Complete Field Guide to Asymmetric BINOL-Phosphate Derived Brønsted Acid and Metal Catalysis: History and Classification by Mode of Activation; Brønsted Acidity, Hydrogen Bonding, Ion Pairing, and Metal Phosphates

Mesoporous silicates (MPS) have an ordered pore structure with dimensions comparable to many biological molecules. They have been extensively explored as supports for proteins and enzymes in biocatalytic applications. Since their initial discovery, novel syntheses methods have led to precise control over pore size and structure, particle size, chemical composition, and stability, thus allowing the adsorption of a wide variety of biological macromolecules, such as heme proteins, lipases, antibody fragments, and proteases, into their structures. This Review discusses the application of ordered, large-pore, functionalized mesoporous silicates to immobilize proteins for biocatalysis.

Proteins in mesoporous silicates.

Enzymes as industrial biocatalysts offer numerous advantages over traditional chemical processes with respect to sustainability and process efficiency. Enzyme catalysis has been scaled up for commercial processes in the pharmaceutical, food and beverage industries, although further enhancements in stability and biocatalyst functionality are required for optimal biocatalytic processes in the energy sector for biofuel production and in natural gas conversion. The technical barriers associated with the implementation of immobilized enzymes suggest that a multidisciplinary approach is necessary for the development of immobilized biocatalysts applicable in such industrial-scale processes. Specifically, the overlap of technical expertise in enzyme immobilization, protein and process engineering will define the next generation of immobilized biocatalysts and the successful scale-up of their induced processes. This review discusses how biocatalysis has been successfully deployed, how enzyme immobilization can improve industrial processes, as well as focuses on the analysis tools critical for the multi-scale implementation of enzyme immobilization for increased product yield at maximum market profitability and minimum logistical burden on the environment and user.

Industrial Applications of Enzymes: Recent Advances, Techniques, and Outlooks

Lipase promiscuity and its biochemical applications

Cross-linked enzyme aggregates (CLEAs) have many economic and environmental benefits in the context of industrial biocatalysis. They are easily prepared from crude enzyme extracts, and the costs of (often expensive) carriers are circumvented. They generally exhibit improved storage and operational stability towards denaturation by heat, organic solvents, and autoproteolysis and are stable towards leaching in aqueous media. Furthermore, they have high catalyst productivities (kilograms product per kilogram biocatalyst) and are easy to recover and recycle. Yet another advantage derives from the possibility to co-immobilize two or more enzymes to provide CLEAs that are capable of catalyzing multiple biotransformations, independently or in sequence as catalytic cascade processes.

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Characteristic features and biotechnological applications of cross-linked enzyme aggregates (CLEAs)

Highly Enantioselective Biginelli Reaction Catalyzed by Double Axially Chiral Bisphosphorylimides

Pseudomonas sp. Lipase (PSL) immobilized with the method of cross-linked enzyme aggregates (CLEAs) using acetone as the optimal precipitant is investigated. The immobilization efficiency (%) and activity retention (%) of the immobilized lipase (CLEA-PSL) are 70.6 and 45.1%, respectively. In the kinetic resolution of N-(2-ethyl-6-methylphenyl) alanine, CLEA-PSL not only keeps excellent enantioselectivity (E-value > 100) as the free PSL, but also shows higher catalytic activity and thermal stability. CLEA-PSL requires only 12 h to obtain 50% conversion whereas the free PSL needs 48 h; the residual activity of CLEA-PSL and free PSL are respectively 72.2 and 23.3% after incubated 24 h at 60 °C. Furthermore, CLEA-PSL can be re-used through ten cycles and the efficiency loss in activity is found to be only 19.1%.

Resolution of N-(2-ethyl-6-methylphenyl) alanine via cross-linked aggregates of Pseudomonas sp. Lipase

The enzyme-catalyzed Henry reaction was realized using deep eutectic solvents (DESs) as a reaction medium. The lipase from Aspergillus niger (lipase AS) showed excellent catalytic activity toward the substrates aromatic aldehydes and nitromethane in choline chloride:glycerol at a molar ratio of 1:2. Addition of 30 vol% water to DES further improved the lipase activity and inhibited DES-catalyzed transformation. A final yield of 92.2% for the lipase AS-catalyzed Henry reaction was achieved under optimized reaction conditions in only 4 h. In addition, the lipase AS activity was improved by approximately 3-fold in a DES-water mixture compared with that in pure water, which produced a final yield of only 33.4%. Structural studies with fluorescence spectroscopy showed that the established strong hydrogen bonds between DES and water may be the main driving force that affects the spatial conformation of the enzyme, leading to a change in lipase activity. The methodology was also extended to the aza-Henry reaction, which easily occurred in contrast to that in pure water. The enantioselectivity of both Henry and aza-Henry reactions was not found. However, the results are still remarkable, as we report the first use of DES as a reaction medium in a lipase-catalyzed Henry reaction.

Enzyme-Catalyzed Henry Reaction in Choline Chloride-Based Deep Eutectic Solvents.

A biocatalytic approach for the production of (S)-N-(2-ethyl-6-methylphenyl)alanine, a key intermediate for (S)-Metolachlor, has been developed by the use of lipase-catalyzed hydrolytic kinetic resolution. Compared with other selected lipases, the lipase from Pseudomonas cepacia (PSL) gives good conversion (48.2%) and excellent enantioselectivity (E-value > 100) to obtain enantiomerically pure (R)-acid (99% e.e.p). Then, a simple second resolution procedure is used to prepare (S)-acid product from the remaining (S)-ester without any reduction in enantiomeric excess (98% e.e.p) using the lipase B from Candida antarctica (CAL-B). Subsequent PSL immobilized on mesoporous SBA-15 molecular sieve is studied. The resulting supported enzyme catalyst exhibits higher activity, stability as well as reusability, compared with free enzyme.

Resolution of N-(2-ethyl-6-methylphenyl)alanine via free and immobilized lipase from Pseudomonas cepacia

Simple N -proline-based dipeptides with two N–H groups in combination with 2,4-dinitrophenol (DNP) catalyze the direct asymmetric aldol reactions of aldehydes with a broad range of ketones to furnish the corresponding aldol products in high yields (up to 99%) and with high enantioselectivities (up to 97%) and diastereoselectivities (up to >99:1, anti / syn ) at room temperature and in brine.

Liangyu Zheng

Papers

Highly Enantioselective Biginelli Reaction Catalyzed by Double Axially Chiral Bisphosphorylimides

Resolution of N-(2-ethyl-6-methylphenyl) alanine via cross-linked aggregates of Pseudomonas sp. Lipase

Enzyme-Catalyzed Henry Reaction in Choline Chloride-Based Deep Eutectic Solvents.

Resolution of N-(2-ethyl-6-methylphenyl)alanine via free and immobilized lipase from Pseudomonas cepacia

Proline-based dipeptides as efficient organocatalysts for asymmetric aldol reactions in brine