Vanillin Production Research Articles

Optimization of Vanillin Production from Lignin Using Catalytic Depolymerization over a CuO/Al2O3Catalyst

The optimal conditions for vanillin production from lignin depolymerization using CuO/Al2O3 catalysts were determined by combining Box-Behnken design (BBD) and response surface methodology (RSM). Independent variables, including temperature (80–140 °C), NaOH loading (0.5–1.5 g), time (30–90 min), and catalyst weight (0.5–1.5 g), were investigated to determine the optimal conditions, with the concentration of vanillin being the dependent variable. A CuO/Al2O3 catalyst was prepared by impregnation method. The vanillin obtained from the reaction was analyzed using high-performance liquid chromatography (HPLC). The maximum obtained vanillin concentration of 59.14 mg·L-1 was achieved with a temperature of 80 °C, a reaction time of 90 min, NaOH loading of 1.5 g, and 1.5 g of catalyst. The amount of NaOH was the most influential factor governing the obtained vanillin concentration. Regression analysis was performed to determine the formula describing the vanillin concentration in terms of the independent variables with a reasonable degree of accuracy (R2 = 0.87). This study shows that the optimal conditions for the depolymerization of lignin to vanillin over a CuO/Al2O3 catalyst can be achieved under milder conditions than those reported previously.

Lactic acid bacteria as a tool for biovanillin production: A review.

Vanilla is the most commonly used natural flavoring agent in industries like food, flavoring, medicine, and fragrance. Vanillin can be obtained naturally, chemically, or through a biotechnological process. However, the yield from vanilla pods is low and does not meet market demand, and the use of vanillin produced by chemical synthesis is restricted in the food and pharmaceutical industries. As a result, the biotechnological process is the most efficient and cost-effective method for producing vanillin with consumer-demanding properties while also supporting industrial applications. Toxin-free biovanillin production, based on renewable sources such as industrial wastes or by-products, is a promising approach. In addition, only natural-labeled vanillin is approved for use in the food industry. Accordingly, this review focuses on biovanillin production from lactic acid bacteria (LAB), which is generally recognized as safe (GRAS), and the cost-cutting efforts that are utilized to improve the efficiency of biotransformation of inexpensive and readily available sources. LABs can utilize agro-wastes rich in ferulic acid to produce ferulic acid, which is then employed in vanillin production via fermentation, and various efforts have been applied to enhance the vanillin titer. However, different designs, such as response surface methods, using immobilized cells or pure enzymes for the spontaneous release of vanillin, are strongly advised.

Significant production of vanillin and in vitro amplification of ech gene in local bacterial isolates

Abstract Vanillin is the major component which is responsible for flavor and aroma of vanilla extract and is produced by 3 ways: natural extraction from vanilla plant, chemical synthesis and from microbial transformation. Current research was aimed to study bacterial production of vanillin from native natural sources including sewage and soil from industrial areas. The main objective was vanillin bio-production by isolating bacteria from these native sources. Also to adapt methodologies to improve vanillin production by optimized fermentation media and growth conditions. 47 soil and 13 sewage samples were collected from different industrial regions of Lahore, Gujranwala, Faisalabad and Kasur. 67.7% bacterial isolates produced vanillin and 32.3% were non-producers. From these 279 producers, 4 bacterial isolates selected as significant producers were; A3, A4, A7 and A10. These isolates were identified by ribotyping as A3 Pseudomonas fluorescence (KF408302), A4 Enterococcus faecium (KT356807), A7 Alcaligenes faecalis (MW422815) and A10 Bacillus subtilis (KT962919). Vanillin producers were further tested for improved production of vanillin and were grown in different fermentation media under optimized growth conditions for enhanced production of vanillin. The fermentation media (FM) were; clove oil based, rice bran waste (residues oil) based, wheat bran based and modified isoeugenol based. In FM5, FM21, FM22, FM23, FM24, FM30, FM31, FM32, FM34, FM35, FM36, and FM37, the selected 4 bacterial strains produced significant amounts of vanillin. A10 B. subtilis produced maximum amount of vanillin. This strain produced 17.3 g/L vanillin in FM36. Cost of this fermentation medium 36 was 131.5 rupees/L. This fermentation medium was modified isoeugenol based medium with 1% of isoeugenol and 2.5 g/L soybean meal. ech gene was amplified in A3 P. fluorescence using ech specific primers. As vanillin use as flavor has increased tremendously, the bioproduction of vanillin must be focused.

