Process development for production of medium chain triglycerides using immobilized lipase in a solvent-free system

The synthesis of tricaprylin, tricaprin, trilaurin, and trimyristin in a solvent-free system was conducted by mixing a commercial immobilized lipase with the organic reagents (glycerol and fatty acid) in a 20-mL batch reactor with constant stirring. The effects of temperature, fatty acid/glycerol molar ratio, and enzyme concentration on the reaction conversion were determined. The reactions were carried out for 26 h and the nonpolar phase was analyzed by gas chromatography. Appreciable levels of medium chain triglycerides were achieved, except for tricaprylin. The higher selectivity values for the production of triglycerides were attained under the following conditions: a fatty acid/glycerol molar ratio of 5; enzyme concentration of 5 or 9% (w/w); and temperatures of 70°C (tricaprin), 80°C (trilaurin), and 90°C (trimyristin). After completion of the esterification reaction under these conditions, the recovery of the triglyceride and fatty acids, and the reusability of the enzyme were studied. The unreacted fatty acid and the produced triglyceride were satisfactorily recovered. The commercial immobilized lipase was used in 10 consecutive batch reactions at 80°C, with 100% selectivity in the trilaurin and trimyristin synthesis. The possibility of enzyme reuse and the recovery of residual fatty acid are relevant results that contribute to increasing the viability of the process.     

Enzymatic synthesis of monolaurin

The aim of this study was to produce monolaurin utilizing a commercial immobilized lipase (Lipozyme IM-20; Novo Nordisk, Bagsvaerd, Denmark) through the direct esterification of lauric acid and glycerol in a solvent-free system. The influence of fatty acid/glycerol molar ratio, temperature, and Lipozyme (IM-20) concentration on the molar fraction of monolaurin were determined using an experimental design. The best conditions employed were 55°C, lauric acid/glycerol molar ratio of 1.0, and 3.0% (w/w) enzyme concentration. The final product, obtained after 6 h of reaction, was 45.5% monolaurin, 26.8% dilaurin, 3.1% trilaurin, and 24.6% lauric acid. The reusability of the enzyme was also studied.     

Preparation of mono- and diacylglycerols by enzymatic esterification of glycerol with conjugated linoleic acid in hexane

Esterification of glycerol with conjugated linoleic acid (CLA) was carried out in hexane. Lipase from Rhizomucor miehei provided a high degree of esterification (80%) in 8 h at 50°C when used at 15% (w/w) in a system containing a 1∶2 molar ratio of glycerol to free fatty acids. Esterification levels >80% were obtained in 8 h at 40°C with 15% (w/w) lipase from Candida antarctica at the same molar ratio of reactants. The extent of esterification of CLA was >90% after 4h of reaction at 50°C with a 5% (w/w) loading of either R. miehei or C. antarctica lipase, together with a 1∶1 molar ratio of substrates. Both enzymes incorporated the original CLA as acylglycerol residues in primarily 1,3-diacylglycerol and 1-monoacylglycerol. The CLA-rich acylglycerols can be employed as emulsifiers or as substitutes for natural fats and oils.     

Optimization of alkaline transesterification of soybean oil and castor oil for biodiesel production

This article reports experimental data on the production of fatty acid ethyl esters from refined and degummed soybean oil and castor oil using NaOH as catalyst. The variables investigated were temperature (30–70°C), reaction time (1–3 h), catalyst concentration (0.5–1.5 w/wt%), and oil-to-ethanol molar ratio (1:3–1:9). The effects of process variables on the reaction conversion as well as the optimum experimental conditions are presented. The results show that conversions >95% were achieved for all systems investigated. In general, an increase in reaction temperature, reaction time, and in oil-to-ethanol molar ratio led to an enhancement in reaction conversion, whereas an opposite trend was verified with respect to catalyst concentration.     

