Highly efficient and selective production of FFCA from CotA-TJ102 laccase-catalyzed oxidation of 5-HMF

Selective electrooxidation of 5-hydroxymethylfurfural to 5-formyl-furan-2-formic acid on non-metallic polyaniline catalysts: structure-function relationships

The biomass-derived HMF oxidation reaction (HMFOR) holds great promise for sustainable production of fine chemicals. However, selective electrooxidation of HMF to high value-added intermediate product 5-formyl-furan-2-formic acid (FFCA) is still challenging. Herein, we report the electrocatalytic HMFOR to selectively produce FFCA using carbon paper (CP) supported polyaniline (PANI) as a catalyst. The PANI/CP non-metallic hybrid catalyst with moderate oxidation capacity exhibitsoptimized FFCA selectivity up to 76% in alkaline media, which has reached the best performance in reported literature studies. Identification and quantification of active sites for the HMFOR are further realized via linking the activity to structural compositions of PANI; both polaronic-type nitrogen (N3) and positively charged nitrogen (N4) species are proved responsible for adsorption and activation of HMF, and the intrinsic activity of N4 is higher than that of N3. The present work provides new physical-chemical insights into the mechanism of the HMFOR on non-metallic catalysts, paving the way for the establishment of structure-function relations and further development of novel electrochemical synthesis systems.

Aerobic Oxidation of 5-Hydroxymethylfurfural via Hydrogen Bonds Reconstruction with Ternary Deep Eutectic Solvents

Hydrogen bonding effect exists widely in various chemical and biochemical systems, primarily stabilizing the molecular structure as a positive factor. However, the presence of intermolecular hydrogen bonds among biomass molecules results in a formidable challenge for the efficient utilization of biomass resources. Here in, a novel strategy of "hydrogen bonds reconstruction" was developed by a series of ternary deep eutectic solvent (DESs) as molecular scissors, which disrupting the initial intermolecular hydrogen bonds and reconstructing the new ones to increase the reactivity of the biomass-based compound. The DESs played a crucial role in enhancing the reactivity of 5-hydroxymethylfurfural (HMF) and promoting its oxidation through reconstructing the hydrogen bonds interactions. Furthermore, DESs was also found to activate the Anderson-type catalyst Na5IMo6O24 (IMo6) through an electron-transfer mechanism, which facilitated the generation of oxygen vacancies and significantly enhances its ability to activate molecular oxygen. With this novel catalytic system, oxidation of HMF exhibited remarkable efficiency as HMF was almost entirely converted into FFCA with an impressive yield of 98 % under the optimized conditions. This finding offers novel insights into the utilization of biomass resources and endows the solvent with new functions in the chemical reaction.

Control of selectivity in the oxidation of 5-hydroxymethylfurfural to 5- formyl-2-furancarboxylic acid catalyzed by laccase in a multiphasic gas-liquid microbioreactor

The selectivity of 5-formyl-2-furancarboxylic acid (FFCA) was studied in a batch bioreactor and microbioreactors with different internal diameters (ID). Using microbioreactors, the effect of the flow rate of the liquid and gas phase on the yield, space time yield (STYFFCA), and gas-liquid mixture velocity (UM) of the reaction was evaluated. The biooxidation in flow microbioreactors, a selectivity of 100 % for FFCA was achieved, while with the batch bioreactor at the same substrate concentration a selectivity of 6.7 % was obtained. The highest yield (30 %) with 15 mM of 5-hydroxymethylfurfural (HMF) was reached at a gas-liquid flow rate of 0.5 µL/min and the highest STYFFCA (0.07 mol m-3 min-1) was achieved at a gas-liquid flow rate of 1.5 µL/min with the microbioreactor with an ID of 0.5 mm. The UM values (0.5 to 1.6 cm min1) indicated that the reaction takes place under a kinetic regime without mass transfer limitations.

