Microwave assisted lipase catalyzed synthesis of isoamyl myristate in solvent-free system

Intensification of Enzymatic Sorbityl Laurate Production in Dissolved and Neat Systems under Conventional and Microwave Heating

Glycolipids such as sugar alcohol esters have been demonstrated to be relevant for numerous applications across various domains of specialty. The use of organic solvents and, more recently, deep eutectic solvents (DESs) to mediate lipase-supported bioconversions is gaining potential for industrial application. However, many challenges and limitations remain such as extensive time of production and relatively low productivities among others, which must be solved to strengthen such a biocatalytic process in industry. In this context, this study focuses on the intensification of sorbityl laurate production, as a model biocatalyzed reaction using Novozym 435, investigating the relevance of temperature, heating method, and solvent system. By increasing the reaction temperature from 50 to 90 °C, the space-time yield and product yield were considerably enhanced for reactions in DES and the organic solvent 2M2B, irrespective of the heating method (conventional or microwave heating). However, positive effects in 2M2B were more pronounced with conventional heating as 98% conversion yield was reached within 90 min at 90 °C, equating thus to a nearly 4-fold increase in performance yielding 118.0 ± 3.6 g/(L·h) productivity. With DES, the overall yield and space-time yield were lower with both heating methods. However, microwave heating enabled a 2-fold increase in both performance parameters when the reaction temperature was increased from 50 to 90 °C. Compared to conventional heating, a 7-fold increase in space-time yield at 50 °C and a 16-fold increase at 90 °C were achieved in DES by microwave heating. Furthermore, microwave irradiation enabled the usage of a neat, solvent-free system, representing an initial proof of concept with productivities of up to 13.3 ± 2.3 g/(L·h).

Microwave-Assisted Enzymatic Esterification Production of Emollient Esters

Currently, esterification production of isopropyl myristate (IPM) or isopropyl palmitate (IPP) uses a homogeneous or heterogeneous acid substance as a catalyst and is conducted at high temperatures and pressures. Utilization of this type of catalyst requires an additional postproduction process (neutralization and purification), which burdens the production cost. Microwave enzymatic esterification is a simple and fast method. The results showed that reaction time, ratio molar of fatty acids to isopropyl alcohol, catalyst weight, and microwave power have a significant effect on the IPM or IPP conversion. Further, the energy consumption of this process is less than other enzymatic esterification and is certainly more energy efficient, which could save 99 and 29% of processing time.

Microwave-assisted enzymatic synthesis of geraniol esters in solvent-free systems: optimization of the reaction parameters, purification and characterization of the products, and biocatalyst reuse

Various geraniol esters act as insect pheromones and display pharmacological activities, especially as neuroprotective agents. Therefore, the search for synthetic strategies alternative to traditional chemical synthesis could help designing ecofriendly routes for the preparation of such bioactive compounds. Hence, this work aims at the microwave-assisted enzymatic synthesis of geranyl esters in solvent-free systems. The process variables were optimized for the synthesis of geranyl acetoacetate, achieving 85% conversion after 60 min using a 1:5 substrates molar ratio (ester to geraniol), 80 °C and 8.4% of Lipozyme 435 lipase without removal of the co-produced methanol. On the other hand, a 95% conversion was reached after 30 min using 1:6 substrates molar ratio, 70 °C and 7% lipase in the presence of 5Å molecular sieves for the methanol capture. In addition, the lipase showed good reusability, maintaining the same activity for five reaction cycles. Finally, under the above optimized conditions, other geraniol esters were successfully synthetized such as the geranyl butyrate (98%), geranyl hexanoate (99%), geranyl octanoate (98%), and geranyl (R)-3-hydroxybutyrate (56%). These results demonstrate the microwave-assisted lipase-catalyzed transesterification in a solvent-free system as an excellent and sustainable catalytic methodology to produce geraniol esters.