Optimization of enzymatic production of biodiesel from castor oil in organic solvent medium

We studied the production of fatty acid ethyl esters from castor oil using n-hexane as solvent and two commercial lipases, Novozym 435 and Lipozyme IM, as catalysts. For this purpose, a Taguchi experimental design was adopted considering the following variables: temperature (35–65°C), water (0–10 wt/wt%), and enzyme (5–20 wt/wt%) concentrations and oil-to-ethanol molar ratio (1∶3 to 1∶10). An empirical model was then built so as to assess the main and cross-variable effects on the reaction conversion and also to maximize biodiesel production for each enzyme. For the system containing Novozym 435 as tatalyst the maximum conversion obtained was 81.4% at 65°C, enzyme concentration of 20 wt/wt%, water concentration of 0 wt/wt%, and oil-to-ethanol molar ratio of 1∶10. When the catalyst was Lipozyme IM, a conversion as high as 98% was obtained at 65°C, enzyme concentration of 20 wt/wt%, water concentration of 0 wt/wt%, and oil-to-ethanol molar ratio of 1∶3.     

Esterification activity and stability of Candida rugosa lipase immobilized into chitosan

Microbial lipase from Candida rugosa immobilized into porous chitosan beads was tested for esterification selectivity with butanol and different organic acids (C2–C12), and butyric acid and different aliphatic alcohols (C2–C10). After 24 h, the acids tested achieved conversions of about 40–45%. Acetic acid was the only exception, and in this case butanol was not consumed. Different alcohols led to butyric acid conversions >40%, except for ethanol, in which case butyric acid was converted only 26%. The system’s butanol and butyric acid were selected for a detailed study by employing an experimental design. The influence of temperature, initial catalyst concentration, and acid:alcohol molar ratio on the formation of butyl butyrate was simultaneously investigated, employing a 2³ full factorial design. The range studied was 37–50°C for temperature (X₁), 1.25–2.5% (w/v) for the catalyst concentration (X₂), and 1 and 2 for the acid:alcohol molar ratio (X₃). Catalyst concentration (X₂) was found to be the most significant factor and its influence was positive. Maximum ester yield (83%) could be obtained when working at the lowest level for temperature (37°C), highest level for lipase concentration (2.5% [w/v]), and center level of acid:alcohol molar ratio (1.5). The immobilized lipase was also used repeatedly in batch esterification reactions of butanol with butyric acid, revealing a half-life of 86 h.     

Kinetics of enzyme-catalyzed alcoholysis of soybean oil in n-hexane

This work investigated the production of fatty acid ethyl esters (FAEEs) from soybean oil using n-hexane as solvent and two commercial lipases as catalysts, Novozym 435 and Lipozyme IM. A Taguchi experimental design was adopted considering the variables temperature (35–65°C), addition of water (0–10 wt/wt%), enzyme (5–20 wt/wt%) concentration, and oil-to-ethanol molar ratio (1:3–1:10). It is shown that complete conversion in FAEE is achieved for some experimental conditions. The effects of process variables on reaction conversion and kinetics of the enzymatic reactions are presented for all experimental conditions investigated in the factorial design.     

The influence of temperature and photoinitiator concentration on photoinitiated polymerization of diacrylate monomer

The behavior of p-methoxybenzoyldiphenylphosphine oxide, previously synthesized, as a photoinitiator for the polymerization of diacrylate monomer, in the presence of 3% (w/w) tertiary amine (triethyl amine) as synergist additive, was studied. The influence of temperature in the range 30–90°C at 3% (w/w) photoinitiator concentration and the influence of the photoinitiator concentration in the range 0.5–3.5% (w/w) at 30°C was investigated by differential scanning photocalorimetry (photo-DSC). In all experiments the photopolymerization was performed at constant light intensity (3 mW cm⁻²). The maximum conversion was obtained at temperature of 90°C at 3% (w/w) photoinitiator concentration and 3% (w/w) triethyl amine. The optimal concentration of photoinitiator to obtain maximum conversion was 3% (w/w), at 30°C. No thermal polymerization occurred at higher temperature.     

