Monomer Of Nylon Research Articles

Rationally Engineering pH Adaptation of Acid-Induced Arginine Decarboxylase from Escherichia coli to Alkaline Environments to Efficiently Biosynthesize Putrescine.

Acid-induced arginine decarboxylase AdiA is a typical homo-oligomeric protein biosynthesizing alkaline nylon monomer putrescine. However, upon loss of the AdiA decamer oligomeric state at neutral and alkaline conditions the activity also diminishes, obstructing the whole-cell biosynthesis of alkaline putrescine. Here, a structure cohesion strategy is proposed to change the pH adaptation of AdiA to alkaline environments based on the rational engineering of meridional and latitudinal oligomerization interfaces. After integrating substitutions of E467K at the latitudinal interface and H736E at the meridional channel interface, the structural stability of AdiA decamer and its substrate transport efficiency at neutral and alkaline conditions are improved. Finally, E467K_H736E is well adapted to neutral and alkaline environments (pH 7.0-9.0), and its enzymatic activity is 35-fold higher than that of wild AdiA at pH 8.0. Using E467K_H736E in the putrescine synthesis pathway, the titer of putrescine is up to 128.9 g·L-1 with a conversion of 0.94 mol·mol-1 in whole-cell catalysis. Additionally, the neutral pH adaptation of lysine decarboxylase, with a decamer structure similar to AdiA, is also improved using this cohesion strategy, providing an option for pH-adaptation engineering of other oligomeric decarboxylases.

Redesigned Nylon 6 Variants with Enhanced Recyclability, Ductility, and Transparency.

Geminal (gem-) disubstitution in heterocyclic monomers is an effective strategy to enhance polymer chemical recyclability by lowering their ceiling temperatures. However, the effects of specific substitution patterns on the monomer's reactivity and the resulting polymer's properties are largely unexplored. Here we show that, by systematically installing gem-dimethyl groups onto ϵ-caprolactam (monomer of nylon 6) from the α to ϵ positions, both the redesigned lactam monomer's reactivity and the resulting gem-nylon 6's properties are highly sensitive to the substitution position, with the monomers ranging from non-polymerizable to polymerizable and the gem-nylon properties ranging from inferior to far superior to the parent nylon 6. Remarkably, the nylon 6 with the gem-dimethyls substituted at the γ position is amorphous and optically transparent, with a higher Tg (by 30 °C), yield stress (by 1.5 MPa), ductility (by 3×), and lower depolymerization temperature (by 60 °C) than conventional nylon 6.

Redesigned Nylon 6 Variants with Enhanced Recyclability, Ductility, and Transparency

AbstractGeminal (gem−) disubstitution in heterocyclic monomers is an effective strategy to enhance polymer chemical recyclability by lowering their ceiling temperatures. However, the effects of specific substitution patterns on the monomer's reactivity and the resulting polymer's properties are largely unexplored. Here we show that, by systematically installing gem‐dimethyl groups onto ϵ‐caprolactam (monomer of nylon 6) from the α to ϵ positions, both the redesigned lactam monomer's reactivity and the resulting gem‐nylon 6’s properties are highly sensitive to the substitution position, with the monomers ranging from non‐polymerizable to polymerizable and the gem‐nylon properties ranging from inferior to far superior to the parent nylon 6. Remarkably, the nylon 6 with the gem‐dimethyls substituted at the γ position is amorphous and optically transparent, with a higher Tg (by 30 °C), yield stress (by 1.5 MPa), ductility (by 3×), and lower depolymerization temperature (by 60 °C) than conventional nylon 6.

Development of a Thermodynamically Favorable Multi-enzyme Cascade Reaction for Efficient Sustainable Production of ω-Amino Fatty Acids and α,ω-Diamines.

Invited for this issue's cover is the group of Huilei Yu at the East China University of Science and Technology. The image shows a sustainable biosynthesis route to nylon monomers from bio-based substrate α, ω-dicarboxylic acids. The Research Article itself is available at 10.1002/cssc.202301477.

