Lipase catalysis in organic solvents: advantages and applications

Lipases are industrial biocatalysts, which are involved in several novel reactions, occurring in aqueous medium as well as non-aqueous medium. Furthermore, they are well-known for their remarkable ability to carry out a wide variety of chemo-, regio- and enantio-selective transformations. Lipases have been gained attention worldwide by organic chemists due to their general ease of handling, broad substrate tolerance, high stability towards temperatures and solvents and convenient commercial availability. Most of the synthetic reactions on industrial scale are carried out in organic solvents because of the easy solubility of non-polar compounds. The effect of organic system on their stability and activity may determine the biocatalysis pace. Because of worldwide use of lipases, there is a need to understand the mechanisms behind the lipase-catalyzed reactions in organic solvents. The unique interfacial activation of lipases has always fascinated enzymologists and recently, biophysicists and crystallographers have made progress in understanding the structure-function relationships of these enzymes. The present review describes the advantages of lipase-catalyzed reactions in organic solvents and various effects of organic solvents on their activity.

Medium-engineering: a useful tool for modulating lipase activity and selectivity

The design of a specific reaction medium capable to enhance activity, stability, and productivity of biocatalysts has been a recurring topic of study during the last three decades. The remarkable properties and valuable applications of enzymes, especially lipases, have inspiried different strategies for improving their performance in near-anhydrous media. As lipases are the most frequently used enzymes in organic synthesis, understanding the influence of reaction media on their activity and selectivity is crucial. In this paper, we review the key features of lipases and demonstrate how medium-engineering is a useful tool to modulate the activity and selectivity of lipase-catalyzed reactions.

Design of a core–shell support to improve lipase features by immobilization

Different core–shell polymeric supports, exhbiting different featured, were produced and utilized in the immobilization and tuning of different lipases.

Unravelling transition metal-catalyzed terpenic alcohol esterification: a straightforward process for the synthesis of fragrances

Iron nitrate, a simple and commercially available Lewis acid, catalyzes terpenic alcohol esterification with acetic acid, achieving high conversion and ester selectivity.

One pot three-component reaction for covalent immobilization of enzymes: application of immobilized lipases for kinetic resolution of rac-ibuprofen

A one pot three-component reaction was used for the covalent immobilization of CALB and RML on epoxy-functionalized supports.

Evaluation of the performance of differently immobilized recombinant lipase B from Candida antarctica preparations for the synthesis of pharmacological derivatives in organic media

This paper shows the production of lipase B fromCandida antarctica(LIPB) after cloning the gene that encoded it inPichia pastorisusing PGK as a constitutive promoter. The lipase was immobilized on different home-made supports for distinct reactions.

Immobilization of Bacillus subtilis lipase on a Cu-BTC based hierarchically porous metal–organic framework material: a biocatalyst for esterification

Bacillus subtilislipase (BSL2) has been successfully immobilized into a Cu-BTC based hierarchically porous MOF material for the first time. The immobilized BSL2 presents high enzymatic activity and perfect reusability during the esterification reaction.

Synthesis of Fe3O4/P(St-AA) nanoparticles for enhancement of stability of the immobilized lipases

Core–shell Fe₃O₄/P(St-AA) nanoparticles were synthesized and employed as a magnetic carrier for lipase immobilization, and the properties of the immobilized lipase were studied.

An enzyme–copper nanoparticle hybrid catalyst prepared from disassembly of an enzyme–inorganic nanocrystal three-dimensional nanostructure

Enzyme–copper nanoparticle hybrid catalysts were prepared with highly retained enzymatic and Cu-catalytic activities, enabling the chemo-enzymatic cascade reactions.

The use of isocyanide-based multicomponent reaction for covalent immobilization of Rhizomucor miehei lipase on multiwall carbon nanotubes and graphene nanosheets

One-pot immobilization of RML on carbon-based nanomaterials was performed by using the Ugi four component reaction under extremely mild conditions.

Studies on lipase-catalyzed asymmetric synthesis of (S)-(hydroxymethyl)glutamic acid (HMG)

(S)-(Hydroxymethyl)glutamic acid was successfully synthesized in total 12 % yield over eight steps from tris(hydroxymethyl)aminomethane hydrochloride (Tris·HCl), employing lipase TL-induced enantioselective acetylation of a prochiral 1,3-diol as the key step.

