High-Efficiency Solar Transformation of Sugars via Heterogeneous Gallium(III) Catalyst.

Extremely limited research exploring the photocatalytic potential of main group metals, such as aluminum, gallium, and tin, has been undertaken due to their weak light harvesting properties. This study reports the efficient transformation of sugars to 5-hydroxymethylfurfural (HMF) with high yield employing an original heterogenous photocatalyst comprising a gallium(III) complex immobilized on an alumina support. Under visible light irradiation, the reaction rate of HMF formation is ~143 times higher than the equivalent thermal reaction performed in the absence of light. The turnover number (TON) the heterogeneous gallium (III) photocatalyst was as high as 1500, which was two orders of magnitude higher than the TON of the homogeneous gallium (III) system. It is proposed that photoirradiation significantly enhances the Lewis acidity of the catalyst by forming a semi-coordination state between gallium(III) and N-donor ligands, enabling the increased interaction of reactant sugar molecules with gallium(III) active sites. Consistent with this, the photoresponsive coordination of the gallium(III) complex and the abstraction of the hydroxy group by the metal under irradiation with visible light is observed by NMR spectroscopy for the first time. These findings demonstrate that efficient photocatalysts derived from the main group elements can facilitate biomass conversion using visible light.

The progress of research on vacancies in HMF electrooxidation.

5-Hydroxymethylfurfural (HMF), serving as a versatile platform compound bridging biomass resource and the fine chemicals industry, holds significant importance in biomass conversion processes. The electrooxidation of HMF plays a crucial role in yielding the valuable product (2,5-furandicarboxylic acid), which finds important applications in antimicrobial agents, pharmaceutical intermediates, polyester synthesis, and so on. Defect engineering stands as one of the most effective strategies for precisely synthesizing electrocatalytic materials, which could tune the electronic structure and coordination environment, and further altering the adsorption energy of HMF intermediate species, consequently increasing the kinetics of HMF electrooxidation. Thereinto, the most routine and effective defect are the anionic vacancies and cationic vacancies. In this concise review, the catalytic reaction mechanism for selective HMF oxidation is first elucidated, with a focus on the synthesis strategies involving both anionic and cationic vacancies. Recent advancements in various catalytic oxidation systems for HMF are summarized and synthesized from this perspective. Finally, the future research prospects for selective HMF oxidation are discussed.

Influence of Hydroxycinnamic Acids on the Maillard Reaction of Arabinose and Galactose beyond Carbonyl-Trapping.

Hydroxycinnamic acids, known for their health benefits and widespread presence in plant-based food, undergo complex transformations during high-temperature processing. Recent studies revealed a high browning potential of hydroxycinnamic acids and reactive Maillard reaction intermediates, but the role of phenolic compounds in the early stage of these reactions is not unambiguously understood. Therefore, we investigated the influence of caffeic acid and ferulic acid on the nonenzymatic browning of arabinose, galactose, and/or alanine, focusing on the implications on the formation of relevant early-stage Maillard intermediates and phenol-deriving products. Contrary to previous assumptions, hydroxycinnamic acids were found to promote nonenzymatic browning instead of solely trapping reactive intermediates. This was reflected by an intense browning, which was attributed to the formation of heterogeneous phenol-containing Maillard products. Although, caffeic acid is more reactive than ferulic acid, the formation of reactive furan derivatives and of heterogeneous phenol-containing colorants was promoted in the presence of both hydroxycinnamic acids.

Built-in electric field in NiO-CuO heterostructures to regulate the hydroxide adsorption sites for 5-hydroxymethylfurfural electrooxidation assisted hydrogen production.

The development of catalysts with suitable adsorption behavior for the reaction molecules and the elucidation of their internal structure-adsorption-catalytic activity relationships are crucial for the electrooxidation of 5-hydroxymethylfurfural (HMF). In this work, NiO-CuO heterostructures with a spontaneous built-in electric field (BEF) are specifically designed and used to regulate the OH- adsorption site for freeing up the active site of HMF for the HMF oxidation reaction (HMFOR). The mechanism driving electron pumping/accumulation of the BEF is examined by X-ray photoelectron spectroscopy (XPS) and ultraviolet photoelectron spectroscopy (UPS). Electrochemical data and theoretical calculations show that BEF modulates the adsorption energy and adsorption site of substrate molecules, thereby enhancing the performance of HMFOR and hydrogen evolution reaction (HER). Notably, the NiO-CuO electrode demonstrates high 2,5-Furandicarboxylic acid (FDCA) selectivity (99.76 %) and generation rate (13.79 mmol gcat-1 h-1). It only requires 1.33 V to obtain a current density of 10 mA cm-2 for HMFOR-coupled H2 evolution. This research introduces a novel approach by regulating the adsorption of reactive molecules for HMFOR-assisted H2 evolution.