Catalytic aerobic oxidation of lignin-based vanillyl alcohol under base–free conditions over an efficient and reusable LaFeO3 perovskite for vanillin production

Conversion of lignin feedstocks into aromatic chemicals is a highly desirable target for biorefineries, whose depolymerization often requires high temperatures and harsh conditions.

Correlation between Lignin-Carbohydrate Complex Content in Grass Lignins and Phenolic Aldehyde Production by Rapid Spray Ozonolysis.

We provide strong evidence that the amounts of phenolic aldehydes (vanillin and p-hydroxybenzaldehyde, pHB) selectively released during rapid ozonolysis of grass lignins are correlated with the unsubstituted aryl carbons of lignin-carbohydrate complexes present in these lignins. In the case of acetosolv lignin from corn stover, we observed a steady yield of vanillin and pHB (cumulatively ∼5 wt % of the initial lignin). We demonstrate the continuous ozonolysis of the lignin in a spray reactor at ambient temperature and pressure. In sharp contrast, similar ozonolysis of acetosolv lignin from corn cobs resulted in a twofold increase in the combined yield (∼10 wt %) of vanillin and pHB. Structural analysis with 1H-13C heteronuclear single quantum coherence (HSQC) nuclear magnetic resonance revealed that signals assigned to unsubstituted aryl carbons of lignin-carbohydrate complexes are quantitatively correlated to phenolic aldehyde production from spray ozonolysis. The ratios of the integrated peak volumes corresponding to coumarates and ferulates in the HSQC spectra of cob and corn stover lignins (SLs) are 2.4 and 2.0, respectively. These ratios are nearly identical to the observed 2.3-fold increase in pHB and 1.8-fold increase in vanillin production rates from corn cob lignin compared to corn SL. Considering that the annual U.S. lignin capacity from these grass lignin sources is ∼60 million MT, the value creation potential from these flavoring agents is conservatively ∼$50 million annually from just 10% of the lignin. These new insights into structure/product correlation and spray reactor characteristics provide rational guidance for developing viable technologies to valorize grass lignins.

Production of various phenolic aldehyde compounds using the 4CL-FCHL biosynthesis platform

Vanillin (3-methoxy-4-hydroxybenzaldehyde) is one of the most important flavoring substances used in the cosmetic and food industries. Feruloyl-CoA hydratase/lyase (FCHL) is an enzyme that catalyzes the production of vanillin from feruloyl-CoA. In this study, we report kinetic parameters and biochemical properties of FCHL from Sphingomonas paucimobilis SYK-6 (SpFCHL). Also, the crystal structures of an apo-form of SpFCHL and two complexed forms with acetyl-CoA and vanillin/CoA was present. Comparing the apo structure to its complexed forms of SpFCHL, a gate loop with an “open and closed” role was observed at the entrance of the substrate-binding site. With vanillin and CoA complexed to SpFCHL, we captured a conformational change in the feruloyl moiety-binding pocket that repositions the catalytic SpFCHLE146 and other key residues. This binding pocket does not tightly fit the vanillin structure, suggesting substrate promiscuity of this enzyme. This observation is in good agreement with assay results for phenylpropanoid-CoAs and indicates important physicochemical properties of the substrate for the hydratase/lyase reaction mechanism. In addition, we showed that various phenolic aldehydes could be produced using the 4CL-FCHL biosynthesis platform.

Analyses of the efficiency of a recombinant vanillyl alcohol oxidase in producing vanillin in the hydrothermal liquefaction aqueous phase

In hydrothermal liquefaction (HTL) of biomass, only the oil and the char phases are considered imperative while the aqueous phase is discarded. However, the aqueous phase is rich in phenolic compounds like guaiacol and vanillyl alcohol that can be upgraded to vanillin. Commercially vanillin is synthesized from phenolic compounds derived from fossil fuels using chemical synthesis methods. In this investigation, the method was developed to use raw materials and enzymatic conversion of substrates which is sustainable and renewable. The purpose of this investigation is to evaluate the applicability of enzymatic vanillin synthesis within the HTL aqueous phase major components. Vanillyl alcohol oxidase was expressed in E. coli BL21 (DE3) bacteria cells and purified to characterize the production of vanillin from vanillyl alcohol. The effect on the enzyme reaction of each of the major components of the aqueous phase as detected by HPLC (High Performance Liquid Chromatography) analysis was evaluated. The components evaluated in this study included different phenolic compounds namely guaiacol, vanillic acid, vanillyl alcohol, phenol, catechol and acetic acid. These components were evaluated individually as well as in different combinations. Vanillic acid increased the reaction rate while guaiacol inhibited the reaction rate. Acetic acid exhibited the largest inhibition of the enzyme reaction after 15 min. It is known that acids are often used to stop enzyme reactions as it results in precipitation of the enzyme. Therefore, to successfully convert vanillin from vanillyl alcohol using a recombinantly expressed vanillyl alcohol oxidase, the acetic acid would first need to be removed from the HTL aqueous phase.