Batch (one- and two-stage) production of biodiesel fuel from rapeseed oil

Biodiesel fuel is an alternative and renewable energy source, which may help to reduce air pollution, as well as our dependence on petroleum for energy. Several processes have already been developed for the production of biodiesel. Alkali-catalyzed transesterification with short-chain alcohols, for example, generates high yields of methyl esters in short reaction times. In this study, we have evaluated the efficacy of batch (one- and two-stage) transesterification of rapeseed oil in the production of rapeseed methyl ester. The conversion of rapeseed oil exhibited similar reaction patterns and yields in 30- and 1-L reaction systems. Approximately 98% of the rapeseed oil was converted at 400 rpm within 20 min, under the following conditions: 1% (w/w) KOH, 1∶10 methanol molar ratio, and at 60°C. In the 30-L, two-stage transesterification process, approx 98.5% of the rapeseed oil was converted at a 1∶4.5 molar ratio and 1% (w/w) KOH at 60°C for 30 min (first reaction condition), and at a 1∶1 molar ratio and 0.2% (w/w) KOH at 60°C for 30 min (second reaction condition).     

Enzymatic synthesis of medium chain monoglycerides in a solvent-free system

The synthesis of monocaprin, monolaurin, and monomyristin in a solvent-free system was conducted by mixing a commercial immobilized lipase with the organic reactants (glycerol and fatty acids) in a 20-mL batch reactor with constant stirring. The effects of temperature, fatty acid/glycerol molar ratio, and enzyme concentration on the reaction conversion were determined. The addition of molecular sieves in the assays of monomyristin synthesis was also evaluated. The reactions were carried out for 5 to 6 h and the nonpolar phase was analyzed by gas chromatography. The best results in terms of selectivity and conversion (defined as the percentage of fatty acid consumed) were achieved when the stoichiometric amount of reagents (molar ratio=1) and 9% (w/w) commercial enzyme were used and the reaction was performed at 60°C. The addition of molecular sieves did not improve the synthesis of monomyristin. Conversions as high as 80%, with monoglycerides being the major products, were attained. After 5 h of reaction, the concentration of monoglyceride was about twice that of diglyceride, and only trace amounts of triglyceride were found. The results illustrate the technical possibility of producing medium chain monoglycerides in a solvent-free medium using a simple batch reactor.     

Effects of Initial Phenol-formaldehyde (PF) Reaction Products on the Curing Properties of PF Resin

Differential scanning calorimetry(DSC) was used to study the effects of varying NaOH concentrations on the thermochemical curing properties of 2,4-dimethylol phenol (2,4-DMP), and 2,6-dimethylol phenol(2,6-DMP). Analysis of the DSC curves showed significant differences in the thermochemical curing behavior of these compounds with increasing NaOH:DMP molar ratios, in terms of the peak shape, position of the reaction peaks, (T _p), along the temperature scale and energy of activation, E. The curves consisted of either a single, two or three exothermic peaks which indicated the occurrence of multiple reactions. One of these peaks was observed for the entire range of NaOH molar ratios, and is attributed to the self-condensation reaction. For the 2,4-DMP, NaOH had the effect of lowering the T _p of curing from 212°C in the uncatalyzed state to135°C between 0.15–0.75 molar ratios. The lowest value of E, however, was 111 kJ mole⁻¹, only through 0.45–0.60 molar ratios and this combined with the above, points to this concentration range as the optimum NaOH level. Similarly, the T _p of curing for the 2,6-DMP was lowered from 211°C in the uncatalyzed state, to a minimum of 116°C at the NaOH:2,6-DMP molar ratio of 0.45. At this ratio, Ealso had the lowest value of 117 kJ mole⁻¹ and this suggests that 0.45 molar ratio is the optimum NaOH level. This revised version was published online in July 2006 with corrections to the Cover Date.     

Monitoring lipase-catalyzed butterfat interesterification with rapeseed oil by Fourier transform near-infrared spectroscopy

This work demonstrates the application of FT-NIR spectroscopy in order to monitor the enzymatic interesterification process for butterfat modification. The reactions were catalyzed by Lipozyme TL IM at 70 °C for the blend of butterfat/rapeseed oil (70/30, w/w) in a packed-bed reactor. The blend and interesterified fat samples were measured in liquid form at 70 °C by transmission mode-based FT-NIR over the spectral region 12000–4000 cm⁻¹. The calibration of FT-NIR for conversion degree (evaluated by the triglyceride profile, which was represented by the triglyceride peak ratio) and solid fat content (SFC) of the interesterified products was carried out using partial least squares (PLS) regression. Good correlations were observed between the NIR spectra and ln (peak ratio), and between the NIR spectra and the SFC at 5 °C over the spectral range 5269–4513 cm⁻¹. Overall, transmission-mode FT-NIR spectroscopy performed at 70 °C yielded conditions close to those used during the interesterification process, implying that this method could be used to control the enzymatic interesterification process online.     