Long-Chain Bio-Based Nylon 514 Salt: Crystal Structure, Phase Transformation, and Polymerization.

Nylon 514 is one of the new long-chain bio-based nylon materials; its raw material, 1,5-pentanediamine (PDA), is prepared by biological techniques, using biomass as the raw material. The high-performance monomer of nylon 514, 1,5-pentanediamine-tetradecanedioate (PDA-TDA) salt, was obtained through efficient crystallization methods. Here, two crystal forms of PDA-TDA, anhydrous and dihydrate, were identified and studied in this paper. From the characterization data, their crystal structures and thermal behaviors were investigated. Lattice energy was calculated to gain further insight into the relationship between thermal stability and crystal structures. The contribution of hydrogen bonds and other intermolecular interactions to the crystal structure stability have been quantified according to detailed Hirshfeld and IRI analyses. Additionally, the transformation mechanism of the anhydrate and dihydrate was established through a series of well-designed stability experiments, in which the temperature and water activity play a significant role in the structural stability of crystalline forms. Eventually, we obtained nylon 514 products with good thermal stability and low absorption using stable dihydrate powders as monomers. The properties of nylon 514 products prepared by different polymerization methods were also compared.

Ionic liquids assisted synthesis of graphite carbon nitride for one-pot aerobic oxidation of cyclohexane to adipic acid

Adipic acid (AA) is a crucial intermediate in the production of nylon monomers, which is generally obtained by the oxidation of cyclohexane. However, difficult C-H activation and easy overoxidation make it extremely challenging to obtain highly selective AA. Herein, ionic liquid (IL) assisted synthesis of graphitic carbon nitride (g-C3N4) was designed for one-pot oxidation of cyclohexane to AA. The incorporation of C and S elements and the formation of N vacancies were brought with the presence of IL. 26.1% conversion and 51.2% AA selectivity were achieved over [Bmim][HSO4] (1-Butyl-3-methylimidazolium hydrogen sulfate) modified g-C3N4, which significantly increased AA selectivity by 18% compared to unmodified g-C3N4. The changes in electronic structure of g-C3N4 were assumed resposible for the improvement of AA selectivity by increasing the adsorption of cyclohexanone. Besides, the reduction of alkaline sites caused by the introduction of S atoms and N vacancies was benefit to remove AA avoiding excessive oxidation.

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.

Marine sponges as bioindicators of pollution by synthetic microfibers in Antarctica

Different marine sponge species from Tethys Bay, Antarctica, were analyzed for contamination by polyester and polyamide microplastics (MPs). The PISA (Polymer Identification and Specific Analysis) procedure was adopted as it provides, through depolymerization and HPLC analysis, highly sensitive mass-based quantitative data. The study focused on three analytes resulting from the hydrolytic depolymerization of polyesters and polyamides: terephthalic acid (TPA), 6-aminohexanoic acid (AHA), and 1–6-hexanediamine (HMDA). TPA is a comonomer found in the polyesters poly(ethylene terephthalate) (PET) and poly(butylene adipate co terephthalate) (PBAT), and in polyamides such as poly(1,4-p-phenylene terephthalamide) (Kevlar™ and Twaron™ fibers) and poly(hexamethylene terephthalamide) (nylon 6 T). AHA is the monomer of nylon 6. HMDA is a comonomer of the aliphatic nylon 6,6 (HMDA-co-adipic acid) and of semi-aromatic polyamides such as, again, nylon 6 T (HMDA-co-TPA). Except for the biodegradable PBAT, these polymers exhibit high to extreme mechanical, thermal and chemical resistance. Indeed, they are used as technofibers in protective clothing able to withstand extreme conditions as those typical of Antarctica. Of the two amine monomers, only HMDA was found above the limit of quantification, and only in specimens of Haliclona (Rhizoniera) scotti, at a concentration equivalent to 27 μg/kg of nylon 6,6 in the fresh sponge. Comparatively higher concentrations, corresponding to 2.5–4.1 mg/kg of either PBAT or PPTA, were calculated from the concentration of TPA detected in all sponge species. Unexpectedly, TPA did not originate from PET (the most common textile fiber) as it was detected in the acid hydrolysate, whereas the PISA procedure results in effective PET depolymerization only under alkaline conditions. The obtained results showed that sponges, by capturing and concentrating MPs from large volumes of filtered marine waters, may be considered as effective indicators of the level and type of pollution by MPs and provide early warnings of increasing levels of pollution even in remote areas.