Spectrophotometric Assay for the Detection of 2,5-Diformylfuran and Its Validation through Laccase-Mediated Oxidation of 5-Hydroxymethylfurfural

Modern biocatalysis requires fast, sensitive, and efficient high-throughput screening methods to screen enzyme libraries in order to seek out novel biocatalysts or enhanced variants for the production of chemicals. For instance, the synthesis of bio-based furan compounds like 2,5-diformylfuran (DFF) from 5-hydroxymethylfurfural (HMF) via aerobic oxidation is a crucial process in industrial chemistry. Laccases, known for their mild operating conditions, independence from cofactors, and versatility with various substrates, thanks to the use of chemical mediators, are appealing candidates for catalyzing HMF oxidation. Herein, Schiff-based polymers based on the coupling of DFF and 1,4-phenylenediamine (PPD) have been used in the set-up of a novel colorimetric assay for detecting the presence of DFF in different reaction mixtures. This method may be employed for the fast screening of enzymes (Z' values ranging from 0.68 to 0.72). The sensitivity of the method has been proved, and detection (8.4 μM) and quantification (25.5 μM) limits have been calculated. Notably, the assay displayed selectivity for DFF and enabled the measurement of kinetics in DFF production from HMF using three distinct laccase-mediator systems.

Effective biosynthesis of 2,5-furandicarboxylic acid from 5-hydroxymethylfurfural via a bi-enzymatic cascade system using bacterial laccase and fungal alcohol oxidase

BACKGROUND

As a cost-effective and eco-friendly approach, biocatalysis has great potential for the transformation of 5-hydroxymethylfurfural (HMF) into 2,5-furandicarboxylic acid (FDCA). However, the compatibility of each enzyme in the cascade reaction limits the transformation efficiency of HMF to FDCA.

RESULTS

Coupled with an alcohol oxidase from Colletotrichum gloeosporioides (CglAlcOx), this study aims to study the potential of bacterial laccase from Bacillus pumilus (BpLac) in an enzymatic cascade for 2,5-furandicarboxylic acid (FDCA) biosynthesis from 5-hydroxymethylfurfural (HMF). BpLac showed 100% selectivity for HMF oxidation and generated 5-hydroxymethyl-2-furancarboxylic acid (HMFCA). CglAlcOx was capable of oxidizing HMFCA to 2-formyl-5-furancarboxylic acid (FFCA). Both BpLac and CglAlcOx could oxidize FFCA to FDCA. At the 5 mM scale, a complete transformation of HMF with a 97.5% yield of FDCA was achieved by coupling BpLac with CglAlcOx in the cascade reaction. The FDCA productivity in the reaction was 5.3 mg/L/h. Notably, BpLac could alleviate the inhibitory effect of FFCA on CglAlcOx activity and boost the transformation efficiency of HMF to FDCA. Moreover, the reaction was scaled up to 40 times the volume, and FDCA titer reached 2.6 mM with a yield of 58.77% at 168 h.

CONCLUSIONS

This work provides a candidate and novel insight for better design of an enzymatic cascade in FDCA production.

Advances in enzymatic conversion of biomass derived furfural and 5-hydroxymethylfurfural to value-added chemicals and solvents

The progress of versatile chemicals and bio-based fuels using renewable biomass has gained ample importance. Furfural and 5-hydroxymethylfurfural are biomass-derived compounds that serve as the cornerstone for high-value chemicals and have a myriad of industrial applications. Despite the significant research into several chemical processes for furanic platform chemicals conversion, the harsh reaction conditions and toxic by-products render their biological conversion an ideal alternative strategy. Although biological conversion confers an array of advantages, these processes have been reviewed less. This review explicates and evaluates notable improvements in the bioconversion of 5-hydroxymethylfurfural and furfural to comprehend the current developments in the biocatalytic transformation of furan. Enzymatic conversion of HMF and furfural to furanic derivative have been explored, while the latter has substantially overlooked a foretime. This discrepancy was reviewed along with the outlook on the potential usage of 5-hydroxymethylfurfural and furfural for the furan-based value-added products' synthesis.

