Highly enantioselective acylation of chlorohydrins using Amano AK lipase from P. fluorescens immobilized on silk fibroin–alginate spheres

Probing the Physicochemical, Nanomorphological, and Antimicrobial Attributes of Sustainable Silk Fibroin/Copaiba Oleoresin-Loaded PVA Films for Food Packaging Applications

We explore the development of biodegradable poly(vinyl alcohol) (PVA) films loaded with silk fibroin (SF) functionalized with copaiba oleoresin (SFCO) for potential use in active food packaging. The films were characterized, showing significant improvements in both their physicochemical and nanomorphological properties. Films containing 10% SFCO exhibited superior mechanical strength, with a Young modulus of 145 MPa and an elongation at break of 385%, compared to the control film with 42 MPa and 314%, respectively. The films also demonstrated barrier properties, with water vapor transmission rates (WVTRs) as low as 25.95 g/h·m2. Antimicrobial activity against Staphylococcus aureus and Escherichia coli was significantly improved, showing inhibition zones of up to 10 ± 1 mm and a minimum inhibitory concentration (MIC) of 100 µg∙mL-1. Three-dimensional nanomorphological analysis via atomic force microscopy (AFM) showed increased roughness in films with higher SFCO content, with root mean square (RMS) roughness values ranging from 2.70 nm to 11.5 nm. These results highlight the potential of SFCO-loaded PVA films as robust, eco-friendly alternatives to conventional packaging materials. They provide improved mechanical and antimicrobial properties, essential for extending the shelf life of perishable foods and advancing sustainability in the packaging industry.

Development of nanostructured formulation from naringenin and silk fibroin and application for inhibition of lipoxygenase (LOX)

A simple low-energy method was used to obtain polymeric nanoparticles containing silk fibroin (SF), fatty butyl esters (oily phase) and the flavonoid naringenin. Experimental planning (Box-Behnken) was applied to investigate the optimal conditions for three factors (variation of the concentrations of SF, naringenin and fatty butyl ester) at three levels, with evaluation of particle size, polydispersity index (PDI) and zeta potential (ZP) as responses. The results showed that the polymeric particle was formed with sizes of 179.6 to 633.9 nm, PDI of 0.33 to 0.77 and ZP of -60.4 to -38.8 mV. The best responses under the optimized conditions (Nari-SF 9 and 15) were characterized through transmission electron microscopy (TEM), Fourier-transform infrared (FT-IR), visible ultraviolet (UV-vis) and fluorescence, which confirmed that coated nanoparticles had been obtained. It was shown that the nanoformulation had excellent stability, the bioavailability of naringenin had been improved through use of the biopolymer and high inhibition of the enzyme lipoxygenase had been achieved in vitro.

Combination of gold and redox enzyme catalysis to access valuable enantioenriched aliphatic β-chlorohydrins

The synthesis of enantioenriched β-chlorohydrins is highly appealing due to their relevance as building-blocks in organic synthesis. However, the approximation to aliphatic derivatives is particularly challenging due to the difficulties to get access to the α-chloroketone precursors. Herein, we propose a straightforward and scalable approach combining in a concurrent manner gold(I) and redox enzyme catalysis through a hydration-bioreduction cascade. A total of nine aliphatic β-chlorohydrins bearing different functional groups were obtained with very high yields (63-88%) and stereoselectivities (>99% ee).

Synthesis of Optically Active syn- and anti-Chlorohydrins through a Bienzymatic Reductive Cascade

A bienzymatic cascade has been designed and optimized to obtain enantiopure chlorohydrins starting from the corresponding 1-aryl-2-chlorobut-2-en-1-ones. For the synthesis of these α-chloroenones, a two-step sequence was developed consisting of the allylation of the corresponding aldehyde with 3-dichloroprop-1-ene, followed by oxidation and further isomerization. The selective cooperative catalytic system involving ene-reductases (EREDs) and alcohol dehydrogenases (ADHs) afforded the desired optically active chlorohydrins under mild reaction conditions in excellent conversions (up to >99%) and selectivities (up to >99:1 diastereomeric ratio (dr), >99% enantiomeric excess (ee)).