Selective recovery of caprolactam from the thermo-catalytic conversion of textile waste over γ-Al2O3 supported metal catalysts

The massive generation of synthetic textile waste has drawn considerable attention. Landfilling/incineration of textile waste has been widely made. To abate the environmental burdensome from the conventional management processes, a thermo-catalytic conversion was used for rapid volume reduction of textile waste and simultaneous valorization by recovering textile monomer in this study. Stockings were chosen as a model feedstock. Because stockings consisted of nylon with other contents, different products (caprolactam (nylon monomer), imines, cyclic dimers, and azepines) were recovered. The yield of caprolactam from the thermal conversion at 500 °C was 53.6 wt%. To selectively enhance the caprolactam yield, catalytic pyrolysis was done using γ-Al2O3 supported metal catalysts (Ni, Cu, Fe, or Co). γ-Al2O3 itself increased the caprolactam yield up to 69.0 wt% via a based-catalyzed reaction of nylon depolymerization and intramolecular cyclization. Under the presence of metal catalysts, the caprolactam yield increased up to 73.3 wt%. To offer desired feature of green chemistry, CO2 was adopted as reactive gas. Under the CO2-mediated catalytic pyrolysis, caprolactam yield was enhanced up to 77.1 wt% over Cu/Al2O3 (basis: stocking mass). Based on the net content of nylon in the stockings, the yield of caprolactam was deemed 95.3 wt%. This study proves that textile waste (stocking) and CO2 are useful resources for recovery of nylon monomer, which can reduce the waste generation with simultaneous recovery of value-added product.

Multienzymatic synthesis of nylon monomers from vegetable oils

Nylons are important polyamide (PA) materials that can be polymerized from different monomers. Bio-based nylon monomers are traditionally obtained through chemical conversion from vegetable oils, but they can be more sustainably obtained through multienzymatic catalysis. For large-scale application of this process, enzyme engineering and process innovation must be combined.

Synthesis of renewable nylon monomers with poplar wood

The substitution of fossil energy with biomass as the feedstock for polymer production has drawn tremendous attention. Here, we describe a process for the synthesis of nylon monomers (3-methylglutaric acid [MGA], glutaric acid [GA], dimethyl adipate [DMAP], and dimethyl methyladipate [DMMAP]) with poplar wood. This process involves the selective hydrogenolysis of cellulose and hemicellulose into 2,5-hexanedione (HD) and cyclopentanone (CPO) in an acid-free system, the cascade intramolecular aldol condensation/hydrogenation of HD to 3-methylcyclopentanone (MCPO), and the catalytic oxidation of MCPO and CPO to GA and MGA (or a condensation/ring-opening reaction of MCPO and CPO to DMAP and DMMAP). Experiments reveal that the presence of Cl− ions restrains the decarbonylation and the furan-ring hydrogenation over the Pd/C catalyst, which leads to high selectivity of HD and CPO in the hydrogenolysis process. This work offers a new method for the direct conversion of raw biomass without the separation of cellulose, hemicellulose, and lignin.

Marine waste upcycling—recovery of nylon monomers from fishing net waste using seashell waste-derived catalysts in a CO2-mediated thermocatalytic process

A strategy for marine waste upcycling and CO2 utilization by the recovery of high-value monomer from fishing net waste using seashell waste-derived catalysts in the presence of CO2.

