Lignin is the most abundant renewable and sustainable source of aromatic compounds to replace fossil resources, causing environmental issues. However, most lignin generated from pulping and biorefinery processes is combusted or discarded as waste. In this work, we first propose a photocatalytic artificial wood platform consisting of lignin and cellulose, inspired by woody cell walls, where lignin is arranged around cellulose fibers. The wood-mimetic particles were fabricated through reconstitution after the complete dissolution of lignin and cellulose. Intensive characterization revealed that the introduction of cellulose suppressed lignin’s self-aggregation, which limits its practical photocatalytic applications. As a result, the artificial wood photocatalyst exhibited a 3.2 times higher production rate of H2O2 from oxygen and water than lignin under solar light. The wood-mimetic photocatalyst was further coupled with an unspecific peroxygenase (UPO) biocatalyst to catalyze the selective oxygenation of inert C–H bonds using H2O2 as an oxidant. The wood-UPO hybrid catalyst demonstrated a universal photobiocatalytic oxyfunctionalization of various hydrocarbons with a higher total turnover number and turnover frequency than the lignin-UPO catalyst. This work suggests a practical strategy to utilize waste lignin as a photocatalyst and further demonstrates sustainable biosolar oxygenation reactions using sunlight and water as green energy and electron sources, respectively.@en

This study explores a chemoenzymatic cascade to synthesise chiral β-hydroxy ketones by integrating the selective oxyfunctionalisation capabilities of peroxygenases with the carbon-carbon bond-forming progress of organocatalysts. Initial results with simple organocatalysts demonstrated poor performance due to mutual inactivation of the biocatalyst and organocatalyst. However, the use of more complex prolinamide derivatives improved the reaction efficiency and enantioselectivity, enabling a one-pot, one-step synthesis process. This methodology was further optimised to produce high yields of enantiomerically pure aldol products and was shown to be extendable to other substituted toluenes and aldol donors.@en

This study presents a three-step one pot enzymatic cascade for the synthesis of a δ-lactone. Utilising acetaldehyde, combining 2-deoxyribose-5-phosphate aldolase (DERA) with an alcohol dehydrogenase (ADH) and a cofactor regeneration system this δ-lactone is synthesised with the same stereochemistry as the statin side chain precursor. The initial stage in this cascade involves the double aldol reaction, catalysed by DERA to produce the chiral lactone precursor from the achiral substrate acetaldehyde. The main challenge at this stage is the instability of DERA in the presence of high acetaldehyde concentrations. Therefore, Lactobacillus brevis DERA with a high natural acetaldehyde tolerance was genetically engineered to further improve this property. LbDERA C42M E78K exhibited improved activity and stability (no activity loss over 2 h) compared to the wild type (20% activity loss). In the second stage of the cascade, the aldol product is selectively oxidised to the lactone. A commercially available ADH was identified to selectively catalyse this oxidation using NADP⁺ as electron acceptor. NADP⁺ regeneration was achieved using O₂ as substrate in two different ways: using either photo-activated flavin or NADPH oxidase (NOX). The lactone was successfully purified from the enzymatic cascades from a preparative scale reaction in 97% purity with an optical rotation [α]_D = +34.2° (c = 0.7), proving the feasibility in a multi-enzyme three-step one-pot cascade.

@en

This review analyzes a development in biochemistry, enzymology and biotechnology that originally came as a surprise. Following the establishment of directed evolution of stereoselective enzymes in organic chemistry, the concept of partial or complete deconvolution of selective multi-mutational variants was introduced. Early deconvolution experiments of stereoselective variants led to the finding that mutations can interact cooperatively or antagonistically with one another, not just additively. During the past decade, this phenomenon was shown to be general. In some studies, molecular dynamics (MD) and quantum mechanics/molecular mechanics (QM/MM) computations were performed in order to shed light on the origin of non-additivity at all stages of an evolutionary upward climb. Data of complete deconvolution can be used to construct unique multi-dimensional rugged fitness pathway landscapes, which provide mechanistic insights different from traditional fitness landscapes. Along a related line, biochemists have long tested the result of introducing two point mutations in an enzyme for mechanistic reasons, followed by a comparison of the respective double mutant in so-called double mutant cycles, which originally showed only additive effects, but more recently also uncovered cooperative and antagonistic non-additive effects. We conclude with suggestions for future work, and call for a unified overall picture of non-additivity and epistasis.@en

