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.

Crystallographic analysis of the Staphylococcus epidermidis lipase involved in esterification in aqueous solution

The Staphylococcus epidermidis lipase (SeLip, GehC) can be used in flavour-compound production via esterification in aqueous solution. This study reports the crystallization and crystallographic analysis of recombinant GehC (rGehC; Lys303-Lys688) with a molecular weight of 43 kDa. rGehC was crystallized at 293 K using PEG 10 000 as a precipitant, and a 99.9% complete native data set was collected from a cooled crystal at 77 K to a resolution of 1.9 Å with an overall Rmerge value of 7.3%. The crystals were orthorhombic and belonged to space group P212121, with unit-cell parameters a = 42.07, b = 59.31, c = 171.30 Å, α = β = γ = 90°. Solvent-content calculations suggest that there is likely to be one lipase subunit in the asymmetric unit.

Kinetics and Optimization of Lipophilic Kojic Acid Derivative Synthesis in Polar Aprotic Solvent Using Lipozyme RMIM and Its Rheological Study

The synthesis of kojic acid derivative (KAD) from kojic and palmitic acid (C16:0) in the presence of immobilized lipase from Rhizomucor miehei (commercially known as Lipozyme RMIM), was studied using a shake flask system. Kojic acid is a polyfunctional heterocycles that acts as a source of nucleophile in this reaction allowing the formation of a lipophilic KAD. In this study, the source of biocatalyst, Lipozyme RMIM, was derived from the lipase of Rhizomucor miehei immobilized on weak anion exchange macro-porous Duolite ES 562 by the adsorption technique. The effects of solvents, enzyme loading, reaction temperature, and substrate molar ratio on the reaction rate were investigated. In one-factor-at-a-time (OFAT) experiments, a high reaction rate (30.6 × 10⁻³ M·min⁻¹) of KAD synthesis was recorded using acetone, enzyme loading of 1.25% (w/v), reaction time of 12 h, temperature of 50 °C and substrate molar ratio of 5:1. Thereafter, a yield of KAD synthesis was optimized via the response surface methodology (RSM) whereby the optimized molar ratio (fatty acid: kojic acid), enzyme loading, reaction temperature and reaction time were 6.74, 1.97% (w/v), 45.9 °C, and 20 h respectively, giving a high yield of KAD (64.47%). This condition was reevaluated in a 0.5 L stirred tank reactor (STR) where the agitation effects of two impellers; Rushton turbine (RT) and pitch-blade turbine (PBT), were investigated. In the STR, a very high yield of KAD synthesis (84.12%) was achieved using RT at 250 rpm, which was higher than the shake flask, thus indicating better mixing quality in STR. In a rheological study, a pseudoplastic behavior of KAD mixture was proposed for potential application in lotion formulation.

Enzymatic Synthesis of Naringin Palmitate

Naringin esters are paid more attention in medical and functional food industry than naringin due to their higher stability and solubility in lipidic environments. Naringin palmitic acid esters were enzymatically synthesized with naringin and palmitic acid. The effects of solvent type, temperature, concentration and types of enzymes and the molar ratio of substrates on the conversion of naringin were investigated. Novozym 435 performed higher catalytic ability in tert-amyl alcohol in the esterification of naringin with palmitic acid. The conversion yield of naringin increased with the increase of temperature (30-70°C) and of the concentration of enzyme. The structure of the naringin palmitate was characterized by FT-IR, 1H-NMR and HPLC-MS. 1H-NMR spectroscopic analysis indicated the presence of an ester bond on the C-6 of the glucose moiety of naringin molecule.