Comparison of singlet oxygen production of ethyl vanillin substituted silicon phthalocyanine using sonophotodynamic and photodynamic methods

Although Sonophotodynamic Therapy (SPDT) studies, which are a new approach that give better results than Photodynamic Therapy (PDT) in which light and sound are used together, are encountered in the literature, studies in this area are limited. Therefore, this study aimed to demonstrate the potentials of the synthesized compound in PDT and SPDT applications. While the calculated ΦΔ value was 0.50 for compound 1 after light irradiation, this value increased to 0.81 after light and ultrasound irradiation were used together. When the PDT and SPDT methods were compared, it proved that the singlet oxygen production increased significantly when the excitation method was changed to light and ultrasound. This study will enrich the literature on increasing singlet oxygen production by SPDT method.

Involvement of Cytochrome P450 in Organic-Solvent Tolerant Bacillus subtilis GRSW1-B1 in Vanillin Production via Ferulic Acid Metabolism

The detection of vanillin during the metabolism of ferulic acid by several Bacillus strains has been reported; however, its occurrence is not yet understood. Herein, the potential enzymes involved in vanillin production during ferulic acid metabolism in the previously reported butanol-tolerant Bacillus subtilis strain GRSW1-B1 were explored. The recombinant E. coli cells that overexpressed phenolic acid decarboxylase (PadC) rapidly converted ferulic acid to 4-vinylguaiacol. The detection of vanillin was concurrent with a decrease in 4-vinylguaiacol. In addition, the reversible abiotic conversion of 4-vinylguaiacol and apocynol was observed. The overexpression of CypD, a Bacillus P450, resulted in notable production of vanillin. The two-step conversion of ferulic acid yielded 145 μM over 72 h at pH 9. Vanillin yields of approximately 258 μM and 212 μM were obtained from ferulic acid metabolism by recombinant E. coli coexpressing PadC and CypD after conversion for 72 h, at pH 9 and 10, respectively. Several possibilities that underlie the production of vanillin were discussed. This information is useful for understanding ferulic acid metabolism by Bacillus strains and for further improving this strain as a host for the production of valuable compounds from biomass.

Enhanced vanillin production from eugenol by Bacillus cereus NCIM-5727.

Biovanillin production by a wild strain of Bacillus cereus NCIM-5727 is studied using eugenol as the precursor aiming to achieve maximum vanillin productivity. Based on shake flask optimization, molar yield and global volumetric productivity of vanillin reached up to 71.2% (6.6 gL-1) and 0.18g(Lh)-1, respectively, at 36h by resting cells of B. cereus NCIM-5727 at the optimum cell concentration of 3 gL-1 using eugenol concentration of 10 gL-1 at 37 ºC, buffer pH 7.0, buffer volume 10%, and shaking speed 180rpm. Furthermore, small-scale optimization in a bioreactor at the controlled aeration rate of 0.5 Lmin-1, agitation rate of 210rpm, and pH 7.0 enhanced the global volumetric productivity of vanillin up to 0.28g(Lh)-1 at 25h of bioconversion. The highest vanillin molar yield (75.2%) is reported using resting cells of B. cereus NCIM-5727 upon eugenol biotransformation and found stable for 10h.

Enhancing the bioconversion of ferulic acid from alkaline hydrolysate of corn cobs to vanillin by Amycolatopsis thermoflava under nutrient limitation and reducing sugar control

