Добірка наукової літератури з теми "Isoamyl acetate"

ABSTRACT Isoamyl acetate is synthesized from isoamyl alcohol and acetyl coenzyme A by alcohol acetyltransferase (AATFase) inSaccharomyces cerevisiae and is hydrolyzed by esterases at the same time. We hypothesized that the balance of both enzyme activities was important for optimum production of isoamyl acetate in sake brewing. To test this hypothesis, we constructed yeast strains with different numbers of copies of the AATFase gene (ATF1) and the isoamyl acetate-hydrolyzing esterase gene (IAH1) and used these strains in small-scale sake brewing. Fermentation profiles as well as components of the resulting sake were largely alike; however, the amount of isoamyl acetate in the sake increased with an increasing ratio of AATFase/Iah1p esterase activity. Therefore, we conclude that the balance of these two enzyme activities is important for isoamyl acetate accumulation in sake mash.

Isoamyl acetate is a natural flavour ester, widely used as a source of banana flavour by the food industry.Williopsis saturnusvar.saturnusis 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 byWilliopsis saturnusvar.saturnusfrom 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 saturnusvar.saturnusshowed a production rate of 0.703 mg L−1 h−1and a specific productivity of 0.0297 mg L−1 cell−1 h−1isoamyl acetate with semiaerobic condition at 25°C. The maximum amount of isoamyl acetate reached with these conditions was 118 mg/L.

This study evaluated the chemical and volatile composition of hawthorn wines fermented with Saccharomyces cerevisiae A3.12 with and without pulp contact and pectase treatment during fermentation. The results indicated that the addition of pectase was in favor of pH decrease and clarification. The pectase-treated wines had significantly higher concentrations of acetic acid, ethyl octanoate, and isoamyl acetate than the non-enzyme-treated wines. Furthermore, the nonextracted wines had significantly higher concentrations of isoamyl alcohol, phenylethyl alcohol, ethyl lactate, and isoamyl acetate than the extracted wines. The first principal component separated the wine from the nonextracted juice with pectase from other samples based on the higher concentrations of isoamyl acetate (0.14 μg/g), diethyl butanedioate (0.07 μg/g), 2-phenylethyl acetate (0.23 μg/g), and acetoin (1.47 μg/g). The wine from nonextracted pulpy juice with pectase was significantly more aromatic than the others and 26.2% of the consumers were found to be willing to purchase this product.

The olive fruit fly, Bactrocera oleae (Rossi) is economically the most important olive pest, causing yield losses in all olive growing areas where is detected. Considering that EU requires the reduction of pesticide use by up to 100% by 2050, more effective non-pesticide lures for B. oleae monitoring and/or controlling are needed. This research was aimed at investigating the attractiveness of different blends of olive fruit fly-associated yeast volatiles toward B. oleae. Three blends of olive fruit fly-associated yeast volatiles: isoamyl alcohol and 2-phenethyl alcohol; isoamyl alcohol, 2-phenethyl alcohol and 2-phenethyl acetate; and isoamyl alcohol, 2-phenethyl acetate and isobutyl acetate were selected and tested on yellow sticky traps for attraction of B. oleae in olive orchard. Results showed that traps containing all tested blends of olive fruit fly-associated yeast volatile compounds, in total, were significantly more attractive to B. oleae and were not significantly attractive to green lacewings, compared to the control. Among them, the most promising was the one containing the blend of isoamyl alcohol, 2-phenethyl acetate and isobutyl acetate because its attractiveness was constantly significant during investigation compared to the others. This blend in the future could lead us to the discovery of a new attractant for the monitoring and/or controlling of B. oleae.

Isoamyl acetate was synthesized from isoamylol and glacial acetic acid with strong acidic cation exchanger as catalyst. The effects of reaction conditions such as acid-alcohol ratio, reaction time, catalyst dosage to esterification reaction have been investigated and the optimum reaction conditions can be concluded as: the molar ratio of acetic acid to isoamylol 0.8:1, reaction time 2h, 25 % of catalyst (quality of acetic acid as benchmark). The conversion rate can reach up to 75.46%. The catalytic ability didn’t reduce significantly after reusing 10 times and the results showed that the catalyst exhibited preferably catalytic activity and reusability.