Biocatalytic approaches for the synthesis of optically pure vic-halohydrins

Enantiopure vicinal halohydrins (vic-halohydrins) are highly valuable building blocks for the synthesis of many different natural products and pharmaceuticals, and biocatalytic methods for their synthesis have received considerable interest. This review emphasizes the application of biocatalytic approaches as an efficient alternative or complement to conventional chemical reactions, with a special focus on the asymmetric reductions catalyzed by ketoreductases, kinetic resolution catalyzed using lipases or esterases, stereoselective biotransformation catalyzed by halohydrin dehalogenases, asymmetric hydroxylation catalyzed by cytochrome P450 monooxygenases, asymmetric dehalogenation catalyzed by haloalkane dehalogenases, and aldehyde condensation catalyzed by aldolases. Although many chiral vic-halohydrins have been successfully synthesized using wild-type biocatalysts, their enantioselectivity is often too low for enantiopure synthesis. To overcome these limitations, catalytic properties of wild-type enzymes have been improved by rational and semi-rational protein design or directed evolution. This review briefly introduces the research status in this field, highlighting aspects of basic academic research in the biocatalytic synthesis of optically active vic-halohydrins by employing such unconventional approaches. KEY POINTS: • Outlines the enzymatic strategies for the production of enantiopure vic-halohydrins • Highlights recent advances in biocatalytic production of enantiopure vic-halohydrins • Provide guidance for efficient preparation of enantiopure vic-halohydrins.

Silk Fibroin-Based Materials for Catalyst Immobilization

Silk fibroin is a widely and commercially available natural protein derived from silkworm cocoons. Thanks to its unique amino acid composition and structure, which lead to localized nanoscale pockets with limited but sufficient hydration for protein interaction and stabilization, silk fibroin has been studied in the field of enzyme immobilization. Results of these studies have demonstrated that silk fibroin offers an important platform for covalent and noncovalent immobilization of enzymes through serving as a stabilization matrix/support with high retention of the biological activity of the enzymes of interest. In the hope of providing suggestions for potential future research directions, this review has been written to briefly introduce and summarize key advances in silk fibroin-based materials for immobilization of both enzymes/biocatalysts (including alkaline phosphatase, β-glucosidase, glucose oxidase, lipase, urease, uricase, horseradish peroxidase, catalase, xanthine oxidase, tyrosinase, acetylcholinesterase, neutral protease, α-chymotrypsin, amylase, organophosphorus hydrolase, β-galactosidase, carbonic anhydrase, laccase, zymolyase, phenylalanine ammonia-lyase, thymidine kinase, and several others) and non-enzymatic catalysts (such as Au, Pd, Fe, α-Fe2O3, Fe3O4, TiO2, Pt, ZnO, CuO, Cu2O, Mn3O4, and MnO2).

Biotransformation of (E)-2-Methyl-3-Phenylacrylaldehyde Using Mycelia of Penicillium citrinum CBMAI 1186, Both Free and Immobilized on Chitosan

This study applied the use of marine-derived fungus Penicillium citrinum CBMAI 1186 in the stereoselective reduction of the C=C double bond of the prochiral (E)-2-methyl-3-phenylacrylaldehyde 1. The fungus immobilized on chitosan, obtained by multistep ultrasound-assisted deacetylation process (Ch-USAD), produced the (S)-(+)-2-methyl-3-phenylpropan-1-ol 3 (c = 49%, 40% ee) isomer and (±)-2-methyl-3-phenylacrilic acid 4 (c = 35%); in contrast, immobilized mycelia on commercial chitosan (Ch-C) yielded the (S)-(+)-2-methyl-3-phenylpropan-1-ol 3 (c = 48%, 10% ee) and (±)-2-methyl-3-phenylpropanal 1a (c = 41%). The reaction using free mycelia gave a 40% yield of (S)-(+)-2-methyl-3-phenylpropan-1-ol 3 with 10% ee. These results showed that the crystallinity form and molecular weight of chitosan (Ch-C or Ch-USAD) used to immobilized mycelia of P. citrinum CBMAI 1186 influenced in the biotransformation of (E)-2-methyl-3-phenylacrylaldehyde 1. Therefore, marine-derived fungus P. citrinum CBMAI 1186 immobilized on chitosan can be a potential alternative in the studies of hydrogenation of the α,β-unsaturated carbon-carbon (α,β-C=C) double bond. Marine-derived fungus Penicillium citrinum CBMAI 1186 immobilized on chitosan in the stereoselective reduction of the C=C double bond of the prochiral (E)-2-methyl-3-phenylacrylaldehyde.

