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Isoamyl alcohol is a precursor of isoamyl acetate, an aromatic compound that imparts the ginjo aroma to sake. The isoamyl alcohol biosynthesis pathway in yeasts involves the genes PDC1 , PDC5 , PDC6 , ARO10 , and THI3 encoding enzymes that decarboxylate α-ketoisocaproic acid to isovaleraldehyde. Among these genes, THI3 is the main gene involved in isoamyl alcohol biosynthesis. Decreased production of isoamyl alcohol has been reported in yeast strains with disrupted THI 3 (Δ thi3). However, it has also been reported that high THI3 expression did not enhance decarboxylase activity. Therefore, the involvement of THI3 in isoamyl alcohol biosynthesis remains unclear. In this study, we investigated the role of THI3 in isoamyl alcohol biosynthesis. While reproducing previous reports of reduced isoamyl alcohol production by the Δ thi3 strain, we observed that the decrease in isoamyl alcohol production occurred only at low yeast nitrogen base concentrations in the medium. Upon investigating individual yeast nitrogen base components, we found that the isoamyl alcohol production by the Δ thi3 strain reduced when thiamine concentrations in the medium were low. Under low-thiamine conditions, both thiamine and thiamine diphosphate (TPP) levels decreased in Δ thi3 cells. We also found that the decarboxylase activity of cell-free extracts of the Δ thi3 strain cultured in a low-thiamine medium was lower than that of the wild-type strain, but was restored to the level of the wild-type strain when TPP was added. These results indicate that the loss of THI3 lowers the supply of TPP, a cofactor for decarboxylases, resulting in decreased isoamyl alcohol production. [ABSTRACT FROM AUTHOR]

For the enzymatic carboxylation of resorcinol to 2,6-dihydroxybenzoic acid (2,6-DHBA) using gaseous CO2 in an aqueous triethanolamine phase, an adsorption-based in situ product removal was demonstrated. The aim is to improve the reaction yield, which is limited by an unfavourable thermodynamic equilibrium. First, a screening for a high-affinity adsorber was carried out. Then, the application of a suitable adsorber was successfully demonstrated. This enabled achieving reaction yields above 80% using the adsorber for in situ product removal. The applied biotransformation was scaled up to 1.5 L at lab-scale. Furthermore, a downstream process based on the elution and purification of the product bound to the adsorber was developed to obtain 2,6-DHBA in high purity. Recycling is one of the key factors in this system, making it possible to recycle the reaction medium, the adsorber and the solvents in additional batches. [ABSTRACT FROM AUTHOR]

Benzoic acid decarboxylases offer an elegant alternative to CO2 fixation by reverse reaction-carboxylation, which is named the bio-Kolbe–Schmitt reaction, but they are unfavorable to carboxylation. Enhancing the carboxylation efficiency of reversible benzoic acid decarboxylases is restricted by the unexplained carboxylation mechanisms. The direction of reversible enzyme catalytic reactions depends on whether catalytic residues at the active center of the enzyme are protonated, which is subjected by the pH. Therefore, the forward and reverse reactions could be separated at different pH values. Reversible 2,3-dihydroxybenzoate acid decarboxylase undergoes decarboxylation at pH 5.0 and carboxylation at pH 8.6. However, it is unknown whether the interaction of enzymes with substrates and products in the forward and reverse reactions can be exploited to improve the catalytic activity of reversible enzymes in the unfavorable direction. Here, we identify a V-shaped tunnel of 2,3-dihydroxybenzoic acid decarboxylase from Aspergillus oryzae (2,3-DHBD_Ao) through which the substrate travels in the enzyme, and demonstrate that the side chain conformation of a tyrosine residue controls the entry and exit of substrate/product during reversible reactions. Together with the kinetic studies of the mutants, it is clarified that interactions between substrate/product traveling through the enzyme tunnel in 2,3-DHBD_Ao are direction-dependent. These results enrich the understanding of the interactions of substrates/products with macromolecular reversible enzymes in different reaction directions, thereby demonstrating a possible path for engineering decarboxylases with higher carboxylation efficiency. Key points: • The residue Trp23 of 2,3-DHBD_Ao served as a switch to control the entry and exit of catechol • A V-shaped tunnel of 2,3-DHBD_Ao for decarboxylation and carboxylation reactions was identified • The results provide a promising strategy for engineering decarboxylases with direction-dependent residues inside the substrate/product traveling tunnel of the enzyme [ABSTRACT FROM AUTHOR]