High temperature adsorption of carbon dioxide on Cu–Al hydrotalcite-derived mixed oxides: kinetics and equilibria by thermogravimetry

The effect of Cu/Al molar ratio on the high-temperature adsorption characteristics of CO₂ on the mixed oxides of Cu–Al hydrotalcite skeletal structure has been studied by thermogravimetry. The Cu/Al molar ratio of the hydrotalcites synthesized was varied between 1.0 and 3.0, and the adsorption temperature ranged from ambient to 600 °C. The hydrotalcite with Cu/Al molar ratio of 2.0 was found to be the most suitable adsorbent for high-temperature CO₂ adsorption, in both the capacity and the rate of adsorption. The activation energy values suggested that the physical adsorption dominates at low temperatures (<400 °C) and the chemisorption dominates at high temperatures (>400 °C).     

Thermal study and solubility tests of films based on amaranth flour starch–protein hydrolysate

The study deals with the effect of chemical and physical modifications on thermal properties and solubility properties of films based on amaranth flour starch–protein hydrolysate. Biodegradable and edible films were prepared by casting a 25% (w/w) solution of hydrolysate containing 20% glycerol and various additions of dialdehyde starch (0, 1 and 5%). After thermal exposure of films at 65 and 95 °C (for 6 and 48 h), thermal properties of films were studied employing differential scanning calorimetry and thermogravimetric analysis. Film solubility tests were performed in an aqueous environment at 25 °C. Chemical and physical modifications of films markedly affect their thermal properties and solubility.     

Influence of temperature on the composition of mixed monolayer formed at the methyl alcohol/acetic acid aqueous solutio–air interface

The influence of temperature on the composition of mixed monolayer formed at the methyl alcohol/acetic acid aqueous solution was examined by surface tension measurements. Surface tension of various two-component solutions was obtained at 10, 20 and 28 °C temperatures in the 0–0.5 M range of bulk concentration of alcohol and acid, respectively. Three independent methods, i.e., the Gibbs adsorption equation (GAE), regular solution approximation (RSA) and Butler adsorption isotherm (BAI) were applied to calculate surface composition of the methyl alcohol/ acetic acid mixed monolayer. It was shown that in the temperature range of 10–28 °C the surface molar fraction of the solutes remained constant for the fixed bulk concentration of alcohol and acid. Additionally, based on the RSA and BAI methods, we showed there were no interactions between solute molecules in the mixed monolayer in the studied range of concentrations. Received: 18 December 1997 Accepted: 8 May 1998     

A kinetic study on lipase-catalyzed interesterification of soybean oil with oleic acid in a continuous packed-bed reactor

To provide a mathematical basis for the design and operation of a continuous, packed-bed reactor for the interesterification of soybean oil, soybean oil that contains 22.7% oleoyl and 54.3% linoleoyl moieties as molar acyl moiety composition was interesterified in hexane with oleic acid, using an immobilized sn-1,3-specific lipase (Lipozyme IM) from Mucor miehei. The reaction was carried out in a U-shaped Pyrex glass-made packed-bed reactor at 37°C in the following system: concentration of soybean oil in the feed stream=12.5 wt%, molar ratio of fatty acid to soybean oil=3.0, and water content in the feed stream=1340–2340 ppm. At these water contents, Lipozyme IM gave practically the same catalytic activity, and the content of triacylglycerols in the product oil was 91–94 wt%. Rate equations for the change in oleoyl and linoleoyl moiety compositions in soybean oil were derived and their validity was confirmed experimentally. On the other hand, the catalytic activity of Lipozyme IM decayed in the first-order fashion. Based on these deactivation kinetics, the flow rate of the feed stream is simulated for the operation of a continuous, packed-bed reactor at 37°C that produces an oil of a fixed composition of oleoyl moiety.     