Process Intensification of Enzymatic Synthesis of Flavor Esters: A Review

The conventional flavor synthesis method suffers from low yields, time inefficiency, and extreme reaction conditions. Therefore, there is a necessity for the green and novel synthesis approach to overcome these limitations. The current review presents a holistic insight into different aspects associated with the synthesis of flavor esters using the immobilized enzyme. The application of process intensification tools such as ultrasound and microwave irradiation can enhance the reaction efficiency because of higher product recovery, less formation of by-products, and decreased energy consumption. This review presents the process intensification of value-added flavor esters synthesis and the mechanism of ultrasound and microwave action on the enzyme to enhance the enzyme activity and increase the reaction rate. It also summarizes the role of process intensification in enzymatic flavor ester synthesis, followed by specific examples as reported in the literature.

Simplified Method to Optimize Enzymatic Esters Syntheses in Solvent-Free Systems: Validation Using Literature and Experimental Data

The adoption of biocatalysis in solvent-free systems is an alternative to establish a greener esters production. An interesting correlation between the acid:alcohol molar ratio and biocatalyst (immobilized lipase) loading in the optimization of ester syntheses in solvent-free systems had been observed and explored. A simple mathematical tool named Substrate-Enzyme Relation (SER) has been developed, indicating a range of reaction conditions that resulted in high conversions. Here, SER utility has been validated using data from the literature and experimental assays, totalizing 39 different examples of solvent-free enzymatic esterifications. We found a good correlation between the SER trends and reaction conditions that promoted high conversions on the syntheses of short, mid, or long-chain esters. Moreover, the predictions obtained with SER are coherent with thermodynamic and kinetics aspects of enzymatic esterification in solvent-free systems. SER is an easy-to-handle tool to predict the reaction behavior, allowing obtaining optimum reaction conditions with a reduced number of experiments, including the adoption of reduced biocatalysts loadings.

Solvent-free esterifications mediated by immobilized lipases: a review from thermodynamic and kinetic perspectives

Esters are a highly relevant class of compounds in the industrial context, and biocatalysis applied to ester syntheses is already a reality for some chemical companies.

Process intensification using immobilized enzymes for the development of white biotechnology

Process intensification of biocatalysed reactions using different techniques such as microwaves, ultrasound, hydrodynamic cavitation, ionic liquids, microreactors and flow chemistry in various industries is critically analysed and future directions provided.

Chemoenzymatic Epoxidation of Limonene Using a Novel Surface-Functionalized Silica Catalyst Derived from Agricultural Waste

Limonene is one of the most important terpenes having wide applications in food and fragrance industries. The epoxide of limonene, limonene oxide, finds important applications as a versatile synthetic intermediate in the chemical industry. Therefore, attempts have been made to synthesize limonene oxide using eco-friendly processes because of stringent regulations on its production. In this regard, we have attempted to synthesize it using a cost-effective and eco-friendly process. Chemoenzymatic epoxidation of limonene to limonene oxide was carried out using in situ generation of peroxy octanoic acid from octanoic acid and H₂O₂. In this study, agricultural-waste rice husk ash (RHA)-derived silica was surface-functionalized using (3-aminopropyl) triethoxysilane (APTS), which was cross-linked using glutaraldehyde for immobilization of Candida antarctica lipase B. Furthermore, the immobilized enzyme was entrapped in calcium alginate beads to avoid enzyme leaching. Thus, limonene oxide was prepared using this catalyst under conventional and microwave heating. The microwave irradiation intensifies the process, reducing the reaction time under the same conditions. Maximum conversion of limonene to limonene oxide of 75.35 ± 0.98% was obtained in 2 h at 50 °C using a microwave power of 50 W. In the absence of microwave irradiation, the conventional heating gave 44.6 ± 1.14% conversion in 12 h. The reaction mechanism was studied using the Lineweaver-Burk plot, which follows a ternary complex mechanism with inhibition due to peroxyoctanoic acid (in other words H₂O₂). The prepared catalyst shows high reusability and operational stability up to four cycles.

