Production Of Adipic Acid Research Articles

Developing a new process for adipic acid production

Developing a new process for adipic acid production

Microbial production of adipic acid from 6-hydroxyhexanoic acid for biocatalytic upcycling of polycaprolactone

To valorize waste polycaprolactone (PCL), one of the most widely used biodegradable plastics, into a value-added chemical, we upcycled 6-hydroxyhexanoic acid (6-HHA), the sole monomer of PCL, into adipic acid (AA) using a microbial method. Recombinant Escherichia coli strains expressing chnD (6-HHA dehydrogenase) and chnE (6-oxohexanoic acid dehydrogenase) genes from three bacteria were constructed, and all these strains successfully produced AA from 6-HHA. Among these, the E. coli strain harboring ChnDE genes from Acinetobacter strain SE19 (E. coli [pKK-AcChn]) showed the highest AA-producing ability. To increase the AA production titer, we optimized the culture temperature of this strain in flask culture and performed fed-batch fermentation in a 5 L bioreactor. After the fed-batch fermentation, the AA production titer increased to 15.6 g/L. As 6-HHA is a monomer of PCL, our results provide the groundwork for the development of a biocatalytic upcycling method of PCL.

Coordinated reprogramming of ATP metabolism strongly enhances adipic acid production in Escherichia coli

Maintaining a delicate balance of adenosine-5′-triphosphate (ATP) is crucial not only for optimal cellular functions but also for improved metabolite production, indicating the need for careful regulation of ATP demands in metabolic engineering. This study explored the modification of ATP metabolism to enhance adipic acid production in Escherichia coli, focusing on the reverse adipate degradation pathway (RADP), and ATP-consuming cycles were fine-tuned by controlling the overexpression of genes (panK and acs) to balance ATP consumption and adipic acid production. As a result, we successfully achieved a significant increase (19.5-fold) in adipic acid production, reaching 1,093.11 mg/L in a shake flask, compared to that in the control strain (wild-type E. coli harboring the RADP). Our transcriptomic analysis indicated that modulation of ATP metabolism, along with a balanced supply of pathway precursors, affects metabolic fluxes, enhancing adipic acid biosynthesis in E. coli. This study suggests the potential of metabolic reprogramming of ATP to meet biosynthetic demands, which may improve the production of adipic acid and other ATP-derived chemicals.

Production of bio-based adipic acid using a combination of engineered Pseudomonas putida strains

Adipic acid is an industrially important dicarboxylic acid and an essential precursor in the synthesis of Nylon-6,6. Due to the environmental impact associated with the current synthetic methods for Nylon-6,6 production, greener alternatives based on renewable and bio-based feedstocks are needed. In the present study, the potential of two Pseudomonas putida strains engineered for muconic acid accumulation was used to produce adipic acid from the lignin-derived aromatic compound guaiacol. This was achieved by expressing genes enabling the conversion of guaiacol to catechol in the first strain, and the conversion of muconic acid to adipic acid via expression of the Bacillus coagulans enoate reductase gene in the second strain. Through process engineering, a 2-step production was designed in which 2.93 mM bio-adipic acid was produced, with a yield of 0.57 mol/mol. This is the first demonstration that process and strain engineering can be combined to obtain a complete bio-based route for adipic acid production from depolymerized lignin compounds using the robust P. putida chassis.

Tin-Based Keggin-Type Phosphomolybdate and Silicomolybdate as Catalysts for the Green Synthesis of Adipic Acid

The catalytic activity of two series of Keggin-type salts of formula Cs4-xSnxSiMo12O40 (x: 0.5 and 1) and Cs3-xSnxPMo12O40 (x: 0.25-1) was examined in the liquid phase cyclohexanone oxidation to adipic acid (AA) in the solvent absence. The materials were prepared and characterized by FTIR, UV-Vis and SEM. The adipic acid synthesis was carried out at 90°C in presence of hydrogen peroxide (30%), a green oxidant that produces only water as by-product. The effects of catalyst/substrate molar ratios and time reaction on dipic acid yields were studied. The results of this study showed that the POM-H2O2 system was found to be efficient for the production of adipic acid from the oxidation of cyclohexanone and the yields were closely dependent on the operating conditions. The highest AA yield (55%) was obtained with Cs2Sn0.5PMo12O40 using a catalyst/substrate molar ratio of 3.7×10-3 and a reaction time of 20h.

