Aromatic Products Research Articles

Improved biosynthesis of tyrosol by epigenetic modification-based regulation and metabolic engineering in Saccharomyces cerevisiae.

Aromatic amino acids and their derivatives are high value chemicals widely used in food, pharmaceutical and feed industries. Current preparation methods for aromatic amino acid products are fraught with limitations. In this study, the efficient biosynthesis of aromatic amino acid compound tyrosol was investigated by epigenetic modification-based regulation and optimization of the biosynthetic pathway of aromatic amino acids. The production of tyrosol was significantly improved by the overexpression of m6A modification writer Ime4 and reader Pho92, and the positive regulator Gcr2. Introduction of Bbxfpk and deletion of Gpp1 further improved tyrosol production. Then the feedback inhibition of the shikimate pathway was relieved by the mutants Aro4K229L and Aro7G141S. The final tyrosol producing engineered strain was constructed by the deletion of PHA2, replacement of the native promoter of ARO10 with the strong promoter PGK1p, and introduction of tyrosine decarboxylase PcAAS. In the background of m6A modification regulation, this strain ultimately produced 954.69 ± 43.72 mg/L of tyrosol, promoted by 61.7-fold in shake-flask fermentation.

Discovery of ketene/acetyl as a potential receptor for hydrogen-transfer reactions in zeolites

Hydrogen-transfer is the primary process responsible for elevating the degree of unsaturation of intermediates in zeolite-catalyzed methanol-to-hydrocarbon reactions, with olefins serving as the typical receptor and alkanes being produced as the by-product. Intriguingly, the introduction of CO was shown to suppress the selectivity of alkanes and enhance the production of aromatics, yet microscopic understanding of this phenomenon remains elusive. Here, based on ab initio molecular dynamics simulations and free energy sampling methods, we discover a non-olefin-induced hydrogen-transfer reaction in the presence of CO, with ketene/acetyl emerging as a more suitable hydrogen-transfer receptor than olefins. This predominant route enhances the degree of unsaturation of olefins without generating additional alkanes, and the produced dienes and acetaldehyde could further contribute to the formation of aromatics. Moreover, we construct a general mechanism applicable to a series of CO-coupled aromatics synthesis reactions, offering distinctive insights and strategies for the optimization of efficiency.

MultiT2: A Tool Connecting the Multimodal Data for Bacterial Aromatic Polyketide Natural Products

MultiT2: A Tool Connecting the Multimodal Data for Bacterial Aromatic Polyketide Natural Products

Involvement of inorganic nitrogen species (NOX- (x=2, 3)) in the degradation of organic contaminants in environmental waters via UV irradiation or chemical oxidation: A dual-edged approach.

OH-mediated advanced oxidation processes (AOPs) are widely used in wastewater treatment and drinking water purification. Recently, an increasing number of studies have indicated that common inorganic nitrogen ions can efficiently generate •OH under UV irradiation, demonstrating strong performance in the degradation of various contaminants. Conversely, the presence of inorganic nitrogen ions in UV or other oxidation processes dramatically increases the yield of toxic nitro (so)-aromatic products and the formation potential of nitrogenous disinfection by-products with high genotoxicity and cytotoxicity. This suggests that the presence of inorganic nitrogen ions in water and wastewater treatment is a 'double-edged sword', offering both benefits and potential harms. Herein, we systematically review the dual roles of inorganic nitrogen ions in contaminant degradation and nitrogenous by-product formation. First, the degradation kinetics of the UV/NOx- (x=2, 3) and oxidant/NO2- processes are summarized for various contaminants. The pseudo-first-order rate constants (kpfo) of contaminant degradation in the UV/NO3- system range from 10-3 to 10-1min-1, while those in the UV/NO2- and peracetic acid/NO2- system vary from 10-3 to 102min-1 and 10-2 to 10-1min-1, respectively. Moreover, the properties of the water matrix (i.e., pH and O2) play a crucial role in the degradation kinetics by influencing the concentrations and distribution of reactive nitrogen species (RNS), as well as the morphology of the contaminants. Second, this review provides a general overview of the sources and properties of key RNS, including •NO2, ONOO-/ONOOH, and free nitrous acid (FNA), which are closely associated with the formation of nitrogenous by-products. Finally, the formation pathways of nitro (so)-aromatic products and nitrogenous disinfection by-products are discussed. These pathways are driven either by RNS alone or by the combination of RNS with reactive oxygen species (ROS).