Enzymatic decarboxylation and carboxylation are emerging as prospective processes to produce high-value compounds under mild conditions. Ferulic acid decarboxylase Fdc1 catalyzes broad substrate tolerance against α, β-unsaturated carboxylic acids, and provides green routes for carbon dioxide fixation with the reversible carboxylation, while the activity of the enzyme is limited by the indispensable cofactor prenylated flavin (prFMN), which is unstable and is rarely detected in nature. In this study, a prFMN efficient synthesis route was built using six exogenous enzymes introduced into E. coli cells, leading to the construction of a powerful cell catalyst named SC-6. Based on the metabolic analysis, the results indicated that the reduction of FMN to FMNH2 was the bottleneck in prFMN synthesis pathway, and introducing FMN reductase increased the production of prFMN 3.8-fold compared with the common flavin prenyltransferase UbiX overexpression strain. Using SC-6 cell catalyst, the decarboxylation activity of Fdc1 increased more than 20 times with cinnamic acid and 4-acetoxycinnamic acid as substrates. Furthermore, the reversible carboxylation reaction was carried out, and the cell catalyst presented 20 times carbon dioxide fixation activity using styrene to produce cinnamic acid. Finally, the maximum yield of cinnamic acid catalyzed by SC-6 achieved 833.68 ± 34.51 mM·mg−1 in two hours. The constructed prFMN pathway in vivo provides fundamentals for efficient decarboxylation and carbon fixation reactions catalyzed by prFMN-dependent enzymes. [ABSTRACT FROM AUTHOR]

[Display omitted] • The mechanism of di-iron Pf UndA decarboxylase was studied by DFT calculations. • It involves O − O homolysis, H transfers, electron transfer, and C − C heterolysis. • A long-distance hydrogen abstraction is achieved by means of two bridging waters. • The drop of high-spin Fe(III)-O• to medium-spin Fe(IV) = O causes a low efficiency. • Pf UndA does not use a sMMO-like mechanism. Terminal olefins synthesized by the decarboxylation of fatty acids are important platform chemicals. Pf UndA is a nonheme di-iron oxidase capable of converting medium-chain (C 10 ∼ C 14) fatty acids into the corresponding 1-alkenes. Using density functional theory calculations, it is demonstrated that the Pf UndA-catalyzed lauric acid decarboxylation is initiated by introducing one pair of H+/e−. The subsequent reaction mainly involves the O − O bond dissociation, the partial interconversion between active high-spin Fe(III)-O• and inactive medium-spin Fe(IV) = O, the formation of triple-hydroxyl intermediates and substrate C β radical resulted from successive hydrogen transfers, the stepwise decarboxylation of substrate radical, and the protonation of Fe-bound hydroxides with H+ and e− added. Other mechanistic possibilities have been excluded. It is further found that the low catalytic efficiency of UndA may be due to the energy penalty caused by the drop of active high-spin Fe(III)-O• to a deeper minimum (inert medium-spin Fe(IV) = O). [ABSTRACT FROM AUTHOR]

Picolinic acid (PA) is a typical mono-carboxylated pyridine derivative produced by human/animals or microorganisms which could be served as nutrients for bacteria. Most Bordetella strains are pathogens causing pertussis or respiratory disease in humans and/or various animals. Previous studies indicated that Bordetella strains harbor the PA degradation pic gene cluster. However, the degradation of PA by Bordetella strains remains unknown. In this study, a reference strain of genus Bordetella, B. bronchiseptica RB50, was investigated. The organization of pic gene cluster of strain RB50 was found to be similar with that of Alcaligenes faecalis, in which the sequence similarities of each Pic proteins are between 60% to 80% except for PicB2 (47% similarity). The 3,6-dihydroxypicolinic acid (3,6DHPA) decarboxylase gene (BB0271, designated as picCRB50) of strain RB50 was synthesized and over-expressed in E. coli BL21(DE3). The PicCRB50 showed 75% amino acid similarities against known PicC from Alcaligenes faecalis. The purified PicCRB50 can efficiently transform 3,6DHPA to 2,5-dihydroxypyridine. The PicCRB50 exhibits optimal activities at pH 7.0, 35 °C, and the Km and kcat values of PicCRB50 for 3,6DHPA were 20.41 ± 2.60 μM and 7.61 ± 0.53 S−1, respectively. The present study provided new insights into the biodegradation of PA by pathogens of Bordetella spp. [ABSTRACT FROM AUTHOR]

