PTFE-Carbon Nanotubes and Lipase B from Candida antarctica-Long-Lasting Marriage for Ultra-Fast and Fully Selective Synthesis of Levulinate Esters

Valorization of Levulinic Acid by Esterification with 1-Octanol Using a Novel Biocatalyst Derived from Araujia sericifera

Levulinic acid, which can be obtained from biomass, has sparked great interest as a biologically-based chemical building block with wide versatility and potential. Its esterification with alcohols of different chain lengths is a promising valorization process for obtaining esters with various applications in the areas of biofuels/biolubricants, food and cosmetics, among others. In this work, the enzymatic esterification of levulinic acid and 1-octanol using a biocatalyst derived from Araujia sericifera latex was studied in systems with and without solvent. The influence of the molar ratio between alcohol and acid (ranging from 2:1 to 1:9), the biocatalyst loading (between 7.5 and 17.5% relative to the acid), the volume of n-heptane used as reaction solvent (from 0 to 4ml), and the reaction time (6hours) were investigated. The activity and stability of the biocatalyst in successive uses were also analyzed. A conversion of 49% was achieved when the reaction was carried out in a solvent-free system, using an alcohol/acid molar ratio of 1:7 and after 5h of reaction. On the other hand, the conversion was 65.1% when the reaction was conducted in a system containing 1ml of n-heptane as solvent, an alcohol/acid molar ratio of 1:8, and 5h of reaction. In both cases, a temperature as low as 30 °C and an agitation speed of 300 RPM were used.

Improved lipase performance by covalent immobilization of Candida antarctica lipase B on amino acid modified microcrystalline cellulose as green renewable support

Development of immobilized lipase with excellent catalytic performance and low cost is the major challenge for large-scale industrial applications. In this study, green renewable microcrystalline cellulose (MCC) that was hydrophobically modified with D-alanine (Ala) or L-lysine (Lys) was used for immobilizing Candida antarctica lipase B (CALB). The improved catalytic properties were investigated by experimental and computational methods. CALB immobilized on MCC-Ala with higher hydrophobicity showed better catalytic activity than CALB@MCC-Lys because the increased flexibility of the lid region of CALB@MCC-Ala favored the formation of open conformation. Additionally, the low root mean square deviation and the high β-sheet and α-helix contents of CALB@MCC-Ala indicated that the structure became more stable, leading to a significantly enhanced stability (54.80% and 90.90% relative activity at 70 °C and pH 9.0, respectively) and good reusability (48.92% activity after 5 cycles). This study provides a promising avenue to develop immobilized lipase with high catalytic properties for industry applications.

Scalability of U-Shape Magnetic Nanoparticles-Based Microreactor–Lipase-Catalyzed Preparative Scale Kinetic Resolutions of Drug-like Fragments

The production of active pharmaceutical ingredients (APIs) and fine chemicals is accelerating due to the advent of novel microreactors and new materials for immobilizing customized biocatalysts that permit long-term use in continuous-flow reactors. This work studied the scalability of a tunable U-shape magnetic nanoparticles (MNPs)-based microreactor. The reactor consisted of a polytetrafluoroethylene tube (PTFE) of various inner diameters (ID = 0.75 mm, 1.50 mm, or 2.15 mm) and six movable permanent magnets positioned under the tube to create reaction chambers allowing the fluid reaction mixture to flow through and above the enzyme-loaded MNPs anchored by permanent magnets. The microreactors with various tube sizes and MNP capacities were tested with the preparative scale kinetic resolution of the drug-like alcohols 4-(3,4-dihydroisoquinolin-2(1H)-yl)butan-2-ol (±)-1a and 4-(3,4-dihydroquinolin-1(2H)-yl)butan-2-ol (±)-1b, utilizing Lipase B from Candida antarctica immobilized covalently onto MNPs, leading to highly enantioenriched products [(R)-2a,b and (S)-1a,b]. The results in the U-shape MNP flow reactor were compared with reactions in the batch mode with CaLB-MNPs using similar conditions. Of the three different systems, the one with ID = 1.50 mm showed the best balance between the maximum loading capacity of biocatalysts in the reactor and the most effective cross-section area. The results showed that this U-shaped tubular microreactor might be a simple and flexible instrument for many processes in biocatalysis, providing an easy-to-set-up alternative to existing techniques.

Process optimization for enzymatic production of a valuable biomass-based ester from levulinic acid

