Synthetic metabolic pathway for the production of 1-alkenes from lignin-derived molecules

Abstract

BackgroundIntegration of synthetic metabolic pathways to catabolically diverse chassis provides new opportunities for sustainable production. One attractive scenario is the use of abundant waste material to produce a readily collectable product, which can reduce the production costs. Towards that end, we established a cellular platform for the production of semivolatile medium-chain α-olefins from lignin-derived molecules: we constructed 1-undecene synthesis pathway in Acinetobacter baylyi ADP1 using ferulate, a lignin-derived model compound, as the sole carbon source for both cell growth and product synthesis.ResultsIn order to overcome the toxicity of ferulate, we first applied adaptive laboratory evolution to A. baylyi ADP1, resulting in a highly ferulate-tolerant strain. The adapted strain exhibited robust growth in 100 mM ferulate while the growth of the wild type strain was completely inhibited. Next, we expressed two heterologous enzymes in the wild type strain to confer 1-undecene production from glucose: a fatty acid decarboxylase UndA from Pseudomonas putida, and a thioesterase ‘TesA from Escherichia coli. Finally, we constructed the 1-undecene synthesis pathway in the ferulate-tolerant strain. The engineered cells were able to produce biomass and 1-undecene solely from ferulate, and excreted the product directly to the culture headspace.ConclusionsIn this study, we employed a bacterium Acinetobacter baylyi ADP1 to integrate a natural aromatics degrading pathway to a synthetic production route, allowing the upgradation of lignin derived molecules to value-added products. We developed a highly ferulate-tolerant strain and established the biosynthesis of an industrially relevant chemical, 1-undecene, solely from the lignin-derived model compound. This study reports the production of alkenes from lignin derived molecules for the first time and demonstrates the potential of lignin as a sustainable resource in the bio-based synthesis of valuable products.Electronic supplementary materialThe online version of this article (10.1186/s12934-019-1097-x) contains supplementary material, which is available to authorized users.

Alkane and wax ester production from lignin‐related aromatic compounds

“…To obtain higher tolerance toward inhibitory substrates, strain optimization could be applied through adaptation and laboratory evolution (Dragosits & Mattanovich, ) or by genetic engineering. In a recent study by Luo, Lehtinen, Efimova, Santala, and Santala (), the tolerance of A. baylyi ADP1 toward ferulate was increased up to 180 mM by adaptive laboratory evolution. For example, Benndorf, Loffhagen, and Babel () showed that by inducing Acinetobacter calcoaceticus 69‐V ( A. baylyi previously referred to as A. calcoaceticus ) with 14 mM of phenols or catechols heat shock proteins were produced to increase tolerance toward oxidative stress.…”

“…Therefore, using substrates such as LRAs pose a challenge for wax ester production and preservation due to their inhibitory effects at elevated concentrations. Unspecific strategies, such as adaptive laboratory evolution could allow the use of higher substrate concentrations (Luo et al, ).…”

Towards bioproduction of poly-α-olefins from lignocellulose

“…[10][11][12][13][14] It is tolerant towards lignocellulose related monomeric compounds, such as phenolic acids, acetate, and ethanol, which typically inhibit microbial growth. [15][16][17][18] Furthermore, it can utilize monomeric lignin compounds through catabolic β-ketoadipate pathway, which efficiently funnels carbon to biomass and storage compound synthesis. 17,19,20 The Acinetobacter genera and A. baylyi ADP1 have also been identified with lignin depolymerizing activities.…”

Hydro(deoxygenation) Reaction Network of Lignocellulosic Oxygenates

“…In microbial oxygen removal, medium‐ to long‐chain hydrocarbons are the target molecules; these are semivolatile compounds, which turns collection from a culture vessel without cell harvesting or production extraction into a reality . In such a microbial process, the resulting molecules may accumulate extracellularly and may be collected from the culture vessel without harvesting of cells.…”

“…Natural fatty acid metabolism in microorganisms through a synthetic route offers the formation of 1‐undecene from glucose. In such a process, a decarboxylase enzyme acts as an oxygen activator, which results in the corresponding terminal alkene . Deoxygenation occurs through the route of one‐step fatty acid decarboxylation of FFAs, which is catalyzed by UndA for the production of 1‐undecene.…”