AbstractBACKGROUNDThe use of commercially available ferulic acid (FA) as a precursor for vanillin production is costly. The utilization of agro‐waste as a starting material provides an alternative to obtain FA at a low cost and establish an economically profitable production system. In this work, optimization of ultrasound‐assisted extraction conditions for releasing FA from corn cobs using alkaline treatment was conducted. Further, bioconversion of FA from the crude hydrolysate of corn cobs to vanillin using Amycolatopsis thermoflava was performed.RESULTSSince autoclaved hydrolysate was unfavorable for cell growth and vanillin formation, pasteurization was proposed. However, the presence of contaminants limited the entire process. Aiming to suppress the growth of contaminants and increase vanillin yield, novel strategies of limiting and controlling the nutrients for the strain were developed. Optimal hydrolysis conditions (NaOH concentration = 0.5 M, solid loading = 10% for 30 min) produced hydrolysate with relatively high titers of FA (715 mg L−1) and p‐coumaric acid (1025 mg L−1). To improve vanillin production from FA, four parameters (including the effects of sterilization method, nutrient limitation, initial biomass concentration, and reducing sugar control) were investigated. By adopting these strategies and performing bioconversion of FA to vanillin with an initial biomass concentration of 1.5 g L−1, the yield of vanillin was significantly increased by 29.5‐fold to 477.4 mg g−1, compared to bioconversion using autoclaved hydrolysate.CONCLUSIONThis approach represents a relatively economical method for vanillin production from agro‐waste because it uses crude hydrolysate, requires minimum nutrients, and involves non‐modified organisms with a relatively short bioconversion time (17 h). © 2022 Society of Chemical Industry (SCI).

De novo biosynthesis of vanillin in engineered Saccharomyces cerevisiae

Vanillin, an important aldehyde compound, is widely used in food and medicine industries. Natural and chemical-synthesized vanillin are facing significant challenge for the sustainabledevelopment.Here, de novo biosynthesis of vanillin inS. cerevisiaewas thus designed. Through integrating sam8, CYP199A2, comt, fcs and echinto the genome of S. cerevisiae, vanillin was successfully biosynthesized with a titer of 26.3 μg/L. Preferred sam5efficiently enriched caffeic acid pool, improving vanillin production to 50.2 μg/L in haploid engineered yeast. Expressing the mutants of ARO4 K229L and ARO7 G141S had reduced the negative feedback of tyrosine, increased the vanillin titer to 700 μg/L. Finally, the titer of vanillin was increased to 8545 μg/L through supplying 400 mg/L ferulic acid. The strategies of metabolic engineering and fermentation optimization achieved de novo biosynthesis of vanillin inS. cerevisiae, showing the feasibility of vanillin production by microbial technology.

Comparative Analysis of Bio-Vanillin Recovery from Bioconversion Media Using Pervaporation and Vacuum Distillation.

The increasing demand for natural products has led to biotechnological vanillin production, which requires the recovery of vanillin (and vanillyl alcohol at trace concentrations, as in botanical vanillin) from the bioconversion broth, free from potential contaminants: the substrate and metabolites of bioconversion. This work discusses the recovery and fractionation of bio-vanillin, from a bioconversion broth, by pervaporation and by vacuum distillation, coupled with fractionated condensation. The objective was to recover vanillin free of potential contaminants, with maximised fluxes and selectivity for vanillin against water and minimised energy consumption per mass of vanillin recovered. In vacuum distillation fractionated condensation, adding several consecutive water pulses to the feed increased the percentage of recovered vanillin. In pervaporation-fractionated condensation and vacuum distillation-fractionated condensation processes, it was possible to recover vanillin and traces of vanillyl alcohol without the presence of potential contaminants. Vacuum distillation–experiments presented higher vanillin fluxes than pervaporation fractionated condensation experiments, 2.7 ± 0.1 g·m−2 h−1 and 1.19 ± 0.01 g·m−2 h−1, respectively. However, pervaporation fractionated condensation assures a selectivity of vanillin against water of 4.5 on the pervaporation step (acting as a preconcentration step) and vacuum distillation fractionated condensation requires a higher energy consumption per mass of vanillin recovered when compared with pervaporation– fractionated condensation, 2727 KWh kgVAN−1 at 85 °C and 1361 KWh kgVAN−1 at 75 °C, respectively.

Process optimization of vanillin production by conversion of ferulic acid by Bacillus megaterium.

Vanillin is an important flavoring and aromatic ingredient found mainly in the pods of the tropical plant vanilla and is widely used in the food industry. Attempts have been made to produce vanillin from ferulic acid esters in agricultural residues of wheat bran. The results showed that a strain with high tolerance to the substrate ferulic acid was isolated and screened from soil and identified as belonging to the genus Bacillus (Bacillus megaterium). The concentration of vanillin produced by this strain was 0.048 g L-1 , and the molar conversion of vanillin was 12.25%. The production of vanillin was optimized by orthogonal experiments. Beef pastes 6.0g L-1 , soybean meal 5.0g L-1 , magnesium sulfate heptahydrate 1.0g L-1 , iron(II) sulfate heptahydrate 1.0g L-1 , calcium chloride 1.0g L-1 , dipotassium hydrogen phosphate trihydrate 1.0g L-1 ; fermentation culture conditions were pH7.0, inoculum level 5%, loading volume 20%, ferulic acid 1.0g L-1 , fermentation culture temperature 35 °C. The concentration of vanillin obtained was 0.218 g L-1 . Finally, transcriptomic analysis of the strain samples before and after the optimization of the fermentation conditions was carried out to study the effect of the optimization of the fermentation conditions on the concentration of vanillin produced by the strain. This study provides a theoretical basis for further improving the yield of vanillin and gradually realizing efficient industrial production. © 2022 Society of Chemical Industry.

