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Mesoporous solids possessing open framework, tunable pores, high surface area, and considerable thermal stability provide an ideal environment to be employed as solid catalysts, host material, adsorbent, etc. Herein, we report the study about the insertion of iron into the mesoporous silicate framework of SBA-1 and utilize the material as a potential heterogeneous catalyst for the selective oxidation of lignin model non-phenolic monomer, i.e. veratryl alcohol under mild reaction conditions. Veratraldehyde and veratric acid were obtained as the oxidation products. FeSBA-1 in combination with hydrogen peroxide was selective towards veratraldehyde, on the other hand, veratric acid was selectively obtained when tert-butyl hydroperoxide was used as the oxidant under identical reaction conditions. X-ray diffraction pattern of FeSBA-1 revealed the formation of a cubic, three-dimensional SBA-1 structure. HRTEM shows uniform and ordered pore structure having dimensions of ∽ 2.3 ̶ 3.4 nm and wall thickness of ∽ 3.5 nm. FESEM showed regular-shaped FeSBA-1 with spherical morphology having a dimension of ∽ 1.6 μm. BET surface area of 1337 m2 g−1 and pore diameter of ∽ 19 Å was determined by N2 adsorption-desorption measurements. The mesoporous nature of FeSBA-1 was further supported by TGA studies. EPR studies indicated the presence of Fe(III) both in tetrahedral and octahedral coordination within the framework of FeSBA-1. DRUV-VIS studies revealed the presence of Fe(III) in both framework and extra-framework locations of the SBA-1 silicate network. IR studies supported the linkage of Fe–O–Si within FeSBA-1. The absence of the Fe2O3 phase was evidenced by Raman studies. [ABSTRACT FROM AUTHOR]

Pseudomonas aeruginosa is an opportunistic pathogen that usually causes chronic infections and even death in patients. The treatment of P. aeruginosa infection has become more challenging due to the prevalence of antibiotic resistance and the slow pace of new antibiotic development. Therefore, it is essential to explore non-antibiotic methods. A new strategy involves screening for drugs that target the quorum-sensing (QS) system. The QS system regulates the infection and drug resistance in P. aeruginosa. In this study, veratryl alcohol (VA) was found as an effective QS inhibitor (QSI). It effectively suppressed the expression of QS-related genes and the subsequent production of virulence factors under the control of QS including elastase, protease, pyocyanin and rhamnolipid at sub-inhibitory concentrations. In addition, motility activity and biofilm formation, which were correlated with the infection of P. aeruginosa, were also suppressed by VA. In vivo experiments demonstrated that VA could weaken the pathogenicity of P. aeruginosa in Chinese cabbage, Drosophila melanogaster, and Caenorhabditis elegans infection models. Molecular docking, combined with QS quintuple mutant infection analysis, identified that the mechanism of VA could target the LasR protein of the las system mainly. Moreover, VA increased the susceptibility of P. aeruginosa to conventional antibiotics of tobramycin, kanamycin and gentamicin. The results firstly demonstrate that VA is a promising QSI to treat infections caused by P. aeruginosa. [ABSTRACT FROM AUTHOR]

Nitrogen-rich carbon nanotubes NCNT700 and NCNT800 were prepared using the chemical vapor deposition method (CVD). The catalysts were characterized via high-resolution transmission electron microscopy (HRTEM) and X-ray photoelectron spectroscopy (XPS) analysis. Both the catalysts were found to have an inverted cup-stack-like morphology. The XPS analysis revealed that the catalysts are rich in pyridinic sites with variable amounts of nitrogen on their surface. The NCTN700, with a higher nitrogen content and more pyridinic sites on its surface, was found to be a good catalyst for the oxidation of benzyl and veratryl alcohols into respective aldehydes. It was observed that toluene and 4-methyl veratrole were also produced in this reaction. The amount of toluene produced was as high as 21%, with 99% conversion of benzaldehyde in the presence of NCNTs-700. The mechanistic pathway was revealed through DFT studies, where the unusual product formation of aromatic alkanes such as toluene and 4-methyl veratrole was explained during the reaction. It was astonishing to observe the reduced product in the reaction that proceeds in the forward direction in presence of a peroxide (tert-butyl hydroperoxide, TBHP). During the computational analysis, it was revealed that the reduced product observed in the reaction did not appear to proceed through a direct disproportionation reaction. Rather, the benzyl alcohol (the reactant) used in the reaction may undergo oxidation by releasing the hydrogen radicals. The hydrogen atoms released during the oxidation reaction appear to have been trapped on pyrrolic sites on the surface of catalyst and later transferred to the reactant molecules to produce toluene as a side product. [ABSTRACT FROM AUTHOR]