Thermus thermophilus as a Source of Thermostable Lipolytic Enzymes

Lipolytic enzymes, esterases (EC 3.1.1.1) and lipases (EC 3.1.1.3), catalyze the hydrolysis of ester bonds between alcohols and carboxylic acids, and its formation in organic media. At present, they represent about 20% of commercialized enzymes for industrial use. Lipolytic enzymes from thermophilic microorganisms are preferred for industrial use to their mesophilic counterparts, mainly due to higher thermostability and resistance to several denaturing agents. However, the production at an industrial scale from the native organisms is technically complicated and expensive. The thermophilic bacterium Thermus thermophilus (T. thermophilus) has high levels of lipolytic activity, and its whole genome has been sequenced. One esterase from the T. thermophilus strain HB27 has been widely characterized, both in its native form and in recombinant forms, being expressed in mesophilic microorganisms. Other putative lipases/esterases annotated in the T. thermophilus genome have been explored and will also be reviewed in this paper.

Interfacial Activation of Candida antarctica Lipase B: Combined Evidence from Experiment and Simulation

Lipase immobilization is frequently used for altering the catalytic properties of these industrially used enzymes. Many lipases bind strongly to hydrophobic surfaces where they undergo interfacial activation. Candida antarctica lipase B (CalB), one of the most commonly used biocatalysts, is frequently discussed as an atypical lipase lacking interfacial activation. Here we show that CalB displays an enhanced catalytic rate for large, bulky substrates when adsorbed to a hydrophobic interface composed of densely packed alkyl chains. We attribute this increased activity of more than 7-fold to a conformational change that yields a more open active site. This hypothesis is supported by molecular dynamics simulations that show a high mobility for a small "lid" (helix α5) close to the active site. Molecular docking calculations confirm that a highly open conformation of this helix is required for binding large, bulky substrates and that this conformation is favored in a hydrophobic environment. Taken together, our combined approach provides clear evidence for the interfacial activation of CalB on highly hydrophobic surfaces. In contrast to other lipases, however, the conformational change only affects large, bulky substrates, leading to the conclusion that CalB acts like an esterase for small substrates and as a lipase for substrates with large alcohol substituents.

Preparation of cobalt nanoparticles from polymorphic bacterial templates: A novel platform for biocatalysis

Nanoparticles have gathered significant research attention as materials for enzyme immobilization due to their advantageous properties such as low diffusion rates, ease of manipulation, and large surface areas. Here, polymorphic cobalt nanoparticles of varied sizes and shapes were prepared using Micrococcus lylae, Bacillus subtilis, Escherichia coli, Paracoccus sp., and Haloarcula vallismortis as bacterial templates. Furthermore, nine lipases/carboxylesterases were successfully immobilized on these cobalt nanoparticles. Especially, immobilized forms of Est-Y29, LmH, and Sm23 were characterized in more detail for potential industrial applications. Immobilization of enzymes onto cobalt oxide nanoparticles prepared from polymorphic bacterial templates may have potential for efficient hydrolysis on an industrial-scale, with several advantages such as high retention of enzymatic activity, increased stability, and strong reusability.

Molecular bioimprinting of lipases with surfactants and its functional consequences in low water media

Lipases from Thermomyces lanuginosa (TLL), Candida rugosa (CRL) and Burkholderia cepacia (BCL) were obtained in the 'open lid' form by adding surfactant molecules like n-octyl-β-d-glucopyranoside (OG), hexadecyl trimethyl ammonium bromide (CTAB), Bis(2-ethylhexyl) sulfosuccinate sodium salt (AOT) and triton X-100 for this purpose. The enzymes were 'dried' by precipitating with 4× (v/v) excess of organic solvents. The imprint surfactant molecules were removed by extensive washing with organic solvents. TLL imprinted with 0.05% CTAB showed 11-fold increase in the transesterification activity and was a better preparation to kinetically resolve (±)-1-phenylethanol. Fluorescence emission spectra confirmed that Trp89 of the lid was indeed affected during bioimprinting. With CRL, bioimprinting with OG gave 7-fold increase in the transesterification rates and resulted in reversal of enantioselectivity of CRL and gave R-phenylethyl acetate instead of the S-product as with the unimprinted precipitate. Bioimprinted BCL was also a 7-fold better catalyst for transesterification as well as enantioselectivity.

