Isoamyl Acetate Production Research Articles

Kinetics Studies on Esterification Reaction of Acetic acid with Iso-amyl Alcohol over Ion Exchange Resin as Catalysts

In this work, the esterification of acetic acid with iso-amyl alcohol catalyzed by acidic ion-exchange resins (TULSION R T-62, T-63 and T-66 MP) has been investigated in a batch reactor to determine the intrinsic reaction kinetics. Iso-amyl acetate is synthesized in this reaction, has the fragrance of strong odor (similar to both banana and pear). The effects of various parameters on the rate of reaction (such as temperature, mole ratio, catalyst loading, and stirrer speed) are studied. The solid- liquid external mass transfer resistance as observed using various stirring speeds is absent and the rate of reaction depends on temperature. Further pseudo-homogenous model is developed for an intrinsically kinetically controlled reaction, which is free from either intra-particle diffusion or external mass transfer resistance. The rate expression developed in this work would be useful in the simulation and design of reactive distillation column for the production of iso-amyl acetate. The resultant kinetic model fitted the experimental data well. The activation energy is found to be 41.88 kJ/kmol for the formation of iso-amyl acetate.

Interactions between Torulaspora delbrueckii and Saccharomyces cerevisiae in wine fermentation: influence of inoculation and nitrogen content

Alcoholic fermentation by an oenological strain of Torulaspora delbrueckii in association with an oenological strain of Saccharomyces cerevisiae was studied in mixed and sequential cultures. Experiments were performed in a synthetic grape must medium in a membrane bioreactor, a special tool designed to study indirect interactions between microorganisms. Results showed that the S. cerevisiae strain had a negative impact on the T. delbrueckii strain, leading to a viability decrease as soon as S. cerevisiae was inoculated. Even for high inoculation of T. delbrueckii (more than 20× S. cerevisiae) in mixed cultures, T. delbrueckii growth was inhibited. Substrate competition and cell-to-cell contact mechanism could be eliminated as explanations of the observed interaction, which was probably an inhibition by a metabolite produced by S. cerevisiae. S. cerevisiae should be inoculated 48 h after T. delbrueckii in order to ensure the growth of T. delbrueckii and consequently a decrease of volatile acidity and a higher isoamyl acetate production. In this case, in a medium with a high concentration of assimilable nitrogen (324 mg L(-1)), S. cerevisiae growth was not affected by T. delbrueckii. But in a sequential fermentation in a medium containing 176 mg L(-1) initial assimilable nitrogen, S. cerevisiae was not able to develop because of nitrogen exhaustion by T. delbrueckii growth during the first 48 h, leading to sluggish fermentation.

Hybrid membrane and conventional processes comparison for isoamyl acetate production

Four process alternatives for the production of isoamyl acetate, by the liquid phase esterification of acetic acid with isoamyl alcohol, were evaluated by simulation in terms of product purity, energy integration and economics. The analysis involves a transition from conventional (two structures that use acetic acid or alcohol in excess) to hybrid membrane process (two distillation–pervaporation hybrid systems). Acetate recovery is identified as a crucial factor to minimize energy costs in all considered processes. For conventional processes, the amount of energy required for separation, at low acetate recovery levels, is considerably lower if acetic acid is used in excess. For the hybrid processes, there is an optimum value of acetate recovery that minimizes the total required heat duty and membrane area. Hybrid distillation–pervaporation process allows obtaining the specified product purity with lower energy requirements and more economical tradeoffs than the considered conventional processes. The economic optimum design maximizes energy savings and minimizes total annualized costs. After optimization and energy integration, the best process alternative includes, in a hybrid system, one packed bed reactor, two pervaporation units and a distillation column.

Optimization of Isoamyl Acetate Production in a Solvent‐Free System

AbstractEnzymatic esterification of isoamyl acetate using Candida antarctica immobilized lipase was studied and optimized using response surface methodology (RSM) by Design of Experiment software. Isoamyl acetate is a colorless organic compound which is used by food industry as additives for its banana flavor. The production of isoamyl acetate is costly, hence, RSM giving advantages by minimizing the number of experiments for studying parameter effect. The model developed by RSM also simplified the relationship that can be used for practical engineering purposes. The parameters investigated in this study are mass of enzyme (1–14 wt %), reaction temperature (30–50C) and reaction time (2–6 h). As reaction temperature increased at any given mass of enzyme, a yield of ester increased up to optimum temperature 40C and thereafter decreased. The model obtained by RSM indicated the optimum conditions for maximum esterification (100% yields) at 34.8C with 1.04 g mass of enzyme after 0.5 h reaction time, which is in good agreement with the experimental value (104%).Practical ApplicationsIsoamyl acetate is a compound that has a strong fruity aroma similar to banana and pear. It is commonly used as food flavor in the food industry. Apart from that, it is also popular as a solvent for varnishes, paints and nitrocellulose lacquers. The compound is also used in rayon, dyes, artificial pearls, film manufacturing and extraction of penicillin.

