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The oxidation of 5‐hydroxymethylfurfural (HMF) to 2,5‐diformylfuran (DFF) is a key reaction in valorizing biomass. DFF is hardly soluble in water, while HMF is often obtained from biorefineries in crude wet organic fractions. Thus, the reaction is challenging for both biocatalysis performed in aqueous media, and for chemocatalysis where the presence of water often results in catalyst poisoning. Galactose oxidase (GalOx) can selectively oxidize HMF to DFF and displays promising activity in aqueous‐organic media. In this study, GalOx was immobilized on ten carriers, assessing the immobilization yield, activity, and stability. Covalently immobilized GalOx catalyzed the oxidation of HMF to DFF in neat and water‐saturated EtOAc, and in biphasic systems of various water contents. At 50 % v/v H2O, the reaction was conducted at a semi‐preparative scale (50 mL) with no adverse effect on DFF yield. Some limitations arise, such as enzyme deactivation, and adsorption of DFF to the support, particularly in the aqueous fraction. Future options to upgrade the route may include designed stable enzymes under the presence of HMF/DFF, and the setup of microaqueous systems where DFF adsorption is minimized. The use of wet EtOAc media would be a promising approach in future biorefineries employing inexpensive crude wet organic fractions. [ABSTRACT FROM AUTHOR]

5‐hydroxymethylfurfural (HMF) is produced upon dehydration of C6 sugars in biorefineries. As the product, it remains either in aqueous solutions, or is in situ extracted to an organic medium (biphasic system). For the subsequent oxidation of HMF to 2,5‐furandicarboxylic acid (FDCA), 'media‐agnostic' catalysts that can be efficiently used in different conditions, from aqueous to biphasic, and to organic (microaqueous) media, are of interest. Here, the concept of a one‐pot biocatalytic cascade for production of FDCA from HMF was reported, using galactose oxidase (GalOx) for the formation of 2,5‐diformylfuran (DFF), followed by the lipase‐mediated peracid oxidation of DFF to FDCA. GalOx maintained its catalytic activity upon exposure to a range of organic solvents with only 1 % (v/v) of water. The oxidation of HMF to 2,5‐diformylfuran (DFF) was successfully established in ethyl acetate‐based biphasic or microaqueous systems. To validate the concept, the reaction was conducted at 5 % (v/v) water, and integrated in a cascade where DFF was subsequently oxidized to FDCA in a reaction catalyzed by Candida antarctica lipase B. [ABSTRACT FROM AUTHOR]

The role and power of biocatalysis in sustainable chemistry has been continuously brought forward step by step to its present outstanding position. The problem‐solving capabilities of biocatalysis have been realized by numerous substantial achievements in biology, chemistry and engineering. Advances and breakthroughs in the life sciences and interdisciplinary cooperation with chemistry have clearly accelerated the implementation of biocatalytic synthesis in modern chemistry. Resource‐efficient biocatalytic manufacturing processes have already provided numerous benefits to sustainable chemistry as well as customer‐centric value creation in the pharmaceutical, food, flavor, fragrance, vitamin, agrochemical, polymer, specialty, and fine chemical industries. Biocatalysis can make significant contributions not only to manufacturing processes, but also to the design of completely new value‐creation chains. Biocatalysis can now be considered as a key enabling technology to implement sustainable chemistry. [ABSTRACT FROM AUTHOR]

The combination of deep eutectic solvents (DESs, ChCl/glycerol 1 : 2) with buffer (up to 15 % v/v) leads to solvent mixtures that exert viscosities below 25 mPa s−1 at 45 °C while keeping their non‐aqueous nature. This enables the setup of efficient enzymatic esterifications, which can also be applied in different continuous systems. Following those premises, the use of microreactors in biocatalytic reactions was explored using (low‐viscous) DES‐buffer media, showing that reactions could be performed efficiently. Under non‐optimized conditions, the microreactor devices led to specific productivities considerably higher than those observed in the batch reactor (14 vs. 0.24 mgproduct min−1 mgbiocat−1) at the same enzyme loadings and conversion of 6 % (to assure a fair comparison). Looking beyond, the combination of several microchannels (e. g., in scale‐out fashion) with DES‐water media may lead to powerful, sustainable, and efficient tools for industrial synthesis. [ABSTRACT FROM AUTHOR]