Energy-efficient thermal waste treatment process with no CO2 emission: A case study of waste tea bag

Everyday waste is a serious matter of concern because of its disruptive impact on the environment. Although disposal and reclaim of such material represent the first lines of intervention to solve this problem, upcycling strategies should eventually be necessary to reconvert huge amounts of the waste. In addition to waste, climate change caused by greenhouse gas emissions (e.g., carbon dioxide (CO2)) is other global environmental problem. Here, we employed a thermal treatment process conducted in CO2 environment to upcycle waste tea bag (a surrogate feedstock for everyday waste) and utilize CO2 simultaneously. Through lab-scale experiments, 6 wt% caprolactam (a value-added nylon monomer), 12.7 wt% combustible gases (higher heating value (HHV): 24.8 MJ kg−1), and 13.8 wt% char (HHV: 28.1 MJ kg−1) were obtained at 500 °C. Based on the experimental results, a large-scale energy analysis of the process was conducted by developing a simulation model of an integrated process to produce caprolactam-rich liquid product. For the integrated process, CO2 in gaseous product mixture is separated, and the separated CO2 is recirculated to the thermal treatment step. The combustible gases and char are used to supply energy to thermal treatment and separation steps. The proposed process has a significant feature that there is no need for external energy with no CO2 emission (i.e., CO2 is fully recirculated in the waste treatment process).

Coupling the fermentation and membrane separation process for polyamides monomer cadaverine production from feedstock lysine.

Nylon is a polyamide material with excellent performance used widely in the aviation and automobile industries, and other fields. Nylon monomers such as hexamethylene diamine and other monomers are in huge demand. Therefore, in order to expand the methods of nylon production, we tried to develop alternative bio‐manufacturing processes which would make a positive contribution to the nylon industry. In this study, the engineered E. coli‐overexpressing Lysine decarboxylases (LDCs) were used for the bioconversion of l‐lysine to cadaverine. An integrated fermentation and microfiltration (MF) process for high‐level cadaverine production by E. coli was established. Concentration was increased from 87 to 263.6 g/L cadaverine after six batch coupling with a productivity of 3.65 g/L‐h. The cadaverine concentration was also increased significantly from 0.43 g cadaverine/g l‐lysine to 0.88 g cadaverine/g l‐lysine by repeated batch fermentation. These experimental results indicate that coupling the fermentation and membrane separation process could benefit the continuous production of cadaverine at high levels.

Catalytic production of hexamethylenediamine from renewable feedstocks

Renewable biomass-derived chemicals have received considerable interest as a potential substitute for petroleum-derived chemicals. Hexamethylenediamine is a key intermediate in manufacturing nylon 66, a synthetic polymer that is broadly used in society. This article reviews the catalytic production of hexamethylenediamine from biomass-derived chemical feedstocks, and specifically the bio-based routes for obtaining hexamethylenediamine. While methods to directly convert biomass to hexamethylenediamine have yet to be commercialized, the use of heterogeneous catalytic systems via combined processes appears to be a promising and emerging chemical pathway to achieve this goal. Current proposed routes for the renewable production of hexamethylenediamine are not yet entirely competitive with petrochemical production techniques, predominantly because of low efficiency and high cost. However, many opportunities exist to advance technologies that exploit renewable and bio-based feedstocks to generate hexamethylenediamine. Thus, the commercialization of biomass-derived nylon monomers appears achievable in the near future.