Production and Kinetics of Isoamyl Acetate from Acetic Anhydride using Candida Antarctica Lipase B in a Solvent-Free System

Isoamyl acetate is the most essential esters in food industry. Studies on isoamyl acetate production were expanded since 1976 through having 1174 patents that contains isoamyl acetate on that year. Most researches have used hexane or heptanes as solvent which are not preferable due to their toxic properties. Therefore, the risk and unfavorable conditions were removed by introducing solvent-free system. In this study, isoamyl acetate was produced using Candida Antarctica Lipase-B (CALB) by esterification reaction between acetic anhydride and isoamyl alcohol in a solvent-free system. The parameters studied were acid-alcohol molar ratio (0.1 – 2), reaction time (2-6 h), temperature (30-50 °C) and mass of enzyme (4-12 wt%). The isoamyl acetate production was maximum (41.6-fold) at acid to alcohol molar ratio of 2, mass of enzyme of 5.78 wt%, at time of 3 h and 44 °C reaction temperature. An enzymatic kinetic model based on modified Michaelis-Menten equation was developed and fitted to the non-linear regression to the experimental data. The model developed was in agreement with the experimental data with R2 value equals to 0.999.

Applicability of Lactobacillus plantarum IMDO 788 as a starter culture to control vegetable fermentations

Fermentation of vegetables and fruits is a traditional preservation technique, e.g. in Eastern Europe. Although usually spontaneous fermentation processes are applied, the addition of lactic acid bacteria (LAB) starter cultures could accelerate processing and improve the consistency and quality of the end-products. The application of Lactobacillus plantarum IMDO 788 as a starter culture strain for cauliflower and mixed vegetable fermentations resulted in accelerated acidification as compared with the spontaneous fermentations. The strain dominated the background microbiota throughout the process, whereas the spontaneous fermentations were characterised by widely variable species diversity. During the spontaneous fermentations, almost all carbohydrates were converted into lactic acid, ethanol, mannitol and acetic acid, indicating the participation of both heterofermentative and homofermentative LAB species. During the starter culture-added fermentations, residual carbohydrates were found and lactic acid and ethanol were the main end-metabolites. Vegetable-associated aromas, ethyl acetate and isoamyl acetate were produced during all fermentations. The high concentration of ethanol and the production of ethyl acetate and isoamyl acetate suggested the involvement of yeasts during all fermentations. Lactobacillus plantarum IMDO 788 was an adequate starter culture strain for vegetable fermentations, prevailing over endogenous LAB communities. Further optimisation of the starter culture formulation is necessary to avoid yeast growth.

Screening of native yeast from Agave duranguensis fermentation for isoamyl acetate production

In this work, fifty yeast strains, isolated from the spontaneous alcoholic fermentation of Agave duranguensis to produce mezcal, were tested using the double coupling system. These yeasts were from the genera Pichia, Torulaspora, Saccharomyces, Kluyveromyces, Deckera, Hanseniaspora, and Candida. P. fermentans ITD00165 was the best isoamyl acetate producer, yielding 0.38 g/L of ester after incubation for 24 h, while K. marxianus ITD00211 produced 0.32 g/L of ester. Thus P. fermentans TD00165 could be considered as an excellent choice for use in optimization studies of the culture medium and bioreactor operating conditions to develop a process for biotechnological production of isoamyl acetate.

Activity model and consistent thermodynamic features for acetic acid–isoamyl alcohol–isoamyl acetate–water reactive system

A new set of parameters for NRTL activity coefficient model was correlated, for the quaternary mixture acetic acid/isoamyl alcohol/isoamyl acetate/water based on the experimental vapor–liquid and liquid–liquid equilibrium data. A complete and consistent thermodynamic topological characterization of the non-reactive and reactive mixtures was proposed, checking if the consistency equations of the residue curve maps are satisfied. The structure of the residue curve maps for the non-reactive quaternary mixture presents three binary azeotropes and one ternary azeotrope. No reactive azeotropes were found for the reactive mixture. The new set of NRTL activity model parameters presented better predictive capabilities for liquid–liquid and vapor–liquid phase equilibria than current available models. A successful liquid–liquid equilibrium phase stability test was also performed using the adjusted model. The results can be used to achieve conceptual design and simulation of conventional and intensified chemical processes for the isoamyl acetate production.

