Efficient odd straight medium chain free fatty acid production by metabolically engineered Escherichia coli

Abstract

Free fatty acids (FFAs) can be used as precursors for the production of biofuels or chemicals. Different composition of FFAs will be useful for further modification of the biofuel/biochemical quality. Microbial biosynthesis of even chain FFAs can be achieved by introducing an acyl-acyl carrier protein thioesterase gene into E. coli. In this study, odd straight medium chain FFAs production was investigated by using metabolic engineered E. coli carrying acyl-ACP thioesterase (TE, Ricinus communis), propionyl-CoA synthase (Salmonella enterica), and β-ketoacyl-acyl carrier protein synthase III (four different sources) with supplement of extracellular propionate. By using these metabolically engineered E. coli, significant quantity of C13 and C15 odd straight-chain FFAs could be produced from glucose and propionate. The highest concentration of total odd straight chain FFAs attained was 1205 mg/L by the strain HWK201 (pXZ18, pBHE2), and 85% of the odd straight chain FFAs was C15. However, the highest percentage of odd straight chain FFAs was achieved by the strain HWK201 (pXZ18, pBHE3) of 83.2% at 48 h. This strategy was also applied successfully in strains carrying different TE, such as the medium length acyl-ACP thioesterase gene from Umbellularia californica. C11 and C13 became the major odd straight-chain FFAs.

Biosynthesis of odd-chain fatty alcohols in Escherichia coli

“…A few works have expanded free fatty acid (FFA) or alkane profile through manipulation of fabH gene in upstream fatty acids biosynthesis pathway (Harger et al, 2013;Howard et al, 2013;Wu and San, 2014). Microbial alkanes are normally odd chain length as the last reaction is decarbonylation that takes off one carbon from the intermediate fatty aldehydes (Lee et al, 2015) (Fig.…”

“…Addition of 6.5 mM propionate only increased the proportion of even chain alkane from 6% to 27%, which indicated that introduction of FabH2 alone did not have the expected effect of significantly changing the product profile. Although combination of heterogenous expression of propionyl-CoA synthase allowed high concentration (1205 mg/L) or high percentage (83.2%) of odd-chain fatty acids biosynthesis (Wu and San, 2014), extracellular propionate was still compulsory to be supplemented. These results suggest that fatty acids biosynthesis process is reluctant to be changed to directly produce unusual FFAs of odd or branched chain length.…”

Optimization of odd chain fatty acid production by Yarrowia lipolytica

“…A metabolic engineering strategy with propionate supplementation achieved a production of 0.276 g/L odd chain free fatty acids in E. coli [ 16 ]. In addition, further engineering of E. coli showed an increased percentage of odd chain free fatty acids in total free fatty acids by 6.25-fold with propionate supplementation [ 17 ]. Odd chain fatty acids have also been produced, with propionate supplementation, in both oleaginous yeasts ( Candida sp., Rhodotorula glutinis , Trichosporon cutaneum , Y. lipolytica , Cryptococcus curvatus ) and non-oleaginous yeast ( Kluyveromyces polysporus , Saccharomyces cerevisiae , Torulaspora delbrueckii ) [ 18 , 19 ].…”

Fatty Acyl Synthetases and Thioesterases in Plant Lipid Metabolism: Diverse Functions and Biotechnological Applications

“…These microbial systems are routinely used to characterize the enzymatic activities of various acyl-ACP thioesterases (Jha et al, 2010;Jing et al, 2011;Jones et al, 1995;Kalinger et al, 2018;Leonard et al, 1998;Pulsifer et al, 2012). Additional focus has also been placed on engineering these microbial systems for increased medium-chain fatty acid yield, and for improved utilization of abundant carbon sources (Cao et al, 2014;Fan et al, 2013;Goh et al, 2012;Goh et al, 2014;Lennen et al, 2011;Lin et al, 2018;Steen et al, 2010;Wu and Sun, 2014;Xu et al, 2019). Another major area of research interest surrounds the development of transgenic oilseed crops that incorporate medium-chain fatty acids into triacylglycerols by heterologously expressing medium-chain specific thioesterases from other plant species, such as the specialized FATB enzymes from Cuphea spp.…”