Fine tuning enzyme activity assays for monitoring the enzymatic hydrolysis of PET

Efficient monitoring of the enzymatic PET-hydrolysis is crucial for developing novel plastic-degrading biocatalysts. Herein, we aimed to upgrade in terms of accuracy the analytical methods useful for monitoring enzymatic PET-degradation. For the HPLC-based assessment, the incorporation of an internal standard within the analytic procedure enabled a more accurate quantification of the overall TPA content and the assessment of molar distributions and relative content of each aromatic degradation product. The provided calibration curves cover a broad concentration range, from µM to low mM scale, facilitating assessment of both lower and higher PETase activities, with a limit of detection positioned below the reported PET-degrading activities. The increased reproducibility and accuracy of the improved HPLC method, compared to the previous methods, was supported by lower dispersion of product concentrations and their lower deviation from theoretical values over multiple measurements. The other predominantly employed UV-spectroscopy assay was also improved in terms of employed wavelength and medium extinction coefficient of the three aromatic degradation products, while being cross-validated by the improved HPLC method. Finally, both methods were used for monitoring the product formation within the leaf-branch compost cutinase (LCC)-mediated PET-hydrolysis and provided individual time-productivity profiles for each aromatic degradation product.

Engineered Passive Glucose Uptake in Pseudomonas taiwanensis VLB120 Increases Resource Efficiency for Bioproduction.

Glucose is the most abundant monosaccharide and a principal substrate in biotechnological production processes. In Pseudomonas, this sugar is either imported directly into the cytosol or first oxidised to gluconate in the periplasm. While gluconate is taken up via a proton-driven symporter, the import of glucose is mediated by an ABC-type transporter, and hence both require energy. In this study, we heterologously expressed the energy-independent glucose facilitator protein (Glf) from Zymomonas mobilis to replace the native energy-demanding glucose transport systems, thereby increasing the metabolic energy efficiency. The implementation of passive glucose uptake in engineered production strains significantly increased product titres and yields of the two different aromatic products, cinnamic acid (+10%-15%) and resveratrol (+26%; 18.1 mg/g) in batch cultures.

Highly efficient oxidative cleavage of lignin β-O-4 linkages via synergistic Co-CoOx/N-doped carbon and recyclable hexaniobate catalysis

Co-CoOx/N-doped carbon combined with the recyclable base K7HNb6O19 synergistically catalyze the selective and rapid cleavage of lignin β-O-4 models into aromatic products.

Hierarchical ZSM-5 nanosheets for production of light olefins and aromatics by catalytic cracking of oleic acid

The bolaform surfactant C6H13-N+(CH3)2-C6H12-N+(CH3)2-C6H12-O-C6H4-C6H4-O-C6H12-N+(CH3)2-C6H12-N+(CH3)2-C6H13 (BCPH-6-6-6) was synthesized and used to guide the synthesis of hierarchical ZSM-5 nanosheets (HZN) for use as zeolite catalysts.

Arabidopsis 3-Deoxy-d-Arabino-Heptulosonate 7-Phosphate (DAHP) Synthases of the Shikimate Pathway Display Both Manganese- and Cobalt-Dependent Activities.

The plant shikimate pathway directs a significant portion of photosynthetically assimilated carbon into the downstream biosynthetic pathways of aromatic amino acids (AAA) and aromatic natural products. 3-Deoxy-d-arabino-heptulosonate 7-phosphate (DAHP) synthase (hereafter DHS) catalyzes the first step of the shikimate pathway, playing a critical role in controlling the carbon flux from central carbon metabolism into the AAA biosynthesis. Previous biochemical studies suggested the presence of manganese- and cobalt-dependent DHS enzymes (DHS-Mn and DHS-Co, respectively) in various plant species. Unlike well-studied DHS-Mn, however, the identity of DHS-Co is still unknown. Here, we show that all three DHS isoforms of Arabidopsis thaliana exhibit both DHS-Mn and DHS-Co activities invitro. A phylogenetic analysis of various DHS orthologs and related sequences showed that Arabidopsis 3-deoxy-D-manno-octulosonate-8-phosphate synthase (KDOPS) proteins were closely related to microbial Type I DHSs. Despite their sequence similarity, these Arabidopsis KDOPS proteins showed no DHS activity. Meanwhile, optimization of the DHS assay conditions led to the successful detection of DHS-Co activity from Arabidopsis DHS recombinant proteins. Compared with DHS-Mn, DHS-Co activity displayed the same redox dependency but distinct optimal pH and cofactor sensitivity. Our work provides biochemical evidence that the DHS isoforms of Arabidopsis possess DHS-Co activity.

