A kinetic study of isoamyl acetate synthesis by immobilized lipase-catalyzed acetylation in n-hexane

Lipase-catalyzed esterification for efficient acylglycerols synthesis in a solvent-free system: Process optimization, mass transfer insights and kinetic modeling

Acylglycerols are widely used in the food industry due to their antimicrobial, emulsifying and nutritional properties. This study investigated the key reaction parameters, mass transfer mechanisms, and kinetic features of lipase-catalyzed esterification in a solvent-free system. Taguchi method was further employed to explore the relationship between "reaction parameter - yield composition". The results revealed that the maximum selectivity were achieved fror MAG (57.72 %), DAG (82.67 %) and TAG (79.29 %) under different enzymatic conditions. Fatty acid-to-glycerol molar ratio had the greatest impact on DAG selectivity, contributing 38.08 % of total impact level. Mass transfer analysis showed that external mass transfer limitation could be effectively overcome at stirring speeds above 600 rpm. Kinetic analysis confirmed that the reaction followed the Ping-Pong BiBi mechanism with alcohol and acid inhibition (SSE = 0.000643). This work provided a theoretical basis for developing more efficient and selective catalytic processes, aiding in quality control, reactor design, and industrial scale-up.

The importance of helical structures to the overall activity and structural stability of a lipase from Pseudomonas aeruginosa PAO1 in n-hexane

Bacterial lipases are versatile extracellular enzymes with a catalytic triad at the active site and a flexible 'lid' that modulates catalytic accessibility. We combined computational modeling with preliminary in vitro testing to assess the structural stability and activity of the Pseudomonas aeruginosa PAO1 lipase (PAL). We evaluated several systems consisting of the native and mutant forms of the lipase in n-hexane using molecular dynamics simulations. Structural stability was assessed by calculating the B-factor for each system. We measured the gorge radius of the catalytic channel and the RMSD of the catalytic triad to approximate enzymatic activity. Based on the correlation of these metrics, mutant forms were selected for their potential activity and stability. Selected mutant forms were expressed in E. coli BL21, mass-produced, and validated through a lipase-catalyzed esterification assay in n-hexane. Several helices outside the 'lid' region were found to influence lid conformational switching. Moreover, our preliminary experimental results show promise in validating our in silico predictions. Our integrated in silico and in vitro pipeline offers a promising approach for designing and producing industrially relevant lipases.

Synthesis of Isoamyl Fatty Acid Ester, a Flavor Compound, by Immobilized Rhodococcus Cutinase

Isoamyl fatty acid esters (IAFEs) are widely used as fruity flavor compounds in the food industry. In this study, various IAFEs were synthesized from isoamyl alcohol and various fatty acids using a cutinase enzyme (Rcut) derived from Rhodococcus bacteria. Rcut was immobilized on methacrylate divinylbenzene beads and used to synthesize isoamyl acetate, butyrate, hexanoate, octanoate, and decanoate. Among them, Rcut synthesized isoamyl butyrate (IAB) most efficiently. Docking model studies showed that butyric acid was the most suitable substrate in terms of binding energy and distance from the active site serine (Ser114) γ-oxygen. Up to 250 mM of IAB was synthesized by adjusting reaction conditions such as substrate concentration, reaction temperature, and reaction time. When the enzyme reaction was performed by reusing the immobilized enzyme, the enzyme activity was maintained at least six times. These results demonstrate that the immobilized Rcut enzyme can be used in the food industry to synthesize a variety of fruity flavor compounds, including IAB.

Enzymatic synthesis of pyridine heterocyclic compounds and their thermal stability

An efficient method was discovered for catalyzing the esterification under air using Novozym 435 to obtain pyridine esters. The following conditions were found to be optimal: 60 mg of Novozyme 435, 5.0 mL of n-hexane, a molar ratio of 2:1 for nicotinic acids (0.4 mmol) to alcohols (0.2 mmol), 0.25 g of molecular sieve 3A, a revolution speed of 150 rpm, a reaction temperature of 50 °C, and reaction time of 48 h. Under nine cycles of Novozym 435, the 80 % yield was consistently obtained. Optimum conditions were used to synthesize 23 pyridine esters, including five novel compounds. Among them, gas chromatography-mass spectrometry-olfactometry (GC-MS-O) showed phenethyl nicotinate (3g), (E)-hex-4-en-1-yl nicotinate (3m), and octyl nicotinate (3n) possessed strong aromas. Thermogravimetric analysis (TG) revealed that the compounds 3g, 3m and 3n exhibited stability at the specified temperature. This finding provides theoretical support for adding pyridine esters fragrance to high-temperature processed food.