A multi-enzyme cascade reaction for the production of α,ω-dicarboxylic acids from free fatty acids

α,ω-Dicarboxylic acids (α,ω-DCAs) have numerous applications, as raw materials for producing various commodities and polymers in chemical industry. For example, dodecanedioic acid (DDDA), a monomer of nylon 612 polymer is used for numerous applications such as plasticizers and adhesive. In this study, firstly the enzymatic production of DDDA from corresponding ω-hydroxy fatty acid was optimized using aldehyde reductase (AHR) and aldehyde dehydrogenase (ALDH), and the cofactor imbalance and proficient regeneration thereof, is a major hurdle for the effective biosynthesis. To circumvent this, NAD(P)H oxidases (NOXs) from Lactobacillus brevis (LbrNOX), Brevibacterium glutamicum (BreNOX) and Lactobacillus reuteri (LreNOX) were examined for the AHR/ALDH/NOX cascade and LreNOX was identified as suitable enzyme. Moreover, LreNOX was fused with AHR and employing this fusion protein in Escherichia. coli (E. coli) holding ALDH, nearly complete conversion (>99%) into DDDA was achieved from 30mM of 12-hydroxy dodecanoic acid within 12h of whole-cell biotransformation (2.2-fold improvement in productivity) turning out to be beneficial. Finally, the synthesis of DDDA from corresponding free fatty acid (dodecanoic acid), was performed by employing combination of AHR/ALDH/NOX cascade with CYP153AL.m, where 2.3mM (0.53g/L) of DDDA was produced in one-pot one step.

Upcycling of waste teabags via catalytic pyrolysis in carbon dioxide over HZSM-11

Disruptive impact of everyday waste on the environment makes it a serious growing concern. Even though disposal and reclaim strategies are firstly considered to overcome this problem, upcycling of the waste via thermochemical transformations (e.g., pyrolysis) will eventually be essential to reconvert massive quantities of waste materials. Here, to seek a method to valorize everyday waste, the effects of CO2 and HZSM-11 catalyst on pyrolytic products produced via pyrolysis of waste teabag were investigated. For non-catalytic pyrolysis of waste teabag, CO2 increased the yield of pyrolytic gases and suppressed the formation of benzenes, phenolics, and polycyclic aromatic hydrocarbons, compared to N2. For catalytic pyrolysis of waste teabag over HZSM-11 more CO2 was transformed to CO than non-catalytic pyrolysis. The extent of CO2 conversion into CO was greater in CO2 environment than in N2 environment. A synergistical use of CO2 and HZSM-11 in pyrolysis of waste teabag enhanced the production of caprolactam (6.8 wt% yield), a value-added nylon monomer. The char derived from waste teabag via the pyrolysis in CO2 over HZSM-11 had higher heating value of 26 MJ kg−1 comparable to HHV of coal. The synergistical employment of HZSM-11 catalyst and CO2 pyrolysis medium has a significant feature of upcycling everyday waste such as waste teabag.

One-pot biocatalytic synthesis of nylon monomers from cyclohexanol usingEscherichia coli-based concurrent cascade consortia

We developed a multienzyme biocatalytic cascade with high atom efficiency and a self-sufficient redox network for the synthesis of nylon monomers without adding auxiliary enzymes to recycle cofactors.

Economically-feasible production of a nylon monomer using RANEY® catalysts

This research was aimed at developing an economically-feasible process to produce a value-added chemical used to synthesize nylon, hexamethylenediamine (HMDA), by hydrogenating adiponitrile (ADN) using an inexpensive catalyst such as RANEY® Ni or RANEY® Co.

An Integrated Cofactor/Co-Product Recycling Cascade for the Biosynthesis of Nylon Monomers from Cycloalkylamines.

We report a highly atom-efficient integrated cofactor/co-product recycling cascade employing cycloalkylamines as multifaceted starting materials for the synthesis of nylon building blocks. Reactions using E. coli whole cells as well as purified enzymes produced excellent conversions ranging from >80 and 95 % into desired ω-amino acids, respectively with varying substrate concentrations. The applicability of this tandem biocatalytic cascade was demonstrated to produce the corresponding lactams by employing engineered biocatalysts. For instance, ϵ-caprolactam, a valuable polymer building block was synthesized with 75 % conversion from 10 mM cyclohexylamine by employing whole-cell biocatalysts. This cascade could be an alternative for bio-based production of ω-amino acids and corresponding lactam compounds.