Oxygen Vacancies Enrichment in Citric Acid-Assisted Synthesis of Zirconia Supported Ni Catalyst for Highly Selective Hydrogenolysis of 5-Hydroxymethylfurfural.

2, 5-Dimethylfuran (DMF), which is a promising new-generation liquid biofuel, has attracted widespread attention owing to the sustainability of biomass-derived energy sources. In this study, a highly dispersed zirconia-supported nickel catalyst (CA-Ni/ZrO2) was prepared via citric acid-assisted wetness impregnation for the selective hydrogenolysis of 5-hydroxymethylfurfural (HMF) to produce DMF. The characterization results confirmed the presence of Zr3+ species in the mesoporous CA-Ni/ZrO2 catalyst and the formation of oxygen vacancies during its preparation, which led to the formation of a large number of catalytically active sites for the adsorption and activation of the C=O/C-O groups. Under appropriate reaction parameters, an excellent DMF selectivity of 99.1% and an HMF conversion of 98.4% were achieved. A suitable kinetic model revealed that DMF was preferentially formed via the 2,5-dihydroxymethylfuran intermediate route, although a 5-methylfurfural route was also observed. Additionally, the interaction between Ni and ZrO2 significantly affected the stability of the catalyst. This study will provide guidelines for optimizing the catalytic conversion of furan derivatives over heterogeneous catalysts.

Utilization of Peptidoglycans from Lactic Acid Bacterial Cell Walls for the Mitigation of Acrylamide and 5-Hydroxymethylfurfural.

Acrylamide (AA) and 5-hydroxymethylfurfural (HMF), which are potentially carcinogenic to humans, are often produced during the hot processing of foods. This study first used a molecular docking model to simulate the binding behavior of four lactic acid bacteria peptidoglycans (PGNs) to AA/HMF, and the binding rate of LAB-based PGNs to AA/HMF was evaluated in vitro. In silico results show that interaction energy is the driving force responsible for the adsorption of LAB-derived PGNs to AA/HMF. In vitro results showed that the PGN of B. lactis B1-04 bound the most AA (28.7%) and HMF (48.0%), followed by L. acidophilus NCFM, B. breve CICC 6079, and L. plantarum CICC 22135. Moreover, an AA/HMF-bound layer on the cell surface of B. lactis B1-04 was observed via AFM and SEM due to adsorption. XPS analysis indicated the removal rate of AA/HMF by selected strains was positively correlated with the proportion of C-O, C=O, and N-H groups of PGNs. The atoms O1, O2, O3, O4, N1, N2, N3, H1, and H2 are involved in the adsorption of LAB-based PGNs to AA/HMF. Thus, the PGNs derived from these four Lactobacillus strains can be regarded as natural adsorbents for the binding of AA/HMF.

Improving 5-(hydroxymethyl)furfural (HMF) tolerance of Pseudomonas taiwanensis VLB120 by automated adaptive laboratory evolution (ALE).

The aldehyde 5-(hydroxymethyl)furfural (HMF) is of great importance for a circular bioeconomy. It is a renewable platform chemical that can be converted into a range of useful compounds to replace petroleum-based products such as the green plastic monomer 2,5-furandicarboxylic acid (FDCA). However, it also exhibits microbial toxicity for example hindering the efficient biotechnological valorization of lignocellulosic hydrolysates. Thus, there is an urgent need for tolerance-improved organisms applicable to whole-cell biocatalysis. Here, we engineer an oxidation-deficient derivative of the naturally robust and emerging biotechnological workhorse P. taiwanensis VLB120 by robotics-assisted adaptive laboratory evolution (ALE). The deletion of HMF-oxidizing enzymes enabled for the first time evolution under constant selection pressure by the aldehyde, yielding strains with consistently improved growth characteristics in presence of the toxicant. Genome sequencing of evolved clones revealed loss-of function mutations in the LysR-type transcriptional regulator-encoding mexT preventing expression of the associated efflux pump mexEF-oprN. This knowledge allowed reverse engineering of strains with enhanced aldehyde tolerance, even in a background of active or overexpressed HMF oxidation machinery, demonstrating a synergistic effect of two distinct tolerance mechanisms.