Influence of Catalyst Surface Structure on the Electrochemical Hydrogenation of Cis,Cis-Muconic Acid

Adipic acid (AA) production from petroleum-based cyclohexane is one of the largest chemical processes in terms of annual volumetric turnover accounting for 3 million tons as of 2022. The current commercial approach to synthesize AA is through the oxidation of petroleum-derived cyclohexane using nitric acid. The release of N2O in stoichiometric amounts makes it one of the most significant greenhouse gas (GhG) emitting processes. The abundance of biomass in the Midwestern United States has driven significant research efforts to synthesize bio-derived and sustainable commodity products and lower the chemical industry’s carbon footprint.1 cis,cis-Muconic acid (ccMA), a biobased C6 diunsaturated diacid platform molecule can be transformed to commodity chemicals like caprolactam, adipic acid, and terephthalic acid, with AA being of particular interest for the synthesis of nylon 6,6.2 For the first time in literature, we demonstrate appreciable production of AA (conversion: 91%, selectivity: >95%) through electrochemical hydrogenation (ECH) of ccMA on PGM catalysts. Carbon-supported palladium (Pd/C) and platinum (Pt/C) selectively produced AA while bulk Pd and Pt yielded the monounsaturated trans-3-hexenedioic acid (t3HDA) intermediate and H2 under all tested conditions. Such an influence of surface structure on the electrochemistry of organics is not unprecedented. Koper et. al3 studied Pt single crystals for the electrochemical hydrogenation of acetone and showed how activity, selectivity, and extent of catalytic poisoning are highly sensitive to the Pt surface structure. Similarly, we used density functional calculations to elucidate the structure-sensitive nature of ccMA ECH and its intermediates by identifying thermodynamically preferred reaction pathways as a function of surface geometry (terrace vs steps). The energetics coupled with experimental observations suggest that the reduction of ccMA to t3HDA occurs through an outer sphere proton-coupled electron transfer mechanism, while the reduction of HDA to AA preferentially occurs on Pd and Pt (111), the most abundant facet in Pd/C and Pt/C. Our calculations also explain the exceptional performance of Pd/C compared to Pt/C by the weaker binding of Pd terrace sites compared to Pt. Overall, combining renewable electricity, in-situ hydrogen generation from water, and a biologically-produced intermediate enabled us to open a sustainable route for bio-adipic acid production. This allows us to further design and optimize the catalyst for the selective production of biobased AA.

Reactive extraction of muconic acid by hydrophobic phosphonium ionic liquids - Experimental, modelling and optimisation with Artificial Neural Networks

Muconic acid is a six-carbon dicarboxylic acid with conjugated double bonds that finds extensive use in the food (additive), chemical (production of adipic acid, monomer for functional resins and bio-plastics), and pharmaceutical sectors. The biosynthesis of muconic acid has been the subject of recent industrial and scientific attention. However, because of its low concentration in aqueous solutions and high purity requirement, downstream separation presents a significant problem. Artificial Neural Networks and Differential Evolution were used to optimize process parameters for the recovery of muconic acid from aqueous streams in a system with n-heptane as an organic diluent and ionic liquids as extractants. The system using 120 g/L tri-hexyl-tetra-decyl-phosphonium decanoate dissolved in n-heptane, pH of the aqueous phase 3, 20 min contact time, and 45 °C temperature assured a muconic acid extraction efficiency of 99,24 %. Low stripping efficiency compared to extraction efficiency was observed for the optimum conditions on the extraction step (120 g/L ionic liquids dissolved in heptane). However, re-extraction efficiencies obtained for the recycled organic phase in three consecutive stages were close to the first extraction stage. The mechanism analysis proved that the analysed phosphonium ionic liquids (PILSs) extracts only undissociated molecules of muconic acid through H-bonding.