This study reports the analysis and design of a liquid phase esterification process to convert acetic acid with isoamyl alcohol into isoamyl acetate via reactive pervaporation, in the presence of an Amberlite IR-120 ion exchange resin catalyst. To accomplish this, a catalytic reactor is coupled with a separation membrane unit (Pervaporation Membrane Reactor (PVMR)). In the proposed unit, the chemical reaction equilibrium is favorably shifted towards isoamyl acetate formation by removing water with the help of a separation membrane. The study is developed by using relevant thermodynamics, kinetics, and membrane transport models, and by considering different catalytic reactor-pervaporator membrane configurations such as: (a) a two-step continuous fixed bed-pervaporator process (FBR+PVMU), (b) a two-step continuous slurry reactor-pervaporator process (SR+PVMU), (c) a single-step integrated fixed bed-pervaporator reactor (IFBPVMR), and d) a single step integrated slurry-pervaporator reactor (ISPVMR). The performance of the PVMRs is evaluated by using a R recycle ratio, a Ω membrane area to reactor volume ratio, and Da Damköhler dimensionless parameters. From the various proposed configurations, it is shown that the integrated plug flow reactor-pervaporation reactor (IFBPVMR) provides the best performance. On the basis of various simulations and design charts developed in the present study, operational conditions leading to optimum ester yields as high as 0.94 are predicted. These results provide a valuable prospect for the industrial scale-up and implementation of isoamyl acetate production units.

In this thesis, isoamyl acetate was synthesized by reaction-distillation , using acetic acid and isoamyl alcohol as starting materials, using acid ion-liquid as catalyst and extracting agent.These are some factors were investigated, including different catalysts, ratio between acid and alcohol, amount of Ion-Liquid, and reflux ratio. Technology to prepare iso-pentyl acetate was optimized with single factor experiments. Results showed that acid ion-liquids are good catalysts and extracting agents, which increased the purity and yield of iso-pentyl acetate, as well as diminished the azeotropic point of iso-pentyl acetate and acetic acid.The optimal technological conditions are as following: ratio of acid:alcohol 2:1 (mol), dosage of ion-liquid V = 2 mL, reflux ratio R = 2.5. Under this condition, purity of obtained iso-pentyl acetate is 99%, and the yield is 85%.