Metal vacancy-enriched layered double hydroxide for biomass molecule electrooxidation coupled with hydrogen production.

The electrochemical oxidation of biomass molecules coupling with hydrogen production is a promising strategy to obtain both green energy and value-added chemicals; however, this strategy is limited by the competing oxygen evolution reactions and high energy consumption. Herein, we report a hierarchical CoNi layered double hydroxides (LDHs) electrocatalyst with abundant Ni vacancies for the efficient anodic oxidation of 5-hydroxymethylfurfural (HMF) and cathodic hydrogen evolution. The unique hierarchical nanosheet structure and Ni vacancies provide outstanding activity and selectivity toward several biomass molecules because of the finely regulated electronic structure and highly-exposed active sites. In particular, a high faradaic efficiency (FE) at a high current density (99% at 100 mA cm-2) is achieved for HMF oxidation, and a two-electrode electrolyzer is assembled based on the Ni vacancies-enriched LDH, which realized a continuous synthesis of highly-pure 2,5-furandicarboxylic acid products with high yields (95%) and FE (90%).

Bioconversion of Furanic Compounds by Chlorella vulgaris-Unveiling Biotechnological Potentials.

Lignocellulosic biomass is abundant on Earth, and there are multiple acidic pretreatment options to separate the cellulose, hemicellulose, and lignin fraction. By doing so, the fermentation inhibitors 5-Hydroxymethylfurfural (HMF) and furfural (FF) are produced in varying concentrations depending on the hydrolyzed substrate. In this study, the impact of these furanic compounds on Chlorella vulgaris growth and photosynthetic activity was analyzed. Both compounds led to a prolonged lag phase in Chlorella vulgaris growth. While the photosynthetic yield Y(II) was not significantly influenced in cultivations containing HMF, FF significantly reduced Y(II). The conversion of 5-Hydroxymethylfurfural and furfural to 5-Hydroxymethyl-2-Furoic Acid and 2-Furoic Acid was observed. In total, 100% of HMF and FF was converted in photoautotrophic and mixotrophic Chlorella vulgaris cultivations. The results demonstrate that Chlorella vulgaris is, as of now, the first known microalgal species converting furanic compounds.

5-Hydroxymethylfurfural mediated developmental toxicity in Drosophila melanogaster.

5-hydroxymethylfurfural is a common byproduct in food. However, its effect on growth and development remains incompletely understood. This study investigated the developmental toxicity of 5-HMF to Drosophila larvae. The growth and development of Drosophila melanogaster fed with 5-50 mM 5-HMF was monitored, and its possible mechanism was explored. It was found that 5-HMF prolonged the developmental cycle of Drosophila melanogaster (25 mM and 50 mM). After 5-HMF intake, the level of reactive oxygen species in the third instar larvae increased by 1.23-1.40 fold, which increased the level of malondialdehyde and caused changes in antioxidant enzymes. Moreover, the nuclear factor erythroid-2 related factor 2 antioxidant signaling pathway and the expression of heat shock protein genes were affected. At the same time, 5-HMF disrupted the glucose and lipid metabolism in the third instar larvae, influencing the expression level of key genes in the insulin signal pathway. Furthermore, 5-HMF led to intestinal oxidative stress, and up-regulated the expression of the pro-apoptotic gene, consequently impacting intestinal health. In short, 5-HMF causes oxidative stress, disturbs glucose and lipid metabolism and induces intestinal damage, damaging related signaling pathways, and ultimately affecting the development of Drosophila melanogaster.

Unravelling caramelization and Maillard reactions in glucose and glucose + leucine model cakes: Formation and degradation kinetics of volatile markers extracted during baking.