Oxoammonium salt mediated conversion of cyclohexylamine toward cyclohexanone with water as the oxygen source

Cyclohexylamine is a key byproduct during the production of cyclohexanone oxime, which is an important bulk chemical in material industry. Here we report a highly efficient approach to oxidize cyclohexylamine toward cyclohexanone with oxoammonium salt as the oxidant and water as the oxygen source, which has non-involvement of metal catalyst. The obtained cyclohexanone is an important raw material for both cyclohexanone oxime and adipic acid production. On basis of control experiments, mass spectrometry, and product analysis, the essential role of water as oxygen source and the reaction mechanism were elucidated. Moreover, the recycling of the oxoammonium salt succeeded to convert another proportion of the substrate. These findings offer new insights and methods for the oxidative conversion of cyclohexylamine.

Computational redesign of an enoate reductase for the in vivo production of adipic acid from muconic acid

Computational redesign of an enoate reductase for the in vivo production of adipic acid from muconic acid

Sustainable Adipic Acid Production via Paired Electrolysis of Lignin-Derived Phenolic Compounds with Water as Hydrogen and Oxygen Sources.

Adipic acid (AA) is an important feedstock for nylon polymers and is industrially produced from fossil-derived aromatics via thermocatalysis. However, this process consumes explosive H2 and corrosive HNO3 as reductants and oxidants, respectively. Here, we report the direct synthesis of AA from lignin-derived phenolic compounds via paired electrolysis using bimetallic cooperative catalysts. At the cathode, phenol is hydrogenated on PtAu catalysts to form ketone-alcohol (KA) oil with 92% yield and 43% Faradaic efficiency (FE). At the anode, KA is electrooxidized into AA on CuCo2O4 catalysts, achieving a maximum of 85% yield and 84% FE. Experimental and theoretical studies reveal that the excellent catalytic activity can be ascribed to the enhanced absorption and activation capability of reactants on the bimetallic cooperative catalysts. A two-electrode flow electrolyzer for AA synthesis realizes a stable electrolysis at 2.5 A for over 200 h as well as 38.5% yield and 70.2% selectivity. This study offers a green and sustainable route for AA synthesis from lignin via paired electrolysis.

Enhancing the activity and succinyl-CoA specificity of 3-ketoacyl-CoA thiolase Tfu_0875 through rational binding pocket engineering

The 3-ketoacyl-CoA thiolase is the rate-limiting enzyme for linear dicarboxylic acids production. However, the promiscuous substrate specificity and suboptimal catalytic performance have restricted its application. Here we present both biochemical and structural analyses of a high-efficiency 3-ketoacyl-CoA thiolase Tfu_0875. Notably, Tfu_0875 displayed heightened activity and substrate specificity for succinyl-CoA, a key precursor in adipic acid production. To enhance its performance, a deep learning approach (DLKcat) was employed to identify effective mutants, and a computational strategy, known as the greedy accumulated strategy for protein engineering (GRAPE), was used to accumulate these effective mutants. Among the mutants, Tfu_0875N249W/L163H/E217L exhibited the highest specific activity (320% of wild-type Tfu_0875), the greatest catalytic efficiency (kcat/KM = 1.00 min−1mM−1), the highest succinyl-CoA specificity (KM = 0.59 mM, 28.1% of Tfu_0875) and dramatically reduced substrate binding energy (−30.25 kcal mol−1v.s. −15.94 kcal mol−1). A structural comparison between Tfu_0875N249W/L163H/E217L and the wild type Tfu_0875 revealed that the increased interaction between the enzyme and succinyl-CoA was the primary reason for the enhanced enzyme activity. This interaction facilitated rapid substrate anchoring and stabilization. Furthermore, a reduced binding pocket volume improved substrate specificity by enhancing the complementarity between the binding pocket and the substrate in stereo conformation. Finally, our rationally designed mutant, Tfu_0875N249W/L163H/E217L, increased the adipic acid titer by 1.35-fold compared to the wild type Tfu_0875 in shake flask. The demonstrated enzymatic methods provide a promising enzyme variant for the adipic acid production. The above effective substrate binding pocket engineering strategy can be beneficial for the production of other industrially competitive biobased chemicals when be applied to other thiolases.