Advances in Selective Electrochemical Oxidation of 5-Hydroxymethylfurfural to Produce High-Value Chemicals

The conversion of biomass is a favorable alternative to the fossil energy route to solve the energy crisis and environmental pollution. As one of the most versatile platform compounds, 5-hydroxymethylfural (HMF) can be transformed to various value-added chemicals via electrolysis combining with renewable energy. Here, the recent advances in electrochemical oxidation of HMF, from reaction mechanism to reactor design are reviewed. First, the reaction mechanism and pathway are summarized systematically. Second, the parameters easy to be ignored are emphasized and discussed. Then, the electrocatalysts are reviewed comprehensively for different products and the reactors are introduced. Finally, future efforts on exploring reaction mechanism, electrocatalysts, and reactor are prospected. This review provides a deeper understanding of mechanism for electrochemical oxidation of HMF, the design of electrocatalyst and reactor, which is expected to promote the economical and efficient electrochemical conversion of biomass for industrial applications.

Evaluating the potential of engineered Trichoderma atroviride and its laccase-mediated system for the efficient bioconversion of 5-hydroxymethylfufural

5-Hydroxymethylfurfural (HMF) is a fermentation inhibitor which is formed during acid-based thermochemical pre-treatment of biomass. The present study involves two approaches for HMF conversion; the first includes screening and identification of fungal strains which produce oxidoreductases for HMF bioconversion, and thereafter evaluating their roles in HMF conversion. Out of the ten fungal strains screened, genetically engineered Trichoderma atroviride (Lac⁺) showed maximum HMF bioconversion and the activities of ligninolytic enzymes produced were noted. Maximum HMF conversion of 99% was achieved at pH 5.0 and 30 °C when 72 h old 10% inoculum of T. atroviride (Lac⁺) was utilized for 6 days. Based on the fungal bioconversion of HMF to 2, 5 diformylfuran with 58% yield, laccase was observed to influence the conversion process. Thus, a comparative study was established on HMF conversion by 100 U/mL of commercial laccases and partially purified laccase from T. atroviride (Lac+). In the presence of TEMPO, T. atroviride laccase showed comparable HMF conversion to commercial laccases, which establishes the efficiency of fungi and ligninolytic enzymes in bioconversion of HMF to value-added products.

Review of the Electrospinning Process and the Electro-Conversion of 5-Hydroxymethylfurfural (HMF) into Added-Value Chemicals

Electrochemical converters (electrolyzers, fuel cells, and batteries) have gained prominence during the last decade for the unavoidable energy transition and the sustainable synthesis of platform chemicals. One of the key elements of these systems is the electrode material on which the electrochemical reactions occur, and therefore its design will impact their performance. This review focuses on the electrospinning method by examining a number of features of experimental conditions. Electrospinning is a fiber-spinning technology used to produce three-dimensional and ultrafine fibers with tunable diameters and lengths. The thermal treatment and the different analyses are discussed to understand the changes in the polymer to create usable electrode materials. Electrospun fibers have unique properties such as high surface area, high porosity, tunable surface properties, and low cost, among others. Furthermore, a little introduction to the 5-hydroxymethylfurfural (HMF) electrooxidation coupled to H₂ production was included to show the benefit of upgrading biomass derivates in electrolyzers. Indeed, environmental and geopolitical constraints lead to shifts towards organic/inorganic electrosynthesis, which allows for one to dispense with polluting, toxic and expensive reagents. The electrooxidation of HMF instead of water (OER, oxygen evolution reaction) in an electrolyzer can be elegantly controlled to electro-synthesize added-value organic chemicals while lowering the required energy for CO₂-free H₂ production.

Copper ions binding regulation for the high-efficiency biodegradation of ciprofloxacin and tetracycline-HCl by low-cost permeabilized-cells

Cu²⁺ plays a decisive role for the bio-oxidation in the active center of laccase. In the fermentation-purified process, the loss of Cu²⁺ reduces the activity and the high cost limits the application of laccase. In this study, a fermentation-permeabilization combined process were developed which based on the regulation of Cu²⁺ binding time to produce the permeabilized-cells containing laccase, in which Cu²⁺ can enter the cells freely to greatly improve the laccase activity and reduce the immobilization cost by about 19 times. So, the permeabilized-cells is suitable for biodegradation of antibiotic pollution in the environment, which was applied for the biodegradation of ciprofloxacin (CIP) and tetracycline-HCl (TCH) and the degradation efficiency reached 95.42% and 98.73%, respectively, with low ecotoxicity of the degradation products. Finally, the degradation mechanism was analyzed theoretically by molecular docking. Therefore, this study provided a low-cost, eco-friendly, and widely applicable method for organic pollutants removal.

