Concentration Of 2-phenylethanol Research Articles

The Effects of Pigeage, Délestage, Remontage and Oxygenation Treatments Applied during Maceration on Phenolic Content, Aroma Composition and Sensory Properties of Red Teran (Vitis vinifera L.) Wine

The aim of this study was to evaluate the effects of mechanical (pigeage, délestage and remontage) and oxygenation treatments on the phenolic and aromatic compounds and sensory characteristics of Teran wines. The experiment included a 20-day maceration period, during which the above-mentioned treatments were applied, as well as the post-fermentation processes of pressing and first rack. The analysis of phenolic, chromatic and aroma compounds and the sensory characterization of the wines were used to describe the effects of the treatments investigated. After the observed maceration period, remontage resulted in wines with the highest total phenols (2682.0 ± 14.8 mg GAE/L). In contrast, délestage resulted in the lowest total phenols (2499.1 ± 17.6 mg GAE/L) and total anthocyanins (530.1 ± 2.8 mg/L) and had the strongest effects on chromatic characteristics. The post-fermentation processes (pressing, racking) showed similar trends and resulted in higher phenolic concentrations in the remontage wine, while the délestage was again characterized by lower total phenol and anthocyanin concentrations. In addition, the délestage wine contained a higher concentration of almost all analyzed esters and two higher alcohols (2-methylpropan-1-ol and 1-hexanol), while the remontage wine had the highest concentration of 2-phenylethanol and 3-methylbutyl acetate. Finally, maceration proved to be a key factor in defining the wines’ sensory characteristics, with the remontage-treated wine showing the best overall quality.

Nonconventional yeasts and hybrids for low temperature handcrafted sparkling ciders elaboration in Patagonia

Yeasts play a crucial role in transforming apple must into cider. While Saccharomyces cerevisiae (Sc) has been traditionally associated to cider fermentations worldwide, cryotolerant species such as Saccharomyces uvarum (Su) as well as natural S. cerevisiae × S. uvarum (Sc×Su) hybrids have also been detected in ciders fermented at low temperatures.This study aimed to evaluate the ability of two Patagonian cryotolerant yeast strains (Su and Se) and their interspecific hybrids with a Sc to conduct handcrafted apple must fermentations and a second fermentation process (champenoise method). The main chemical parameters and sensory quality of the resulting sparkling beverages was also analysed.Firstly, Sc×Se and Sc×Su hybrids were evaluated in their fermentative features at laboratory scale. Hybrids were compared with their respective parental species evidencing significant differences in the physicochemical and aromatic composition of the obtained base ciders.Both Su parental strain and the hybrid Sc×Se were selected for performing pilot scale fermentations (250 L) using natural (non-sterilized) apple juice at two different temperatures: 20 °C and 13 °C. Sc parental strain was also evaluated for comparative purposes. All base ciders obtained were then subjected to a second fermentation.A high implantation capacity of both Su and the hybrid was evidenced at the lowest evaluated temperature, while commercial Sc strain was not detected at the final fermentation stage, independently from the temperature. All sparkling ciders exhibited distinct physicochemical profiles. Ciders inoculated with commercial Sc (but effectively fermented with local Sc strains) allowed the development of malolactic fermentation (MLF) in processes carried out at both temperatures. Contrarily, no MLF was observed in ciders inoculated with either Su or the hybrid. Sparkling ciders fermented with Su displayed the highest concentrations of 2-phenylethanol and 2-phenylethyl acetate, regardless of the fermentation temperature. Conversely, ciders fermented with the hybrid at 20 °C exhibited the highest concentrations of ethyl octanoate and ethyl decanoate, contributing to floral and fruity notes in the beverage.Sensory analysis conducted with untrained individuals revealed a preference for sparkling ciders produced with the hybrid strain at both 20 °C and 13 °C. The cider fermented at 20 °C exhibited floral notes, sweetness, and a full body, while ciders fermented at 13 °C displayed moderate acidity and a well-balanced profile. Conversely, a trained panel described the cider fermented at 20 °C with Su as a fruity and acidic beverage, whereas the ciders fermented at 13 °C exhibited intense bitterness and acidity.This study highlights the potential of cryotolerant Saccharomyces species and hybrids in the development of new starter cultures for producing artisanal sparkling ciders with distinctive properties.