Enantioselective ene-reduction of E-2-cyano-3-(furan-2-yl) acrylamide by marine and terrestrial fungi and absolute configuration of (R)-2-cyano-3-(furan-2-yl) propanamide determined by calculations of electronic circular dichroism (ECD) spectra

This work reports the green organic chemistry synthesis of E-2-cyano-3(furan-2-yl) acrylamide under microwave radiation (55 W), as well as the use of filamentous marine and terrestrial-derived fungi, in the first ene-reduction of 2-cyano-3-(furan-2-yl) acrylamide to (R)-2-cyano-3-(furan-2-yl)propanamide. The fungal strains screened included Penicillium citrinum CBMAI 1186, Trichoderma sp. CBMAI 932 and Aspergillus sydowii CBMAI 935, and the filamentous terrestrial fungi Aspergillus sp. FPZSP 146 and Aspergillus sp. FPZSP 152. A compound with an uncommon CN-bearing stereogenic center at the α-C position was obtained by enantioselective reactions mediated in the presence of the microorganisms yielding the (R)-2-cyano-3-(furan-2-yl) propanamide 3a. Its isolated yield and e.e. ranged from 86% to 98% and 39% to 99%, respectively. The absolute configuration of the biotransformation products was determined by time-dependent density functional theory (TD-DFT) calculations of electronic circular dichroism (ECD) spectra. Finally, the tautomerization of 2-cyano-3-(furan-2-yl) propanamide 3a to form an achiral ketenimine was observed and investigated in presence of protic solvents.

Immobilization of Amano lipase from Pseudomonas fluorescens on silk fibroin spheres: an alternative protocol for the enantioselective synthesis of halohydrins

Amano lipase from Pseudomonas fluorescens immobilized on silk fibroin spheres and used in the enzymatic kinetic resolution of halohydrins, to obtain optically active epoxides, important precursors in the synthesis of antifungal azoles.

Immobilization of Lipase from Pseudomonas fluorescens on Porous Polyurea and Its Application in Kinetic Resolution of Racemic 1-Phenylethanol

A porous polyurea (PPU) was prepared through a simple protocol by reacting toluene diisocyanate with water in binary solvent of water-acetone. Its amine group was determined through spectrophotometric absorbance based on its iminization with p-nitrobenzaldehyde amines. PPU was then used as a novel polymer support for enzyme immobilization, through activation by glutaraldehyde followed by immobilization of an enzyme, lipase from Pseudomonas fluorescens (PFL), via covalent bonding with the amine groups of lipase molecules. Influences of glutaraldehyde and enzyme concentration and pH in the process were studied. The results revealed that the activity of the immobilized PFL reached a maximum at GA concentration of 0.17 mol/L and at pH 8. Immobilization rate of 60% or higher for PFL was obtained under optimized condition with an enzyme activity of 283 U/mg. The porous structure of PPU, prior to and after GA activation and PFL immobilization, was characterized. The activity of the immobilized PFL at different temperature and pH and its stability at 40 °C as well as its reusability were tested. The immobilized enzyme was finally used as enantioselective catalyst in kinetic resolution of racemic 1-phenylethanol (1-PEOH), and its performance compared with the free PFL. The results demonstrate that the enzyme activity and stability were greatly improved for the immobilized PFL, and highly pure enantiomers from racemic 1-PEOH were effectively achieved using the immobilized PFL. Noticeable deactivation of PFL in the resolution was observed by acetaldehyde in situ formed. In addition, the immobilized PFL was readily recovered from the reaction system for reuse. A total of 73% of the initial activity was retained after 5 repeated reuse cycles. This work provides a novel route to preparation of a polyurea porous material and its enzyme immobilization, leading to a novel type of immobilized enzyme for efficient kinetic resolution of racemic molecules.