Deciphering the mechanisms of bacterial fatty acid biosynthesis is crucial for both the engineering of bacterial hosts to produce fatty acid-derived molecules and the development of new antibiotics. However, gaps in our understanding of the initiation of fatty acid biosynthesis remain. Here, we demonstrate that the industrially relevant microbe Pseudomonas putida KT2440 contains three distinct pathways to initiate fatty acid biosynthesis. The first two routes employ conventional β-ketoacyl-ACP synthase III enzymes, FabH1 and FabH2, that accept short- and medium-chain-length acyl-CoAs, respectively. The third route utilizes a m alonyl- A CP d ecarboxylase enzyme, MadB. A combination of exhaustive in vivo alanine-scanning mutagenesis, in vitro biochemical characterization, X-ray crystallography, and computational modeling elucidate the presumptive mechanism of malonyl-ACP decarboxylation via MadB. Given that functional homologs of MadB are widespread throughout domain Bacteria, this ubiquitous alternative fatty acid initiation pathway provides new opportunities to target a range of biotechnology and biomedical applications. • P. putida KT2440 harbors three pathways to initiate fatty acid biosynthesis. • FabH1 and FabH2, are KASIII enzymes with differing specificity to acyl-CoAs. • The third pathway proceeds through MadB-catalyzed decarboxylation of malonyl-ACP. • MadB catalyzes its reaction by stabilizing the C3-carbonyl moiety of the substrate. • Functional homologs of MadB are prevalent in the domain Bacteria. [ABSTRACT FROM AUTHOR]

The ability to biosynthesize oxalic acid can provide beneficial functions to plants; however, uncontrolled or prolonged exposure to this strong organic acid results in multiple physiological problems. Such problems include a disruption of membrane integrity, mitochondrial function, metal chelation, and free radical formation. Recent work suggests that a CoA-dependent pathway of oxalate catabolism plays a critical role in regulating tissue oxalate concentrations in plants. Although this CoA-dependent pathway of oxalate catabolism is important, large gaps in our knowledge of the enzymes catalyzing each step remain. Evidence that an oxalyl-CoA decarboxylase (OXC) catalyzes the second step in this pathway, accelerating the conversion of oxalyl-CoA to formyl-CoA, has been reported. Induction studies revealed that OXC gene expression was upregulated in response to an exogenous oxalate supply. Phylogenetic analysis indicates that OXCs are conserved across plant species. Evolutionarily the plant OXCs can be separated into dicot and monocot classes. Multiple sequence alignments and molecular modeling suggest that OXCs have similar functionality with three conserved domains, the N-terminal PYR domain, the middle R domain, and the C-terminal PP domain. Further study of this CoA-dependent pathway of oxalate degradation would benefit efforts to develop new strategies to improve the nutrition quality of crops.

Biocatalytic cascades are uniquely powerful for the efficient, asymmetric synthesis of bioactive compounds. However, high substrate specificity can hinder the scope of biocatalytic cascades because the constituent enzymes may have non‐complementary activity. In this study, we implemented a substrate multiplexed screening (SUMS) based directed evolution approach to improve the substrate scope overlap between a transaldolase (ObiH) and a decarboxylase for the production of chiral 1,2‐amino alcohols. To generate a promiscuous cascade, we engineered a tryptophan decarboxylase to act efficiently on β‐OH amino acids while avoiding activity on l‐threonine, which is needed for ObiH activity. We leveraged this exquisite selectivity with matched substrate scope to produce a variety of enantiopure 1,2‐amino alcohols in a one‐pot cascade from aldehydes or styrene oxides. This demonstration shows how SUMS can be used to guide the development of promiscuous, C−C bond forming cascades. [ABSTRACT FROM AUTHOR]