Intensification of isoamyl acetate production: transport properties of silica membranes

Fuel ethanol production by fermentation generates isoamyl alcohol as by-product. Its conversion to isoamyl acetate is an alternative to obtain a higher value product. An intensified reaction–pervaporation process is an attractive option compared to conventional distillation. The design of this process requires the characterization of the transport properties of the membrane used. Xerogel type ceramic membranes were prepared by dip-coating and analyzed by using Brunauer-Emmett-Teller method, fourier transform infrared spectroscopy, and scanning electron microscopy–energy dispersive spectrometer methods. Their hydrophilic and microporous character was confirmed. Using quaternary mixtures of the esterification process, a membrane was evaluated for water separation in a laboratory scale pervaporation unit. A special experimental protocol for membrane evaluation was proposed for the multicomponent reactive mixture. Experimental membrane flux and selectivity were determined and used to correlate three basic mass transport models. Among them, the most suitable and reliable was the thermodynamic Fick model, which can be used for reaction-pervaporation process design and simulation.

Effects of Fermentation Temperature and Aeration on Production of Natural Isoamyl Acetate byWilliopsis saturnusvar.saturnus

Isoamyl acetate is a natural flavour ester, widely used as a source of banana flavour by the food industry. Williopsis saturnus var. saturnus is a yeast which can produce isoamyl acetate by esterification of amyl alcohols with acetyl coenzyme A via fermentation. The evaluation of this kind of production as an alternative way to obtain natural banana flavour could be possible, if the levels produced were high enough to make a commercial product. In this study, the effects of temperature (15°C and 25°C) and aeration (aerobic, semiaerobic, and anaerobic) on the production of isoamyl acetate by Williopsis saturnus var. saturnus from sugar beet molasses were examined. According to the results obtained, isoamyl acetate production rate and specific productivity were higher at 25°C than at 15°C and at semiaerobic condition than aerobic and anaerobic conditions. Williopsis saturnus var. saturnus showed a production rate of 0.703 mg L−1 h−1 and a specific productivity of 0.0297 mg L−1 cell−1 h−1 isoamyl acetate with semiaerobic condition at 25°C. The maximum amount of isoamyl acetate reached with these conditions was 118 mg/L.

Isoamylacetate production by entrapped and covalently bound Candida rugosa and porcine pancreatic lipases

Candida rugosa lipase (CRL) and porcine pancreatic lipase (PPL) were immobilised by entrapping and also by covalent binding for use in synthesis of isoamyl acetate (IAAc), which has a typical banana flavour. Lipase entrapment was carried out by dripping sodium alginate (Na-Alg)-chitosan (Chi)-lipase mixture into CaCl2-glutaraldehyde (GAL) solution to obtain Ca-Alg/ChiCRL/PPL. Immobilisation conditions were optimised as 1.5% Na-Alg, 1.5% chitosan and 0.15% GAL. Ca-Alg/ChiCRL/PPL samples showed the highest activity when they were dried upon reaching 27% of their initial weights. Covalent binding was achived with Chi modified with spacerarm via glutaraldehyde to get ChiCRL/PPL. The highest IAAc production was observed when 1,3-diaminopropane was used as a spacer arm. The best ester yield was achieved in heptane, at 40 and 45°C reaction temperatures, 50mM IAA and 50 or 75mM AA concentrations. The amount of IAAc was nearly 10 times higher for the batch type than for the continuous packed bed column reactor.

A Dynamic Analysis of Higher Alcohol and Ester Release During Winemaking Fermentations

Isobutanol, isoamyl acetate and ethyl hexanoate production during winemaking fermentations was precisely described. Volatile compound concentrations and their rates of change and losses in the exhausted gas were determined throughout the fermentation. Negligible amounts of isobutanol were lost, whatever the fermentation temperature. In contrast, 56 % of the ethyl hexanoate and 34 % of the isoamyl acetate were stripped by CO2 when the temperature profile simulated red winemaking conditions. Even at a moderate temperature of 20 °C, typical of white wine fermentations, 40 % of the ethyl hexanoate and 21 % of the isoamyl acetate were lost. The effect of temperature on the production of the volatile compounds was assessed by running fermentations at different temperatures, with the same medium and strain. By taking into account the volatile compound losses in the exhausted gas, changes in volatile compound production were found to be smaller than those usually calculated from the concentrations in the wine. These findings highlight the potential importance of knowledge concerning aroma gas–liquid balances for both an understanding of yeast metabolism and the identification of innovative control strategies minimizing aroma losses.

