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

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.

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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

Biocatalytic oxidation reactions of toluene derivates to the corresponding aldehydes are typically challenged by regio- and chemoselectivity issues. In this contribution we address both challenges by a combined reactant- and reaction engineering approach. We demonstrate that the peroxygenase-catalysed transformation of ring-substituted toluenes proceeds highly regioselectively in benzylic position. Furthermore, neat reaction conditions not only enable attractive product concentrations (up to 185 mM) but also result in highly chemoselective oxidations to the aldehyde level.

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Non-thermal plasmas are used in various applications to inactivate biological agents or biomolecules. A complex cocktail of reactive species, (vacuum) UV radiation and in some cases exposure to an electric field together cause the detrimental effects. In contrast to this disruptive property of technical plasmas, we have shown previously that it is possible to use non-thermal plasma-generated species such as H2O2 as cosubstrates in biocatalytic reactions. One of the main limitations in plasma-driven biocatalysis is the relatively short enzyme lifetime under plasma-operating conditions. This challenge could be overcome by immobilizing the enzymes on inert carrier materials. Here, we tested whether immobilization is suited to protect proteins from inactivation by plasma. To this end, using a dielectric barrier discharge device (PlasmaDerm), plasma stability was tested for five enzymes immobilized on ten different carrier materials. A comparative analysis of the treatment times needed to reduce enzyme activity of immobilized and free enzyme by 30% showed a maximum increase by a factor of 44. Covalent immobilization on a partly hydrophobic carrier surface proved most effective. We conclude from the study, that immobilization universally protects enzymes under plasma-operating conditions, paving the way for new emerging applications.

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Utilisation of fatty acids generally relies on pre-existing functional groups such as the carboxylate group or C=C-double bonds. Addition of new functionalities into the hydrocarbon part opens up new possibilities for fatty acid valorisation. In this contribution we demonstrate the synthetic potential of a peroxygenase mutant AaeUPO−Fett for selective fatty acid oxyfunctionalisation. The ω-1 hydroxy fatty acid (esters) produced are further transformed into lactones, alcohols, esters and amines via multi-enzyme cascades thereby paving the way for new fatty acid valorisation pathways.

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Chiral sulfoxides are valuable building blocks in asymmetric synthesis. However, the biocatalytic synthesis of chiral sulfoxides is still challenged by low product titres. Herein, we report the use of peroxygenase as a catalyst for asymmetric sulfoxidation under non-aqueous conditions. Upon covalent immobilisation, the peroxygenase showed stability and activity under neat reaction conditions. A large variety of sulfides was converted into chiral sulfoxides in very high product concentration with moderate to satisfactory optical purity (e. g. 626 mM of (R)-methyl phenyl sulfoxide in approx. 89 % ee in 48 h). Further polishing of the ee value via cascading methionine reductase A (MsrA) gave>99 % ee of the sulfoxide. The robustness of the enzymes and high product titer is superior to the state-of-the-art methodologies. Gram-scale synthesis has been demonstrated. Overall, we demonstrated a practical and facile catalytic method to synthesize chiral sulfoxides.

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In this contribution, we report chemoenzymatic bromodecarboxylation (Hunsdiecker-type) of α,ß-unsaturated carboxylic acids. The extraordinarily robust chloroperoxidase from Curvularia inaequalis (CiVCPO) generated hypobromite from H2O2 and bromide, which then spontaneously reacted with a broad range of unsaturated carboxylic acids and yielded the corresponding vinyl bromide products. Selectivity issues arising from the (here undesired) addition of water to the intermediate bromonium ion could be solved by reaction medium engineering. The vinyl bromides so obtained could be used as starting materials for a range of cross-coupling and pericyclic reactions.

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Bioelectrochemical technologies such as electro-fermentation and microbial CO₂ electrosynthesis are emerging interdisciplinary technologies that can produce renewable fuels and chemicals (such as carboxylic acids). The benefits of electrically driven bioprocesses include improved production rate, selectivity, and carbon conversion efficiency. However, the accumulation of products can lead to inhibition of biocatalysts, necessitating further effort in separating products. The recent discovery of a new photoenzyme, capable of converting carboxylic acids to bio-alkanes, has offered an opportunity for system integration, providing a promising approach for simultaneous product separation and valorisation. Combining the strengths of photo/bio/electrochemical catalysis, we discuss an innovative circular cascading system that converts biomass and CO₂ to value-added bio-alkanes (C_nH_2n+2, n = 2 to 5) whilst achieving carbon circularity.

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The oxidation of alkanes into valuable chemical products is a vital reaction in organic synthesis. This reaction, however, is challenging, owing to the inertness of C−H bonds. Transition metal catalysts for C−H functionalization are frequently explored. Despite chemical alternatives, nature has also evolved powerful oxidative enzymes (e. g., methane monooxygenases, cytochrome P450 oxygenases, peroxygenases) that are capable of transforming C−H bonds under very mild conditions, with only the use of molecular oxygen or hydrogen peroxide as electron acceptors. Although progress in alkane oxidation has been reviewed extensively, little attention has been paid to small alkane oxidation. The latter holds great potential for the manufacture of chemicals. This Minireview provides a concise overview of the most relevant enzyme classes capable of small alkanes (C_<6) oxyfunctionalization, describes the essentials of the catalytic mechanisms, and critically outlines the current state-of-the-art in preparative applications.

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Versatile bio-derived catalysts have been under dynamic investigation as potential substitutes to conventional chemical catalysts for sustainable biodiesel production. This is because of their unique, low-cost benefits and production processes that are environmentally and economically acceptable. This critical review aspires to present a viable approach to the synthesis of environmentally benign and cost-effective heterogeneous solid-base catalysts from a wide range of biological and industrial waste materials for sustainable biodiesel production. Most of these waste materials include an abundance of metallic minerals like potassium and calcium. The different approaches proposed by researchers to derive highly active catalysts from large-scale waste materials of a re-usable nature are described briefly. Finally, this report extends to present an overview of techno-economic feasibility of biodiesel production, its environmental impacts, commercial aspects of community-based biodiesel production and potential for large-scale expansion.

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Peroxyzymes simply use H2O2 as a cosubstrate to oxidize a broad range of inert C-H bonds. The lability of many peroxyzymes against H2O2 can be addressed by a controlled supply of H2O2, ideally in situ. Here, we report a simple, robust, and water-soluble anthraquinone sulfonate (SAS) as a promising organophotocatalyst to drive both haloperoxidase-catalyzed halogenation and peroxygenase-catalyzed oxyfunctionalization reactions. Simple alcohols, methanol in particular, can be used both as a cosolvent and an electron donor for H2O2 generation. Very promising turnover numbers for the biocatalysts of up to 318 »000 have been achieved.

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