Immobilization, Regiospecificity Characterization and Application of Aspergillus oryzae Lipase in the Enzymatic Synthesis of the Structured Lipid 1,3-Dioleoyl-2-Palmitoylglycerol

The enzymatic synthesis of 1,3-dioleoyl-2-palmitoylglycerol (OPO), one of the main components of human milk fats, has been hindered by the relatively high cost of sn-1,3-specific lipases and the deficiency in biocatalyst stability. The sn-1,3-specific lipase from Aspergillus oryzae (AOL) is highly and efficiently immobilized with the polystyrene-based hydrophobic resin D3520, with a significant 49.54-fold increase in specific lipase activity compared with the AOL powder in catalyzing the synthesis of OPO through the acidolysis between palm stearin and oleic acid (OA). The optimal immobilization conditions were investigated, including time course, initial protein concentration and solution pH. The sn-1,3 specificity of lipases under different immobilization conditions was evaluated and identified as positively associated with the lipase activity, and the pH of the immobilization solution influenced the regiospecificity and synthetic activity of these lipases. Immobilized AOL D3520, as the biocatalyst, was used for the enzymatic synthesis of the structured lipid OPO through the acidolysis between palm stearin and OA. The following conditions were optimized for the synthesis of structured lipid OPO: 65 °C temperature; 1:8 substrate molar ratio between palm stearin and OA; 8% (w/w) enzyme load; 3.5% water content of the immobilized lipase; and 1 h reaction time. Under these conditions, highly efficient C52 production (45.65%) was achieved, with a tripalmitin content of 2.75% and a sn-2 palmitic acid (PA) proportion of 55.08% in the system.

Interfacial Polymerization of Dopamine in a Pickering Emulsion: Synthesis of Cross-Linkable Colloidosomes and Enzyme Immobilization at Oil/Water Interfaces

Colloidosomes are promising carriers for immobilizing enzyme for catalytic purposes in aqueous/organic media. However, they often suffer from one or more problems regarding catalytic performance, stability, and recyclability. Here, we report a novel approach for the synthesis of cross-linkable colloidosomes by the selective polymerization of dopamine at oil/water interfaces in a Pickering emulsion. An efficient enzyme immobilization method was further developed by covalently bonding enzymes to the polydopamine (PDA) layer along with the formation of such colloidosomes with lipase as a model enzyme. In this enzyme system, the PDA layer served as a cross-linking layer and enzyme support for simultaneously enhancing the colloidosomes' stability and improving surface availability of the enzymes for catalytic reaction. It was found that the specific activity of lipases immobilized on the colloidosome shells was 8 and 1.4 times higher than that of free lipase and encapsulated lipase positioned in the aqueous cores of colloidosomes, respectively. Moreover, the immobilized lipases demonstrated excellent operational stability and recyclability, retaining 86.6% of enzyme activity after 15 cycles. It is therefore reasonable to expect that this novel approach for enzyme immobilization has great potential to serve as an important technique for the construction of biocatalytic systems.

Tuning the catalytic properties of lipases immobilized on divinylsulfone activated agarose by altering its nanoenvironment

Lipase from Thermomyces lanuginosus (TLL) and lipase B from Candida antarctica (CALB) have been immobilized on divinylsulfone (DVS) activated agarose beads at pH 10 for 72 h. Then, as a reaction end point, very different nucleophiles have been used to block the support and the effect of the nature of the blocking reagent has been analyzed on the features of the immobilized preparations. The blocking has generally positive effects on enzyme stability in both thermal and organic solvent inactivations. For example, CALB improved 7.5-fold the thermal stability after blocking with imidazole. The effect on enzyme activity was more variable, strongly depending on the substrate and the experimental conditions. Referring to CALB; using p-nitrophenyl butyrate (p-NPB) and methyl phenylacetate, activity always improved by the blocking step, whatever the blocking reagent, while with methyl mandelate or ethyl hexanoate not always the blocking presented a positive effect. Other example is TLL-DVS biocatalyst blocked with Cys. This was more than 8 times more active than the non-blocked preparation and become the most active versus p-NPB at pH 7, the least active versus methyl phenylacetate at pH 5 but the third one most active at pH 9, versus methyl mandelate presented lower activity than the unblocked preparation at pH 5 and versus ethyl hexanoate was the most active at all pH values. That way, enzyme specificity could be strongly altered by this blocking step.