Contemporary Biocatalysis heavily relies on enzyme engineering as natural enzymes frequently lack the requisite attributes for effective organic synthesis. The inherent limitations in stability, catalytic activity, and selectivity of wild-type enzymes often hinder their suitability for chemical synthesis. Over the past 25 years, there has been an unprecedented advancement in protein engineering tools, empowering enzymologists to customise enzymes to precisely meet the demands of organic synthesis. In this discussion, we delineate some of the most crucial techniques in enzyme engineering and their significance in facilitating chemical synthesis.

@en

Synthetic biohybrid systems by coupling artificial system with nature's machinery may offer a disruptive solution to address the global energy crisis. We developed a versatile electroenzymatic pathway for the continuous synthesis of valuable chemicals, facilitated by formate-driven NADH regeneration. Utilizing a bismuth electrocatalyst, we achieved stable CO2 reduction to formate with approximately 90 % Faraday efficiency at a current density of 150 mA cm−2. The generated formate acts as a mediator to regenerate NADH, which is then coupled with immobilized redox enzymes—alcohol dehydrogenase (ADH), L-lactate dehydrogenase (LDH), and L-glutamate dehydrogenase (GDH)—to produce targeted chemicals at significant rates and exceptionally high turnover numbers (1.8×106 to 3.1×106). These achievements not only underscore the efficiency of the system but also its practical applicability in industrial settings. By leveraging in situ generated formate, this innovative approach demonstrates the potential of integrating electrocatalysis with enzymatic reactions for sustainable and efficient chemical production on a practical scale.@en

Ene-reductases from the old yellow enzyme (OYE) family have been traditionally employed in the reduction of conjugated C═C double bonds. This study explores the underutilized oxidative potential of OYEs, demonstrating their capability to catalyze the enantioselective desaturation of carbonyl compounds. Utilizing a deprotonated tyrosine residue as a catalytic base, we developed a method to enable OYE-catalyzed desaturation at ambient temperature and alkaline pH without the need for high-temperature conditions. Through screening of various OYE enzymes, we identified several candidates from different genera with enhanced desaturase activity across different substrates. This work broadens the scope of biocatalytic applications for OYEs, introducing a novel approach to the synthesis of chiral α,β-unsaturated carbonyl compounds.@en

Vicinal halohydrins are key building blocks to produce bioactive molecules and drugs, especially if they can be obtained in enantiomerically pure form. In this study, we present a bi-enzymatic sequence that allows to obtain vic-halohydrins through a photochemoenzymatic olefin hydroxy halogenation followed by a lipase catalysed kinetic resolution. The absolute configuration of the resulting products was determined using Mosher's method.@en

Cofactor imbalance obstructs the productivities of metabolically engineered cells. Herein, we employed a minimally perturbing system, xylose reductase and lactose (XR/lactose), to increase the levels of a pool of sugar phosphates which are connected to the biosynthesis of NAD(P)H, FAD, FMN, and ATP in Escherichia coli. The XR/lactose system could increase the amounts of the precursors of these cofactors and was tested with three different metabolically engineered cell systems (fatty alcohol biosynthesis, bioluminescence light generation, and alkane biosynthesis) with different cofactor demands. Productivities of these cells were increased 2-4-fold by the XR/lactose system. Untargeted metabolomic analysis revealed different metabolite patterns among these cells, demonstrating that only metabolites involved in relevant cofactor biosynthesis were altered. The results were also confirmed by transcriptomic analysis. Another sugar reducing system (glucose dehydrogenase) could also be used to increase fatty alcohol production but resulted in less yield enhancement than XR. This work demonstrates that the approach of increasing cellular sugar phosphates can be a generic tool to increase in vivo cofactor generation upon cellular demand for synthetic biology.

