Improved biosynthesis of 2,5-Furandicarboxylic acid through coupling of heterologous pathways in Escherichia coli and native pathways in Pseudomonas putida

Characterisation and Harnessing of 5-Hydroxymethylfurfural Metabolism in Pseudomonas umsongensis GO16 for the Production of 2,5-Furandicarboxylic Acid

In the search for biobased alternatives to traditional fossil plastics, 2,5-furandicarboxylic acid (FDCA) represents a potential substitute to terephthalic acid (TPA), a monomer of the ubiquitous polyester, polyethylene terephthalate (PET). Pseudomonas umsongensis GO16, which can metabolise TPA and ethylene glycol (EG), can also oxidise 5-hydroxymethylfurfural (HMF), a precursor to FDCA. The enzymes involved in the oxidation to FDCA, PsfA and PsfG, were identified and characterised. Deletion of FDCA decarboxylase HmfF involved in the conversion of FDCA to furoic acid, and subsequently to a central metabolic intermediate, 2-ketoglutarate, allowed for the accumulation of FDCA. GO16 ΔhmfF cells were grown on glycerol, TPA, EG or mock PET hydrolysate, and the catalyst was then used for the biotransformation of HMF to FDCA. When TPA was used as a growth substrate and to power the biotransformation, the transport of 5-hydroxymethyl-2-furancarboxylic acid (HMFCA) into the cytoplasm represented a rate-limiting step in HMF oxidation. De-bottlenecking transport limitations through in trans overexpression of the HMFCA transporter (HmfT) along with the PsfA aldehyde dehydrogenase and PsfG alcohol dehydrogenase allowed 100% conversion of 50 mM HMF to FDCA within 24 h when TPA, EG or mock PET hydrolysate were used to grow the biocatalyst and subsequently to power the biotransformation. This expands the repertoire of valuable products obtained from engineered P. umsongensis GO16 in the strategy to bio-upcycle post-consumer PET.

Efficient bio-oxidation of biomass-derived furan-2,5-dicarbaldehyde to 5-formyl-2-furoic acid and 2,5-furandicarboxylic acid via whole-cell biocatalysis

The production of bio-based fine chemicals is increasingly important to address fossil energy shortages, climate change, and other environmental issues. Using abundant and renewable bioresource as starting material to manufacture bio-based fine chemicals will achieve a green circular economy. 5-Formyl-2-furoic acid (FFCA) and 2,5-furandicarboxylic acid (FDCA) have broad application prospects in fuels, chemical intermediates, polymers and pharmaceuticals. In this research, a green and effectual biotransformation process was built to manufacture FFCA and FDCA from biomass-derived furan-2,5-dicarbaldehyde (DFF) in DMSO-H2O using recombinant Escherichia coli cells carrying AAOase (aryl-alcohol oxidase) as biocatalyst. Under mild performance conditions, FFCA could be produced from 75 mM DFF in a high yield (92.3 %) within 24 h. 25 mM DFF was fully oxidized to FDCA within 24 h. The research established an effectual biocatalytic system for transforming HMF-derived DFF with AAOase biocatalysts into valuable biomass-derived products. This study holds great promising for sustainably synthesizing FFCA and FDCA.

Engineering an Mn(II)-oxidizing Pseudomonas whole-cell catalyst chassis to efficiently biosynthesize 2,5-furandicarboxylic acid from hydroxymethylfurfural

2,5-Furandicarboxylic acid (FDCA) is a high-value chemical extensively used in the production of bio-based polymers, but bioconversion of furan derivatives like 5-hydroxymethylfurfural (HMF) into FDCA remains challenging owing to substrate cytotoxicity. Here, we engineered an Mn(II)-oxidizing Pseudomonas sp. MB04B for efficient FDCA biosynthesis from HMF. We deleted 4.6 % of the MB04B genome to generate the engineered MB04C-6 chassis, then introduced two exogenous gene cassettes, PMP00-hmfH and PJ23119-hmfH'. Using the resulting MB04C-6/pHMF as a whole-cell catalyst, optimizing the reaction system, and incorporating CaCO3 increased the FDCA yield by approximately 63.4-fold compared to MB04C-6. We also enhanced the CRISPR-associated transposases system for single-step chromosomal integration of exogenous genes. The optimal chassis strain MB04S-HMF8, rapidly produced 97 mmol/L FDCA from 100 mmol/L HMF in 12 h, with an FDCA production rate of 1.26 g L-1h-1, showcasing its potential as a robust, cost-effective, and environmentally sustainable whole-cell biocatalyst for industrial-scale FDCA production.