A large number of volatile compounds are formed during the baking of foods by reactions such as caramelization and Maillard reactions. Elucidating the reaction mechanisms may be useful to predict and control food quality. Ten reaction volatile markers were extracted during baking of solid model cakes implemented with known amounts of precursors (glucose with or without leucine) and then quantified by Thermal desorption-Gas chromatography-Mass spectrometry. The kinetic data showed that the level of air convection in the oven had no significant influence on the reaction rates. In contrast, increasing baking temperatures had a nonlinear accelerating impact on the generation of newly formed volatile compounds with a bell-shaped kinetic curve found for most of the markers at 200 °C. The presence of leucine triggered the activation of the Maillard and Strecker routes with a specific and very rapid formation of 3-Methylbutanal and pyrazines. A dynamic model was developed, combining evaporation flow rate and kinetic formation and consumption of reaction markers. It can be used to describe, for two furanic compounds of different volatilities, the vapor concentrations in the oven from the concentrations measured in the model cakes.

Cobalt telluride regulated by nickel for efficient electrooxidation of 5-hydroxymethylfurfural.

Replacing the anodic oxygen evolution reaction (OER) in water splitting with 5-hydroxymethylfurfural oxidation reaction (HMFOR) can not only reduce the energy required for hydrogen production but also yield the valuable chemical 2,5-furandicarboxylic acid (FDCA). Co-based catalysts are known to be efficient for HMFOR, with high-valent Co being recognized as the main active component. However, efficiently promoting the oxidation of Co2+ to produce high-valent reactive species remains a challenge. In this study, Ni-doped CoTe (CoNiTe) nanorods were prepared as efficient catalysts for HMFOR, achieving a high HMFOR current density of 65.3 mA cm-2 at 1.50 V. Even after undergoing five successive electrolysis processes, the Faradaic efficiency (FE) remained at approximately 90.7 %, showing robust electrochemical durability. Mechanistic studies indicated that Ni doping changes the electronic configuration of Co, enhancing its charge transfer rate and facilitating the oxidation of Co2+ to high-valent CoO2 species. This work reveals the effect of Ni doping on the reconfiguration of the active phase during HMFOR.

Heteropolyacid promoted lignin-MOF derived spherical catalyst for catalytic hydrogen transfer of 5-hydroxymethylfurfural.

Catalytic conversion of biomass-derived value-added chemicals was of great significance for the utilization of renewable biomass resources to instead of fossil chemicals. Biomass-derived lignin was regarded as an important support and 5-hydroxymethylfurfural (HMF) was a vital platform chemical derived from cellulose. Herein, a series of lignin-MOF hybrid catalysts were prepared and modified with different heteropolyacids (HPAs), which were then successfully introduced into the selective conversion of HMF to 5-hydroxymethylfurfuryl alcohol (MFA). The effect of different HPA, calcination temperature, etc. were all studied, and all catalysts were well characterized. It was confirmed that silicotungstic acid modified catalyst (Ni3Co-MOF-LS@HSiW) exhibited the best catalytic performance, while the highest conversion of HMF was up to 100%, with the best MFA yield of 86.5%. The finding in this study could provide novel insights for the utilization of lignin and preparation of value-added biomass-derived chemicals.

The Role of Alkali Cations on the Selectivity of 5-Hydroxymethylfurfural Electroreduction on Glassy Carbon.

In the past decade, organic electrosynthesis has emerged as an atom- and energy-efficient strategy for harvesting renewable electricity that provides exceptional control over the reaction parameters. A profound and fundamental understanding of electrochemical interfaces becomes imperative to advance the knowledge-based development of electrochemical processes. The major strategy toward an efficient electrochemical system is based on the advancement in material science for electrocatalysis. Studies on the complex interplay among electrode surface, electrolyte, and transformation intermediates have only recently started to emerge. It involves acquiring atomic-scale insights into the electrochemical double layer, for which the identity and concentration of composing ions play a crucial role. In this study, we present how the identity and concentration of alkali cations impact the selectivity of aldehyde functionality electroreduction. As a case-study transformation, we set the electrochemical conversion of 5-hydroxymethylfurfural (HMF), a promising biomass-derived feedstock for the sustainable production of polymer or fuel precursors. Our findings reveal a consistent trend of the selectivity shift towards 2,5-bis(hydroxymethyl)furan (BHMF) as a function of cation size and concentration, rationalized by specific cation adsorption at the glassy carbon (GC), followed by the increase in the electrode surface charge density.