Laccase-catalyzed soy protein and gallic acid complexation: Effects on conformational structures and antioxidant activity

The ability of laccase to oxidize polyphenols arouses our interest that laccase can be applied for protein-polyphenol cross-linking. In this study, laccase promoted the cross-linking of gallic acid (GA) and soy protein isolate (SPI) under neutral pH. SPI-GA complexes changed the secondary structures with a decrease in β-fold and an increase in α-helix and β-turn. The free-radical scavenging activity and reducing power determination results suggested that GA elevated the SPI antioxidant activity significantly. Specifically, DPPH free radical scavenging rate and ABTS free radical scavenging ability increased almost 5- and 1.5-fold compared with unmodified SPI, respectively. Moreover, the reducing power had more than 3-fold compared to the SPI control. This study provided a novel enzyme-induced approach to modulate the physicochemical properties of SPI binding polyphenol.

Efficient decolorization of recalcitrant dyes at neutral/alkaline pH by a new bacterial laccase-mediator system

Laccases and laccase-mediator systems (LMS) are versatile catalysts that can oxidize a broad range of substrates coupled to the sole reduction of dioxygen to water. They possess many biotechnological applications in paper, textile, and food industries, bioethanol production, organic synthesis, detection and degradation of pollutants, and biofuel cell development. In particular, bacterial laccases are getting relevance due to their activity in a wide range of pH and temperature and their robustness under harsh conditions. However, the enzyme and the redox mediator's availability and costs limit their large-scale commercial use. Here we demonstrate that β-(10-phenothiazyl)-propionic acid can be used as an efficient and low-cost redox mediator for decolorizing synthetic dyes by the recombinant laccase SilA from Streptomyces ipomoeae produced in E. coli. This new LMS can decolorize more than 80% indigo carmine and malachite green in 1 h at pH = 8.0 and 2 h in tap water (pH = 6.8). Furthermore, it decolorized more than 40% of anthraquinone dye remazol brilliant blue R and 80% of azo dye xylidine ponceau in 5 h at 50 °C, pH 8.0. It supported at least 3 decolorization cycles without losing activity, representing an attractive candidate for a cost-effective and environmentally friendly LMS functional at neutral to alkaline pH.

Biotechnological production and high potential of furan-based renewable monomers and polymers

Of the 25 million tons of plastic waste produced every year in Europe, 40% of these are not reused or recycled, thus contributing to environmental pollution, one of the major challenges of the 21st century. Most of these plastics are made of petrochemical-derived polymers which are very difficult to degrade and as a result, a lot of research efforts have been made on more environmentally friendly alternatives. Bio-based monomers, derived from renewable raw materials, constitute a possible solution for the replacement of oil-derived monomers, with furan derivatives that emerged as platform molecules having a great potential for the synthesis of biobased polyesters, polyamides and their copolymers. This review article summarizes the latest developments in biotechnological production of furan compounds that can be used in polymer chemistry as well as in their conversion into polymers. Moreover, the biodegradability of the resulting materials is discussed.

An effective enzymatic assay for pH selectively measuring direct and total bilirubin concentration by using of CotA

In this study, we aimed to develop B. subtilis spore coat protein A (CotA) for the enzymatic determination of bilirubin. Firstly, molecular docking and oxidation kinetic analysis confirmed the feasibility of CotA for oxidizing bilirubin. Secondly, CotA showed pH-preferable oxidization performance to direct bilirubin (DB) in acidic conditions and an alkaline-catalytic oxidation capacity to total bilirubin (TB). Mechanism analysis results confirm that the conformational changes of CotA, DB and UB caused by pH changes are responsible for the selective oxidation of DB and TB by CotA. Then, CotA exhibits better structural characteristics and enzymatic performance than M. verrucaria-derived bilirubin oxidase (Mv-BOD). Besides, the strong anti-interference ability helps CotA adapt to complex catalytic environment in the detection of DB and TB. Our results prove that CotA can be used as a promising candidate bio-enzymatic detection reagent for DB and TB.