Biocatalysis enables the scalable conversion of biobased furans into various furfurylamines

Biobased furans have emerged as chemical building blocks for the development of materials because of their diverse scaffolds and as they can be directly prepared from sugars. However, selective, efficient, and cost-effective scalable conversion of biobased furans remains elusive. Here, we report a robust transaminase (TA) from Shimia marina (SMTA) that enables the scalable amination of biobased furanaldehydes with high activity and broad substrate specificity. Crystallographic and mutagenesis analyses provide mechanistic insights and a structural basis for understanding SMTA, which enables a higher substrate conversion. The enzymatic cascade process established in this study allows one-pot synthesis of 2,5-bis(aminomethyl)furan (BAMF) and 5-(aminomethyl)furan-2-carboxylic acid from 5-hydroxymethylfurfural. The biosynthesis of various furfurylamines, including a one-pot cascade reaction for BAMF generation using whole cells, demonstrates their practical application in the pharmaceutical and polymer industries.

Engineering 5-hydroxymethylfurfural (HMF) oxidation in Pseudomonas boosts tolerance and accelerates 2,5-furandicarboxylic acid (FDCA) production

Due to its tolerance properties, Pseudomonas has gained particular interest as host for oxidative upgrading of the toxic aldehyde 5-hydroxymethylfurfural (HMF) into 2,5-furandicarboxylic acid (FDCA), a promising biobased alternative to terephthalate in polyesters. However, until now, the native enzymes responsible for aldehyde oxidation are unknown. Here, we report the identification of the primary HMF-converting enzymes of P. taiwanensis VLB120 and P. putida KT2440 by extended gene deletions. The key players in HMF oxidation are a molybdenum-dependent periplasmic oxidoreductase and a cytoplasmic dehydrogenase. Deletion of the corresponding genes almost completely abolished HMF oxidation, leading instead to aldehyde reduction. In this context, two HMF-reducing dehydrogenases were also revealed. These discoveries enabled enhancement of Pseudomonas' furanic aldehyde oxidation machinery by genomic overexpression of the respective genes. The resulting BOX strains (Boosted OXidation) represent superior hosts for biotechnological synthesis of FDCA from HMF. The increased oxidation rates provide greatly elevated HMF tolerance, thus tackling one of the major drawbacks of whole-cell catalysis with this aldehyde. Furthermore, the ROX (Reduced OXidation) and ROAR (Reduced Oxidation And Reduction) deletion mutants offer a solid foundation for future development of Pseudomonads as biotechnological chassis notably for scenarios where rapid HMF conversion is undesirable.

Current Advances in the Sustainable Conversion of 5-Hydroxymethylfurfural into 2,5-Furandicarboxylic Acid

2,5-Furandicarboxylic acid (FDCA) is currently considered one of the most relevant bio-sourced building blocks, representing a fully sustainable competitor for terephthalic acid as well as the main component in green polymers such as poly(ethylene 2,5-furandicarboxylate) (PEF). The oxidation of biobased 5-hydroxymethylfurfural (HMF) represents the most straightforward approach to obtain FDCA, thus attracting the attention of both academia and industries, as testified by Avantium with the creation of a new plant expected to produce 5000 tons per year. Several approaches allow the oxidation of HMF to FDCA. Metal-mediated homogeneous and heterogeneous catalysis, metal-free catalysis, electrochemical approaches, light-mediated procedures, as well as biocatalytic processes share the target to achieve FDCA in high yield and mild conditions. This Review aims to give an up-to-date overview of the current developments in the main synthetic pathways to obtain FDCA from HMF, with a specific focus on process sustainability.