Rosa damascena Mill. Essential Oil: Analysis of In Vitro and In Vivo Genotoxic and Cytotoxic Potentials by Employing Three Cytogenetic Endpoints.

The highly valued oil of Rosa damascena Mill. (Rosaceae), widely used in high perfumery, cosmetics, and other spheres of human life, obliges us to know and study the safety profile of the product obtained from the water-steam distillation of fresh rose petals. The genotoxicity of the essential oil (EsO) has not been thoroughly studied despite its wide range of applications. That predetermined the object of this study-to evaluate, through classical cytogenetic methods, the possible cytotoxic/genotoxic activities of R. damascena Mill. EsO (EsORdm) in three different test systems: plant root meristem cells, mammalian bone marrow cells, and human lymphocyte cultures. The rose essential oil showed varying concentration- and time-dependent cytotoxic and genotoxic effects depending on the test system used, and it was established that the oil showed moderate cytotoxicity in lymphocyte cultures and non-high cytotoxicity in ICR mice but none in barley. Both barley and human lymphocytes showed a genotoxic effect with a dose-dependent increase in chromosomal aberrations (CAs) and a substantial rise in micronucleus (MN) frequency, while no genotoxicity was observed in bone marrow cells at the applied concentrations. Human lymphocytes exhibited the highest susceptibility to cytotoxic and genotoxic actions of the EsO. As a valuable plant-derived aromatic product with versatile uses in human life, R. damascena Mill. essential oil should be used in an appropriate concentration range tailored to cellular sensitivity.

Effect of Organic Manures on Growth and Yield Attributes of Citronella Java (Cymbopogon winterianus) under Moringa (Moringa oleifera) based Agroforestry and Open-field Systems

A field investigation was conducted to evaluate the effects of farmyard manure (FYM) vermicompost and neem-cake on the growth and yield of citronella java (Cymbopogon winterianus) under moringa-based agroforestry and open-field systems during 2022 and 2023. Growth parameters like plant height, number of leaves per plant and number of tillers per plant and yield attributing parameters like fresh weight (kg ha-1), Dry Weight (kg ha-1) and total herbage yield (t ha-1). The findings highlight the superior performance of the treatment combining FYM, vermicompost, and neem cake (T13), particularly in shaded conditions provided by moringa trees, which created a favourable microclimate. This study demonstrates the significant role of integrated organic amendments in enhancing citronella productivity while fostering environmental sustainability. The findings offer valuable insights for farmers and policymakers, advocating for the adoption of sustainable practices in aromatic crop production through agroforestry systems.

Synthesis of Hollow Zn/ZSM-5 Nanosheets via Different Alkali Treatments with ZIF-8 as a Zn Source for Efficient Aromatization of Methanol.