The conversion of lignocellulose into its building blocks and their further transformation into valuable platform chemicals (e. g., furfural) are key technologies to move towards the use of renewable resources. This paper explored the disentanglement of lignocellulose into hemicellulose‐derived sugars, cellulose, and lignin in a biphasic solvent system (water/2‐methyltetrahydrofuran) using phosphoric acid as recyclable catalyst. Integrated with the biomass fractionation, in a second step hemicellulose‐derived sugars (mainly xylose) were converted to furfural, which was in situ extracted into 2‐methyltetrahydrofuran with high selectivity (70 %) and yield (56 wt %). To further increase the economic feasibility of the process, a downstream and recycling strategy enabled recovery of phosphoric acid without loss of process efficiency over four consecutive cycles. This outlines a more efficient and sustainable use of phosphoric acid as catalyst, as its inherent costs can be significantly lowered. [ABSTRACT FROM AUTHOR]

Enzyme catalysis (biocatalysis) is a mature strategy to perform organic synthesis with high selectivity and under mild reaction conditions. However, despite their origin and biodegradability, the simple use of enzymes is not sufficient to validate a process as green or sustainable. To reinforce the value that biocatalysis may offer, enzymatic processes can be established in environmentally‐friendly media, such as water, neoteric solvents (e. g. deep‐eutectic‐solvents, DES), biogenic solvents (e. g. 2‐MeTHF or terpenes), or even solvent‐free systems (if substrates allow that). Furthermore, these options can be conducted in continuous biocatalytic processes, which are more efficient and sustainable. Hence, a triple synergy is generated, and very promising environmentally‐friendly options can be envisaged. This conceptual paper discusses these alternatives, providing relevant, recently reported, successful examples. [ABSTRACT FROM AUTHOR]

The quest for sustainable solvents is currently a matter of intense research and development, as solvents significantly contribute heavily to the waste generated by chemical industries. Cyclopentyl methyl ether (CPME) is a promising eco‐friendly solvent with valuable properties such as low peroxide formation rate, stability under basic and acidic conditions, and relatively high boiling point. This Review discusses the potential use of CPME for applications in biotechnology (e.g. biotransformations, as solvent or cosolvent), biorefineries, and bioeconomy (e.g. for furan synthesis or as an extractive agent in liquid–liquid separations), as well as for other purposes, such as chromatography or peptide synthesis. Although CPME is currently produced by petrochemical means with a remarkably high atom economy, its biogenic production can be envisaged from substrates such as cyclopentanol or cyclopentanone, which can be derived from furfural or from (bio‐based) adipic acid, respectively. The combination of the promising properties of CPME as a (co)solvent with a future (economic) biogenic origin would be advantageous for setting strategies aligned with the sustainable chemistry principles. [ABSTRACT FROM AUTHOR]

In this series of articles, the board members of ChemSusChem discuss recent research articles that they consider of exceptional quality and importance for sustainability. This entry features Dr. P. Domínguez de María, who introduces the biocatalytic synthesis of esters and amides in aqueous media by means of some acyltransferases that seem to proceed against Le Chatelier's principle. Continuous processes with immobilized forms of these enzymes enable the efficient production of aroma esters and important amides (e. g. melatonin) in aqueous solutions and using natural substrates with limited environmental impact. [ABSTRACT FROM AUTHOR]

Abstract: To develop novel biorefinery concepts, the use of bio‐based catalysts and solvents must be aligned with the principles of green chemistry. In this context, biogenic 2,5‐furandicarboxylic acid (FDCA) is a very promising yet underused molecule with high potential for application as an acid catalyst, combining feasibility and sustainability with efficient and straightforward recovery. In this study, FDCA was evaluated as a catalyst in the recently developed OrganoCat pretreatment, a biphasic lignocellulose fractionation system. The catalyst was investigated for the efficient fractionation of the three main components—lignin, cellulose and noncellulosic sugars—with particular focus on the lignin quality, on the effect on enzymatic hydrolysis of the cellulosic residue, and on the noncellulosic sugar extraction. To address recovery of FDCA from the OrganoCat system, a method was developed, leading to the recovery of >97 % of FDCA with a spectroscopic purity of >99 %, maintaining full activity in consecutive runs. [ABSTRACT FROM AUTHOR]