Verataldehyde (3,4-dimethoxybenzaldehyde) was used as a precursor for various industrial applications, such as flavouring agents, odorants, and pharmaceuticals. The major approach of this study is to convert veratryl alcohol to veratraldehyde, and the whole reaction was carried out in a continuous-process reactor. A bimetallic catalyst was prepared by the wet impregnation method in four different ratios by varying the metal percentage (Mn-10 % and Zn-5–20 %). These metals were incorporated into the activated carbon, which has a high mesoporous nature and was prepared from the used waste surgical mask. The catalysts were subjected to analysis and characterization. Textural characteristics, morphology, chemical properties, and stability of the catalyst were ascertained by utilizing X-ray diffraction, Brunauer-Emmett-Teller, N2 adsorption–desorption isotherm, Fourier transform infrared spectroscopy, and a transmission electron microscope. By varying the continuous reactor parameters such as pressure, temperature, WHSV−1, and reaction time, the catalysts were optimised to achieve the maximum conversion and selectivity of the veratryl alcohol. The AC-Mn (10 %)/Zn (15 %) catalyst was carried out under ideal conditions: 90 °C, 5 mL of TBHP as the solvent, 15 bar of pressure, and 3.2 g of catalyst proven a greater result in the reaction with a conversion and selectivity of 98 %. The stability and reusability of the catalyst were confirmed by delivering a 95.8 % yield even after five reaction runs. A continuous reaction study can provide valuable inputs for the commercial exploitation of veratryl alcohol (VA) to veratraldehyde (VAld). Again, catalytic support was synthesised utilising waste products, and the metal components are cost-effective as compared to noble metals.

This study demonstrates the selective oxidation of propylene glycol and veratryl alcohol utilizing silver oxide nanoparticles. This work adopted employing Panchakavyam, a medicinally rich bio-fertilizer for synthesizing silver oxide nanoparticles. In the present study, panchakavyam was prepared as a supporting material for the synthesis of silver oxide nanoparticles (Ag2O NPs). The traditional source of panchakavyam makes it cost effective, eco-friendly and the positive alteration of structure and shape of the catalyst enabled to deliver high yield of value added products. The synthesized silver oxide nanoparticle’s structure, shape, reactivity, stability, nature of the catalyst, thermal behaviour were studied and analysed through standard catalyst characterization techniques. Post synthesis of nanoparticles, selective oxidation reaction was carried out by confining the silver oxide nanoparticles as a nano catalyst. The tert-butyl hydroperoxide was chosen as the solvent for the oxidation studies of propylene glycol and veratryl alcohol. This study was performed by varying the reaction parameters such as temperature, pressure, time, WHSV−1 etc., to obtain the maximum yield of most desired product. The study involving conversion of propylene glycol(PG) to hydroxy acetone(HA) showed a conversion and selectivity of 100 and 99%, respectively. Similarly conversion of veratryl alcohol(VAOL) to veratraldehyde(VAL) showed a conversion and selectivity of 100 and 97.8%, respectively. The result of the study provides a path to explore the adoption of sustainable catalyst in the conversion of propylene glycol and veratryl alcohol to an industrially important products.