Efficient hydrodeoxygenation of tetrahydrofuran 2,5-dicarboxylic acid to adipic acid over Pt-MOx catalysts: An experimental and computational study

The production of adipic acid (AA) from the ring-opening hydrogenolysis (hydrodeoxygenation - HDO) of tetrahydrofuran 2,5-dicarboxylic acid (THFDCA) by metal-metal oxide catalysts (Pt-MOx/TiO2 and Pt/MOx) was evaluated. Correlations between AA yield, or products distribution, and the type of active centers in the catalyst surface were established by studying the type (MOx: WOx, MoOx, and ZrOx), the amount of metal oxide (MOx:Pt molar ratio), and the reaction temperature (180ºC, 220ºC, and 240ºC) in Pt-MOx/TiO2 and Pt/MOx. The activity results show that only the catalysts that contain both Pt and Mo produced AA at 220ºC, with yields of 24% for Pt-MoOx/TiO2 (4 wt% Pt, 1:1 Mo:Pt molar ratio) and 34% for 4 wt% Pt/MoO3. At 180ºC, these catalysts exhibited high selectivity towards reducing the carboxyl group. Computational studies using DFT suggest that this behavior is due to the preferential interaction between the oxygen vacancy (O-VAC) in MoO3 and the CO bond in the carboxyl group in 2-hydroxyadipic acid (2-HAA), the first observed intermediate from the HDO of THFDCA. Coverage of this adsorption configuration decreases at temperatures above 200ºC, where the interaction between the alcohol group in the 2 C position in 2-HAA and the Brønsted acid site (BAS) on the surface of MoO3 is preferred. This latter interaction could promote the acid-catalyzed dehydration of the alcohol group to obtain AA. Increasing the amount of Mo to 5:1 Mo:Pt in Pt-MoOx/TiO2 and decreasing the Pt content to 0.1 wt % in Pt/MoO3 decreases the selectivity to alcohols, increasing the AA yield to 55% at 220ºC and 65% at 240ºC for both catalysts. This enhancement in performance is consistent with the findings from the DFT studies. To our knowledge, this is the highest yield reported for AA production from THFDCA or FDCA by metal-metal oxide catalysts.

Depolymerization of the polyester-polyurethane by amidase GatA250 and enhancing the production of 4,4'-methylenedianiline with cutinase LCC.

Polyurethane (PU) is a complex polymer synthesized from polyols and isocyanates. It contains urethane bonds that resist hydrolysis, which decreases the efficiency of biodegradation. In this study, we first expressed the amidase GatA250, and then, assessed the enzymatic characterization of GatA250 and its efficiency in degrading the polyester-PU. GatA250 degraded self-synthesized thermoplastic PU film and postconsumption foam with degradation efficiency of 8.17% and 4.29%, respectively. During the degradation, the film released 14.8µm 4,4'-methylenedianiline (MDA), but 1,4-butanediol (BDO) and adipic acid (AA) were not released. Our findings indicated that GatA250 only cleaved urethane bonds in PU, and the degradation efficiency was extremely low. Hence, we introduced the cutinase LCC, which possesses hydrolytic activity on the ester bonds in PU, and then used both enzymes simultaneously to degrade the polyester-PU. The combined system (LCC-GatA250) had higher degradation efficiency for the degradation of PU film (42.2%) and foam (13.94%). The combined system also showed a 1.80 time increase in the production of the monomer MDA, and a 1.23 and 3.62 times increase in the production of AA and BDO, respectively, compared to their production recorded after treatment with only GatA250 or LCC. This study provides valuable insights into PU pollution control and also proposes applicable solutions to manage PU wastes through bio-recycling.