The enzymatic production of isoamyl levulinate via esterification of isoamyl alcohol (IA) and levulinic acid (LA), a biomass-based platform chemical with attractive properties, in a solvent system has been performed in this study. For such a purpose, a low-cost liquid lipase (Eversa^® Transform 2.0) immobilized by physical adsorption via hydrophobic interactions (mechanism of interfacial activation) on mesoporous poly(styrenene-divinylbenzene) (PSty-DVB) beads was used as heterogeneous biocatalyst. It was prepared at low ionic strength (5 mmol.L^-1 buffer sodium acetate pH 5.0) and 25 ℃ using an initial protein loading of 40 mg.g^-1 of support. Maximum protein loading of 31.2 ± 2.8 mg.g^-1 of support and an immobilization yield of 83% was achieved. The influence of relevant factors (biocatalyst concentration and reaction temperature) on ester production was investigated using a central composite rotatable design (CCRD). Maximum acid conversion percentage of 65% was achieved after 12 h of reaction at 40 °C, 20% of mass of heterogeneous biocatalyst per mass of reaction mixture (20% m.m^-1), and LA:IA molar ratio of 1:1.5 in a methyl isobutyl ketone (MIBK) medium. The biocatalyst retained around of 30% of its initial activity after five consecutive esterification batches under optimal experimental conditions. The proposed experimental procedure can be considered as an acceptable green process (EcoScale score of 66.5), in addition to the fact that a new strategy is proposed to sustainably produce a valuable industrial ester (isoamyl levulinate) from biomass-based materials using an immobilized and low-cost commercial lipase as catalyst.

Improved catalytic properties of Candida antarctica lipase B immobilized on cetyl chloroformate-modified cellulose nanocrystals

The catalytic activity of Candida antarctica lipase B (CALB) immobilized on modified cellulose nanocrystals (CNC) with different hydrophobicity was investigated using experimental and theoretical approaches. Firstly, the modified CNC were characterized by multi-spectroscopic methods, water contact angle, scanning electron microscopy and thermogravimetric analysis. Moderately hydrophobic CNC were found to be an optimal support for CALB immobilization. Secondly, model systems contained a CALB molecule and different numbers of modified CNC molecules (CALB@3CNC-C16, CALB@10CNC-C16 and CALB@15CNC-C16) were prepared for molecular dynamics (MD) simulation. Root-mean-square fluctuation values (0.61-2.61 Å) of lid region were relatively high in CALB@10CNC-C16, indicating that modified CNC with moderate hydrophobicity favored forming a lid-open conformation of CALB. Finally, the esterification of oleic acid catalyzed by the immobilized CALB showed higher conversion (54.68 %) than free CALB (12.98 %). Insights into modified CNC with tunable properties provided by this study may be a potential support for improving the catalytic performance of lipases.

Chemo-Enzymatic Baeyer-Villiger Oxidation Facilitated with Lipases Immobilized in the Supported Ionic Liquid Phase

A novel method for chemo-enzymatic Baeyer–Villiger oxidation of cyclic ketones in the presence of supported ionic liquid-like phase biocatalyst was designed. In this work, multi-walled carbon nanotubes were applied as a support for ionic liquids which were anchored to nanotubes covalently by amide or imine bonds. Next, lipases B from Candida antarctica, Candida rugosa, or Aspergillus oryzae were immobilized on the prepared materials. The biocatalysts were characterized using various techniques, like thermogravimetry, IR spectroscopy, XPS, elemental analysis, and SEM-EDS microscopy. In the proposed approach, a biocatalyst consisting of a lipase as an active phase allowed the generation of peracid in situ from the corresponding precursor and a green oxidant–hydrogen peroxide. The activity and stability of the obtained biocatalysts in the model oxidation of 2-adamantanone were demonstrated. High conversion of substrate (92%) was achieved under favorable conditions (toluene: n-octanoic acid ratio 1:1 = v:v, 35% aq. H₂O₂ 2 eq., 0.080 g of biocatalyst per 1 mmol of ketone at 20 °C, reaction time 4 h) with four reaction cycles without a drop in its activity. Our ‘properties-by-design’ approach is distinguished by its short reaction time at low temperature and higher thermal stability in comparison with other biocatalysts presented in the literature reports.

Outperformance in Acrylation: Supported D-Glucose-Based Ionic Liquid Phase on MWCNTs for Immobilized Lipase B from Candida antarctica as Catalytic System

This study presents a highly efficient method of a synthesis of n-butyl acrylate via esterification of acrylic acid and n-butanol in the presence of supported ionic liquid phase (SILP) biocatalyst consisting of the lipase B from Candida antarctica (CALB) and multi-walled carbon nanotubes (MWCNTs) modified by D-glucose-based ionic liquids. Favorable reaction conditions (acrylic acid: n-butanol molar ratio 1:2, cyclohexane as a solvent, biocatalyst 0.150 g per 1 mmol of acrylic acid, temperature 25 °C) allowed the achievement of a 99% yield of n-butyl acrylate in 24 h. Screening of various ionic liquids showed that the most promising result was obtained if N-(6-deoxy-1-O-methoxy-α-D-glucopyranosyl)-N,N,N-trimethylammonium bis-(trifluoromethylsulfonyl)imide ([N(CH3)3GlcOCH3][N(Tf)2]) was selected in order to modify the outer surface of MWCNTs. The final SILP biocatalyst-CNTs-[N(CH3)3GlcOCH3][N(Tf)2]-CALB contained 1.8 wt.% of IL and 4.2 wt.% of CALB. Application of the SILP biocatalyst led to the enhanced activity of CALB in comparison with the biocatalyst prepared via physical adsorption of CALB onto MWCNTs (CNTs-CALB), as well as with commercially available Novozyme 435. Thus, the crucial role of IL in the stabilization of biocatalysts was clearly demonstrated. In addition, a significant stability of the developed biocatalytic system was confirmed (three runs with a yield of ester over 90%).