Pseudomonas aeruginosa is an opportunistic pathogen that usually causes chronic infections and even death in patients. The treatment of P. aeruginosa infection has become more challenging due to the prevalence of antibiotic resistance and the slow pace of new antibiotic development. Therefore, it is essential to explore non-antibiotic methods. A new strategy involves screening for drugs that target the quorum-sensing (QS) system. The QS system regulates the infection and drug resistance in P. aeruginosa. In this study, veratryl alcohol (VA) was found as an effective QS inhibitor (QSI). It effectively suppressed the expression of QS-related genes and the subsequent production of virulence factors under the control of QS including elastase, protease, pyocyanin and rhamnolipid at sub-inhibitory concentrations. In addition, motility activity and biofilm formation, which were correlated with the infection of P. aeruginosa, were also suppressed by VA. In vivo experiments demonstrated that VA could weaken the pathogenicity of P. aeruginosa in Chinese cabbage, Drosophila melanogaster, and Caenorhabditis elegans infection models. Molecular docking, combined with QS quintuple mutant infection analysis, identified that the mechanism of VA could target the LasR protein of the las system mainly. Moreover, VA increased the susceptibility of P. aeruginosa to conventional antibiotics of tobramycin, kanamycin and gentamicin. The results firstly demonstrate that VA is a promising QSI to treat infections caused by P. aeruginosa.

Nitrogen-rich carbon nanotubes NCNT700 and NCNT800 were prepared using the chemical vapor deposition method (CVD). The catalysts were characterized via high-resolution transmission electron microscopy (HRTEM) and X-ray photoelectron spectroscopy (XPS) analysis. Both the catalysts were found to have an inverted cup-stack-like morphology. The XPS analysis revealed that the catalysts are rich in pyridinic sites with variable amounts of nitrogen on their surface. The NCTN700, with a higher nitrogen content and more pyridinic sites on its surface, was found to be a good catalyst for the oxidation of benzyl and veratryl alcohols into respective aldehydes. It was observed that toluene and 4-methyl veratrole were also produced in this reaction. The amount of toluene produced was as high as 21%, with 99% conversion of benzaldehyde in the presence of NCNTs-700. The mechanistic pathway was revealed through DFT studies, where the unusual product formation of aromatic alkanes such as toluene and 4-methyl veratrole was explained during the reaction. It was astonishing to observe the reduced product in the reaction that proceeds in the forward direction in presence of a peroxide (tert-butyl hydroperoxide, TBHP). During the computational analysis, it was revealed that the reduced product observed in the reaction did not appear to proceed through a direct disproportionation reaction. Rather, the benzyl alcohol (the reactant) used in the reaction may undergo oxidation by releasing the hydrogen radicals. The hydrogen atoms released during the oxidation reaction appear to have been trapped on pyrrolic sites on the surface of catalyst and later transferred to the reactant molecules to produce toluene as a side product.

Lignin valorization through heterogeneous photocatalysis is a promising pathway for obtaining value-added products, including chemical building blocks, biofuels, etc. However, several challenges still demand attention and resolution in this field. One of the key parameters in the heterogeneous photocatalytic process is the synthesis of efficient photocatalysts that can accomplish efficient and selective reactions. Selective conversion of lignin can be achieved by using heterojunction photocatalysts which can efficiently separate charge carriers' and promote selective reactions by band structure modulation. This work details a straightforward approach for synthesizing heterojunction photocatalysts based on Bi 4 Ti 3 O 12 and BiOI involving the hydrothermal and co-precipitation methods. Additionally, the synthesized composites were employed in the selective oxidation of veratryl alcohol, a lignin-derived model compound, to produce high-value-added veratraldehyde. The experimental results showed that the BiOI/Bi 4 Ti 3 O 12 heterojunction (12.5 mol % BiOI) showed superior activity with a veratraldehyde yield of 5.4 and 27.2 times higher than those of Bi 4 Ti 3 O 12 and BiOI, respectively. The mechanistic studies revealed that the improved activity and selectivity were due to the enhanced charge carriers' separation and the suppression of reactive oxygen species formation through modulation of band structure. This study allows a green approach to lignin-derived biomass valorization to obtain high-value chemicals., (© 2024 Wiley-VCH GmbH.)