Enzymatic Cascade for the Synthesis of 2,5-Furandicarboxylic Acid in Biphasic and Microaqueous Conditions: 'Media-Agnostic' Biocatalysts for Biorefineries

5-hydroxymethylfurfural (HMF) is produced upon dehydration of C6 sugars in biorefineries. As the product, it remains either in aqueous solutions, or is in situ extracted to an organic medium (biphasic system). For the subsequent oxidation of HMF to 2,5-furandicarboxylic acid (FDCA), 'media-agnostic' catalysts that can be efficiently used in different conditions, from aqueous to biphasic, and to organic (microaqueous) media, are of interest. Here, the concept of a one-pot biocatalytic cascade for production of FDCA from HMF was reported, using galactose oxidase (GalOx) for the formation of 2,5-diformylfuran (DFF), followed by the lipase-mediated peracid oxidation of DFF to FDCA. GalOx maintained its catalytic activity upon exposure to a range of organic solvents with only 1 % (v/v) of water. The oxidation of HMF to 2,5-diformylfuran (DFF) was successfully established in ethyl acetate-based biphasic or microaqueous systems. To validate the concept, the reaction was conducted at 5 % (v/v) water, and integrated in a cascade where DFF was subsequently oxidized to FDCA in a reaction catalyzed by Candida antarctica lipase B.

Whole Cell Biocatalysis of 5-Hydroxymethylfurfural for Sustainable Biorefineries

The implementation of cost-effective and sustainable biorefineries to substitute the petroleum-based economy is dependent on coupling the production of bioenergy with high-value chemicals. For this purpose, the US Department of Energy identified a group of key target compounds to be produced from renewable biomass. Among them, 5-hydroxymethylfurfural (HMF) can be obtained by dehydration of the hexoses present in biomass and is an extremely versatile molecule that can be further converted into a wide range of higher value compounds. HMF derivatives include 2,5-bis(hydroxymethyl)furan (BHMF), 5-hydroxymethyl-furan-2-carboxylic acid (HMFCA), 2,5-diformylfuran (DFF), 5-formyl-2-furancarboxylic acid (FFCA) and 2,5-furandicarboxylic acid (FDCA), all presenting valuable applications, in polymers, bioplastics and pharmaceuticals. Biocatalysis conversion of HMF into its derivatives emerges as a green alternative, taking into account the high selectivity of enzymes and the mild reaction conditions used. Considering these factors, this work reviews the use of microorganisms as whole-cell biocatalysts for the production of HMF derivatives. In the last years, a large number of whole-cell biocatalysts have been discovered and developed for HMF conversion into BHMF, FDCA and HMFCA, however there are no reports on microbial production of DFF and FFCA. While the production of BHMF and HMFCA mainly relies on wild type microorganisms, FDCA production, which requires multiple bioconversion steps from HMF, is strongly dependent on genetic engineering strategies. Together, the information gathered supports the possibility for the development of cell factories to produce high-value compounds, envisioning economical viable biorefineries.

New (and Old) Monomers from Biorefineries to Make Polymer Chemistry More Sustainable

This opinion article describes recent approaches to use the "biorefinery" concept to lower the carbon footprint of typical mass polymers, by replacing parts of the fossil monomers with similar or even the same monomer made from regrowing dendritic biomass. Herein, the new and green catalytic synthetic routes are for lactic acid (LA), isosorbide (IS), 2,5-furandicarboxylic acid (FDCA), and p-xylene (pXL). Furthermore, the synthesis of two unconventional lignocellulosic biomass derivable monomers, i.e., α-methylene-γ-valerolactone (MeGVL) and levoglucosenol (LG), are presented. All those have the potential to enter in a cost-effective way, also the mass market and thereby recover lost areas for polymer materials. The differences of catalytic unit operations of the biorefinery are also discussed and the challenges that must be addressed along the synthesis path of each monomers.