The Production of Bioaroma by Auriporia aurulenta Using Agroindustrial Waste as a Substrate in Submerged Cultures

The present study was carried out to investigate the potential of the basidiomycete Auriporia aurulenta to metabolize residues remaining from the processing of umbu, cajá, plum, and persimmon fruits for the production of natural aroma compounds using submerged fermentation. The volatile compounds obtained from the fermentation of A. aurulenta cultivated in these residues were extracted via stir bar sorptive extraction (SBSE) and analyzed using a gas chromatography-mass spectrometry (GC-MS) system. Esters and alcohols were the main compounds produced, with emphasis on the compounds 2-phenethyl acetate and 2-phenylethanol, which were mainly produced from umbu residue. The acid medium favored the production of 2-phenethyl acetate, reaching its maximum value (11.38 mg/L) on day 3.5, while higher concentrations of 2-phenylethanol were found in the basic medium, with optimal production (2.27 mg/L) on the 7th day. By varying the concentrations of pre-inoculum and residue in the optimization of this fermentation process, it was possible to double the production (24.47 mg/L) of 2-phenethyl acetate and obtain a seven times higher concentration (15.56 mg/L) of 2-phenylethanol. The diversity and expressive production of these aromatic compounds found in the fermentation media using these agroindustrial residues indicate that their use as substrates is an economical and environmentally viable alternative.

Comparison of Preference for Chemicals Associated with Fruit Fermentation between Drosophila melanogaster and Drosophila suzukii and between Virgin and Mated D. melanogaster.

Two taxonomically similar Drosophila species, Drosophila melanogaster and Drosophila suzukii, are known to have distinct habitats: D. melanogaster is mostly found near overripe and fermented fruits, whereas D. suzukii is attracted to fresh fruits. Since chemical concentrations are typically higher in overripe and fermented fruits than in fresh fruits, D. melanogaster is hypothesized to be attracted to higher concentrations of volatiles than D. suzukii. Therefore, the chemical preferences of the two flies were compared via Y-tube olfactometer assays and electroantennogram (EAG) experiments using various concentrations of 2-phenylethanol, ethanol, and acetic acid. D. melanogaster exhibited a higher preference for high concentrations of all the chemicals than that of D. suzukii. In particular, since acetic acid is mostly produced at the late stage of fruit fermentation, the EAG signal distance to acetic acid between the two flies was higher than those to 2-phenylethanol and ethanol. This supports the hypothesis that D. melanogaster prefers fermented fruits compared to D. suzukii. When comparing virgin and mated female D. melanogaster, mated females showed a higher preference for high concentrations of chemicals than that of virgin females. In conclusion, high concentrations of volatiles are important attraction factors for mated females seeking appropriate sites for oviposition.

Disparity in pseudohyphal morphogenic switching response to the quorum sensing molecule 2-phenylethanol in commercial brewing strains of Saccharomyces cerevisiae.

Saccharomyces cerevisiae can undergo filamentous growth in response to specific environmental stressors, particularly nitrogen-limitation, whereby cells undergo pseudohyphal differentiation, a process where cells transition from a singular ellipsoidal appearance to multicellular filamentous chains from the incomplete scission of the mother-daughter cells. Previously, it was demonstrated that filamentous growth in S. cerevisiae is co-regulated by multiple signaling networks, including the glucose-sensing RAS/cAMP-PKA and SNF pathways, the nutrient-sensing TOR pathway, the filamentous growth MAPK pathway, and the Rim101 pathway, and can be induced by quorum-sensing aromatic alcohols, such as 2-phenylethanol. However, the prevalent research on the yeast-pseudohyphal transition and its induction by aromatic alcohols in S. cerevisiae has been primarily limited to the strain Σ1278b. Due to the prospective influence of quorum sensing on commercial fermentation, the native variation of yeast-to-filamentous phenotypic transition and its induction by 2-phenylethanol in commercial brewing strains was investigated. Image analysis software was exploited to enumerate the magnitude of whole colony filamentation in 16 commercial strains cultured on nitrogen-limiting SLAD medium; some supplemented with exogenous 2-phenylethanol. The results demonstrate that phenotypic switching is a generalized, highly varied response occurring only in select brewing strains. Nevertheless, strains exhibiting switching behavior altered their filamentation response to exogenous concentrations of 2-phenylethanol.