Biogenic furans (furfural and 5-hydroxymethylfurfural) are expected to become relevant building blocks based on their high degree of functionality and versatility. However, the inherent instability of furans poses considerable challenges for their synthetic modifications. Valorization routes of furans typically generate byproducts, impurities, wastes, and a cumbersome downstream processing, compromising their ecological footprint. Biocatalysis may become an alternative, given the high selectivity of enzymes, together with the mild reaction conditions applied. This Review critically discusses the options for enzymes in the upgrading of furans. Based on previous reports, a variety of biocatalytic transformations have been applied to furans, with successful cases both in aqueous and in water-free media. Options comprise the biodetoxification of toxic furans in hydrolysates, selective syntheses based on oxidation-reduction processes, solvent-free esterifications, or carboligations to afford C12 derivatives. Reported strategies show in general promising but still modest productivities (2-30 gproduct L−1 d−1, depending on the example). There are opportunities with high potential and deserving of further development, scale-up, and technoeconomic assessment, to entirely validate them as realistic alternatives. [ABSTRACT FROM AUTHOR]

The use of deep eutectic solvent (DES)/water mixtures were explored for the selective enzymatic synthesis of α-monobenzoate glycerol (α-MBG) from glycerol and benzoic acid as substrates. Experiments were performed with four DES, three of them containing choline chloride (ChCl), combined with urea (URA), glycerol (GLY), and ethylene glycol (ETA) (in all cases ChCl/HBD 1:2 mol ratio), and another one formed with methylammonium chloride and glycerol (MA/GLY 1:3 mol ratio). The best conversions (99 %) were achieved with immobilized lipase B from Candida antarctica (CAL-B) when ChCl/GLY was used as the solvent and the substrate at the same time. The use of water as a cosolvent (8 % v/ v) led to a significant decrease in the viscosity of the DES, and full conversions were then reached. Reusability studies of the biocatalyst revealed a 37 % decrease in activity after the first batch, but the activity remained mostly constant for the rest of the cycles. [ABSTRACT FROM AUTHOR]

In their Editorial for the Special Issue on Biocatalysis as Key to Sustainable Industrial Chemistry, Guest Editors Andrés Alcántara, Pablo Domínguez de María, Jennifer Littlechild, and Roland Wohlgemuth and their co‐workers on the European Society of Applied Biocatalysis' (ESAB) Working Group on Sustainable Chemistry Martin Schürmann and Roger Sheldon discuss the Special Issue and the importance of biocatalysis in carrying out cutting‐edge industrial chemistry in a sustainable way, as well as the future prospects for the field. [ABSTRACT FROM AUTHOR]

Deep eutectic solvents (DES) have emerged as promising solutions in many areas of chemistry. DES have many of the advantages of ionic liquids (e.g., low vapor pressure, nonflammability, tunability, etc.) but have lower costs, straightforward syntheses, and are often biodegradable. In this minireview, we discuss briefly the applications of DES in areas such as biotransformations, organocatalysis, and combinations of these that lead to multistep processes. DES can be used as solvents, cosolvents, performance additives for bio- and organocatalysis, tools to anchor organocatalysts selectively, or for extraction/separation. Several DES have been used both as solvents and organocatalysts at the same time. Given their promising features, it may be expected that many applications in these areas will appear in the coming years. [ABSTRACT FROM AUTHOR]

Deep-eutectic solvents (DES) are cost-effective, nonhazardous solvents that may be used in biocatalysis as nonconventional media that enable biotransformations with industrially sound high substrate loadings. Based on promising prognoses, this paper explores successfully the use of whole cells overexpressing oxidoreductases as biocatalysts for the stereoselective reduction of ketones in different DES-aqueous-media solutions. Enzymes like Ralstonia sp. alcohol dehydrogenase (ADH) and horse liver ADH, overexpressed in Escherichia coli, remain active at different DES proportions (for example, DES:buffer, 80:20 v/v) to enable nonconventional biotransformations. Furthermore, the enantiomeric excesses obtained for a broad range of aromatic substrates increase significantly if DES is added, which provides a useful tool for combining high substrate loadings and improved enzymatic selectivities while working with nonhazardous solvents. Different DES are successfully employed, which gives hints of the potential that these emerging solvents may have. [ABSTRACT FROM AUTHOR]