Immobilized Candida antarctica lipase B: Hydration, stripping off and application in ring opening polyester synthesis

This work reviews the stripping off, role of water molecules in activity, and flexibility of immobilized Candida antarctica lipase B (CALB). Employment of CALB in ring opening polyester synthesis emphasizing on a polylactide is discussed in detail. Execution of enzymes in place of inorganic catalysts is the most green alternative for sustainable and environment friendly synthesis of products on an industrial scale. Robust immobilization and consequently performance of enzyme is the essential objective of enzyme application in industry. Water bound to the surface of an enzyme (contact class of water molecules) is inevitable for enzyme performance; it controls enzyme dynamics via flexibility changes and has intensive influence on enzyme activity. The value of pH during immobilization of CALB plays a critical role in fixing the active conformation of an enzyme. Comprehensive selection of support and protocol can develop a robust immobilized enzyme thus enhancing its performance. Organic solvents with a log P value higher than four are more suitable for enzymatic catalysis as these solvents tend to strip away very little of the enzyme surface bound water molecules. Alternatively ionic liquid can work as a more promising reaction media. Covalent immobilization is an exclusively reliable technique to circumvent the leaching of enzymes and to enhance stability. Activated polystyrene nanoparticles can prove to be a practical and economical support for chemical immobilization of CALB. In order to reduce the E-factor for the synthesis of biodegradable polymers; enzymatic ring opening polyester synthesis (eROPS) of cyclic monomers is a more sensible route for polyester synthesis. Synergies obtained from ionic liquids and immobilized enzyme can be much effective eROPS.

Aggregation and homogenization, surface charge and structural change, and inactivation of mushroom tyrosinase in an aqueous system by subcritical/supercritical carbon dioxide

The subcritical/supercritical carbon dioxide (SS CO(2)) has gained considerable attention in green chemistry industry for its advantage as nontoxic, nonflammable, and inexpensive. The effects of SS CO(2) treatments on aggregation and homogenization, surface charge, secondary and tertiary structure, and activity of mushroom tyrosinase in an aqueous system were investigated using a number of methods including dynamic light scattering (DLS), zeta potential measurement, circular dichroism (CD) spectropolarimeter, and spectrofluorometer. With a treatment time of 20 min, three treatment temperatures (35, 45, and 55 °C) and four pressures (5, 8, 12, and 15 MPa) had been selected. The aggregation and homogenization of the globular protein particles was induced by SS CO(2) as suggested by the particle size distribution (PSD) patterns that were closely related to the pressure and temperature. The surface charge of the tyrosinase decreased following the SS CO(2) treatments, and its variation tendency shows a favorable consistency with that of its PSD patterns. The α-helix conformation in secondary structure and fluorescence intensity reflecting tertiary structure also decreased, together with the λ(max) red-shifted with the increasing pressure. The results also indicated that SS CO(2) could enhance inactivation effect of the temperature on the tyrosinase with its lowest residual activity being about 60% under the condition of 8 MPa, 55 °C, and 20 min treatment time. The loss in the activity of the tyrosinase was correlated to its aggregation and homogenization effect induced by SS CO(2), which led to the change of surface charge as well as secondary and tertiary structure.

Biodiesel fuel production by the transesterification reaction of soybean oil using immobilized lipase

The enzymatic alcoholysis of soybean oil with methanol and ethanol was investigated using a commercial, immobilized lipase (Lipozyme RMIM). The effect of alcohol (methanol or ethanol), enzyme concentration, molar ratio of alcohol to soybean oil, solvent, and temperature on biodiesel production was determined. The best conditions were obtained in a solvent-free system with ethanol/oil molar ratio of 3.0, temperature of 50 degrees C, and enzyme concentration of 7.0% (w/w). Three-step batch ethanolysis was most effective for the production of biodiesel. Ethyl esters yield was about 60% after 4 h of reaction.

Microbial lipases: at the interface of aqueous and non-aqueous media. A review

In recent times, biotechnological applications of microbial lipases in synthesis of many organic molecules have rapidly increased in non-aqueous media. Microbial lipases are the 'working horses' in biocatalysis and have been extensively studied when their exceptionally high stability in non-aqueous media has been discovered. Stability of lipases in organic solvents makes them commercially feasibile in the enzymatic esterification reactions. Their stability is affected by temperature, reaction medium, water concentration and by the biocatalyst's preparation. An optimization process for ester synthesis from pilot scale to industrial scale in the reaction medium is discussed. The water released during the esterification process can be controlled over a wide range and has a profound effect on the activity of the lipases. Approaches to lipase catalysis like protein engineering, directed evolution and metagenome approach were studied. This review reports the recent development in the field ofnon-aqueous microbial lipase catalysis and factors controlling the esterification/transesterification processes in organic media.

