not limited to, heavy metal (HM) and fluoride (F – ) ions, as well as chalcogen-containing compounds such as hydrogen sulfide (H 2 S) and hydrogen peroxide (H 2 O 2 ).…”