5-Hydroxymethylfurfural and its Downstream Chemicals: A Review of Catalytic Routes.

Biomass assumes an increasingly vital role in the realm of renewable energy and sustainable development due to its abundant availability, renewability, and minimal environmental impact. Within this context, 5-hydroxymethylfurfural (HMF), derived from sugar dehydration, stands out as a critical bio-derived product. It serves as a pivotal multifunctional platform compound, integral in synthesizing various vital chemicals, including furan-based polymers, fine chemicals, and biofuels. The high reactivity of HMF, attributed to its highly active aldehyde, hydroxyl, and furan ring, underscores the challenge of selectively regulating its conversion to obtain the desired products. This review highlights the research progress on efficient catalytic systems for HMF synthesis, oxidation, reduction, and etherification. Additionally, it outlines the techno-economic analysis (TEA) and prospective research directions for the production of furan-based chemicals. Despite significant progress in catalysis research, and certain process routes demonstrating substantial economics, with key indicators surpassing petroleum-based products, a gap persists between fundamental research and large-scale industrialization. This is due to the lack of comprehensive engineering research on bio-based chemicals, making the commercialization process a distant goal. These findings provide valuable insights for further development of this field.

Multistep Biooxidation of 5-(Hydroxymethyl)furfural to 2,5-Furandicarboxylic Acid with H2O2 by Unspecific Peroxygenases.

5-(Hydroxymethyl)furfural (HMF) is a key platform chemical derived from renewable biomass sources, holding great potential as starting material for the synthesis of valuable compounds, thereby replacing petrochemical-derived counterparts. Among these valorised compounds, 2,5-furandicarboxylic acid (FDCA) has emerged as a versatile building block. Here we demonstrate the biocatalytic synthesis of FDCA from HMF via a one-pot three-step oxidative cascade performed via two operative steps under mild reaction conditions employing two unspecific peroxygenases (UPOs) using hydrogen peroxide as the only oxidant. The challenge of HMF oxidation by UPOs is the chemoselectivity of the first step, as one of the two possible oxidation products is only a poor substrate for further oxidation. The unspecific peroxygenase from Marasmius oreades (MorUPO) was found to oxidize 100 mM of HMF to 5-formyl-2-furoic acid (FFCA) with 95 % chemoselectivity. In the sequential one-pot cascade employing MorUPO (TON up to 13535) and the UPO from Agrocybe aegerita (AaeUPO, TON up to 7079), 100 mM of HMF were oxidized to FDCA reaching up to 99 % conversion and yielding 861 mg isolated pure crystalline FDCA, presenting the first example of a gram scale biocatalytic synthesis of FDCA involving UPOs.

Nitrogen-doped ordered mesoporous carbon supported ruthenium metallic nanoparticles: Opportunity for efficient hydrogenolysis of biomass-derived 5-hydroxymethylfurfural to 2,5-dimethylfuran by catalytic transfer hydrogenation.

One of the most promising solutions to the current energy crisis is an efficient catalytic transformation of abundant low-cost renewable raw biomass into high-quality biofuel. Herein, a highly effective catalyst was constructed systematically for the selective synthesis of 2,5-dimethylfuran (DMF) biofuel from biomass-derived 5-hydroxymethylfurfural (HMF) via green catalytic transfer hydrogenolysis (CTH) using a nitrogen-doped ordered mesoporous carbon (N-CMK-1) decorated ruthenium (Ru)-based catalyst in i-propanol as hydrogen source. The structures and properties of different catalysts were characterized by different characterization techniques such as FTIR, XRD, N2-sorption, CO2-sorption, TGA, TEM, ICP-AES, CHNO analysis, and acid-base back titration. A complete HMF conversion with a high DMF yield of 88% was achieved under optimized reaction conditions. Regarding substrate conversion and product yield, the influence of reaction temperature, time, and hydrogen donors was thoroughly investigated. The nitrogen-promoted carbon support enhanced the dispersion of Ru due to the formation of appropriate basic site density which could efficiently promote the activation of alcohol hydroxyl in i-propanol and subsequent release of active hydrogen species. In the meantime, highly dispersed surface Ru nanoparticles (NPs) were beneficial for hydrogen transfer and activation of both carbonyl and hydroxyl groups in HMF. Moreover, Arrhenius kinetic analysis was studied by identifying 5-methyl furfural (5-MF) and 2,5-bishydroxymethylfuran (BHMF) as two key intermediates that dominate a distinct reaction pathway during hydrogenolysis of HMF to DMF via CTH. Furthermore, high stability without obvious loss of activity after three consecutive cycles was observed in a fabricated N-CMK-1 decorated Ru-based catalyst as a result of superior metal-support interaction and the mesoporous framework nature of the catalyst. These findings would not only offer a robust catalyst synthetic approach but also open a new avenue for the exploitation of biomass to specialty chemicals and advanced biofuels.