Diffusion limitations and monofunctional acidity of ZSM-5 molecular sieves affect the catalyst stability and aromatic yield in the reaction of methanol to aromatics (MTA). In this study, based on ZSM-5 nanosheets as parent molecular sieves, Zn-modified hollow ZSM-5 nanosheets were obtained after hydrothermal treatment by adding ZIF-8 or zinc nitrate as a source of Zn while treating with different types and concentrations of alkali solutions. The physical and chemical properties of the fabricated samples and their catalytic performance of methanol aromatization were systematically investigated by a combination of XRD, TEM, N2 adsorption-desorption, NH3-TPD, Py-IR, 27Al MAS NMR, 29Si MAS NMR, XPS, and TG characterization analyses and MTA experimental evaluation. The results indicated that a hollow structure emerged in the samples after alkaline treatment, with a significant increase in the proportion of mesopores, which further increased with the concentration of the alkaline solution. Both alkaline treatment and the introduction of Zn led to changes in the acidity of the catalyst. The increase in tetrahedrally coordinated aluminum during the alkaline treatment resulted in a higher content of B acid sites, while the introduction of Zn formed Zn-Lewis acid sites. Among the prepared samples, the catalyst obtained using ZIF-8 as the Zn source and treated with a mixed alkaline solution of 0.15 M sodium hydroxide and tetrapropylammonium hydroxide (ZnZ8(N+T)/Z5) exhibited higher relative crystallinity, more appropriate micromesopore ratio, a greater amount of Zn(OH)+, and a suitable B/L ratio (0.74). Under the same conditions (450 °C, atmospheric pressure, weight hourly space velocity (WHSV) = 5 h-1), the aromatic product yield of ZnZ8(N+T)/Z5 reached 26.2%, which is 14 percentage points higher than that of the parent ZSM-5 and 4 percentage points higher than that of ZnZN(N+T)/Z5 modified with zinc nitrate as the Zn source. After 8 h of reaction, the aromatic yield over ZnZ8(N+T)/Z5 could still be maintained above 18.5% with good catalyst stability.

Novel Hierarchical Disordered Li- and Al-KIL-2 Catalysts for the Pyrolysis of Biomass Model Compounds and Wool Waste: A Comparison with ZSM-5.

In this study, we investigated the pyrolysis of cellulose, lignin, phenylalanine and textile wool waste using microscale thermogravimetric analysis (TGA) and a gram-scale fixed bed reactor. The pyrolysis was conducted at 500 °C and 1 bar N2, using Al- and Li-doped mesoporous KIL-2 and ZSM-5 catalysts for comparison. Our results show that amorphous Al-KIL-2 catalyst was the most efficient in producing aromatics from cellulose and lignin. This efficiency is attributed to Al-KIL-2 large mesoporosity, wide pore size distribution, and mild acid sites. Additionally, Al-KIL-2 promoted esterification and denitrogenation reactions, indicating its potential application in the pyrolysis of biomass and protein-rich feedstocks. Conversely, the Li-KIL-2 catalyst demonstrated activity primarily in the depolymerisation of cellulose to sugars and promoted ketonisation and alcohol formation. In summary, our findings indicate that Al-KIL-2 is a promising catalyst for efficient aromatic production from biomass.

Low‐Temperature Catalytic Approaches for Upcycling Plastics into Oxygenated Aromatic Compounds

AbstractPlastic upcycling is an emerging strategy to address the global plastic waste crisis, where these abundant polymers are converted into products of higher economic value. This not only complements and adds to existing recycling efforts, but also offers opportunities to retain the inherent chemical value of the plastics within circular loops, albeit in different forms for alternative uses. With aromatics constituting a major component of current petrochemical production, the production of aromatics from post‐synthetic conversion of plastics can potentially alleviate the demand on fossil fuels. Although BTX (benzene, toluene, and xylenes) production has been a major focus of these efforts, oxygenated aromatic compounds (OACs), such as benzoic acids, are also highly‐valued across various industrial sectors, and necessitate fundamentally different processes from BTX synthesis from plastics. In this concepts article, some of the most promising emerging methods for direct synthesis of OACs from commodity petroleum‐based plastics are spotlighted, including from nonoxygenated hydrocarbon polymers such as polystyrene. With a special emphasis on emerging low temperature technologies (<150 °C), which encompass but are not limited to photo‐ and biocatalysis, this concepts article aims to position plastics as a viable source of OACs accessible under sustainable conditions for future industrial translations.

Reaction synergy of RuFe bimetallic catalysts on mordenite in lignin hydrogenolysis for aromatic compounds production