Nanoporous solids find wide spread applications in the field adsorption science, catalysis and host guest chemistry owing to their tunable pore size, unusually high surface area, good thermal stability and chemical inertness etc. Herein we report the facile synthesis of nanoporous SBA-1; a silica based cubic material having three dimensional pore architecture. The samples were prepared at room temperature from a gel containing TEOS, CTAB and HCl. The samples were characterized by XRD, HRTEM, FESEM, nitrogen adsorption–desorption, TG, FTIR and Raman measurements. The reflections observed in XRD studies are typical of ordered SBA-1 structure. HRTEM analysis show uniform and well ordered pore channels possessing long range ordering. FESEM patterns showed perfectly spherical morphology and uniform particles size of 1–1.5 μ. Nitrogen adsorption–desorption studies indicated the surface area of 1138 m2 g−1, pore volume of 0.63 cm3 g−1 and average pore size of ~ 23 Å. About 43 % of total weight loss was noticed in TGA referred the highly porous nature of SBA-1. Apart from normal zeolitic vibrations, SBA-1 possesses large number of internal surface hydroxyl groups as revealed by FTIR studies. The typical vibrations of silicate and cetyltrimethylammonium bromide were observed in Raman studies. Catalytic oxidation studies of veratryl alcohol over SBA-1, resulted in formation of two important fine chemicals such as veratryldehyde and/or veratric acid. The product selectivity was tuned by optimizing the reaction conditions. Surface hydroxyl groups in combination with oxidant are presumed to play a key role for the observed activity. [ABSTRACT FROM AUTHOR]

Dye-decolorizing peroxidases (DyPs) are heme-containing peroxidases, which have promising application in biodegradation of phenolic lignin compounds and in detoxification of dyes. In this study, the crystal structure of Bs DyP- veratryl alcohol (VA) complex delves deep into the binding of small substrate molecules within the DyP heme cavity. The biochemical analysis shows that Bs DyP oxidizes the VA with a turnover number of 0.065 s−1, followed by the oxidation of 2,6-dimethoxyphenol (DMP) and guaiacol with a comparable turnover number (k cat) of 0.07 s−1 and 0.07 s−1, respectively. Moreover, biophysical and computational studies reveal the comparable binding affinity of substrates to Bs DyP and produce lower-energy stable Bs DyP-ligand(s) complexes. All together with our previous findings, we are providing a complete structural description of substrate-binding sites in DyP. The structural insight of Bs DyP helps to modulate its engineering to enhance the activity towards the oxidation of a wide range of substrates. • The Bs DyP crystal structure has been determined in complex with veratryl alcohol. • The complex structure reveals the binding site for small substrates. • Bs DyP shows activity towards lignin model compounds. • In silico studies endorse the binding of small substrates at active site in Bs DyP. [ABSTRACT FROM AUTHOR]

Verataldehyde (3,4-dimethoxybenzaldehyde) was used as a precursor for various industrial applications, such as flavouring agents, odorants, and pharmaceuticals. The major approach of this study is to convert veratryl alcohol to veratraldehyde, and the whole reaction was carried out in a continuous-process reactor. A bimetallic catalyst was prepared by the wet impregnation method in four different ratios by varying the metal percentage (Mn-10 % and Zn-5–20 %). These metals were incorporated into the activated carbon, which has a high mesoporous nature and was prepared from the used waste surgical mask. The catalysts were subjected to analysis and characterization. Textural characteristics, morphology, chemical properties, and stability of the catalyst were ascertained by utilizing X-ray diffraction, Brunauer-Emmett-Teller, N 2 adsorption–desorption isotherm, Fourier transform infrared spectroscopy, and a transmission electron microscope. By varying the continuous reactor parameters such as pressure, temperature, WHSV−1, and reaction time, the catalysts were optimised to achieve the maximum conversion and selectivity of the veratryl alcohol. The AC-Mn (10 %)/Zn (15 %) catalyst was carried out under ideal conditions: 90 °C, 5 mL of TBHP as the solvent, 15 bar of pressure, and 3.2 g of catalyst proven a greater result in the reaction with a conversion and selectivity of 98 %. The stability and reusability of the catalyst were confirmed by delivering a 95.8 % yield even after five reaction runs. A continuous reaction study can provide valuable inputs for the commercial exploitation of veratryl alcohol (VA) to veratraldehyde (VAld). Again, catalytic support was synthesised utilising waste products, and the metal components are cost-effective as compared to noble metals. [ABSTRACT FROM AUTHOR]

