Construction of an artificial consortium of Escherichia coli and cyanobacteria for clean indirect production of volatile platform hydrocarbons from CO2

Abstract

Ethylene and isoprene are essential platform chemicals necessary to produce polymers and materials. However, their current production methods based on fossil fuels are not very efficient and result in significant environmental pollution. For a successful transition more sustainable economic model, producing these key polymeric building blocks from renewable and sustainable resources such as biomass or CO2 is essential. Here, inspired by the symbiotic relationship of natural microbial communities, artificial consortia composed of E. coli strains producing volatile platform chemicals: ethylene and isoprene and two strains of cyanobacteria phototrophically synthesizing and exporting sucrose to feed these heterotrophs were developed. Disaccharide produced by transgenic cyanobacteria was used as a carbon and electron shuttle between the two community components. The E. coli cscB gene responsible for sucrose transport was inserted into two cyanobacterial strains, Thermosynechococcus elongatus PKUAC-SCTE542 and Synechococcus elongatus PCC7942, resulting in a maximal sucrose yield of 0.14 and 0.07 g/L, respectively. These organisms were co-cultured with E. coli BL21 expressing ethylene-forming enzyme or isoprene synthase and successfully synthesized volatile hydrocarbons. Productivity parameters of these co-cultures were higher than respective transgenic cultures of E. coli grown individually at similar sucrose concentrations, highlighting the positive impact of the artificial consortia on the production of these platform chemicals.

Cyanobacteria as cell factories for the photosynthetic production of sucrose

“…Additional expression of a sucrose porin (cscY) and a sucrose operon repressor (cscR) further improved sucrose utilization (Löwe et al, 2020), while further optimization of the nitrogen-deficiency response pathway (Hobmeier et al, 2020) and culture conditions could boost PHA titer further (Kratzl et al, 2023; Table 2). Other co-culture products include the metabolites ethylene, isoprene, 3-hydroxypropionic acid (3-HP), and 2,3-butanediol (Table 2), which are compounds in a broader class of industrially relevant precursors widely used for chemical synthesis (e.g., diols, organic acids, gaseous alkenes; Cui et al, 2022;Li C. et al, 2022;Ma et al, 2022). In most of these reports, the heterotrophic microbe utilized were E. coli substrains, although the rapidly growing halophile Vibrio natriegens was able to produce a relatively high amount of 2,3-butanediol in co-culture (Li C. et al, 2022).…”

“…Other co-culture products include the metabolites ethylene, isoprene, 3-hydroxypropionic acid (3-HP), and 2,3-butanediol ( Table 2 ), which are compounds in a broader class of industrially relevant precursors widely used for chemical synthesis (e.g., diols, organic acids, gaseous alkenes; Cui et al, 2022 ; Li C. et al, 2022 ; Ma et al, 2022 ). In most of these reports, the heterotrophic microbe utilized were E. coli substrains, although the rapidly growing halophile Vibrio natriegens was able to produce a relatively high amount of 2,3-butanediol in co-culture ( Li C. et al, 2022 ).…”

“…For instance, cyanobacterial growth was enhanced in mixed culture with several heterotrophic species ( Hays et al, 2017 ; Li et al, 2017 ; Hobmeier et al, 2020 ; Ma et al, 2022 ), although the partner species were evolutionarily “naïve” to one another. Similarly, heterotrophic productivity in co-culture can be significantly higher than can be attributed to the cyanobacterially secreted sucrose ( Hays et al, 2017 ; Cui et al, 2022 ; Ma et al, 2022 ). Conversely, when cyanobacteria are allowed to overpopulate a synthetic co-culture, heterotrophic partners may exhibit reduced viability ( Hays et al, 2017 ).…”

Thermophilic cyanobacteria—exciting, yet challenging biotechnological chassis

“…This is the simplest and most convenient way to introduce foreign DNA into cyanobacteria including thermophilic strains (Onai et al 2004). Secondly, there is conjugative transfer that relies on E. coli as a carrier of conjugative plasmids, such as RP4 or constructs based on RSF1010 origin of replication (Cui et al 2022) and subsequently delivers DNA through conjugation. The method is most established in UTEX 2973 that cannot be transformed using natural transformation protocol (Yu et al 2015).…”

Biological formation of ethylene

“…The industrial production of this gas leads to the emission of high levels of carbon dioxide and other greenhouse gases, 1 which has spurred interest in exploring alternative methods to make ethylene in a more sustainable manner from renewable sources. [2][3][4] Here, we describe four different approaches used in biology for the enzymatic synthesis of ethylene, focusing on the first two reactions.…”