Improved biocatalytic activity of steapsin lipase in supercritical carbon dioxide medium for the synthesis of benzyl butyrate: A commercially important flavour compound

Enzymatic synthesis of flavours, fragrances and food additives compounds have great demand and market value. Benzyl butyrate is commercially important flavour and food additive compound having global use around 100 metric tons/year and widely used in various industrial sectors. However, industrial synthesis of food additive benzyl butyrate is carried out by conventional chemical process which demands for the green biobased sustainable synthetic process. The present work reports steapsin catalyzed synthesis of benzyl butyrate for the first time in supercritical carbon dioxide (Sc-CO2) reaction medium. All reaction variables are optimized in details to obtain competent conversion of 99% in Sc-CO2 reaction medium. The developed steapsin catalyzed synthesis in Sc-CO2 medium offered almost four-fold higher conversion to benzyl butyrate than organic (conventional) solvent. The steapsin biocatalyst was effectually recycled up to five reaction cycles in Sc-CO2 medium. Moreover, the developed steapsin catalyzed protocol in Sc-CO2 medium was extended to synthesize different ten industrially significant flavour fragrance compounds that offers 99% conversion and three to five-folds higher conversion than organic medium. Thus, the present steapsin catalyzed protocol offered improved synthesis of various commercially significant flavour compounds in Sc-CO2. medium.

Enhanced Enzymatic Synthesis of Puerarin Palmitate with Different Acyl Donors for Lipid Solubility Improvement

Puerarin is a flavonoid known as a natural antioxidant found in the root of Pueraria robata. Its antioxidant, anticancer, and anti-inflammatory effects have attracted attention as a potential functional ingredient in various bioindustries. However, puerarin has limited bioavailability owing to its low lipid solubility and stability. Acylation is proposed as a synthesis method to overcome this limitation. In this study, lipase-catalyzed acylation of puerarin and various acyl donors was performed, and the enzymatic synthetic condition was optimized. Under the condition (20 g/L of Novozym 435, palmitic anhydride, 1:15, 40 °C, tetrahydrofuran (THF)), the synthesis of puerarin ester achieved a significantly high conversion (98.97%) within a short time (3 h). The molecule of the synthesized puerarin palmitate was identified by various analyses such as liquid chromatography-mass spectrometry (LC-MS), Fourier-transform infrared spectroscopy (FT-IR), and carbon-13 nuclear magnetic resonance (13C NMR). The lipid solubility and the radical scavenging activity were also evaluated. Puerarin palmitate showed a slight decrease in antioxidant activity, but lipid solubility was significantly improved, improving bioavailability. The high conversion achieved for puerarin esters in this study will provide the foundation for industrial applications.

Efficient Production of Naringin Acetate with Different Acyl Donors via Enzymatic Transesterification by Lipases

Naringin, one of the citrus flavonoids and known as a natural antioxidant, has limited bioavailability owing to its low stability and solubility. However, naringin esters formed via acylation have recently been reported to possess improved physical and chemical properties. The development of these compounds has a great potential in the food, cosmetic and pharmaceutical industries, but low conversion and productivity are barriers to industrial applications. This study aimed to improve the conversion of naringin acetate, which is formed via the enzymatic reaction between naringin and an acyl donor. An optimal reaction condition was determined by evaluating the effect of various variables (enzyme type, enzyme concentration, acyl donor, molar ratio of reactants, reaction temperature, and solvent) on the synthesis of naringin acetate. The optimal condition was as follows: 3 g/L of Lipozyme TL IM, molar ratio of 1:5 (naringin:acyl donor), reaction temperature of 40 °C, and acetonitrile as the reaction solvent. Under this condition, the maximum conversion to naringin acetate from acetic anhydride and vinyl acetate was achieved at approximately 98.5% (8 h) and 97.5% (24 h), respectively. Compared to the previously reported values, a high conversion was achieved within a short time, confirming the commercial potential of the process.

Choline Chloride-urea Deep Eutectic Mixture Water for the Synthesis of an Amphiphilic Compound of Glyceryl Monocaffeate

The Lipase-catalyzed synthesis of glyceryl monocaffeate (GMC) in choline chloride-urea of natural deep eutectic solvent (NADES) media is reported to provide amphiphilic character to caffeic acid (CA). The modification of CA into GMC could potentially increase its solubility and widen the application of CA's biological activities in water and oil-based systems. The high conversion was achieved when the reaction was carried out with the addition of more than 20 %v/v water, at a high molar ratio of glycerol and 40°C. It was found that the lipase-catalyzed transesterification of ethyl caffeate (EC) and glycerol in choline chloride-urea of DES media obeyed ping-pong bi-bi mechanism with V_max = 10.9 mmol.min^-1, K_mEC = 126.5 mmol and K_mGly = 1842.7 mmol.