Thesis (MSc)--University of Stellenbosch, 2002.
ENGLISH ABSTRACT: The production of wine is a complex process, which involves the conversion of sugar in grape must to ethanol, carbon dioxide and other byproducts. The principal organism in winemaking is yeast, of which Saccharomyces cerevisiae is the most important due to its ability to survive winemaking conditions, its GRAS (Generally Regarded As Safe) status and the favourable flavours it imparts during the winemaking process. However, due to the demands of the consumer and the emergence of sophisticated wine markets, a demand is developing for specialised yeast strains with enhanced and new oenological properties. For these reasons, research into the contribution of wine yeast to the aroma bouquet as well the influence of wine or brandy maturation in wood on the aroma bouquet is important for consumer demands to be met. The fruity aroma of wine is associated with esters, which are produced during the alcoholic fermentation by yeast. Important acetate esters in wine and brandy are ethyl acetate, which has a fruity, solvent-like aroma, and isoamyl acetate, which has a banana-like aroma. These esters are produced through the action of acetyltransferases (AATases), which catalyse the reaction between a higher alcohol and acyl Coenzyme A. Esters are mainly a product of alcoholic fermentation. However, their concentration changes during wood maturation and it has been found that the concentration of acetate esters can increase during the maturation period. In this study, the aim was to investigate the influence of AATase I and AATase II, which are encoded by the ATF1 and ATF2 genes respectively, on the aroma bouquet of wine and brandy. Therefore, the first objective of this study was to clone the ATF2 gene from a commercial wine yeast strain and to overexpress this gene in a commercial wine yeast strain and in a wine yeast strain that already has the A TF1 gene overexpressed. Disruption cassettes were also designed in order to disrupt the ATF1 and ATF2 genes in a commercial wine yeast strain. The resultant recombinant wine yeast strains were used for the production of wine and brandy. GC analyses and tasting trials were conducted to determine the effect of the overexpression or disruption of these genes on the aroma bouquet of wine. The results obtained indicated that there are differences in the aroma bouquet of wine and brandy when changes are made in gene expression. The results indicated that the A TF1 gene plays a large role in the production of ethyl and isoamyl acetate. When this gene was overexpressed, the level of ethyl acetate was 5.6-fold more than that of the control and the level of isoamyl acetate was 3.5-fold higher than that of the control. However, no increase in ethyl acetate or isoamyl acetate was observed when the A TF2 gene was overexpressed. An increase in 2-phenylethyl acetate and diethyl succinate was observed in brandy, although there was a decrease in total ester concentration. A decrease in acetic acid was also observed in the brandy produced, which could be an indication of ester production. Similarly, no increase in ethyl acetate or isoamyl acetate was observed in the wine or brandy produced when both the ATF1 and ATF2 genes were overexpressed in a single yeast. Once again, a marked decrease was observed in acetic acid concentration in both the wine and brandy. In conclusion, it is clear that changes in gene expression can change the aroma profile of wine or brandy. However, the role of the ATF2 gene still remains unclear and further studies are needed to clarify its role in yeast. Future studies involving the effect of wood maturation on ester concentration will also be of importance, so that the winemaker or distiller can make a product that suits the ever-changing market.
AFRIKAANSE OPSOMMING: Die produksie van wyn is 'n komplekse proses wat die omskakeling van die suiker in mos tot etanol, koolstofdioksied en ander byprodukte tot gevolg het. Die hooforganisme betrokke in die wynmaakproses is gis, waarvan Saccharomyces cerevisiae as een van die belangrikste geag word as gevolg van die vermoë daarvan om onder die wynfermentasietoestande te kan oorleef, die "GRAS"-status (Generally Regarded As Safe) daarvan en die invloed wat dit op die aroma van die uiteindelike produk het weens die werking daarvan gedurende alkoholiese fermentasie. Die behoefte aan wyn met nuwe, verbeterde eienskappe het die vraag na meer gespesialiseerde gisrasse deur beide die verbruiker en nuwe wynmarkte gedurende die afgelope paar jaar drasties laat toeneem. Dit is om dié redes dat navorsing oor die bydrae van wyngis en houtveroudering tot die aroma van beide wyn en brandewyn so belangrik geag word. Die vrugtige aroma van wyn word geassosieer met die esters wat gedurende die alkoholiese fermentasie deur gis gevorm word. Die belangrikste asetaatesters in wyn en brandewyn is etielasetaat, wat vir 'n oplosmiddelagtige, vrugtige aroma bekend is, en isoamielasetaat, wat 'n piesangaroma veroorsaak. Die esters word geproduseer deur die werking van asetieltransferases (AATases), wat as katalis in die reaksie tussen 'n hoër alkohol en asetiel-Ko-ensiem A optree. Alhoewel esters hoofsaaklik 'n produk van alkoholiese fermentasie is, wissel die konsentrasie daarvan gedurende houtveroudering. Daar is gevind dat die konsentrasie van die asetaatesters gedurende die verouderingsproses kan verhoog. Die studie het ten doelom die invloed van AATase I en AATase II, wat onderskeidelik deur die ATF1- en ATF2-gene geënkodeer word, op die aroma van wyn en brandewyn te ondersoek. Die eerste doelwit van die studie was vervolgens om die ATF2-geen vanaf 'n kommersiële wyngisras te kloneer en dit daarna te ooruitdruk in 'n kommersiële wyngisras, asook die geen te ooruitdruk in 'n kommersiële wyngisras wat reeds die ATF1-geen ooruitdruk. Disrupsiekassette is ook vir die disrupsie van die ATF1- en ATF2-gene in 'n kommersiële wyngisras ontwerp. Die rekombinante wyngisrasse wat gedurnde die studie gemaak is, is vir die produksie van wyn en brandewyn gebruik. Gas chromatografise-ontledings en sensoriese evaluerings is ook op die wyn en brandewyn uitgevoer. Die resultate van die studie het bewys dat daar wel veranderings plaasvind wanneer 'n verandering in geenuitdrukking gemaak is. Die resultate het weereens bevestig dat die ATF1-geen 'n belangrike rol in die produksie van etiel- en isoamielasetaat speel. Wanneer die ATF1-geen ooruitgedruk is, is die etielasetaatproduksie 5.6 keer meer en die isoamielasetaatproduksie 3.5 keer meer as in die kontrole. Die ooruitdrukking van die ATF2-geen het geen verhoging in etielasetaat of isoamielasetaat of in totale esters in die wyn getoon nie, alhoewel die ras 2.7 keer meer diëtielsuksinaat geproduseer het. In die brandewyn wat geproduseer is met die gisras waarin ATF2 ooruitgedruk is, was daar wel 'n verlaging in die asynsuur, wat 'n aanduiding van estervorming kan wees, alhoewel die totale esters wat geproduseer is minder was as in die kontrole. 'n Verhoging in diëtielsuksinaat en 2-fenielasetaat is ook gevind. Daar is geen verhoging in etiel- of isoamielasetaat getoon wanneer die ATF1- en ATF2-geen saam ooruitgedruk is nie. Die ras het minder totale sure in wyn en brandewyn geproduseer en ook geen verhoging in totale esters getoon nie. Uit die resultate is dit duidelik dat veranderings in geenuitdrukking 'n verandering in die aromaprofiel van wyn en brandewyn kan veroorsaak. Die rol van dié A TF2-geen is nog steeds onduidelik en verdere studies sal moet plaasvind om die rol van die geen te verduidelik. Studies wat konsentreer op die invloed van houtveroudering op esterkonsentrasie is ook belangrik vir die toekoms, want dit sal die wyn- of brandewynmaker meer beheer oor die uiteindelike produk gee en daardeur die wyn- of brandewynmaker help om 'n produk te vervaardig wat sy mark bevredig.