Synthesis of proton conductive inorganic–organic hybrid membranes through copolymerization of dimethylethoxyvinylsilane with vinylphosphonic acid

Proton conductive inorganic–organic hybrid membranes were synthesized from dimethylethoxyvinylsilane (DMEVS), vinylphosphonic acid (VPA) and 3-glycidoxypropyltrimethoxysilane (GPTMS) through copolymerization followed by sol–gel process. The ratio of phosphorus to silicon in the copolymer almost corresponded to the charged molar ratio of VPA to DMEVS when the ratio of VPA to DMEVS was below 1/2. Self-standing, homogeneous, highly transparent membranes were synthesized from DMEVS–VPA copolymer and GPTMS via sol–gel condensation. Differential thermal analysis-thermogravimetry analyses indicated that these membranes were thermally stable up to 200 °C. The results of Fourier transform infrared and ¹³C NMR revealed that phosphonic acid groups of VPA were chemically bound to organosiloxane network. The copolymerization and condensation of (DMEVS–VPA)/GPTMS were confirmed by ³¹P and ²⁹Si NMR spectra. The proton conductivity of the hybrid membranes increased with phosphonic acid content. The membrane of (DMEVS–VPA)/GPTMS showed a remarkable conductivity of 6.3 × 10⁻² S cm⁻¹ at 130 °C and 100% relative humidity.     

Glucose Oxidase-dextran Conjugates with Enhanced Stabilities Against Temperature and pH

Multipoint covalent bonding of glucose oxidase (EC 1.1.3.4) to hydrophilic natural polymer dextran and optimization of procedures to obtain, with enhanced temperature and pH stabilities, were studied. Purified enzyme was conjugated with various molecular weight dextrans (17.5, 75, and188 kD) in a ratio of 20:1, 10:1, 1:1, 1:5, 1:10, 1:15, and 1:20. After 1 h of incubation at pH 7, the activities of purified enzyme and conjugates were determined at different temperatures (25°C, 30°C, 35°C, 40°C, 50°C, 60°C, 70°C, and 80°C), and the results were evaluated for thermal resistance. Increases in temperature from 25°C to 50°C did not change the activities of the conjugates. The conjugate, which was prepared with 75 kDa dextran in a molar ratio of 1:5, showed the highest thermal resistance and even the activity still remains at 80°C at pH 7.0. This conjugate also displayed activity in a wide pH range (pH 4.0–7.0) at high temperatures. Conjugate, which was synthesized with 75 kDa dextran in a molar ratio of 1:5, appears to be feasible and useful for biotechnological applications.     

Specific heat capacities of pure triglycerides by heat-flux differential scanning calorimetry

The specific heat capacities of some triglycerides commonly found in palm oil were determined with a heat-flux differential scanning calorimeter. The specific heat capacity measurements were made under the optimum operating conditions determined earlier: scan rate 17 deg·min^?1, sample mass 21 mg and purge gas (nitrogen) flow rate 50 ml/min. Pure triglycerides (four simple and four mixed) were used in the experiments. The four simple triglycerides were trilaurin, trimyristin, tripalmitin and tristearin, and the mixed triglycerides were 1,2-dimyristoyl-3-oleoyl, 1,2-dimyristoyl-3-palmitoyl, 1,2-dipalmitoyl-3-oleoyl and 1,2-dioleoyl-3-palmitoyl. The results of this study are compared with literature values and also with values obtained by using estimation methods. The experimental specific heat capacities are within ±1% precision with a 95% confidence level.     

Synthesis and physicochemical study of ZSM-5 high-silica zeolite from natural raw materials

ZSM-5 high-silica zeolite was obtained from metakaolinite, Dzhenranchel’sk volcanic ash, and silica gel at T = 150–220°C, pH 9–13, and τ = 48–240 h with the use of an organic structure-forming additive, butanediol-1,4, in an alkaline solution. Optimum conditions for the synthesis of ZSM-5 zeolite were found (T = 200°C, pH 10, τ = 144 h). The catalytic properties of its H-form in vapor-phase esterification of acetic acid (I) with ethanol (II) were studied at 140–180°C and a I: II molar ratio from 1 to 2. Synthesized HZSM-5 showed high activity and selectivity in this reaction.