ACMSD (α-amino-β-carboxymuconate-ε-semialdehyde decarboxylase) is a key metalloenzyme critical for regulating de novo endogenous NAD + /NADH biosynthesis through the tryptophan-kynurenine pathway. This decarboxylase is a recognized target implicated in mitochondrial diseases and neurodegenerative disorders. However, unraveling its enzyme-substrate complex has been challenging due to its high catalytic efficiency. Here, we present a combined biochemical and structural study wherein we determined the crystal structure of ACMSD in complex with malonate. Our analysis revealed significant rearrangements in the active site, particularly in residues crucial for ACMS decarboxylation, including Arg51, Arg239* (a residue from an adjacent subunit), His228, and Trp194. Docking modeling studies proposed a putative ACMS binding mode. Additionally, we found that ACMSD catalyzes oxaloacetic acid (OAA) tautomerization at a rate of 6.51 ± 0.42 s -1 but not decarboxylation. The isomerase activity of ACMSD on OAA warrants further investigation in future biological studies. Subsequent mutagenesis studies and crystallographic analysis of W194A variant shed light on the roles of specific second-coordination sphere residues. Our findings indicate that Arg51 and Arg239* are crucial for OAA tautomerization. Moreover, our comparative analysis with related isomerase superfamily members underscores a general strategy employing arginine residues to promote OAA isomerization. Given the observed isomerase activity of ACMSD on OAA and its structural similarity to ACMS, we propose that ACMSD may facilitate isomerization to ensure ACMS is in the optimal tautomeric form for subsequent decarboxylation initiated by the zinc-bound hydroxide ion. Overall, these findings deepen the understanding of the structure and function of ACMSD, offering insights into potential therapeutic interventions., Competing Interests: CONFLICT OF INTEREST The authors declare that they have no conflicts of interest with the contents of this article., (Copyright © 2024 The Authors. Published by Elsevier Inc. All rights reserved.)

Acid-adapted strains of Escherichia coli K-12 W3110 were obtained by serial culture in medium buffered at pH 4.6 (M. M. Harden, A. He, K. Creamer, M. W. Clark, I. Hamdallah, K. A. Martinez, R. L. Kresslein, S. P. Bush, and J. L. Slonczewski, Appl Environ Microbiol 81:1932-1941, 2015, https://doi.org/10.1128/AEM.03494-14). Revised genomic analysis of these strains revealed insertion sequence (IS)-driven insertions and deletions that knocked out regulators CadC (acid induction of lysine decarboxylase), GadX (acid induction of glutamate decarboxylase), and FNR (anaerobic regulator). Each acid-evolved strain showed loss of one or more amino acid decarboxylase systems, which normally help neutralize external acid (pH 5 to 6) and increase survival in extreme acid (pH 2). Strains from populations B11, H9, and F11 had an IS5 insertion or IS-mediated deletion in cadC, while population B11 had a point mutation affecting the arginine activator adiY The cadC and adiY mutants failed to neutralize acid in the presence of exogenous lysine or arginine. In strain B11-1, reversion of an rpoC (RNA polymerase) mutation partly restored arginine-dependent neutralization. All eight strains showed deletion or downregulation of the Gad acid fitness island. Strains with the Gad deletion lost the ability to produce GABA (gamma-aminobutyric acid) and failed to survive extreme acid. Transcriptome sequencing (RNA-seq) of strain B11-1 showed upregulated genes for catabolism of diverse substrates but downregulated acid stress genes (the biofilm regulator ariR, yhiM, and Gad). Other strains showed downregulation of H2 consumption mediated by hydrogenases (hya and hyb) which release acid. Strains F9-2 and F9-3 had a deletion of fnr and showed downregulation of FNR-dependent genes (dmsABC, frdABCD, hybABO, nikABCDE, and nrfAC). Overall, strains that had evolved in buffered acid showed loss or downregulation of systems that neutralize unbuffered acid and showed altered regulation of catabolism.IMPORTANCE Experimental evolution of an enteric bacterium under a narrow buffered range of acid pH leads to loss of genes that enhance fitness above or below the buffered pH range, including loss of enzymes that may raise external pH in the absence of buffer. Prominent modes of evolutionary change involve IS-mediated insertions and deletions that knock out key regulators. Over generations of acid stress, catabolism undergoes reregulation in ways that differ for each evolving strain.

Enzymatic decarboxylation and carboxylation are emerging as prospective processes to produce high-value compounds under mild conditions. Ferulic acid decarboxylase Fdc1 catalyzes broad substrate tolerance against α, β-unsaturated carboxylic acids, and provides green routes for carbon dioxide fixation with the reversible carboxylation, while the activity of the enzyme is limited by the indispensable cofactor prenylated flavin (prFMN), which is unstable and is rarely detected in nature. In this study, a prFMN efficient synthesis route was built using six exogenous enzymes introduced into E. coli cells, leading to the construction of a powerful cell catalyst named SC-6. Based on the metabolic analysis, the results indicated that the reduction of FMN to FMNH2 was the bottleneck in prFMN synthesis pathway, and introducing FMN reductase increased the production of prFMN 3.8-fold compared with the common flavin prenyltransferase UbiX overexpression strain. Using SC-6 cell catalyst, the decarboxylation activity of Fdc1 increased more than 20 times with cinnamic acid and 4-acetoxycinnamic acid as substrates. Furthermore, the reversible carboxylation reaction was carried out, and the cell catalyst presented 20 times carbon dioxide fixation activity using styrene to produce cinnamic acid. Finally, the maximum yield of cinnamic acid catalyzed by SC-6 achieved 833.68 ± 34.51 mM·mg−1 in two hours. The constructed prFMN pathway in vivo provides fundamentals for efficient decarboxylation and carbon fixation reactions catalyzed by prFMN-dependent enzymes.