Abstract Background Manganese peroxidase is one of the Class II fungal peroxidases that are able to oxidize the low redox potential phenolic lignin compounds. For high redox potential non-phenolic lignin degradation, mediators such as GSH and unsaturated fatty acids are required in the reaction. However, it is not known whether carboxylic acids are a mediator for non-phenolic lignin degradation. Results The white rot fungus Irpex lacteus is one of the most potent fungi in degradation of lignocellulose and xenobiotics. Two manganese peroxidases (IlMnP1 and IlMnP2) from I. lacteus CD2 were over-expressed in Escherichia coli and successfully refolded from inclusion bodies. Both IlMnP1 and IlMnP2 oxidized the phenolic compounds efficiently. Surprisingly, they could degrade veratryl alcohol, a non-phenolic lignin compound, in a Mn2+-dependent fashion. Malonate or oxalate was found to be also essential in this degradation. The oxidation of non-phenolic lignin was further confirmed by analysis of the reaction products using LC–MS/MS. We proved that Mn2+ and a certain carboxylate are indispensable in oxidation and that the radicals generated under this condition, specifically superoxide radical, are at least partially involved in lignin oxidative degradation. IlMnP1 and IlMnP2 can also efficiently decolorize dyes with different structures. Conclusions We provide evidence that a carboxylic acid may mediate oxidation of non-phenolic lignin through the action of radicals. MnPs, but not LiP, VP, or DyP, are predominant peroxidases secreted by some white rot fungi such as I. lacteus and the selective lignocellulose degrader Ceriporiopsis subvermispora. Our finding will help understand how these fungi can utilize MnPs and an excreted organic acid, which is usually a normal metabolite, to efficiently degrade the non-phenolic lignin. The unique properties of IlMnP1 and IlMnP2 make them good candidates for exploring molecular mechanisms underlying non-phenolic lignin compounds oxidation by MnPs and for applications in lignocellulose degradation and environmental remediation.

Adsorbable organic halogen (AOX) is generally formed by the reaction of residual lignin in pulps with chlorine dioxide during bleaching. Lignin has a complex structure. Different functional groups and bonds are present in lignin structures. Phenolic hydroxyl is one of the important functional groups in lignin, and it significantly influences the chemical properties and reactivity. To study the effect of phenolic hydroxyl on AOX formation, vanillyl alcohol (VA) was selected as the phenolic lignin model compound, and veratryl alcohol (VE) was selected as the non-phenolic lignin model compound in this study. The kinetics of AOX formation by the reaction of VA or VE with chlorine dioxide was studied. The effects of pH, chlorine dioxide, lignin model compound concentration and reaction temperature on AOX formation are discussed. The activation energies of the reaction of VA and VE with chlorine dioxide are 16 242.47 J mol−1 and 281.34 J mol−1, respectively. Thus, we found that the non-phenolic lignin can react with chlorine dioxide to form AOX more easily than phenolic lignin.

Using the original technique of treating biomass with β-glucosidase, a pool of extracellular fungal enzymes was obtained for the first time from the mycelium of basidiomycete Neonothopanus nambi. Two protein fractions containing enzymes with oxidase activity were isolated from the extract by gel-filtration chromatography and conventionally called F1 and F2. Enzyme F1 has a native molecular weight of 80–85 kDa and does not contain chromophore components; however, it catalyzes the oxidation of veratryl alcohol with Km = 0.52 mM. Probably, this enzyme is an alcohol oxidase. Enzyme F2 with a native molecular weight of approximately 60 kDa is a FAD-containing protein. It catalyzes the cooxidation of phenol with 4-aminoantipyrine without the addition of exogenous hydrogen peroxide, which distinguishes it from the known peroxidases. It was assumed that this enzyme may be a mixed-function oxidase. F2 oxidase has Km value 0.27 mM for phenol. The temperature optimums for oxidases F1 and F2 are 22–35 and 55–70°C, and pH optimums are 6 and 5, respectively. [ABSTRACT FROM AUTHOR]