Enzymatic synthesis of isoamyl butyrate catalyzed by immobilized lipase on poly-methacrylate particles: optimization, reusability and mass transfer studies

Isoamyl butyrate (banana flavor) was synthesized by esterification reaction of isoamyl alcohol and butyric acid in heptane medium. Immobilized Thermomyces lanuginosus lipase (TLL) prepared via physical adsorption on mesoporous poly-methacrylate particles (PMA) was used as biocatalyst. The factors that affect the esterification reaction were optimized by response surface methodology (RSM). Under optimal experimental conditions, maximum ester conversion percentage of 96.1 and 73.6% was reached after 50 and 90 min, respectively, for esterification reaction performed at equimolar ratio alcohol:acid at 500 and 2000 mM of each substrate. Under these experimental conditions, the esterification reaction was not controlled by external and intra-particle mass transfer effects. The product (isoamyl butyrate) was confirmed by proton nuclear magnetic resonance ((1)H NMR) spectroscopy. Reusability tests showed that the biocatalyst retained around 96 and 31% of its initial activity after eight successive esterification cycles performed at 500 and 2000 mM, respectively. The application of the biocatalyst prepared showed to be a promising strategy to catalyze flavor ester synthesis in a non-aqueous medium.

Improved activity of lipase immobilized in microemulsion-based organogels for (R, S)-ketoprofen ester resolution: Long-term stability and reusability

Microemulsion-based organogels (MBGs) were effectively employed for the immobilization of four commonly used lipases. During the asymmetric hydrolysis of ketoprofen vinyl ester at 30 °C for 24 h, lipase from Rhizomucor miehei and Mucor javanicus immobilized in microemulsion-based organogels (RML MBGs and MJL MBGs) maintained good enantioselectivities (ee_p were 86.2% and 99.2%, respectively), and their activities increased 12.8-fold and 7.8-fold, respectively, compared with their free forms. They gave higher yields compared with other lipase MBGs and exhibited better enantioselectivity than commercial immobilized lipases. Immobilization considerably increased the tolerance to organic solvents and high temperature. Both MJL MBGs and RML MBGs showed excellent reusability during 30 cycles of repeated 24 h reactions at 30 °C (over 40 days). The system maintained yields of greater than 50%, while the ee_s values of RML MBGs and MJL MBGs remained nearly constant at 95% and 88%, respectively.

Improvement of efficiency in the enzymatic synthesis of lactulose palmitate

Sugar esters are considered as surfactants due to its amphiphilic balance that can lower the surface tension in oil/water mixtures. Enzymatic syntheses of these compounds are interesting both from economic and environmental considerations. A study was carried out to evaluate the effect of four solvents, temperature, substrate molar ratio, biocatalyst source, and immobilization methodology on the yield and specific productivity of lactulose palmitate monoester synthesis. Lipases from Pseudomonas stutzeri (PsL) and Alcaligenes sp. (AsL), immobilized in porous silica functionalized with octyl groups (adsorption immobilization, OS) and with glyoxyl-octyl groups (both adsorption and covalent immobilization, OGS), were used. The highest lactulose palmitate yields were obtained at 47 °C in acetone, for all biocatalysts, while the best lactulose:palmitic acid molar ratio differed according to the immobilization methodology, being 1:1 for AsL-OGS biocatalyst (20.7 ± 3%) and 1:3 for the others (30-50%).

Increasing importance of protein flexibility in designing biocatalytic processes

Enzymes require some flexibility for catalysis. Biotechnologists prefer stable enzymes but often this stabilization comes at the cost of reduced efficiency. Enzymes from thermophiles have low flexibility but poor catalytic rates. Enzymes from psychrophiles are less stable but show good catalytic rates at low temperature. In organic solvents enzymes perform poorly as the prior drying makes the enzyme molecules very rigid. Adding water or increasing reaction temperature improves flexibility and catalytic rates. In case of hydrolases, flexibility and enantioselectivity have interdependence. Understanding the complex role of protein flexibility in biocatalysis can help in designing biotechnological processes.