Exploring the value-added utilization of lignin showed the great significant to realize the efficient conversion of lignocellulosic biomass, which had good environmental, economic, and social benefits. However, the catalytic hydrogenolysis of lignin faced the great problems, including harsh reaction conditions and low product yield. In this research, the FeOx modified Ru/mordenite (M) was synthesized by deposition–precipitation method and strengthened the effective lignin conversion process. Ru2.5%Fe2.5%/M showed the high catalytic hydrogenolysis activity of β-O-4 and α-O-4 bond under the condition of 260 °C, 1 MPa H2, and 3 h in the methanol. Though the research about reaction of model compounds and several characterizations, synergistic action of highly dispersion RuFe nanoparticles and acidic sites significantly promoted the breakage of C-O bond. The introduction of Fe species can reduced the size of metal nanoparticles. The lignin oil reached the high value of 47.8 wt%, and contained the low RC value of phenolic compounds. Finally, the reaction mechanism of lignin catalytic hydrogenolysis was discussed, and it found that the highly dispersed RuFe nanoparticles enhanced the synergistic transfer ability of H2 and methanol to release H•. This research would give some useful understandings for the efficient thermochemical conversion of lignin.

(Ga, Al)-H-MFI Catalysts with Highly Dispersed Ga Sites and Proximal Protonic Sites Enable Methane-Propane Coaromatization.

Methane-propane coaromatization (MPCA) upgrades two abundant and inexpensive light alkanes into value-added aromatic products. While Ga-loaded MFI zeolites represent by far the most promising catalysts for MPCA reaction, they often contain a sizable portion of Ga species at the external surface of zeolites, which are remote from the Brønsted acid sites (BAS) within MFI pores and thus inefficient for MPCA. Here, we show that Ga can be introduced into MFI pores at fairly high loadings via a simple cocrystallization approach, yielding catalysts possessing well-dispersed Ga sites predominantly residing inside the pores and framework. Adjacency between Ga and BAS within the constraints of MFI channels makes these (Ga, Al)-H-MFI catalysts more active toward methane and propane activation and more selective toward aromatics compared to the Ga/MFI counterparts prepared by impregnation that inevitably leaves a large fraction of Ga at the external surface (i.e., without confinement and few adjacent BAS). Further, the effects of the Si/Al ratio on MPCA performance have been investigated for (Ga, Al)-H-MFI catalysts. Due to the multifold roles of BAS in the overall reaction sequence, an increased BAS concentration generally results in higher propane conversion and productivity of aromatics together with lower net methane conversion and severer coking.

Hydrogen isotope fractionation during aromatization to form alkylnaphthalene: Insights from pyrolysis experiments of 1-n-butyldecalin

Alkylnaphthalene homologues are important components of aromatic fraction in sedimentary organic matter and contain significantly geochemical information relative to formation and evolution of the host organic matter. They mainly originate from hydrocarbon aromatization reaction which involves the dehydrogenation of aliphatic rings resulting in the fractionation of stable hydrogen isotopes between aromatic hydrocarbons and their precursors. To examine these processes, this study thermally pyrolysed 1-n-butyldecalin (BD) at different time intervals under 360 °C/50 MPa to study the aromatization and hydrogen isotope fractionation during alkylnaphthalene formation and evolution. The relative content of aromatic products, such as naphthalene (N) and 1-methylnaphthalene (1-MN), increases with increasing aromatization. Sulfur enhanced the degree of aromatization during BD thermal evolution, resulting in greater N and 1-MN formation. For the compounds with the same carbon skeleton, i.e. tran-1-methyldecalin (1-MD), 5-methyltetraline (5-MT) and 1-MN, the 2H enrichment follows the order δ2H1-MD < δ2H5-MT < δ2H1-MN during the low thermal conversion of BD. However, the order was subsequently destroyed with increasing aromatization. The results indicate that hydrocarbon aromatization can enrich aromatic hydrocarbon in 2H, resulting in a higher δ2H value of higher aromatic-ring-number hydrocarbon than that of a lower aromatic-ring-number at low aromatization. However, 2H enrichment will decrease and even result in a reverse order with enhanced aromatization. Our findings are beneficial for understanding genetic mechanism and hydrogen isotope fractionation effect during the formation and evolution of aromatic hydrocarbons.