@en

Editorial.@en

An enzymatic method for the selective hydroxylation of phenols using a peroxygenase from Aspergillus brasiliensis (AbrUPO) is reported. A broad range of phenolic starting materials can be selectively transformed into the corresponding hydroquinones. Semi-preparative syntheses of several hydroquinones were realised without further optimization pointing out the applicability of this enzyme as biocatalyst.

@en

The biocatalytic oxidative deamination of β-amino alcohols holds significant practical potential in kinetic resolution and/or deracemization process to access (R)-β-amino alcohols. This study exemplifies a notable instance of acquisition and utilization of this valuable oxidative deamination activity. Initially, the mutation N261M (M0) was identified to endow a native valine dehydrogenase with oxidative deamination activity toward a few (S)-β-amino alcohols. Subsequently, a phylogenetic analysis-guided, double-code saturation mutagenesis strategy was proposed to engineer M0's side-chain binding site. This strategy facilitated the substrate-specific evolution of M0, resulting in the creation of a panel of mutants (M1-M4) with noteworthy oxidative deamination activity toward structurally diverse (S)-β-amino alcohols. Using these engineered amine dehydrogenases, termed as β-amino alcohol dehydrogenases (β-AADHs), the complete kinetic resolution and even deracemization of a range of β-amino alcohols have been achieved. This work reports distinct biocatalysts and a synthetic strategy for the synthesis of enantiopure (R)-β-amino alcohols and offers an innovative approach for substrate-specificity engineering of enzymes.

@en

Unspecific peroxygenase from Agrocybe aegerite (AaeUPO) is a remarkable catalyst for the oxyfunctionalization of non-activated C−H bonds under mild conditions. It exhibits comparable activity to P450 monooxygenase but offers the advantage of using H₂O₂ instead of a complex electron transport chain to reductively activate O₂. Here, we demonstrate the successful oxidation of cyclohexane to cyclohexanol/cyclohexanone (KA-oil) using sol-gel encapsulated AaeUPO. Remarkably, cyclohexane serves both as a solvent and a substrate in this system, which simplifies product isolation. The ratio of cyclohexanone to cyclohexanol using this approach is remarkably higher compared to the oxidation using free AaeUPO in aqueous media using acetonitrile as a cosolvent. The utilization of sol-gel encapsulated AaeUPO offers a promising approach for oxyfunctionalization reactions and improves the chances for this enzyme to be incorporated in the same pot with other chemical transformations.

@en

Photobiocatalysis is currently in vogue. The number of reports combining the disciplines of biocatalysis and photocatalysis is rapidly increasing. While the synthetic possibilities enabled by photobiocatalysis are fascinating, the economic feasibility and environmental impact are largely neglected in the current literature. In this contribution, we present a range of key indicators for economic feasibility and environmental impact that may be useful for readers to assess their own work and thereby avoid unrealistic exaggerations. We also critically review the current state of the art in photobiocatalysis and question its synthetic practicability beyond the laboratory. With this contribution, we aim to provoke an open discussion.@en

Chemoenzymatic cascade catalysis has emerged as a revolutionary tool for streamlining traditional retrosynthetic disconnections, creating new possibilities for the asymmetric synthesis of valuable chiral compounds. Here we construct a one-pot concurrent chemoenzymatic cascade by integrating organobismuth-catalyzed aldol condensation with ene-reductase (ER)-catalyzed enantioselective reduction, enabling the formal asymmetric α-benzylation of cyclic ketones. To achieve this, we develop a pair of enantiocomplementary ERs capable of reducing α-arylidene cyclic ketones, lactams, and lactones. Our engineered mutants exhibit significantly higher activity, up to 37-fold, and broader substrate specificity compared to the parent enzyme. The key to success is due to the well-tuned hydride attack distance/angle and, more importantly, to the synergistic proton-delivery triade of Tyr28-Tyr69-Tyr169. Molecular docking and density functional theory (DFT) studies provide important insights into the bioreduction mechanisms. Furthermore, we demonstrate the synthetic utility of the best mutants in the asymmetric synthesis of several key chiral synthons.