A Network of Processes for Biorefining Burdock Seeds and Roots.

In this work, a novel sustainable approach was proposed for the integral valorisation of Arctium lappa (burdock) seeds and roots. Firstly, a preliminary recovery of bioactive compounds, including unsaturated fatty acids, was performed. Then, simple sugars (i.e., fructose and sucrose) and phenolic compounds were extracted by using compressed fluids (supercritical CO2 and propane). Consequently, a complete characterisation of raw biomass and extraction residues was carried out to determine the starting chemical composition in terms of residual lipids, proteins, hemicellulose, cellulose, lignin, and ash content. Subsequently, three alternative ways to utilise extraction residues were proposed and successfully tested: (i) enzymatic hydrolysis operated by Cellulases (Thricoderma resei) of raw and residual biomass to glucose, (ii) direct ethanolysis to produce ethyl levulinate; and (iii) pyrolysis to obtain biochar to be used as supports for the synthesis of sulfonated magnetic iron-carbon catalysts (Fe-SMCC) to be applied in the dehydration of fructose for the synthesis of 5-hydroxymethylfurfural (5-HMF). The development of these advanced approaches enabled the full utilisation of this resource through the production of fine chemicals and value-added compounds in line with the principles of the circular economy.

Exploring correlations between soy sauce components and the formation of thermal contaminants during low-salt solid-state fermentation.

Soy sauce is a traditional seasoning in Asia and provides a unique flavor to food. However, some harmful Maillard reaction products (MRPs) were inevitably formed during the manufacturing process. Fermentation is a critical step of soy sauce manufacturing and has a significant impact on MRPs formation. Therefore, this study investigated the formation of some characteristic MRPs (e.g., furan, carboxymethyl lysine (CML), 5-hydroxymethylfurfural (5-HMF), α-dicarbonyl compounds) and their correlation with major quality indicators (e.g., free amino acids, reducing sugar, total acid, ammonia nitrogen, total nitrogen, non-salt soluble solids) in low-salt solid-state fermentation soy sauce (LSFSS). The result showed that the levels of furan, CML, and 5-HMF continue to increase during the fermentation process, reaching a maximum after sterilization. Further testing using Person correlation showed that the formation of furan, CML, and 5-HMF in LSFSS was positively correlated with glucose, fructose, α-dicarbonyl compounds, and most of the amino acids, while it was negatively correlated with sucrose and methionine. Among them, the contribution of lysine, valine, isoleucine, leucine, and arginine to furan formation has rarely been reported. Our results provide a good theoretical basis for the control of MRPs during LSFSS fermentation.

Highly Effective Non-Noble MnO2 Catalysts for 5-Hydroxymethylfurfural Oxidation to 2,5-Furandicarboxylic Acid.

Noble metal-free catalyst or catalytic oxidation of 5-hydroxymethylfurfural into 2,5-furandicarboxylic acid are proposed in this study as a proposal to solve one of the great disadvantages of this reaction of using preferably noble metal-based catalysts. The catalytic activity of six MnO2 crystal structures is studied as alternative. The obtained results showed a strong connection between catalytic activity the type of MnO2 structure organization and redox behavior. Among all tested catalysts, ϵ-MnO2 showed the best performance with an excellent yield of 74 % of 2,5-furandicarboxylic acid at full -hydroxymethylfurfural conversion.