Microbial β-etherases, which selectively cleave the β- O-4 aryl ether linkage present in lignin, hold great promise for future applications in lignin valorization. However, very few members have been reported so far and little is known about these enzymes. By using a database mining approach, four novel bacterial β-etherases were identified, recombinantly produced in Escherichia coli, and investigated together with known β-etherases in the conversion of various lignin and non-lignin-type model compounds. The resulting activities revealed the significant influence of the substituents at the phenyl ring adjacent to the ether bond. Finally, β-etherase activity on polymeric substrates, measured by using a fluorescently labeled synthetic lignin, was also proven; this underlined the applicability of the enzymes for the conversion of lignin into renewable chemicals. [ABSTRACT FROM AUTHOR]

Recent years have witnessed the use of different ionic liquids for biomass processing, either at the level of lignocellulose pre-treatment, to fractionate biomass in its main components, separating hemicellulose and lignin from cellulose, or directly in cellulose decrystallization by dissolving it in the ionic liquid and subsequent precipitation by adding anti-solvents. Yet, most of the ILs employed in these strategies (e.g. imidazolium-based solvents) are (still) expensive for such applications, and provide discussable ecological footprints. In an attempt to combine the highly useful generated knowledge with novel neoteric solvents with improved properties, economics, availability and ecology, several new trends have appeared in these areas during recent years. They comprise the use of switchable ILs, based on strong organic bases and CO2, the application of distillable ILs, as well as the use of bio-based and low-cost ILs and deep-eutectic-solvents (DES), e.g. choline chloride-based derivatives. Apart from other emerging uses, for all these solvents some preliminary applications in biomass processing involving pretreatments, cellulose dissolution and other applications have been successfully reported. This Minireview contextualizes these recent trends and discusses them with emphasis on future use of them in biorefineries and biomass valorization. © 2013 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

Hydrolases catalyze synthetic reactions in nonaqueous media, whereas they perform hydrolysis under aqueous solutions. An acyl transferase from Mycobacterium smegmatis (MsAcT) is able to catalyze synthetic reactions in buffer because of its highly hydrophobic active site, which enables efficient transesterification reactions even at 99.9 % v/v buffer solution. This unique feature of MsAcT among hydrolases may open new opportunities to conduct synthetic (bio)catalysis in aqueous media. With these goals in mind, this paper explores some evidence of such potential: MsAcT can perform enantioselective transesterifications (e.g., ( S)-2-octanol), which could be combined with other aqueous multistep (asymmetric) reactions; 5-hydroxymethylfurfural (HMF) can be esterified to produce more hydrophobic and easily extractable HMF esters (e.g., for downstream processing or wastewater treatment); and upon addition of dilute H2O2, MsAcT works efficiently as a perhydrolase to form in situ peracids-in bulk water-that can be used for oxidations (e.g., furfural to furoic acid oxidation). Overall, these and many other new applications can be envisaged by using MsAcT in aqueous solutions. [ABSTRACT FROM AUTHOR]

Advanced manufacturing, biocatalysis, green chemistry, industrial chemistry, sustainable chemistry Keywords: advanced manufacturing; biocatalysis; green chemistry; industrial chemistry; sustainable chemistry EN advanced manufacturing biocatalysis green chemistry industrial chemistry sustainable chemistry 1 1 1 05/10/22 20220506 NES 220506 B The Front Cover b shows the treasure box of biocatalysis, which can now be considered as a key enabling technology for the development of sustainable chemistry. [Extracted from the article]