Engineered Corynebacterium glutamicum as the Platform for the Production of Aromatic Aldehydes.

Aromatic aldehydes, including 4-hydroxybenzaldehyde (4-HB aldehyde), protocatechuic (PC) aldehyde, and vanillin, are used as important flavors, fragrances, and pharmaceutical precursors and have several biological and therapeutic effects. Production of aromatic aldehydes in microbial hosts poses a challenge due to its rapid and endogenous reduction to alcohols. To address this hurdle, prospecting of the genome of Corynebacterium glutamicum yielded 27 candidate proteins that were used in comprehensive screening with a 4-hydroxybenzyl (4-HB) alcohol–producing strain. We identified that NCgl0324 has aromatic aldehyde reductase activity and contributed to 4-HB aldehyde reduction in vivo since the NCgl0324 deletion strain HB-Δ0324 produced 1.36 g/L of 4-HB aldehyde, that is, about 188% more than its parental strain. To demonstrate that NCgl0324 knockout can also improve production of PC aldehyde and vanillin, first, a basal MA303 strain that produces protocatechuate was engineered from 4-hydroxybenzoate-synthesizing C. glutamicum APS963, followed by deletion of NCgl0324 to generate PV-Δ0324. The PC aldehyde/alcohol or vanillin/vanillyl alcohol biosynthetic pathways, respectively, were able to be expanded from protocatechuate upon introduction of carboxylic acid reductase (CAR) and catechol O-methyltransferase encoded by a mutated comt m gene. In shake flask culture, the resulting NCgl0324 deletion strains PV-IΔ0324 and PV-IYΔ0324 were shown to produce 1.18 g/L PC aldehyde and 0.31 g/L vanillin, respectively. Thus, modulation of the identified NCgl0324 gene was shown to have the potential to boost production of valuable aromatic aldehydes and alcohols.

Effective Biotransformation of Variety of Guaiacyl Lignin Monomers Into Vanillin by Bacillus pumilus.

Biotransformation has gained increasing attention due to its being an eco-friendly way for the production of value-added chemicals. The present study aimed to assess the potential of Bacillus pumilus ZB1 on guaiacyl lignin monomers biotransformation for the production of vanillin. Consequently, isoeugenol, eugenol, and vanillyl alcohol could be transformed into vanillin by B. pumilus ZB1. Based on the structural alteration of masson pine and the increase of total phenol content in the supernatant, B. pumilus ZB1 exhibited potential in lignin depolymerization and valorization using masson pine as the substrate. As the precursors of vanillin, 61.1% of isoeugenol and eugenol in pyrolyzed bio-oil derived from masson pine could be transformed into vanillin by B. pumilus ZB1. Four monooxygenases with high specific activity were identified that were involved in the transformation process. Thus, B. pumilus ZB1 could emerge as a candidate in the biosynthesis of vanillin by using wide guaiacyl precursors as the substrates.

Recombinant expression, purification and characterization of an active bacterial feruloyl-CoA synthase with potential for application in vanillin production

The ferulic acid (FA) represents a high-value molecule with applications in the cosmetic and pharmaceutical industries. This aromatic molecule is derived from lignin and can be enzymatically converted in other commercially interesting molecules, such as vanillin and bioplastics. This process starts with a common step of FA activation via CoA-thioesterification, catalyzed by feruloyl-CoA synthetases. Therefore, here, we report the successfully expression, purification as well as the initial structural and biochemical characterization of a stable, correctly folded, and catalytically active bacterial feruloyl-CoA synthase (here named FCS3) isolated from a lignin-degrading microbial consortium. The purification of recombinant FCS3 to near homogeneity was achieved using affinity chromatography. The FCS3 structure is composed of a mixture of α and β secondary structures and most likely forms stable homodimers in solution. The FCS3 presented a notable structural stability at alkaline pH values and it was able to convert FA and coenzyme A (CoA) into feruloyl-CoA complex at room temperature. This study should provide a useful basis for future biotechnological applications of FCS3, especially in the field of conversion of lignin-derived FA into high value compounds.