Sol-Gel Immobilisation of Lipases: Towards Active and Stable Biocatalysts for the Esterification of Valeric Acid

Alkyl esters are high added value products useful in a wide range of industrial sectors. A methodology based on a simple sol-gel approach (biosilicification) is herein proposed to encapsulate enzymes in order to design highly active and stable biocatalysts. Their performance was assessed through the optimization of valeric acid esterification evaluating the effect of different parameters (biocatalyst load, presence of water, reaction temperature and stirring rate) in different alcoholic media, and comparing two different methodologies: conventional heating and microwave irradiation. Ethyl valerate yields were in the 80–85% range under optimum conditions (15 min, 12% m/v biocatalyst, molar ratio 1:2 of valeric acid to alcohol). Comparatively, the biocatalysts were slightly deactivated under microwave irradiation due to enzyme denaturalisation. Biocatalyst reuse was attempted to prove that good reusability of these sol-gel immobilised enzymes could be achieved under conventional heating.

Acoustic cavitation promoted lipase catalysed synthesis of isobutyl propionate in solvent free system: Optimization and kinetic studies

The present work highlights the effect of ultrasound on enzymatic synthesis of isobutyl propionate, a rum flavor by esterification of isobutanol and propionic acid in non-aqueous, solvent free system (SFS) using Fermase CALB™10000. The optimization study for different variables in presence of ultrasound showed a maximum conversion of 95.14% at 60°C temperature, 4% w/w enzyme dose, 1:3 acid:alcohol ratio, 40W power, 25kHz frequency, 50% duty cycle and 150rpm speed in 3h as compared to 10h of conventional method. The optimal enzyme loading was reduced to 4% w/w using ultrasound irradiation compared to 5% w/w of conventional. The efficiency of enzyme improved notably and can be reused up to seven cycles preserving its former activity. The application of ultrasound greatly enhanced esterification reactions by maintaining enzyme stability and improving the production yield. Moreover, owing towards a green approach, the synthesis is carried out in SFS for development of lucrative flavor ester. Bisubstrate kinetic models like random bi-bi, ping pong bi-bi and ordered bi-bi were applied to the experimental data using non-linear regression analysis. The experimental data and kinetic study revealed that reaction obeyed Ping-Pong bi-bi model with kinetic parameters, V_max=50.0M/min/gcatalyst, K_A=4.87×10^-2M, K_B=9.06×10^-4M, K_iA=9.8×10^-1M, K_iB=1.05×10^-3M &SSE=2.74×10^-4 for lipase catalysed synthesis of isobutyl propionate under ultrasound with inhibition by both acid and alcohol.

Synthesis of Geraniol Esters in a Continuous-Flow Packed-Bed Reactor of Immobilized Lipase: Optimization of Process Parameters and Kinetic Modeling

With increasing demand for perfumes, flavors, beverages, and pharmaceuticals, the various associated industries are resorting to different approaches to enhance yields of desired compounds. The use of fixed-bed biocatalytic reactors in some of the processes for making fine chemicals will be of great value because the reaction times could be reduced substantially as well as high conversion and yields obtained. In the current study, a continuous-flow packed-bed reactor of immobilized Candida antarctica lipase B (Novozym 435) was employed for synthesis of various geraniol esters. Optimization of process parameters such as biocatalyst screening, effect of solvent, mole ratio, temperature and acyl donors was studied in a continuous-flow packed-bed reactor. Maximum conversion of ~ 87% of geranyl propionate was achieved in 15 min residence time at 70 °C using geraniol and propionic acid with a 1:1 mol ratio. Novozym 435 was found to be the most active and stable biocatalyst among all tested. Ternary complex mechanism with propionic acid inhibition was found to fit the data.