Preparation of highly diffusible porous cross-linked lipase B from Candida antarctica conjugates: Advances in mass transfer and application in transesterification of 5-Hydroxymethylfurfural

The present work pronounces the three phase partitioning (TPP)-facilitated preparation of porous cross-linked Candida antarctica lipase B (CaLB) aggregates (pCLEAs) for 5-Hydroxymethylfurfural (HMF) esters synthesis. CLEAs and pCLEAs of CaLB were prepared with eupergit as the support under the optimized conditions of pH 8.0, eupergit/protein ratio of 3.0:1.0, 50 mM cross-linker concentration and 3.3 mg/mL BSA concentration in 4 h. The optimum starch concentration for pCLEAs was 0.20%, m/v. The maximum biocatalytic load was 650 U/g (CLEAs) and 721 U/g (pCLEAs), and the immobilized biocatalysts were stable over a pH range of 6.0-9.0 and temperature range of (40-60)°C. The BET surface area of CLEAs and pCLEAs were 21.3 and 29.1 m²/g, respectively, and the catalytic efficiency of pCLEAs was 2.2-fold higher than that of CLEAs. Subsequently, the pCLEAs of CaLB were utilized for the manufacturing of industrially significant HMF esters. Under the optimized transesterification conditions, HMF conversion with pCLEAs CaLB was 1.41- and 1.25-fold higher than with free and CLEAs CaLB, respectively. The pCLEAs were reused upto 8 consecutive transesterification cycles and the produced HMF esters reduced the surface tension of water from 72 mN/m to 32.6 mN/m, proving its potential application as surface-active compounds.

Preparation of kapa carrageenan-based acidic heterogeneous catalyst for conversion of sugars to high-value added materials

A novel composite based on kappa-Carrageenan (κC) was prepared using N,N-methylene bisacrylamide (MBA) as the crosslinking agent. 5-Hydroxymethylfurfural (5-HMF) was produced by catalytic dehydration of fructose and glucose with MBA grafted κC (κC-g-MBA) as the solid acid catalyst due to sulfonic acid groups in biopolymer skeletons. Various reaction parameters such as optimization of the quantity of the catalyst, temperature, reaction time, and solvent were performed. It was established that for fructose dehydration, the best reaction conditions were the 160 °C as the optimized reaction temperature and 1 h reaction time, respectively. Under these conditions, the HMF yield and fructose conversion were 94.2% and 95.5%, respectively. Furthermore, 160 °C and 2 h were the best reaction temperature and reaction time for glucose dehydration, respectively. Under similar conditions, the HMF yield and glucose conversion are 47% and 93%, respectively. The catalyst was readily prepared from inexpensive materials with considerable reusability and reactivity.

Experimental and DFT Study of Metal-Free Catalyst for Selective Oxidation of Biomass-Derived Molecule (HMF)

Catalytic conversion of biomass or biomass-derived intermediate to value-added chemicals is important for both biomass waste management and production of industrially important chemicals. Oxidation of 5-hydroximethyl furfural (HMF) is considered one of the most important biomass conversion processes, which resulted in many value-added products such as 2,5-diformylfuran (DFF), 2,5-furandicarboxylic acid (FDCA), 5-hydroxymethyl-2-furancarboxylic acid (HMFCA), and 5-formyl-2-furancarboxylic acid (FFCA). In this study, the three morphologies of CdS catalyst (nanorod, nanosheet, and nanosphere) with two different crystalline structures are synthesized and characterized by SEM, TEM, and XRD analysis. The oxidation of HMF to FFCA is performed using the synthesized catalysts in the presence of different solvents and oxidizing agents. We find that CdS nanorod provides the selective oxidation of HMF to FFCA in the presence of dimethyl sulfoxide solvent and tert-butyl hydrogen peroxide oxidizing agent. The density functional theory (DFT) simulations are carried out to explain the catalytic activity of the CdS catalyst for oxidation of HMF to FFCA. The DFT simulations show that CdS is an excellent catalyst for binding HMF on the CdS surface. Our findings provide the way of effective oxidation of biomass into value-added products using the cheap CdS catalyst.