Novel nanostructured tin dioxide as promising carrier for Candida rugosa lipase

This is the first report on lipase immobilization on nanostructured tin dioxide. The material was applied as a support for Candida rugosa lipase. All biocatalytic characteristics obtained for this novel biocatalyst (nano-SnO2-CRL) were compared with those for lipase immobilized on polypropylene (PP-CRL). Nano-SnO2-CRL has shown a specific activity eight times higher than that found for PP-CRL. The tin dioxide preparation preserved up to 45% of the initial lipase activity after 1h incubation at pH 10.0, while PP-CRL was completely inactivated. The immobilization on the inorganic carrier enhanced lipase thermal stability. Upon heating for 1h at 55°C, nano-SnO2-CRL retained 77% active, while PP-CRL was half inactivated. The synthetic activity and the effect of several parameters on isoamyl acetate production for both biocatalysts were evaluated. Among four tested acyl donors, acetic anhydride was the most efficient for nano-SnO2-CRL. The reaction proceeded with a high reaction rate and resulted in 88.2% yield of the target ester for 2h. Among various solvents, n-decane proved to be the best for both catalysts. The increase in the reaction temperature from 50°C to 60°C enhanced the reaction rate 1.5 and 1.7 fold, for nano-SnO2-CRL and PP-CRL, respectively. A considerable decline in activity for both enzyme preparations was observed after the second esterification run due to prolonged heating and probably also to inhibition by substrates and product.

Enhanced synthesis of isoamyl acetate using an ionic liquid–alcohol biphasic system at high hydrostatic pressure

Isoamyl acetate has a banana flavor that can be considered a “natural” ingredient when synthesized using a lipase-catalyzed reaction. Production of isoamyl acetate was up to 10-fold higher with free lipase versus immobilized Candida antarctica lipase B (CALB) after 3 h at 300 MPa and 80 °C in 1-butyl-3-methylimidazolium hexafluoro-phosphate, isoamyl alcohol biphasic system. Rate of catalysis by free CALB was 15-fold greater at 500 MPa, 40 °C than at 0.1 MPa, 40 °C and 14-fold at 500 MPa, 80 °C than at 0.1 MPa, 80 °C. Activation energy of free lipase calculated between 40 and 80 °C at 0.1 MPa (55.6 ± 4.2 kJ mol−1) or 300 MPa (56.2 ± 4.6 kJ mol−1) was not significantly different. Similarly, activation volume (ΔV‡) of free lipase calculated between 0.1 and 500 MPa at 40 °C (−16.1 ± 1.5 cm3 mol−1) or 80 °C (−16.7 ± 1.4 cm3 mol−1) was not significantly different. After treatment at high pressure and upon pressure release, the free lipase was temporarily suspended in a semi-solid IL phase. This study is the first to combine the use of a room temperature ionic liquid (RTIL) and high hydrostatic pressure (HHP) for enhanced enzyme catalysis.

Metabolic engineering of the anaerobic central metabolic pathway in Escherichia coli for the simultaneous anaerobic production of isoamyl acetate and succinic acid

An in vivo method of producing isoamyl acetate and succinate simultaneously has been developed in Escherichia coli to maximize yields of both high value compounds as well as maintain the proper redox balance between NADH and NAD(+). Previous attempts at producing the ester isoamyl acetate anaerobically did not produce the compound in high concentrations because of competing pathways and the need for NAD(+) regeneration. The objective of this study is to produce succinate as an example of a reduced coproduct to balance the ratio of NADH/NAD(+) as a way of maximizing isoamyl acetate production. Because the volatility of the two compounds differs greatly, the two could be easily separated in an industrial setting. An ldhA, adhE double mutant strain (SBS110MG) served as the control strain to test the effect of an additional ackA-pta mutation as found in SBS990MG. Both strains overexpressed the two heterologous genes pyruvate carboxylase and alcohol acetyltransferase (for ester production). The triple mutant SBS990MG was found to produce higher levels of both isoamyl acetate and succinate. At the optimal condition of 25 degrees C, the culture produced 9.4 mM isoamyl acetate and 45.5 mM succinate. SBS990MG produced 36% more ester and over 700% more succinate than SBS110MG. In addition, this study demonstrated that a significantly higher isoamyl acetate concentration can be attained by simultaneously balancing the carbon and cofactor flow; the isoamyl acetate concentration of 9.4 mM is more than seven times higher than an earlier report of about 1.2 mM.

