Abstract
Phenol is an important petrochemical that is conventionally used as a precursor for synthesizing an array of plastics and fine chemicals. As an emerging alternative to its traditional petrochemical production, multiple enzyme pathways have been engineered to date to enable its renewable biosynthesis from biomass feedstocks, each incorporating unique enzyme chemistries and intermediate molecules. Leveraging all three of the unique phenol biosynthesis pathways reported to date, a series of synthetic ‘metabolic funnels’ was engineered, each with the goal of maximizing net precursor assimilation and flux towards phenol via the parallel co-expression of multiple distinct pathways within the same Escherichia coli host. By constructing and evaluating all possible binary and tertiary pathway combinations, one ‘funnel’ was ultimately identified, which supported enhanced phenol production relative to all three individual pathways by 16 to 69%. Further host engineering to increase endogenous precursor availability then allowed for 26% greater phenol production, reaching a final titer of 554 ± 19 mg/L and 28.8 ± 0.34 mg/g yield on glucose. Lastly, using a diphasic culture including dibutyl phthalate for in situ phenol extraction, final titers were further increased to a maximum of 812 ± 145 mg/L at a yield of 40.6 ± 7.2 mg/g. The demonstrated ‘funneling’ pathway holds similar promise in support of phenol production by other, non-E. coli hosts, while this general approach can be readily extended towards a diversity of other value-added bioproducts of interest.
Highlights
As it has been estimated that roughly 40% of bulk petrochemicals possess at least one or more aromatic functional groups [1], aromatic chemicals clearly represent an important class of molecules, which predominantly serve as precursors for diverse synthetic applications
Among aromatic bioproduction targets investigated to date is phenol—a bulk chemical and building-block molecule used in the synthesis of various fine chemicals as well as many plastics and polymers [9,10]
Inspired by natural ‘funneling’ mechanisms used by various microbes to degrade aromatic compounds [16,17], we recently developed a synthetic ‘metabolic funnel’ to enInspired by natural ‘funneling’ mechanisms used by various microbes to degrade hance muconic acid production in E. coli [18]
Summary
The complete microbial biosynthesis of phenol was first demonstrated and is still commonly achieved from endogenous tyrosine via the expression of heterologous tyrosine phenol lyase (TPL; Pathway 1, Figure 1) [11,12]. In addition to this established route, in efforts to help improve phenol biosynthesis, alternative pathways for phenol biosynthesis have recently been reported. This includes two different pathways derived from endogenous chorismate, each involving different downstream enzyme chemistries and associated intermediates.
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