Picolinic acid (PA) is a typical mono-carboxylated pyridine derivative produced by human/animals or microorganisms which could be served as nutrients for bacteria. Most Bordetella strains are pathogens causing pertussis or respiratory disease in humans and/or various animals. Previous studies indicated that Bordetella strains harbor the PA degradation pic gene cluster. However, the degradation of PA by Bordetella strains remains unknown. In this study, a reference strain of genus Bordetella, B. bronchiseptica RB50, was investigated. The organization of pic gene cluster of strain RB50 was found to be similar with that of Alcaligenes faecalis, in which the sequence similarities of each Pic proteins are between 60% to 80% except for PicB2 (47% similarity). The 3,6-dihydroxypicolinic acid (3,6DHPA) decarboxylase gene (BB0271, designated as picCRB50) of strain RB50 was synthesized and over-expressed in E. coli BL21(DE3). The PicCRB50 showed 75% amino acid similarities against known PicC from Alcaligenes faecalis. The purified PicCRB50 can efficiently transform 3,6DHPA to 2,5-dihydroxypyridine. The PicCRB50 exhibits optimal activities at pH 7.0, 35 °C, and the Km and kcat values of PicCRB50 for 3,6DHPA were 20.41 ± 2.60 μM and 7.61 ± 0.53 S−1, respectively. The present study provided new insights into the biodegradation of PA by pathogens of Bordetella spp.

Quantum chemical calculations are today an extremely valuable tool for studying enzymatic reaction mechanisms. In this mini-review, we summarize our recent work on several metal-dependent decarboxylases, where we used the so-called cluster approach to decipher the details of the reaction mechanisms, including elucidation of the identity of the metal cofactors and the origins of substrate specificity.Decarboxylases are of growing potential for biocatalytic applications, as they can be used in the synthesis of novel compounds of, e.g., pharmaceutical interest. They can also be employed in the reverse direction, providing a strategy to synthesize value‐added chemicals by CO2 fixation. A number of non-redox metal-dependent decarboxylases from the amidohydrolase superfamily have been demonstrated to have promiscuous carboxylation activities and have attracted great attention in the recent years. The computational mechanistic studies provide insights that are important for the further modification and utilization of these enzymes in industrial processes. The discussed enzymes are: 5‐carboxyvanillate decarboxylase, γ‐resorcylate decarboxylase, 2,3‐dihydroxybenzoic acid decarboxylase, and iso-orotate decarboxylase.

Human α-amino-β-carboxymuconate-ε-semialdehyde decarboxylase (ACMSD) stands at a branch point of the de novo NAD+ synthesis pathway and plays an important role in maintaining NAD+ homeostasis. It has been recently identified as a novel therapeutic target for a wide range of diseases, including inflammatory, metabolic disorders, and aging. So far, in absence of potent and selective enzyme inhibitors, only a crystal structure of the complex of human dimeric ACMSD with pseudo-substrate dipicolinic acid has been resolved. In this study, we report the crystal structure of the complex of human dimeric ACMSD with TES-1025, the first nanomolar inhibitor of this target, which shows a binding conformation different from the previously published predicted binding mode obtained by docking experiments. The inhibitor has a Ki value of 0.85 ± 0.22 nM and binds in the catalytic site, interacting with the Zn2+ metal ion and with residues belonging to both chains of the dimer. The results provide new structural information about the mechanism of inhibition exerted by a novel class of compounds on the ACMSD enzyme, a novel therapeutic target for liver and kidney diseases.