Featured Application: Kraft pulp bleaching and delignification. Lignin and other colored structures need to be bleached after the Kraft process in the pulp industry. Development of environmentally-safe bleaching catalysts or electrocatalysts constitutes an attractive strategy for selective removal of lignin. Seven manganese(III)-complexes with Schiff base ligands 1–7 were synthetized and characterized by different analytical and spectroscopic techniques. The tetragonally elongated octahedral geometry for the manganese coordination sphere and the global µ-aquo dimeric structure were revealed by X-ray diffraction (XRD) studies for 1, Mn2L12(H2O)2(N(CN)2)2 (N(CN)2 = dicyanamide). Complexes 1–4 behave as more efficient peroxidase mimics as compared to 5–7. Electrochemical oxidation of the lignin model veratrylalcohol (VA) to veratrylaldehyde (VAH) is efficiently catalyzed by a type of dimanganese(III) complexes in a chlorine-free medium. The electrocatalytic reaction proceeds through the oxidation of chloride into hypochlorite at alkaline pH along with the formation of hydrogen from water as a subproduct. [ABSTRACT FROM AUTHOR]

Lignin and other colored structures need to be bleached after the Kraft process in the pulp industry. Development of environmentally-safe bleaching catalysts or electrocatalysts constitutes an attractive strategy for selective removal of lignin. Seven manganese(III)-complexes with Schiff base ligands 1−7 were synthetized and characterized by different analytical and spectroscopic techniques. The tetragonally elongated octahedral geometry for the manganese coordination sphere and the global µ-aquo dimeric structure were revealed by X-ray diffraction (XRD) studies for 1, Mn2L12(H2O)2(N(CN)2)2 (N(CN)2 = dicyanamide). Complexes 1−4 behave as more efficient peroxidase mimics as compared to 5−7. Electrochemical oxidation of the lignin model veratrylalcohol (VA) to veratrylaldehyde (VAH) is efficiently catalyzed by a type of dimanganese(III) complexes in a chlorine-free medium. The electrocatalytic reaction proceeds through the oxidation of chloride into hypochlorite at alkaline pH along with the formation of hydrogen from water as a subproduct.

• The first attempt to transform veratryl alcohol to veratryl aldehyde using a continuous reactor. • A brand-new catalyst was developed using SBA-15-TiO 2 /SO 4 /Ni (4–8%). • Achieved the highest selectivity and conversion, with values of 100 and 98.5%, respectively. • Even after seven consecutive reactions, the technique still produced a similar yield. Veratraldehyde is a crucial industrial component used to make important chemicals, drugs, flavours, perfumes, mosquito repellents and cancer-fighting substances. This research focuses on the continuous processing of veratryl alcohol to veratraldehyde using the catalyst system composed of SBA-15/TiO 2 /SO 4 /Ni. The objective of this study is to explore variations in continuous processing parameters and catalyst loading to achieve maximum conversion and selectivity of veratraldehyde. The catalyst was synthesized and then characterized using the X-ray diffraction (XRD), Fourier Transform infrared spectroscopy (FT-IR), Brunauer-Emmett-Teller (BET) surface area analysis, and transmission electron microscopy (TEM), and Temperature Programmed Desorption (TPD). The catalyst was successfully synthesized, and the results of these characterization procedures revealed its particular porosity structure and composition. By attaining maximum conversion and selectivity at a lower temperature of 90 °C, the continuous process highlighted the catalyst's energy efficiency. The findings demonstrated that the highest veratraldehyde selectivity and yield were obtained under optimal reaction conditions, including a reaction time of 2 h for the catalyst SBA-15/TiO 2 /SO 4 /Ni(8%). This catalyst produced the best results, with a veratraldehyde selectivity and conversion of 100 and 99.5%, respectively. In addition to optimising the reaction conditions, the catalyst's reusability was assessed by running the same catalyst through the reaction seven times. The outcomes demonstrated that even after numerous applications, the catalyst maintained good activity and selectivity. This shows the promise of the SBA-15/ TiO 2 /SO 4 /Ni(8) catalyst system for the selective oxidation of veratryl alcohol to veratraldehyde in terms of excellent selectivity, good yield, and reusability. Veratraldehyde could be produced industrially at low cost and with minimal impact on the environment thanks to this investigation of a continuous process. [Display omitted] [ABSTRACT FROM AUTHOR]