Density Functional Theory Study of Mechanism of Reduction of N2O by CO over Fe-ZSM-5 Zeolites

Nitrous oxide (N2O) is an industrial waste gas (e.g., from the production of adipic acid), which damages the ozone layer and causes the greenhouse effect. Density functional theory calculations were employed to investigate the mechanism of direct catalytic decomposition of N2O and selective catalytic reduction (SCR) of N2O by CO over Fe-ZSM-5 zeolites. Two stable Fe-active sites with six-membered ring structures on Fe-ZSM-5 were considered. The calculations indicate that the decomposition of N2O is affected by the coordination environment around Fe and can occur through two reaction pathways. However, there is invariably a more considerable energy hurdle for the initiation of the second stage of N2O decomposition. When CO participated in the reaction, it showed good reactivity and stability, the reaction energy barriers of the rate-limiting step were reduced by roughly 20.57 kcal/mol compared to the direct catalytic decomposition of N2O. CO exhibited a superior electron-donating ability and orbital hybridization performance during the reaction, which enhanced the cyclicity of the N2O reduction catalytic process. Our calculations confirmed the significant role of CO in N2O reduction over Fe-ZSM-5 observed in previous studies. This study provides a valuable theoretical reference for exploring CO-SCR methods for N2O reduction over Fe-based zeolite catalysts.

Bioprocess development and scale-up for cis,cis-muconic acid production from glucose and xylose by Pseudomonas putida

Bioprocess development enhanced muconate titers and productivities from mixed sugars, leading to reduced production costs and a significant decrease in GHG emissions compared to fossil carbon-based adipic acid production. Created with BioRender.com.

Graphdiyne as an Electron Modifier for Boosting Electrochemical Production of Adipic Acid

AbstractAdipic acid (AA) is a crucial feedstock for nylon polymers, and is industrially produced by thermal oxidation of cyclohexanone/cyclohexanol mixture (KA oil). However, this process consumes large quantities of corrosive nitric acid as oxidants, while emits ozone‐depleting greenhouse gas N2O. Here, an electrocatalytic strategy for selective oxidation of KA oil to AA coupled with H2 evolution over a Co3O4/graphdiyne cooperative catalyst (Co3O4/GDY) is reported. The Co3O4/GDY displays high electrooxidation activity of KA oil to AA (100 mA cm−2 at ≈1.5 V vs RHE), outperforming all the reported findings. Detailed ex situ and in situ experimental studies, theoretical calculations, and molecular dynamic simulations reveal that GDY not only facilitates the enrichment of cyclohexanone on the catalyst surface in aqueous medium, but also upshifts the d‐band center of Co sites, strengthening the adsorption/activation of cyclohexanone. This study offers a green route for AA synthesis and proposes a GDY interface engineering strategy for efficient electrooxidation.

Highly efficient one-pot aerobic oxidation of cyclohexane to adipic acid using task-specific metal-based ionic liquid

Adipic acid is a significant building block of polymers and is manufactured on a massive scale, primarily to produce nylon. However, the current route depends heavily on using corrosive HNO3 while releasing N2O as a potent greenhouse gas. Herein, we developed an efficient strategy for the highly selective aerobic oxidation of cyclohexane into adipic acid using metal-based ionic liquid as a catalyst. Particularly, the optimised catalyst 1-carboxymethyl-3-methylimidazolium chloride cobalt exhibited a high selectivity towards adipic acid (73.9%). It was discovered that the electron-donating ability of anions and the electrostatic between cations and anions could influence the charge density of Co(II) by anion coordination and then influence the oxidation performance. Meanwhile, the hydrogen bond interaction between the hydrogen-bond donor groups of the IL and cyclohexanone, as well as between the hydrogen-bond donor groups of the IL and the carboxylic radicals could promote the formation of adipic acid. This simple, efficient and green protocol has great potential for industrial applications in adipic acid production.