Selection of Lipases for the Synthesis of Biodiesel from Jatropha Oil and the Potential of Microwave Irradiation to Enhance the Reaction Rate

The present study deals with the enzymatic synthesis of biodiesel by transesterification of Jatropha oil (Jatropha curcas L.) with ethanol in a solvent-free system. Seven commercial lipase preparations immobilized by covalent attachment on epoxy-polysiloxane-polyvinyl alcohol composite (epoxy-SiO₂-PVA) were tested as biocatalysts. Among them, immobilized lipases from Pseudomonas fluorescens (lipase AK) and Burkholderia cepacia (lipase PS) were the most active biocatalysts in biodiesel synthesis, reaching ethyl ester yields (FAEE) of 91.1 and 98.3% at 72 h of reaction, respectively. The latter biocatalyst exhibited similar performance compared to Novozym® 435. Purified biodiesel was characterized by different techniques. Transesterification reaction carried out under microwave irradiation exhibited higher yield and productivity than conventional heating. The operational stability of immobilized lipase PS was determined in repeated batch runs under conventional and microwave heating systems, revealing half-life times of 430.4 h and 23.5 h, respectively.

Synthesis of macromolecular systems via lipase catalyzed biocatalytic reactions: applications and future perspectives

This review highlights the application of lipases in the synthesis of pharmaceutically important small molecules and polymers for diverse applications.

Lipase catalysed synthesis of cetyl oleate using ultrasound: Optimisation and kinetic studies

The current paper exemplifies the application of ultrasound technology to enzymatic synthesis of a cosmetic emollient ester, cetyl oleate. Fermase CALB™10000, a commercial Candida antarctica lipase B was used as a catalyst to accomplish the ultrasound supported synthesis. Multiple process parameters like reaction time, temperature, enzyme dose, alcohol to acid molar ratio, ultrasound power, frequency and speed of agitation were optimised. Maximum conversion of ∼95.96% was discerned at optimum conditions, i.e., 60°C temperature, 5% enzyme dose, 2:1 alcohol:acid ratio, 60 W ultrasound power, 25 kHz ultrasound frequency, 80% duty cycle and 80 rpm speed of agitation after purification steps. It was observed that the reaction reached equilibrium in a short duration of 30 min under the optimised conditions. This was considerably lesser than the time required for attaining equilibrium in conventional mechanical stirring method which was over 2h. Bisubstrate kinetic models like random bi-bi, ping pong bi-bi and ordered bi-bi were applied to the experimental data to determine initial rates and other kinetic parameters. Ordered bi-bi model showed the best fit with kinetic parameters, Vmax=0.029 M/min/gcatalyst, KA=0.00001 M, KB=4.8002 M, KiA=0.00014 M, KiB=3.7914 M & SSE=0.00022 for enzymatic cetyl oleate synthesis under ultrasound irradiation with inhibition by both acid and alcohol at high concentrations.

Ultrasound assisted lipase catalyzed synthesis of cinnamyl acetate via transesterification reaction in a solvent free medium

Cinnamyl acetate is known for its use as flavor and fragrance material in different industries such as food, pharmaceutical, cosmetic etc. This work focuses on ultrasound assisted lipase (Novozym 435) catalyzed synthesis of cinnamyl acetate via transesterification of cinnamyl alcohol and vinyl acetate in non-aqueous, solvent free system. Optimization of various parameters shows that a higher yield of 99.99% can be obtained at cinnamyl alcohol to vinyl acetate ratio of 1:2 with 0.2% of catalyst, at 40°C and 150 rpm, with lower ultrasound power input of 50 W (Ultrasound intensity 0.81 W/cm(2)), at 25 kHz frequency, 50% duty cycle. Further, the time required for the maximum conversion is reduced to 20 min as compared to 60 min of conventional process. Similarly, the enzyme can be successfully reused seven times without loss of enzyme activity. Thus, ultrasound helps to enhance the enzyme catalyzed synthesis of flavors.

Green synthesis of isopropyl myristate in novel single phase medium Part I: Batch optimization studies

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Green synthesis of isopropyl ester in homogenous phase reaction system.