Deep eutectic solvents (DESs) are formed by mixing quaternary ammonium salts (e.g., choline chloride) and hydrogen-bond donors (e.g., glycerol or urea), which leads to biodegradable and readily available ionic solvents at room temperature. Analogous to other ionic liquids, DESs represent a promising reaction media if hydrophobic and hydrophilic substrates need to be combined. This paper assesses DESs as reaction media for chymotrypsin-catalyzed peptide synthesis. After careful determination of the reaction conditions (e.g., water content, enzyme loading), α-chymotrypsin displayed high activity for peptide synthesis in choline chloride/glycerol mixtures to afford productivities of ca. 20 g L-1 h-1 and with complete selectivity for the peptide, which is in contrast to the detrimental hydrolysis pathway observed in aqueous media. The nonimmobilized suspended enzyme could be reused several times by simple filtration with excellent to moderate activities. Overall, the results reported suggest that choline chloride based DESs may become promising neoteric solvents for peptide synthesis through biocatalysis. [ABSTRACT FROM AUTHOR]

Enzymatic multistep reactions are presently an important research field, from which integrated and efficient synthetic protocols can be created, accompanied by a diminished waste formation (avoiding downstream units operations). This article explores the benzaldehyde lyase (BAL) catalyzed crossed carboligation of benzaldehyde with different aliphatic aldehydes to afford optically active α-hydroxyketones. To this end, different biobased aliphatic alcohols were in situ oxidized to aldehydes by oxidase from Hansenula sp. and subsequently carboligated with benzaldehyde by BAL in the same reactor system. For short nonbranched aliphatic alcohols, moderate to high conversions in carboligations (15-99 %) with excellent enantioselectivities (98-99 %, R), were achieved. Both enzymes also exhibited activities at high concentrations of benzaldehyde (up to 200 m M) and with butanol as cosolvent, albeit at the cost of lower conversions, presumably owing to kinetic reasons. After needed optimization of the biocatalyst (e.g., through genetic evolution, whole-cell setup) and the process setup (e.g., stepwise addition of substrates, reaction time), the herein reported concept might provide promising entries in the field of asymmetric synthesis, delivering useful building blocks starting from biobased materials, and in an integrative manner. [ABSTRACT FROM AUTHOR]

Biorefineries are expected to take over the production of chemicals and biofuels in the coming decades, in parallel to the depletion of fossil resources. Considerable research efforts have been made to develop efficient (bio)catalytic systems for the production of bio-based solvents and novel products with improved ecological footprints and 'smart' properties. Among other challenges, water consumption will be an important aspect to assess in the full sustainability of biorefineries, which are envisaged for large-scale operations. The already existing fresh water shortage in many regions of our overpopulated planet has brought more pressure and uncertainties to these aims. Thus, over the past years, a number of enzymatic, fermentative, and chemocatalytic applications using seawater as a reaction medium for large-scale biorefineries have been reported by several research groups, which emphasize the use of nonpotable water resources for coastal regions and for locally available biomass (e.g., algae). This article contextualizes in detail these seawater-based applications for biorefineries. Overall, the use of such nonpotable water resources is promising, provided that applied catalytic systems can lead to straightforwardly treatable waste(sea)water effluents. Opportunities at the interface between biology, chemistry, and chemical engineering are foreseeable for (holistic) innovation and further research. [ABSTRACT FROM AUTHOR]

Furfural and 5-hydroxymethylfurfural (HMF) are important biomass-derived platform chemicals that can be obtained from the dehydration of lignocellulosic sugars. A possible route for the derivatization of furanics is their oxidation to afford a broad range of chemicals with promising applications (e.g., diacids, hydroxyl acids, aldehyde acids, monomers for novel polymers). Herein we explore the organic peracid-assisted oxidation of furanics under mild reaction conditions. Using lipases as biocatalysts, alkyl esters as acyl donors, and aqueous solutions of hydrogen peroxide (30 % v/ v) added stepwise, peracids are formed in situ, which subsequently oxidize the aldehyde groups to afford carboxylic acids with high yields and excellent selectivities. Furthermore, the use of an immobilized silica-based 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) affords the selective oxidation of the hydroxymethyl group of HMF to afford 2,5-diformylfuran. That product can be subsequently oxidized using again lipases for the in situ peracid formation to yield 2,5-furandicarboxylic acid, which is considered to be a key building block for biorefineries. These lipase-mediated reactions proceeded efficiently even with high substrate loadings under still non-optimized conditions. Overall, a proof-of-concept for the oxidation of furanics (based on in situ formed organic peracids as oxidants) is provided. [ABSTRACT FROM AUTHOR]