@en

Oleate hydratases open a biocatalytic access to hydroxy fatty acids by hydration of unsaturated fatty acids. Their practical applicability, however, is hampered by their low stability. In this study we report the immobilization of the oleate hydratase from Rhodococcus erythropolis PR4 on functionalized porous, spherical polymer beads. Different carrier materials promoting covalent, hydrophobic, ionic and his-tag affinity were screened and immobilization yields typically >95 % were observed. The highest activity recovery of 32 % was achieved by immobilization via ionic interaction with quaternary ammonium functionalized beads. Biochemical properties of the enzyme immobilized via ionic interaction remain unchanged upon immobilization. The immobilized enzyme was applied for synthesis of 10-hydroxystearic acid remaining stable under process conditions. Conversion of up to 100 mM oleic acid gave 10-hydroxystearic acid achieving a TON of up to 19,000. Successful recycling of the biocatalyst for up to ten cycles further demonstrate its potential for the synthesis of 10-hydroxystearic acid.@en

The downstream product transformation of lignin depolymerization is of great interest in the production of high-value aromatic chemicals. However, this transformation is often impeded by chemical oxidation under harsh reaction conditions. In this study, we demonstrate that hypohalites generated in situ by the vanadium-containing chloroperoxidase from Curvularia inaequalis (CiVCPO) can halogenate various electron-rich and electron-poor phenol and phenolic acid substrates. Specifically, CiVCPO enabled decarboxylative halogenation, deformylative halogenation, halogenation, and direct oxidation reactions. The versatile transformation routes for the valorization of phenolic compounds showed up to 99% conversion and 99% selectivity, with a turnover number of 60,700 and a turnover frequency of 60 s^-1 for CiVCPO. This study potentially expands the biocatalytic toolbox for lignin valorization.

@en

Enzymes are making a significant impact on chemical synthesis. However, the range of chemical products achievable through biocatalysis is still limited compared to the vast array of products possible with organic synthesis. For instance, azoxy products have rarely been synthesized using enzyme catalysts. In this study, we discovered that fungal unspecific peroxygenases are promising catalysts for synthesizing azoxy products from simple aniline starting materials. The catalytic features (up to 48,450 turnovers and a turnover frequency of 6.7 s–1) and substrate transformations (up to 99% conversion with 98% chemoselectivity) highlight the synthetic potential. We propose a mechanism where peroxygenase-derived hydroxylamine and nitroso compounds spontaneously (non-enzymatically) form the desired azoxy products. This work expands the reactivity repertoire of biocatalytic transformations in the underexplored field of azoxy compound formation reactions.@en

Mol-scale oxyfunctionalization of cyclohexane to cyclohexanol/cyclohexanone (KA-oil) using an unspecific peroxygenase is reported. Using AaeUPO from Agrocybe aegerita and simple H2O2 as an oxidant, cyclohexanol concentrations of more than 300 mM (>60% yield) at attractive productivities (157 mM h-1, approx. 15 g L-1 h-1) were achieved. Current limitations of the proposed biooxidation system have been identified paving the way for future improvements and implementation.

@en

Solar-driven N₂ fixation offers a green alternative to the highly energy-intensive Haber-Bosch process that releases more than 300 million metric tons of CO₂ annually to form NH₃. However, N₂-reducing photoelectrochemical (PEC) studies have not elucidated how an oxidation reaction affects the N₂ reduction reaction (NRR). Here, we report a bias-free PEC platform for N₂ reduction to NH₃ and H₂O oxidation to O₂ and H₂O₂. Under solar light, the molybdenum-doped bismuth vanadate-based photoanodes extract electrons from H₂O and transfer them to the silicon photovoltaic-wired hematite photocathode. The light-absorbing cathode receives the electrons to drive the NRR, which is influenced by the H₂O oxidation reaction's conditions. Furthermore, the integration of PEC NRR with H₂O₂-dependent biocatalytic oxyfunctionalization achieves simultaneous synthesis of valuable chemicals on both electrodes. This work presents the first example of a PEC NRR platform coupled with H₂O oxidation and H₂O₂-dependent oxygenation for unbiased chemical synthesis using N₂, H₂O, and sunlight.

@en