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Candida antarctica Lipase B (CAL-B) enzyme has efficiently catalyzed the esterification of myristic acid and isopropyl alcohol.

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CAL-B activity depends on the polarity of an organic solvent.

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Good operation stability of the enzyme was found in the single phase reaction system.

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High purity of isopropyl myristate was obtained by the cold centrifugation technique.

Isopropyl myristate finds many applications in food, cosmetic and pharmaceutical industries as an emollient, thickening agent, or lubricant. Using a homogeneous reaction phase, non-specific lipase derived from Candida antartica, marketed as Novozym 435, was determined to be most suitable for the enzymatic synthesis of isopropyl myristate. The high molar ratio of alcohol to acid creates novel single phase medium which overcomes mass transfer effects and facilitates downstream processing. The effect of various reaction parameters was optimized to obtain a high yield of isopropyl myristate. Effect of temperature, agitation speed, organic solvent, biocatalyst loading and batch operational stability of the enzyme was systematically studied. The conversion of 87.65% was obtained when the molar ratio of isopropyl alcohol to myristic acid (15:1) was used with 4% (w/w) catalyst loading and agitation speed of 150 rpm at 60 °C. The enzyme has also shown good batch operational stability under optimized conditions.

Chemoenzymatic Solvent-free Synthesis of 1-Monopalmitin Using a Microwave Reactor

An environmentally friendly method for the synthesis of 1-monopalmitin has been developed. The procedure consists of a two-step, solvent-free chemoenzymatic reaction. In the first step, palmitic acid is esterified with solketal (4-hydroxymethyl-2,2-dimethyl-1,3-dioxolane) using Novozym 435 by both conventional heating and microwave irradiation. The use of a microwave reactor allows the enzymatic synthesis of the intermediate compound with a similar yield as that achieved using conventional heating. In the second step, 1,2-acetonide-3-palmitoyl glycerol is cleaved to yield 1-monopalmitin by means of a cation-exchange resin and water or aliphatic alcohols as hydrolytic reagent in solvent-free conditions. The hydrolysis was accomplished in 15 min at 85°C. The best yield was obtained using 1-pentanol. We conclude that the yield achieved depends on the batch and nature of the cation-exchange resin used as catalyst.

A sensitive colorimetric high-throughput screening method for lipase synthetic activity assay

A sensitive and practical high-throughput screening method for assaying lipase synthetic activity is described. Lipase-catalyzed transesterification between vinyl acetate and n-butanol in n-hexane was chosen as a model reaction. The released acetaldehyde was determined by the colorimetric method using 3-methyl-2-benzothialinone (MBTH) derivatization. In comparison with other methods, the major advantages of this process include high sensitivity, simple detection, inexpensive reagents, and low requirements for instruments.

Efficient bifunctional catalyst lipase/organophosphonic acid-functionalized silica for biodiesel synthesis by esterification of oleic acid with ethanol

An efficient bifunctional catalyst lipase/organophosphonic acid-functionalized silica (SG-T-P-LS) has been successfully developed, and biodiesel production of fatty acid ethyl ester (FAEE) from free fatty acid (FFA) oleic acid with short-chain alcohol ethanol catalyzed by SG-T-P-LS was investigated. The process optimization using response surface methodology (RSM) was performed and the interactions between the operational variables were elucidated, and it was found that the molar ratio of alcohol to acid was the most significant factor. The optimum values for maximum conversion ratio can be obtained by using a Box-Behnken center-united design, and the conversion ratio could reach 89.94 ± 0.42% under the conditions that ethanol/acid molar ratio was 1.05:1 and SG-T-P-LS to FFA weight ratio was 14.9 wt.% at 28.6°C. The research results show that SG-T-P and LS-20 could work cooperatively to promote the esterification reaction, and the bifunctional catalyst SG-T-P-LS is a potential catalyst for biodiesel production.