Applying biochemical and structural characterization of hydroxycinnamate catabolic enzymes from soil metagenome for lignin valorization strategies

The biocatalytic production of fuels and chemicals from plant biomass represents an attractive alternative to fossil fuel-based refineries. In this context, the mining and characterization of novel biocatalysts can promote disruptive innovation opportunities in the field of lignocellulose conversion and valorization. In the present work, we conducted the biochemical and structural characterization of two novel hydroxycinnamic acid catabolic enzymes, isolated from a lignin-degrading microbial consortium, a feruloyl-CoA synthetase, and a feruloyl-CoA hydratase-lyase, named LM-FCS2 and LM-FCHL2, respectively. Besides establishing the homology model structures for novel FCS and FCHL members with unique characteristics, the enzymes presented interesting biochemical features: LM-FCS2 showed stability in alkaline pHs and was able to convert a wide array of p-hydroxycinnamic acids to their respective CoA-thioesters, including sinapic acid; LM-FCHL2 efficiently converted feruloyl-CoA and p-coumaroyl-CoA into vanillin and 4-hydroxybenzaldehyde, respectively, and could produce vanillin directly from ferulic acid. The coupled reaction of LM-FCS2 and LM-FCHL2 produced vanillin, not only from commercial ferulic acid but also from a crude lignocellulosic hydrolysate. Collectively, this work illuminates the structure and function of two critical enzymes involved in converting ferulic acid into high-value molecules, thus providing valuable concepts applied to the development of plant biomass biorefineries. KEY POINTS: • Comprehensive characterization of feruloyl-CoA synthetase from metagenomic origin. • Novel low-resolution structures of hydroxycinnamate catabolic enzymes. • Production of vanillin via enzymatic reaction using lignocellulosic hydrolysates.

Effect of Physicochemical Properties of Co and Mo Modified Natural Sourced Hierarchical ZSM-5 Zeolite Catalysts on Vanillin and Phenol Production from Diphenyl Ether

The conversion of lignocellulose biomass to value-added chemicals is challenging. In this paper, the conversion process of diphenyl ether (DPE) as a model lignin compound to phenol and vanillin compounds involved a bifunctional catalyst in reaching the simultaneous one-pot reaction in mild conditions with a high yield product. The catalysts used in this conversion are hierarchical ZSM-5 zeolites and their cobalt oxide and molybdenum oxide impregnated derivate. The ZSM-5 zeolites were synthesized using alternative precursors from natural resources, i.e., Indonesian natural zeolite and kaolin. The physicochemical properties of the catalysts were determined with various characterization methods, such as: X-ray Diffraction (XRD), Fourier Transform Infra Red (FT-IR), Scanning Electron Microscope - Energy Dispersive X-ray (SEM-EDX), X-ray Fluorescence (XRF), Surface Area Analyzer (SAA), and NH3-Temperature Programmed Desorption (NH3-TPD). The catalytic activity on conversion of DPE substrates showed that the MoOx/HZSM-5 produced the highest %yield for phenol and vanillin products; 31.96% at 250 °C and 7.63% at 200 °C, respectively. The correlation study between the physicochemical properties and the catalytic activity shows that the dominance of weak acid (>40%) and mesoporosity contribution (pore size of ~ 9 nm) play roles in giving the best catalytic activity at low temperatures. Copyright © 2022 by Authors, Published by BCREC Group. This is an open access article under the CC BY-SA License (https://creativecommons.org/licenses/by-sa/4.0).

Novel iron carbide based catalysts for biomass valorisation

The present contribution explores alternative catalysts for a more practical biomass conversion and valorisation, in particular, iron carbide (with and without the presence of metallic iron) and iron manganese carbide-based nanocomposites were tested for the first time as catalysts toward the sustainable production of vanillin. The catalysts are crystalline, well-defined in composition, have a remarkable high relative surface area (233 m2/g for iron carbide and 202 m2/g for iron-manganese carbide) and were prepared in a greener way, i.e. using cellulose as carbon source. All tested catalysts have high activity and selectivity both in the oxidation of isoeugenol and vanillyl alcohol, two biomass-derived feedstock, into vanillin. Interestingly, it was observed that although the incorporation of manganese in the iron carbide structure does not improve the catalytic activity compared to the pure iron carbide, it has an effect on the material stability and selectivity towards vanillin, suggesting that ternary systems might allow controllable oxidation reactions.