Abstract Background Histamine is a key mediator of the anti-inflammatory activity conferred by the probiotic organism Lactobacillus reuteri ATCC PTA 6475 in animal models of colitis and colorectal cancer. In L. reuteri, histamine synthesis and secretion requires l-histidine decarboxylase and a l-histidine/histamine exchanger. Chloride channel (ClC)-family proton/chloride antiporters have been proposed to act as electrochemical shunts in conjunction with amino acid decarboxylase systems, correcting ion imbalances generated by decarboxylation through fixed ratio exchange of two chloride ions for one proton. This family is unique among transporters by facilitating ion flux in either direction. Here we examine the histidine decarboxylase system in relation to ClC antiporters in the probiotic organism Lactobacillus reuteri. Results In silico analyses reveal that L. reuteri possesses two ClC transporters, EriC and EriC2, as well as a complete histidine decarboxylase gene cluster (HDC) for the synthesis and export of histamine. When the transport activity of either proton/chloride antiporter is disrupted by genetic manipulation, bacterial histamine output is reduced. Using fluorescent reporter assays, we further show that ClC transporters affect histamine output by altering intracellular pH and membrane potential. ClC transport also alters the expression and activity of two key HDC genes: the histidine decarboxylase (hdcA) and the histidine/histamine exchanger (hdcP). Conclusions Histamine production is a potentially beneficial feature for intestinal microbes by promoting long-term colonization and suppression of inflammation and host immune responses. ClC transporters may serve as tunable modulators for histamine production by L. reuteri and other gut microbes.

Bacterial outer membrane vesicles (OMVs) are small unilamellar proteoliposomes, involved in various functions including cell‐to‐cell signalling and protein excretion. We have engineered the OMVs of Escherichia coli to nano‐scaled bioreactors for the biotransformation of fatty acids by targeting a fatty acid double bond hydratase of Stentrophomonas maltophilia (SmOhyA) and/or a photoactivated fatty acid decarboxylase from Chlorella variabilis NC64 A (CvFAP) into OMVs. Engineered OMVs containing both SmOhyA and CvFAP were able to catalyse the transformation of oleic acid ((Z)‐octadec‐9‐enoic acid) into 9‐hydroxyheptadecane via (R)‐10‐hydroxyoctadecanoic acid. The specific biotransformation rates of oleic acid reached 8.0×10−12 μmol/min per OMV. [ABSTRACT FROM AUTHOR]

The epoxide-containing phosphonate natural product fosfomycin is a broad-spectrum antibiotic used in the treatment of cystitis. Fosfomycin is produced by both the plant pathogen Pseudomonas syringae and soil-dwelling streptomycetes. While the streptomycete pathway has recently been fully elucidated, the pseudomonad pathway is still mostly elusive. Through a systematic evaluation of heterologous expression of putative biosynthetic enzymes, we identified the central enzyme responsible for completing the biosynthetic pathway in pseudomonads. The missing transformation involves the oxidative decarboxylation of the intermediate 2-phosphonomethylmalate to a new intermediate, 3-oxo-4-phosphonobutanoate, by PsfC. Crystallographic studies reveal that PsfC unexpectedly belongs to a new class of diiron metalloenzymes that are part of the polymerase and histidinol phosphatase superfamily. [ABSTRACT FROM AUTHOR]

[Display omitted] • A novel biocatalytic CCU process for the production of carboxylic acids is proposed. • The process exploits pyrolytic phenols as electron-rich carboxylation substrates. • Integration of CO 2 enzymatic reactive absorption and phenols carboxylation is assessed. • Alternative process layouts yielding different degrees of CO 2 fixation are compared. • The proposed process is amenable for retrofitting of an existing capture plant. The search for less energy-intensive processes is pushing toward a diversification of Carbon-Capture and Utilization/Sequestration (CCU/S) pathways. Biocatalytic processes offer sustainable solutions characterized by extremely mild operating conditions. Over the last decade, post-combustion CO 2 capture based on enzymatic reactive absorption experienced remarkable growth from the laboratory to the demonstration scale. The present study explores a novel CCU concept based on phenol carboxylation catalyzed by cofactor-free decarboxylases. The design of the CCU process includes CO 2 capture by alkaline solvents boosted by carbonic anhydrase followed by bicarbonate fixation via enzymatic phenol carboxylation. Phenols generated from fractional pyrolysis of biomass were assumed as carboxylation substrates. Two process layouts have been developed and modelled, and reliable experimental data and kinetic model supported the computations. Simulated best cases prove to be feasible options for integrating the enzyme cascade with the conventional CO 2 absorption/desorption loop and lignocellulose biomass-derived substrates. [ABSTRACT FROM AUTHOR]