Glycerol triacetate as solvent and acyl donor in the production of isoamyl acetate with Candida antarctica lipase B

Glycerol triacetate was successfully used as a green solvent and as the acyl donor in the transesterification of isoamyl alcohol to produce isoamyl acetate using free and immobilized Candida antarctica lipase B. Immobilized lipase was more catalytically active than free lipase and could be easily separated from the reaction mixture by filtration. In addition, it was found that increasing either the reaction temperature or the enzyme to substrate ratio increased the conversion of isoamyl alcohol. Using triacetin as the solvent also enabled the separation of product by simple extraction with petroleum ether and catalyst recycling.

Semi-continuous enzymatic production and membrane assisted separation of isoamyl acetate in alcohol — ionic liquid biphasic system

Enzymatic production of an important natural flavor ester, isoamyl acetate, was studied by using immobilized Candida antarctica lipase B in [bmim]PF 6 ionic liquid. The reaction was completed by removing water produced in the reaction by zeolite adsorption, and practically 100% yield was achieved. An integrated system was developed for the separation of the isoamyl alcohol‒water‒isoamyl acetate ternary azeotropic mixture, combining pervaporation and osmotic distillation. The Sulzer “Pervap 2256” flat sheet hydrophobic pervaporation membrane was found to be 100% selective for isoamyl alcohol.

Redistribution of Metabolic Fluxes in the Central Aerobic Metabolic Pathway of E. coli Mutant Strains with Deletion of the ackA-pta and poxB Pathways for the Synthesis of Isoamyl Acetate

Although the bacterium E. coli is chosen as the host in many bioprocesses, products derived from the central aerobic metabolic pathway often compete with the acetate-producing pathways poxB and ackA-pta for glucose as the substrate. As such, a significant portion of the glucose may be excreted as acetate, wasting substrate that could have otherwise been used for the desired product. The production of the ester isoamyl acetate from acetyl-CoA by ATF2, a yeast alcohol acetyl transferase, was used as a model system to demonstrate the beneficial effects of reducing acetate production. All strains tested for ester production also overexpressed panK, a native E. coli gene that previous studies have shown to increase free intracellular CoA levels when fed with pantothenic acid. A recombinant E. coli strain with a deletion in ackA-pta produces less acetate and more isoamyl acetate than the wild-type E. coli strain. When both acetate-producing pathways were deleted, the acetate production was greatly reduced. However, pyruvate began to accumulate, so that the overall ester production remained largely unchanged. To produce more ester, a previously established strategy of increasing the flux from pyruvate to acetyl-CoA was adopted by overexpressing pyruvate dehydrogenase. The ester production was then 80% higher in the poxB, ackA-pta strain (0.18 mM) than that found in the single ackA-pta mutant (0.10 mM), which also overexpressed PDH.

Enhanced production of isoamyl acetate from beet molasses with addition of fusel oil by Williopsis saturnus var. saturnus

Fusel oil which contains high level of amyl alcohols (approximately 45–55%) is a by-product obtained from the distillation of alcohol made by fermentation of molasses. Williopsis saturnus is a yeast which is able to convert isoamyl alcohol into isoamyl acetate. The aim of this study was to increase the formation of isoamyl acetate by the addition of fusel oil at the ratios of 1%, 2% and 3% (v/v) to molasses based fermentation medium using W. saturnus. It was found out that bioconversion of added fusel oil into isoamyl acetate was possible and an addition of 1% fusel oil led to an increase in isoamyl acetate concentration from 118 to 354 mg/L.

Production of Isoamyl Acetate from Sugar Beet Molasses by Williopsis saturnus var. saturnus

Three strains of Williopsis saturnus var. saturnus were employed for the production of natural isoamyl acetate (the character impact compound of banana flavour) using sugar beet molasses as the carbon source and batch cultivation at 25°C under anaerobic conditions. Of the three strains, strain HUT 7087 was the best producer of isoamyl acetate, producing 20.7 mg/L. Sugar beet molasses was deemed to be an acceptable carbon source for the production of this flavour compound.