Effects of Nitrogen Concentration in Nutrient Solution on Growth, Yield and Phytochemical and Aromatic Compounds of Persicaria minor Cultivated Using Hydroponics System

Persicaria minor, locally known as kesum and belonging to the family Polygonaceae, is a widely used aromatic herb in Malaysia. Cultivating kesum hydroponically using a deep-water culture (DWC) system presents an alternative method for growers to enhance crop yields. This system delivers a liquid fertilizer solution directly to the plant roots, eliminating the need for a growth medium or water flow. Kesum contains phytochemical compounds such as quercetin-3-glucuronide and quercitrin, which have medicinal properties. The primary objective of this study was to assess the effects of nitrogen concentration on the growth, yield, phytochemical (quercetin-3-glucuronide and quercitrin) and aromatic (aldehyde and caryophyllene) content of kesum cultivated in a hydroponic system. Plants were grown under four nitrogen concentration regimes: 200 mg/L, 100 mg/L, 50 mg/L, and 0 mg/L. The experiment was conducted under a side-netted rain shelter and arranged in a Randomized Complete Block Design (RCBD) with four replications. The plants were harvested eight weeks after planting. The result indicted those supplemented with 100 mg/L of nitrogen exhibited the best growth performance and biomass yield, along with the highest levels of aromatic compounds (aldehyde C-10: 5.80% and aldehyde C-12: 12.23%). Plants treated with 50 mg/L of nitrogen produced the highest amounts of quercetin-3-glucuronide (98.261 µg/mL) and quercitrin (61.367 µg/mL) compared to other treatments. Additionally, plants receiving 200 mg/L of nitrogen had the highest caryophyllene content (12.53%). In conclusion, the deep-water culture system in hydroponics can effectively cultivate kesum, allowing for adjustments in nitrogen concentration to achieve optimal yields, phytochemical levels, or aromatic compound production based on specific objectives.

Constructing hollow bivalve nanocomposite ZSM-5 with inverse Al zoned distribution to strengthen the stepwise conversion of methanol to aromatics

ZSM-5 catalyzed methanol aromatization was one of the alternative routes for petroleum aromatics production, but its performance was limited to the unreasonable acid distribution and pore structure of ZSM-5. Herein, a series of dual-ZSM-5 nanocomposite catalysts with inverse Al zoned distribution have been constructed by seed growth-desiliconization-recrystallization strategy. It was found that the solid ZSM-5 with decreased Al gradient distribution promoted the conversion of light hydrocarbons intermediates, which obtained high aromatic selectivity of 23.7 % even at a low acid density. However, the diffusion of aromatics generated in interior area was inhibited by external shell and tended to be deep alkylated and transform into coke precursors, resulting in poor catalytic lifetime of 37 h. Desiliconization and recrystallization in Na+-containing alkali liquor over a composite ZSM-5 with conventional Al zoned distribution could realize the reversal of Al zoned distribution. Not only that, a huge internal cavity and a large amount of interlayer cavity were generated, which promoted the diffusion of olefin intermediates and aromatic products. Because of this, the catalytic lifetime of hollow bivalve ZSM-5 catalyst signally improved to 58 h. Based on this, directly stacking the high Si/Al ratio ZSM-5 crystals on low high Si/Al ratio core could signally improve anti-coking performance due to the abundant surface accumulation mesoporous, and the lifetime further prolonged to 99 h with the aromatic selectivity of 24.0 %. This work could provide a reference for the design of ZSM-5 catalyst with special composite structure and Al zoned distribution for stepwise aromatization of methanol with high stability.

Exploring the Photocatalytic Cleavage Pathway of the β-5 Linkage Lignin Model Compound on Carbon Nitride.

As a globally abundant source of biomass, lignocellulosic biomass has been the centre of attention as a potential resource for green energy generation and value-added chemical production. A key component of lignocellulosic biomass, lignin, which is comprised of aromatic monomers, is a potential feedstock for value added chemical production. The cleavage processes of the linkages between monomers to obtain high value products, however, requires significant investigation as it is a complex, non-facile process. This study focuses on the photocatalytic valorization of a β-5 lignin model compound, a key linkage in the lignin structure. It was found that greater yields of aromatic products were obtained from the photocatalytic conversion of β-5 lignin model compound using carbon nitride (CN) when compared to Evonik P25 titanium dioxide (TiO2). Products of the β-5 model compound photocatalytic conversion were determined and C-C bond cleavage was observed. It was also determined that the solvent participated in the reactions with the introduction of a cyano group to one of the products. Radical quenching experiments revealed that superoxide radicals participated in the CN photocatalytic conversion. These results reveal for the first time the products and possible mechanism of the photocatalytic transformation of β-5 model compounds using CN photocatalysis.