Invited for this month′s cover is the Working Group Sustainable Chemistry of the European Society of Applied Biocatalysis (ESAB). The image shows the significant contributions of Biocatalysis to ...science, industry, society, and environment as a technology of first choice for Sustainable Chemistry in the 21st century. The Perspective itself is available at 10.1002/cssc.202102709.
“A “Golden Age” of biocatalysis is on the horizon…” This and more about the story behind the research that inspired the Cover image is presented in the Cover Profile. Read the full text of the corresponding research at 10.1002/cssc.202102709. View the Front Cover here: 10.1002/cssc.202200707.
Achieving convergent synthetic strategies has long been a gold standard in constructing complex molecular skeletons, allowing for the rapid generation of complexity in comparatively streamlined ...synthetic routes. Traditionally, biocatalysis has not played a prominent role in convergent laboratory synthesis, with the application of biocatalysts in convergent strategies primarily limited to the synthesis of chiral fragments. Although the use of enzymes to enable convergent synthetic approaches is relatively new and emerging, combining the efficiency of convergent transformations with the selectivity achievable through biocatalysis creates new opportunities for efficient synthetic strategies. This Perspective provides an overview of recent developments in biocatalytic strategies for convergent transformations and offers insights into the advantages of these methods compared to their small molecule-based counterparts.
The combination of sequential biocatalytic reactions, via non-natural synthetic cascades, is a rapidly developing field and leads to the generation of complex valuable chemicals from simple ...precursors. As the toolbox of available biocatalysts continues to expand, so do the options for biocatalytic retrosynthesis of a target molecule, leading to alternative routes employing enzymatic transformations. The implementation of such cascade reactions requires careful consideration, particularly with respect to whether the pathway is constructed in vitro or in vivo. In this Perspective, we describe the relative merits of in vitro, in vivo, and hybrid approaches to building biocatalytic cascades and showcase recent developments in the area. We also highlight the factors that influence the design and implementation of purely enzymatic or chemoenzymatic, one-pot, multistep pathways.
The use of biocompatible ionic liquids (bio-ILs) as a "green" solvent with uniquely tunable cations and anions, specific selectivity, and many other desirable physicochemical properties in ...biocatalysis has shown great promises to address many challenges. A plethora of studies have demonstrated ILs possess a range of exceptional capabilities in coordinating biocatalysis such as stabilizing enzyme structure, enhancing enzyme-substrate interaction, increasing substrate solubility and product separation/removal, and improving enzyme immobilization/recycling. Therefore, bio-ILs have been explored for biocatalysis in a wide range of homogenous as well as multiphasic systems including biphasic, multiphasic, microemulsion, and whole-cell systems. This review provides an overview of IL-enabled biocatalysis including enzymatic and whole-cell reactions in homogeneous and multiphasic systems. First, the properties of IL concentration, specific ion effect, pH, viscosity, alkyl chain length, hydrophobicity, and polarity on the structures and activities of enzymes are discussed together with characterization techniques to elucidate the mechanisms of IL-enzyme interactions. Second, while homogenous biocatalysis systems containing ILs are briefly introduced and summarized, particular attention is given to multiphasic systems. Furthermore, recent progress in using bio-ILs to modify emerging new enzyme carrier materials including carbonaceous and magnetic nanomaterials, gel microspheres, and membranes as well as their effect on increasing enzyme stability and recycling are highlighted. Finally, we provide our expert opinion for more innovative research in the field and future outlook for the industrial application of ILs in biocatalysis.
The challenges of light-dependent biocatalytic transformations of lipophilic substrates in aqueous media are manifold. For instance, photolability of the catalyst as well as insufficient light ...penetration into the reaction vessel may be further exacerbated by a heterogeneously dispersed substrate. Light penetration may be addressed by performing the reaction in continuous flow, which allows two modes of applying the catalyst: (i) heterogeneously, immobilized on a carrier, which requires light-permeable supports, or (ii) homogeneously, dissolved in the reaction mixture. Taking the light-dependent photodecarboxylation of palmitic acid catalyzed by fatty-acid photodecarboxylase from Chlorella variabilis (CvFAP) as a showcase, strategies for the transfer of a photoenzyme-catalyzed reaction into continuous flow were identified. A range of different supports were evaluated for the immobilization of CvFAP, whereby Eupergit C250 L was the carrier of choice. As the photostability of the catalyst was a limiting factor, a homogeneous system was preferred instead of employing the heterogenized enzyme. This implied that photolabile enzymes may preferably be applied in solution if repair mechanisms cannot be provided. Furthermore, when comparing different wavelengths and light intensities, extinction coefficients may be considered to ensure comparable absorption at each wavelength. Employing homogeneous conditions in the CvFAP-catalyzed photodecarboxylation of palmitic acid afforded a space-time yield unsurpassed by any reported batch process (5.7 g·L–1·h–1, 26.9 mmol·L–1·h–1) for this reaction, demonstrating the advantage of continuous flow in attaining higher productivity of photobiocatalytic processes.
The selective introduction of amine groups within deconstruction products of lignin could provide an avenue for valorizing waste biomass while achieving a green synthesis of industrially relevant ...building blocks from sustainable sources. Here, we built and characterized enzyme cascades that create aldehydes and subsequently primary amines from diverse lignin‐derived carboxylic acids using a carboxylic acid reductase (CAR) and an ω‐transaminase (TA). Unlike previous studies that have paired CAR and TA enzymes, here we examine multiple homologs of each of these enzymes and a broader set of candidate substrates. In addition, we compare the performance of these systems in cell‐free and resting whole‐cell biocatalysis formats using the conversion of vanillate to vanillyl amine as model chemistry. We also demonstrate that resting whole cells can be recycled for multiple batch reactions. We used the knowledge gained from this study to produce several amines from carboxylic acid precursors using one‐pot biocatalytic reactions, several of which we report for the first time. These results expand our knowledge of these industrially relevant enzyme families to new substrates and contexts for environmentally friendly and potentially low‐cost synthesis of diverse aryl aldehydes and amines.
Amine containing side chains can confer useful properties to polymers but are not naturally found in lignin monomers. Furthermore, their selective installation can be challenging using traditional synthetic strategies. Here, we propose a sustainable process for synthesizing value‐added aryl amine monomers from lignin‐derived carboxylates, using carboxylic acid reductase/ω‐transaminase enzymatic functionalization for eventual synthesis of materials.
A biohybrid photobioanode mimicking the Z-scheme has been developed by functional integration of photosystem II (PSII) and PbS quantum dots (QDs) within an inverse opal TiO
architecture giving rise ...to a rather negative water oxidation potential of about -0.55 V vs. Ag/AgCl, 1 m KCl at neutral pH. The electrical linkage between both light-sensitive entities has been established through an Os-complex-modified redox polymer (P
), which allows the formation of a multi-step electron-transfer chain under illumination starting with the photo-activated water oxidation at PSII followed by an electron transfer from PSII through P
to the photo-excited QDs and finally to the TiO
electrode. The photobioanode was coupled to a novel, transparent, inverse-opal ATO cathode modified with an O
-reducing bilirubin oxidase for the construction of a H
O/O
photobioelectrochemical cell reaching a high open-circuit voltage of about 1 V under illumination.
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