Optimization, kinetic, and scaling-up of solvent-free lipase-catalyzed synthesis of ethylene glycol oleate emollient ester

The use of enzymatic catalysts is an alternative to chemical catalysts as they can help to obtain products with less environmental impact, considered sustainable within the concept of green chemistry. The optimization, kinetic, lipase reuse, and scale-up of enzymatic production of ethylene glycol oleate in the batch mode were carried out using the NS 88011 lipase in a solvent-free system. For the optimization step, a 2³ Central Composite Design was used and the optimized condition for the ethylene glycol oleate production, with conversions above 99%, was at 70 °C, 600 rpm, substrates molar ratio of 1:2, 1 wt% of NS 88011 in 32 H of reaction. Kinetic tests were also carried out with different amounts of enzyme, and it showed that by decreasing the amount of the enzyme, the conversion also decreases. The lipase reuse showed good conversions until the second cycle of use, after which it had a progressive reduction reaching 83% in the fourth cycle of use. The scale-up (ninefold increase) showed promising results, with conversion above 99%, achieving conversions similar to small-scale reactions. Therefore, this work proposed an environmentally safe route to produce an emollient ester using a low-cost biocatalyst in a solvent-free system.

Microwave-Assisted Synthesis and Ionic Liquids: Green and Sustainable Alternatives toward Enzymatic Lipophilization of Anthocyanin Monoglucosides

Anthocyanins recycling and transformations into novel compounds have been of great interest of the scientific community to improve the circular economy and enhance their technological applications. The enzymatic acylation of anthocyanins into lipophilic derivatives by conjugation with fatty acids emerged as one of the approaches; however, the literature describes only the use of organic solvents and conventional heating. In this work, the production of cyanidin-3-glucoside-octanoic acid conjugate combining ionic liquids (ILs), microwave (MW) irradiation, and Candida antarctica lipase B as a biocatalyst was attempted for the first time. Overall, the use of MW irradiation could reduce drastically the reaction time, allowing the formation of an acylated product with similar concentrations to the conventional method. On the other hand, the study of the lipophilic conjugate synthesis using different ILs showed that their composition is crucial to achieve the desired enzymatic reaction, and in this case, the combination of an imidazolium derivative as the cation with the triflate as the anion was suitable for the production of this derivative. These promising results achieved through the combination of greener alternatives to those reported in the literature are a starting point for further developments to produce this kind of anthocyanin derivatives exploring such sustainable and ecofriendly conditions.

A reactor designed for the ultrasonic stimulation of enzymatic esterification

A laboratory scale ultrasonic flow reactor capable of enhancing enzymatic reactions has been built and characterized using as a model reaction the enzymatic synthesis of isoamyl acetate using Lipozyme 435 immobilized on a macroporous anion exchange resin. The efficiency of the reactor was determined in relation to ultrasonic power density (measured by 4-nitrophenol dosimetry), position of ultrasonic horn and temperature. The results show that ultrasound can enhance the process efficiency and also reduce the reaction time.

Novozym 40086 as a novel biocatalyst to improve benzyl cinnamate synthesis

Benzyl cinnamate is one of the derivatives of cinnamic acid, which can be used as the main constituent in perfume, UV filters and medicines. In this work, several commercial immobilized lipases (Novozym 40086, Novozym 435 and Lipozyme TLIM) and free lipases (lipase A and B from Candida sp., and lipozyme from Thermomyces linuginosous) were used as catalysts for benzyl cinnamate preparation by the esterification of benzyl alcohol with cinnamic acid. The effect of various esterification parameters (reaction time, reaction temperature, lipase concentration and substrate ratio) on benzyl cinnamate yield were also optimized and evaluated using response surface methodology (RSM). Among all tested lipases, Novozym 40086, as a new commercial immobilized lipase from Rhizomucor miehei immobilized on acrylic resin beads, showed the best activity for the esterification. Esterification parameters were optimized as follows: reaction temperature 46.3 °C, substrate molar ratio 1 : 3 (cinnamic acid/benzyl alcohol), Novozym 40086 concentration 23.1 mg mL-1, reaction time 11.3 h, and maximum benzyl cinnamate yield (96.2 ± 1.4%) were achieved under the optimal conditions. Novozym 40086 can be reused 9 times without significant decrease in benzyl cinnamate yield (90.1% yield after nine times). The activation energy for the Novozym 40086-catalyzed esterification was 14.96 ± 0.25 kJ mol-1. These results showed that Novozym 40086 was a novel and efficient biocatalyst for the esterification, which can be used as a good alternative for benzyl cinnamate production.