5-Hydroxymethylfurfural (HMF) is a valuable biomass-derived building block. Among possible HMF valorization products, a broad range of HMF esters can be synthesized. These HMF esters have found some promising applications, such as monomers, fuels, additives, surfactants, and fungicides, and thus several catalytic approaches for HMF (trans)esterifications have been reported. The intrinsic reactivity of HMF is challenging, forcing the use of mild reaction conditions to avoid by-product formation. This paper explores the lipase-catalyzed (trans)esterification of HMF with different acyl donors (carboxylic acids and methyl- and ethyl esters) mostly in solvent-free conditions. The results demonstrate that lipases may be promising alternatives for the synthesis of HMF esters-with high productivities and reactions at high substrate loadings-provided that robust systems for lipase immobilization are applied to assure an adequate reusability of the enzymes. Once (trans)esterifications have been conducted, the separation of unreacted HMF and HMF esters is performed by using deep-eutectic solvents (DES) as separation agents. DES are able to dissolve hydrogen-bond donors (e.g., HMF), whereas non-hydrogen-bond donors (in this case HMF esters) form a second phase. By using this approach, high ester purities (>99 %) and efficiencies (up to >90 % HMF ester recovery) in separations were obtained by using choline chloride-based DES. [ABSTRACT FROM AUTHOR]

Pulp & Oil: We report the unprecedENted formation of de ‐ aromatized lignin oil together with a white polysaccharide fraction whEN lignocellulose is treated with peracids, which are formed in situ by ENzymes. A preliminary characterization of the lignin oil is provided, together with the evidENce that the delignified lignocellulose is accessible to cellulases to afford fermENtable sugars. As a first proof ‐ of ‐ concept, the reported approach may bring promising new research lines in the future. [ABSTRACT FROM AUTHOR]

2-Methyl-tetrahydrofuran (2-MeTHF) can be derived from renewable resources (e.g., furfural or levulinic acid) and is a promising alternative solvent in the search for environmentally benign synthesis strategies. Its physical and chemical properties, such as its low miscibility with water, boiling point, remarkable stability compared to other cyclic-based solvents such as THF, and others make it appealing for applications in syntheses involving organometallics, organocatalysis, and biotransformations or for processing lignocellulosic materials. Interestingly, a significant number of industries have also started to assess 2-MeTHF in several synthetic procedures, often with excellent results and prospects. Likewise, preliminary toxicology assessments suggest that the use of 2-MeTHF might even be extended to more processes in pharmaceutical chemistry. This Minireview describes the properties of 2-MeTHF, the state-of-the-art of its use in synthesis, and covers several outstanding examples of its application from both industry and academia. [ABSTRACT FROM AUTHOR]

Whole-cell biocatalysis with the use of baker's yeast is demonstrated in different mixtures of water with deep eutectic solvents (DESs; choline chloride/glycerol, 1:2 mol/mol). Enantioselective ketone reduction is observed for long reaction times (>200 h), which suggests that the whole cells remain stable in these neoteric solvents. By changing the proportion of the DES added, a complete inversion of enantioselectivity is observed, from approximately 95 % enantiomeric excess ( ee) ( S) in pure water to approximately 95 % ee ( R) in the pure DES. Presumably, some ( S)-oxidoreductases present in baker's yeast are inhibited by DESs. [ABSTRACT FROM AUTHOR]

The article discusses a study which assessed whether the enzymatically formed acetaldehyde can be used as a further reagent for domino processes in aqueous media. The study investigated the hydrolytic activity of immobilized lipase B from Candida antarctica, CAL-B. It tested three different vinyl esters in the reaction under various conditions. It was shown that acetaldehyde can be efficiently formed in situ by means of lipases in aqueous solutions and in biphasic systems.

The article discusses a study on a novel type of enzymes, the nitrile reductases or nitrile oxidoreductases which catalyze the four-electron reduction to afford primary amines from nitriles. It cites efforts for the elucidation of the nitrile reduction mechanism proposing a reaction pathway that involve two molecules of cofactor in each catalytic turnover. It suggests the these enzymes may be widely spread in nature and opens the lead for new biocatalytic applications in the nitrile chemistry.