Comparison of hydrolytic activity in water and heptane for thirty-two commercial lipase preparations

The protein content and the rates of hydrolysis of p-nitrophenyl palmitate (pNPP) in water (soluble enzyme and emulsified substrate) and in heptane (soluble substrate and insoluble enzyme) were measured for thirty-two commercial lipase preparations. The protein content of the powders varied in a wide range as well as the activity on emulsified pNPP showing the high heterogeneity of the commercial samples. Activity in heptane also varied but to a lesser extent than that in water. There was no direct correlation between activities in water and in heptane as assayed with the same hydrolytic reaction. The ratio of activity in heptane to that in water, R(O/A) ratio, was introduced to characterize activity in organic media. Six lipases showed R(O/A) values higher than 1 demonstrating a higher activity in organic solvent than in water. A linear correlation of R(O/A) with activity in water (log plot) suggested the strong influence of diffusional limitations on activity of solid enzyme suspended in organic solvents.

Highly enantioselective esterification of racemic ibuprofen in a packed bed reactor using immobilised Rhizomucor miehei lipase

A systematic study of the enantioselective resolution of ibuprofen by commercial Rhizomucor miehei lipase (Lipozyme(R) IM20) has been carried out using isooctane as solvent and butanol as esterificating agent. The main variables controlling the process (temperature, ibuprofen concentration, ratio butanol:ibuprofen) have been studied using an orthogonal full factorial experimental design, in which the selected objective function was enantioselectivity. This strategy has resulted in a polynomial function that describes the process. By optimizing this function, optimal conditions for carrying out the esterification of racemic ibuprofen have been determined. Under these conditions, enantiomeric excess and total conversion values were 93.8% and 49.9%, respectively, and the enantioselectivity was 113 after 112 h of reaction. These conditions have been considered in the design of a continuous reactor to scale up the process. The esterification of ibuprofen was properly described by pseudo first-order kinetics. Thus, a packed bed reactor operating as a plug-flow reactor (PFR) is the most appropriate in terms of minimizing the residence time compared with a continuous stirred tank reactor (CSTR) to achieve the same final conversion. This reactor shows a similar behavior in terms of enantioselectivity, enantiomeric excess, and conversion when compared with batch reactors. A residence-time distribution (RTD) shows that the flow model is essentially a plug flow with a slight nonsymmetrical axial dispersion (Peclet number = 43), which was also corroborated by the model of CSTR in series. The stability of the system (up to 100 h) and the possibility of reutilization of the enzyme (up to four times) lead to consider this reactor as a suitable configuration for scale up of the process.

Large-scale preparation of (Z)-3-hexen-1-yl acetate using candida antarctica-immobilized lipase in hexane

A kilogram-scale synthesis of (Z)-3-hexen-1-yl acetate, in hexane, on direct esterification of (Z)-3-hexen-1-ol with acetic acid in the presence of 2% (w/w reactants) of an immobilized lipase from Candida antarctica (Novozym 435) is reported. Conversion yields ranging from 92 to 96% were obtained after optimization of various parameters. In that respect, elimination of the water proved crucial. Using at both the laboratory large scale (preparation of 200-400 g of ester) and the pilot scale (1-5 kg) a "reflux" rotary evaporator equipped with a graduated decantation flask, we were able to trap the water evolved during esterification while at the same time monitor the time course of the reaction. As a consequence of both an efficient water trapping and of a gentle dispersion of the immobilized lipase into the reaction medium, the lifetime of the enzyme was significantly prolonged. At the laboratory large scale (LLS), the yield was still >/=90% after seven consecutive utilizations whereas at the pilot scale (PS), it reached 93% after reusing the enzyme four times. In those conditions, the amount of immobilized enzyme necessary to produce 1 kg of (Z)-3-hexen-1-yl acetate was 18 g (1. 8%) and 60 g (6%) at the LLS and the PS, respectively. Copyright 1998 John Wiley & Sons, Inc.