Lipase-catalyzed solvent-free synthesis of erythorbyl laurate in a gas-solid-liquid multiphase system

Erythorbyl laurate is a potential food additive as a multi-functional emulsifier having antioxidant and antimicrobial activities. In this study, a gas-solid-liquid multiphase system (GSL-MPS) was established to enhance the production yield of erythorbyl laurate in a lipase-catalyzed solvent-free synthesis. The significant reaction variables were optimized as follows: substrate molar ratio of 2:1 (lauric acid:erythorbic acid) and enzyme concentration of 120 mg/mL (840 PLU/mL). Under these conditions, the maximum production yield in GSL-MPS was 13.974 mg/mL, which is 8.60- and 4.26-fold higher than the yields obtained in an organic solvent monophase system (OS-MPS) and a solid-liquid biphase system (SL-BPS), respectively. Moreover, the operational stability of the immobilized lipase was significantly improved in GSL-MPS compared with OS-MPS. These results indicate that GSL-MPS can be an enzymatic reaction system facilitating efficient production of ester compounds as a means of increasing production yields and the reusability of the immobilized lipase.

Lipase catalyzed transesterification of ethyl butyrate synthesis in n-hexane- a kinetic study

Kinetics of lipase catalyzed transesterification of ethyl caprate and butyric acid was investigated. The objective of this work was to propose a reaction mechanism and develop a rate equation for the synthesis of ethyl butyrate by transesterification using surfactant coated lipase from Candida rugosa. The reaction rate could be described in terms of Michaelis-Menten equation with a Ping-Pong Bi-Bi mechanism and competitive inhibition by both the substrates. The values of kinetic parameters computed were V_max = 2.861 μmol/min/mg; K_m(acid) = 0.0746 M; K_m(ester) = 0.125 M; K_i acid = 0.450 M. This study indicated a competitive enzyme inhibition by butyric acid during lipase catalyzed transesterification reaction. Experimental observations had clearly indicated that the substrates as well as product act as dead-end inhibitors.

Kinetic resolution of (RS)-1-chloro-3-(4-(2-methoxyethyl)phenoxy)propan-2-ol: a metoprolol intermediate and its validation through homology model of Pseudomonas fluorescens lipase

Kinetic resolution of (±)-1-chloro-3-(4-(2-methoxyethyl)phenoxy)propan-2-ol: a metoprolol intermediate and its validation through homology model of Pseudomonas fluorescens lipase.

A novel esterase from a marine mud metagenomic library for biocatalytic synthesis of short-chain flavor esters

Background

Marine mud is an abundant and largely unexplored source of enzymes with unique properties that may be useful for industrial and biotechnological purposes. However, since most microbes cannot be cultured in the laboratory, a cultivation-independent metagenomic approach would be advantageous for the identification of novel enzymes. Therefore, with the objective of screening novel lipolytic enzymes, a metagenomic library was constructed using the total genomic DNA extracted from marine mud.

Results

Based on functional heterologous expression, 34 clones that showed lipolytic activity were isolated. The five clones with the largest halos were identified, and the corresponding genes were successfully overexpressed in Escherichia coli. Molecular analysis revealed that these encoded proteins showed 48–79 % similarity with other proteins in the GenBank database. Multiple sequence alignment and phylogenetic tree analysis classified these five protein sequences as new members of known families of bacterial lipolytic enzymes. Among them, EST4, which has 316 amino acids with a predicted molecular weight of 33.8 kDa, was further studied in detail due to its strong hydrolytic activity. Characterization of EST4 indicated that it is an alkaline esterase that exhibits highest hydrolytic activity towards p-nitrophenyl butyrate (specific activity: 1389 U mg⁻¹) at 45 °C and pH 8.0. The half-life of EST4 is 55 and 46 h at 40 and 45 °C, respectively, indicating a relatively high thermostability. EST4 also showed remarkable stability in organic solvents, retaining 90 % of its initial activity when incubated for 12 h in the presence of hydrophobic alkanes. Furthermore, EST4 was used as an efficient whole-cell biocatalyst for the synthesis of short-chain flavor esters, showing high conversion rate and good tolerance for high substrate concentrations (up to 3.0 M). These results demonstrate a promising potential for industrial scaling-up to produce short-chain flavor esters at high substrate concentrations in non-aqueous media.

Conclusions

This manuscript reports unprecedented alcohol tolerance and conversion of an esterase biocatalyst identified from a marine mud metagenomic library. The high organic solvent tolerance and thermostability of EST4 suggest that it has great potential as a biocatalyst.

Electronic supplementary material

The online version of this article (doi:10.1186/s12934-016-0435-5) contains supplementary material, which is available to authorized users.

Enantio-conversion and -selectivity of racemic atenolol kinetic resolution using free Pseudomonas fluorescens lipase (Amano) conducted via transesterification reaction

Effects of reaction parameters on kinetic resolution of racemic atenolol usingPseudomonas fluorescenslipase were investigatedviatransesterification for production of pharmacologically active eutomer (S)-atenolol with high enantiomeric purity.