Drosophila suzukii (Diptera: Drosophilidae), an invasive pest from Asia, colonized US and Europe in 2008 and since then has economically damaged multi-million commercial fruit production. With fruit-breaking serrated ovipositor the female lays eggs in the unwounded ripening fruits making them unmarketable. To know the genetic likelihood of D. suzukii with other Drosophila species its genome and transcriptome were sequenced. The whole genome was mined to understand the origin, speciation and adaptation and was correlated with the ecology of the species. Genomic analyses revealed that D. suzukii is adapted to temperate climate and has lower selective pressure and gene-sequencing rate compared to its sibling sp. D. biarmipes. From the genomic and ecological studies, one of the objectives was to understand the role of olfaction in host fruit recognition and identify key volatile compound/s involved in female decision-making for oviposition on fresh fruits. Based on gas chromatography mass spectrometer (GC-MS) and GC-electro-antennal detector activity, isoamylacetate was found to be one of the key compounds involved in the oviposition site selection. The phylogenetic analysis revealed that D. suzukii not only possess the full repertoire of genes encoding olfactory receptors activated by isoamyl acetate in D. melanogaster, but showed that Or67a (Or67a1 to Or67a5) is even represented by duplicated copies. Another aim was to investigate the pheromone communication in this species. The extraction and identification of cuticular hydrocarbons from the males inherently showed that the species trans-evolved by terminating the production of sex pheromone cis vaccenyl acetate (cVA), which is used by species throughout melanogaster group, but able to smell it with ‘fewer’ T1 sensilla. Being under highly selective pressure D. suzukii has i) scaled-down the size of ejaculatory bulb in males, ii) fewer T1 tricoid sensilla, and iii) comparatively smaller glomerulus, in the antennal lobe (AL), involved in receiving sensory impulses from T1 sensilla when compared to D. melanogaster. However D. suzukii shares all functional fatty acid synthase (FAS) genes responsible to CH production. On applying D. melanogaster male equivalent synthetic cVA on males of D. suzukii, it significantly reduced the mating acceptance in the females, which otherwise increased in D. melanogaster. Therefore, by adapting not to produce cVA as a sex pheromone D. suzukii tend to avoid competition with congeneric species for oviposition. The whole spectrum of the present and future studies would help to understand the evolution of the olfactory code among the closely related species of Drosophila and, as a consequence, contribute to develop alternative control methods of D. suzukii. Indeed, comparison of D. suzukii with sibling species and D. melanogaster could shed light on the evolution of ecological innovations and help researchers in understanding what makes a species to be an invasive pest

Proyecto Integrador (IQ)--FCEFN-UNC, 2019
Trata del estudio experimental de la producción de acetato de isoamilo a partir del alcohol isoamílico recuperado del aceite de fusel, mediante deshidratación y destilación batch del mismo. Caracteriza el aceite de fusel y evalúa alternativas tecnológicas de deshidratación del aceite de fusel: por agregado de óxido de calcio

碩士
國立中央大學
化學工程學系
86
The aim of this study will probe into the thermodynamic behavior of acetic acid,isoamyl alcohol,water,isoamyl acetate mixture,during manufacturing the specialtychemical,isoamyl acetate by reactive distillation process.This approach is consideringthe chemical reaction equilibrium and phase equilibrium simultaneously. The experiments of chemical equilibrium and phase equilibrium were conducted in a modified Othmer type equilibrium cell.The commercial NaY catalyst(Y typezeolite)was added to increase chemical reaction rate,and found no effect on thephase equilibrium.51 experimental data were collected for this study. The experimental VLE data were correlated by activity coefficient models ofUNIQUAC,NRTL,Wilson respectively,with consideration of the strongly associationof acetic acid molecules in vapor phase.Our calculated results show that the correlation by UNIQUAC model was in good agreement with the experimental data.It is also found that the reactive azeotrope does not exist in this study byusing Barbosa and Doherty's criterion of a reactive system[5].