Glutaric acid purification by coupled solution crystallization and melt crystallization

The mixed dibasic acids (DBA) is a by-product during adipic acid (ADA) production by oxidation of cyclohexanol or cyclohexanone, which contains large amount of glutaric acid (GA) with ADA and succinic acid (SA). In this work, we have explored the feasibility of the coupled solution crystallization and melt crystallization for the purification of GA. To obtain fundamental thermodynamic properties for the process design, the gravimetric method was used to measure the solubility of the three dibasic acids in water from 293.15 K to 345.15 K at atmospheric pressure. The results showed that GA was the most soluble component while all solubility increased with increasing temperature. Therefore, it is reasonable to concentrate GA in the liquid phase by cooling crystallization. Similarly, the ternary solid-liquid melt equilibrium phase diagram was constructed based on the experimental data of the three binary subsystems (GA-ADA, GA-SA, ADA-SA). It was found that the concentrated GA after solvent evaporation could be purified by melt crystallization efficiently. Thus a coupled solution crystallization and melt crystallization process was designed. With the operated operating parameters, the purity of GA could reach 99.06% by secondary melt crystallization. Overall, the coupled solution crystallization and melt crystallization method to separate DBA has proven to be effective.

In Silico Design of Engineering Optimization via OptHandle for Effective Synthesis of Adipic Acid Precursor, α-Aminoadipate

The green biosynthesis of adipic acid, an important monomer of nylon 6,6, has become a research hotspot. α-Aminoadipate is a key intermediate in the metabolic pathway that converts L-lysine to produce adipic acid. In addition, metabolic flux analysis has become an important part of metabolic engineering. Many metabolic optimization algorithms have been developed to predict engineering intervention strategies with the aim of improving the production of target chemicals. Here, OptHandle, a new metabolic optimization algorithm, has been developed. And, we use OptHandle to optimize the biosynthesis of α-aminoadipate. Based on the results of OptHandle, an engineered Escherichia coli with a 13-fold higher titer was obtained, and 1.10 ± 0.02 g/L of α-aminoadipate was produced. The efficient synthesis of α-aminoadipate lays a foundation for the green production of adipic acid.

A critical review of multiple alternative pathways for the production of a high-value bioproduct from sugarcane mill byproducts: the case of adipic acid

Biobased fuels, chemicals, and materials can replace fossil fuel products and mitigate climate change. Sugarcane mills have the potential to produce a wider range of biobased chemicals in a similar approach to bioethanol production, including adipic acid. Multiple alternative pathways for converting simple sugars into adipic acid have been described, with the potential for integration into a sugar mill. The economics and expected greenhouse gas emissions reductions compared to fossil-based adipic acid were investigated in the present study to identify preferred pathways for implementation in sugarcane biorefineries. Nine biobased pathways for adipic acid production were screened for technical performances, resulting in the selection of four preferred options for rigorous comparison, i.e., direct microbial conversion of sugars, and production via cis,cis-muconic acid, glucaric acid, and glycerol as intermediate, obtained from sugars. The minimum selling prices of adipic acid for an attractive return on investment were determined for these pathways, using either A-molasses or a combination of A-molasses and pretreated sugarcane lignocelluloses in biorefineries designed to be energy-self-sufficient. Adipic acid production from A-molasses via cis,cis-muconic acid was the best overall performing scenario with the lowest minimum selling price of USD 2,538/Mt and lowered greenhouse gas emissions (2,325 g CO2 eq/kg wet) compared to fossil-based adipic acid production. The scenarios with combined A-molasses and lignocellulosic feedstock had increased minimum selling prices by 29 to 101% compared to adipic acid production from A molasses via cis,cis-muconic acid.