Photoautotrophic synthesis of butyrate by metabolically engineered cyanobacteria

Abstract

Direct conversion of carbon dioxide into chemicals using engineered autotrophic microorganisms offers a potential solution for both sustainability and carbon mitigation.Butyrate is an important chemical used in various industries, including fragrance, food, and plastics. A model cyanobacterium Synechococcus elongatus PCC 7942 was engineered for the direct photosynthetic conversion of CO 2 to butyrate. An engineered Clostridium Coenzyme A (CoA)-dependent pathway leading to the synthesis of butyryl-CoA, the precursor to butyrate, was introduced into S. elongatus PCC 7942. Two CoA removal strategies were then individually coupled to the modified CoA-dependent pathway to yield butyrate production. Similar results were observed between the two CoA removal strategies. The best butyrate producing strain of S. elongatus resulted in an observed butyrate titer of 750 mg/L and a cumulative titer of 1.1 g/L. These results demonstrated the feasibility of photosynthetic butyrate production and expanded the chemical repertoire accessible for production by photoautotrophs. K E Y W O R D Sbutyrate kinase, butyric acid, cyanobacteria, metabolic engineering, phosphotransbutyrylase, thioesterase

Identification, cloning, expression and functional interrogation of the biosynthetic pathway of the polychlorinated triphenyls ambigol A–C fromFischerella ambigua108b

“…Related problems were observed by Moore et al when expressing selected genes of the bmp BGC of cyanobacterial origin, 13 while the bmp genes from γ-proteobacteria, by contrast, were expressible in E. coli. 12,30,39,44 We thus focused on the recombinant production of ambigols in a phylogenetically more closely related species when compared to F. ambigua, i.e., the cyanobacterial heterologous host Synechococcus elongatus PCC 7942 45,46 previously utilized for the production of PBDEs 13 and industrially important compounds such as butyrate, 47 2-deoxy-scyllo-inose 48 and propanediol. 48,49 Due to the size of the ab BGC and the known difficulties in introducing large DNA fragments into S. elongatus by natural transformation, we decided to split the ab BGC in two halves of approx.…”

Third-generation biorefineries as the means to produce fuels and chemicals from CO2

“…A wide variety of 3G-based products have been reported. For example, many photoautotrophs, such as microalgae and cyanobacteria, can assimilate CO 2 from freshwater, sea water and wastewater for the production of a wide variety of fuels and chemicals, including butyrate 139 , pharmaceuticals 140 , aromatics 141 , lipids 142 and hydrocarbon fuels 143 . Within chemoautotrophs, Clostridium species are attractive platforms for producing a wide range of products, including butanol (C. carboxidivorans and C. acetobutylicum), 2-oxobutyrate (Clostridium aceticum) and 3-butanediol (Clostridium autoethanogenum and C. ljungdahlii) 126,144 .…”

Future trends in synthetic biology in Asia

“…In pursuit of a paradigm shift from the petrochemical‐reliant industry, synthetic biology researchers and entrepreneurs are exploring alternative renewable feedstocks, as well as producing products that are more environmentally friendly. In Taiwan, researchers developed CO 2 ‐based photosynthetic pathways to produce butyrate with the cyanobacteria Synechococcus elongatus 95 . Similarly, other metabolic engineering demonstrations sought to improve the production efficiency of cyanobacteria for a myriad of high‐value chemicals 96 .…”