An effective in-situ method for laccase immobilization: Excellent activity, effective antibiotic removal rate and low potential ecological risk for degradation products

In this study, we used a simple in-situ biomineralization method to immobilize Bacillus subtilis (B. subtilis)-derived laccase into the copper-Trimesic acid framework (Cu-BTC), and the synthesized Laccase@Cu-BTC particles were used to degrade tetracycline and ampicillin. Compared with free laccase, the Laccase@Cu-BTC showed 16.5-fold of activity recovery, higher thermo-tolerant performance, more excellent acid-proof ability and reusability. Without any mediators, Laccase@Cu-BTC displayed high degradation efficiency (nearly 100%) for tetracycline and ampicillin in some actual water. The degradation mechanism and proposed degradation pathways of tetracycline and ampicillin were discussed technically. Besides, bacteriostatic assay and survival test of Escherichia coli (E. coli) and B. subtilis confirmed the loss of antibiotic activity for tetracycline and ampicillin, as well as the low ecotoxicity of the degradation products. Our research demonstrates that Laccase@Cu-BTC has excellent performance in the effective removal of antibiotics and the detoxification of degradation products, which make it a promising candidate for environmental recovery.

Construction of luffa sponge-based magnetic carbon nanocarriers for laccase immobilization and its application in the removal of bisphenol A

The raw material of resin, Bisphenol A (BPA), is an endocrine-disrupting compound that can be continuously released into the environment and directly harms health. In this study, luffa sponge was used as the raw material to prepare magnetic carbon chemicals for laccase immobilization and BPA degradation. The MLC-1 was synthesized by one-step carbonization-magnetization method, which showed good magnetic properties and a strong load capacity for laccase. Compared with free laccase, Laccase@MLC-1 showed stronger thermal stability, better acid-tolerate performance and reusability. Moreover, Laccase@MLC-1 showed higher BPA degradation efficiency than free laccase. 100 mg/L of BPA can be completely removed by Laccase@MLC-1 in 4 h, while only 62.70% of BPA was removed by the same amount of free laccase. By improving reuse strategies, a complete BPA degradation ratio was obtained in each reoperation process. All results proved that Laccase@MLC-1 might be a suitable biocatalyst candidate for BPA removal.

Synthesis of 2,5-furandicarboxylic acid by a TEMPO/laccase system coupled with Pseudomonas putida KT2440

A novel biological approach for the production of FDCA by a TEMPO/laccase system coupled with Pseudomonas putida KT2440 was established.

One-Pot Enzyme Cascade for Controlled Synthesis of Furancarboxylic Acids from 5-Hydroxymethylfurfural by H2 O2 Internal Recycling

Furancarboxylic acids are promising biobased building blocks in pharmaceutical and polymer industries. In this work, dual-enzyme cascade systems composed of galactose oxidase (GOase) and alcohol dehydrogenases (ADHs) are constructed for controlled synthesis of 5-formyl-2-furancarboxylic acid (FFCA) and 2,5-furandicarboxylic acid (FDCA) from 5-hydroxymethylfurfural (HMF), based on the catalytic promiscuity of ADHs. The byproduct H₂ O₂ , which is produced in GOase-catalyzed oxidation of HMF to 2,5-diformylfuran (DFF), is used for horseradish peroxidase (HRP)-mediated regeneration of the oxidized nicotinamide cofactors for subsequent oxidation of DFF promoted by an ADH, thus implementing H₂ O₂ internal recycling. The desired products FFCA and FDCA are obtained with yields of more than 95 %.