Products derived from the central aerobic metabolic pathway in Escherichia coli often compete with the acetate-producing pathways poxB and ackA-pta for glucose. The production of isoamyl acetate from acetyl-CoA by ATF2, a yeast alcohol acetyltransferase, was a model system to demonstrate the beneficial effects of reducing aerobic acetate production. Ester production was 80% higher in the poxB, ackA-pta strain (0.18 mM) than found in the single ackA-pta mutant, when both overexpressed the PDH complex, panK, and ATF2. Anaerobically, succinate was produced alongside isoamyl acetate to maintain the proper redox balance between NADH and NAD+. The two compounds could be easily separated in an industrial setting because of the difference in their volatilities. An ldhA, adhE double mutant strain served as the control strain to test the effect of an additional ackA-pta mutation. The triple mutant produced 36% more ester (9.4 mM) and 7 times more succinate (45.5 mM) than the control.

Traditional metabolic engineering focused on pathway manipulation strategies like amplification addition or deletion of pathway to manipulate fluxes. However, cofactors play an essential role in cellular metabolism and their manipulation has the potential to be used, as an additional tool to achieve desired metabolic engineering goals. Coenzyme A and its derivative acetyl-CoA are important cofactors involved in many biosynthetic pathways and precursors for many industrially useful compounds. Our study focused on increasing the intracellular level/fluxes of CoA and acetyl-CoA. This was accomplished by overexpression of key rate controlling enzyme panK in the CoA biosynthesis pathway along with simultaneous supplementation of precursor pantothenic acid. The effect of such precise alteration of CoA metabolism on extracellular metabolite formation was studied. The utility of CoA manipulation system in enhancing production of isoamyl acetate, an industrially useful compound derived from acetyl-CoA was demonstrated. This novel approach of cofactor manipulation was combined with the more traditional approach of competing pathway deletion, acetate production pathway in this case, to further enhance isoamyl acetate productivity. Overexpression of panK led to a significant increase in CoA levels. Acetyl-CoA levels also increased but not as much as CoA leaving much of it in an unacetylated form. The central carbon flux was enhanced, either by overexpression of pdh or pps to increase acetyl-CoA, under elevated CoA levels. The flux through the acetyl-CoA node increased under such conditions. This enhanced carbon flux was efficiently channeled to isoamyl acetate production pathway by inactivating the acetate production pathway. The combination of these metabolic engineering strategies led to a significant increase in isoamyl acetate production. We used production of isoamyl acetate as a model system to demonstrate the beneficial effects of CoA/acetyl-CoA manipulations in enhancing product productivity. This methodology can be easily extended to any other production systems involving the cofactors CoA/acetyl-CoA. Additional studies in our lab have shown that CoA/acetyl-CoA manipulation system is useful in improving productivities of succinate and lycopene.

碩士
大同大學
生物工程學系(所)
94
Isoamyl acetate is an important flavor compound in wine and beverage. It is formed from isoamyl alcohol and acetyl-CoA catalyzed by alcohol acetyltransferase (AATase) in Saccharomyces cerevisiae. In this study, the gene ATF1 coded for AATase from S. cerevisiae BCRC 21731 was cloned and constructed into a constitutive expression vector pGAPZA. A recombinant Pichia pastoris strain was obtained express high level natural flavor to produce isoamyl acetate. The optimal culture condition to enhance the production of isoamyl acetate by recombinant P. pastoris was also investigated. The results showed that recombinant strain GS115/GAPZA-ATF1 produced twice as much isoamyl acetate as GS115/GAPZA (control strain). When glucose, other than glycerol or methanol, was used as carbon source, recombinant strain produced the highest amount of isoamyl acetate. The optimal medium composition for isoamyl acetate production by recombinant strain was 2% glucose, 1% yeast extract and 20 mM isoamyl alcohol. The highest production of isoamyl acetate, is 0.87 mM, was obtained when the recombinant strain GS115/GAPZA-ATF1 was cultivated in the optimal medium at 30℃ for 4 days.

Volatile substances are responsible for the fragrance features not only sparkling wines. According to research there are more than 400 compounds.In this thesis is shortly mentioned technology of the sparkling wines and sparkling wines in the Czech Republic. Most of the work is devoted to the characterization of volatile substances found in sparkling wines. In the experimental part, 26 of samples were evaluated by sensory evaluation but the priority is given to volatile substances. By GC-MS were measured 65 volatile substances, which were subsequently evaluated. The focus is primarily on substances for which there is a decline during aging (amyl acetate), or growth (diethyl succinate, furfural, etc.). Volatile substances are evaluated not only by producers, but also by country of origin and in the last chapter is compared between the technology productions.