Effects of micro-oxygenation on the aroma of Cabernet Sauvignon wine from Ningxia, China

Micro-oxygenation (MOX) is an effective post-harvest technique for the flavor improvement of grape wine. This study investigated the effect of MOX on the aroma quality of Ningxia wine for the first time. Three sub-region Cabernet Sauvignon dry red wines were treated with different levels of oxygen before or after malolactic fermentation. The wine aroma was analyzed through gas chromatography-mass spectrometry (GC-MS) and quantitative descriptive analysis (QDA) after six months of aging. The data obtained demonstrated that the dose and timing of oxygen addition were both key factors influencing the effectiveness of MOX. The most noticeable modifications in wine aroma compounds were generated by an oxygen dosage of 30 mL·month/L added before malolactic fermentation. Predominantly, the concentrations of 2-phenylethanol, benzaldehyde, diacetyl, and 2,3-pentanedione showed an increased pattern upon MOX treatments. The sensory analysis revealed that MOX improved the aroma quality of wine by decreasing green and animal odors, meanwhile enhancing the olfactory intensities of dried fruits, flowers, and nuts. This work confirmed that MOX was suitable for aroma modification of Cabernet Sauvignon dry red wine from Ningxia and established a preliminary MOX procedure that can serve as a reference for future applications. Keywords: grape wine, micro-oxygenation, volatile organic compounds, aroma profiles, Ningxia DOI: 10.25165/j.ijabe.20221504.7158 Citation: Zhang Z, Zhang Q C, Wang H Q, Xia H C, Sun L J, Zhang J X. Effects of micro-oxygenation on the aroma of Cabernet Sauvignon wine from Ningxia, China. Int J Agric & Biol Eng, 2022; 15(4): 251–263.

Aromatic Higher Alcohols in Wine: Implication on Aroma and Palate Attributes during Chardonnay Aging.

The higher alcohols 2-phenylethanol, tryptophol, and tyrosol are a group of yeast-derived compounds that have been shown to affect the aroma and flavour of fermented beverages. Five variants of the industrial wine strain AWRI796, previously isolated due to their elevated production of the ‘rose-like aroma’ compound 2-phenylethanol, were characterised during pilot-scale fermentation of a Chardonnay juice. We show that these variants not only increase the concentration of 2-phenylethanol but also modulate the formation of the higher alcohols tryptophol, tyrosol, and methionol, as well as other volatile sulfur compounds derived from methionine, highlighting the connections between yeast nitrogen and sulfur metabolism during fermentation. We also investigate the development of these compounds during wine storage, focusing on the sulfonation of tryptophol. Finally, the sensory properties of wines produced using these strains were quantified at two time points, unravelling differences produced by biologically modulating higher alcohols and the dynamic changes in wine flavour over aging.

Persistence of a Yeast-Based (Hanseniaspora uvarum) Attract-and-Kill Formulation against Drosophila suzukii on Grape Leaves.

Simple SummaryDrosophila suzukii is an invasive pest species that feeds on yeast-laden fruits and is attracted to fermentation products. In nature, numerous yeast species are associated with Drosophila suzukii. Yeasts constitute a food source and produce volatile compounds attractive to the fly. The production of attractants and chemical compounds that stimulate feeding by Drosophila suzukii make the use of yeasts promising for the development of attract-and-kill formulations. In the present work, the efficacy and the persistence over a one-week period of a yeast-based attract-and-kill formulation was evaluated treating grape plants in a greenhouse. The efficacy was assessed by measuring the survival and oviposition rate of Drosophila suzukii. The concentrations or presence/absence of potential feeding stimulants and attractants were assessed by quantitative measurement of carbohydrates, sugar alcohols, amino acids, and volatile compounds. Results show that the formulation was still effective and that some of the chemical compounds monitored were still present on the surface of treated leaves one week after treatment, though changes in the chemical profiles were observed over this period.The production of phagostimulant and attractive volatile organic compounds (VOCs) by yeasts can be exploited to improve the efficacy of attract-and-kill formulations against the spotted wing drosophila (SWD). This study evaluated the persistence over one week of a yeast-based formulation under greenhouse conditions. Potted grape plants were treated with: (i) potato dextrose broth (PDB), (ii) PDB containing spinosad (PDB + S), and (iii) H. uvarum fermentation broth grown on PDB containing spinosad (H. u. + S). Laboratory trials were performed to determine the survival and the oviposition rate of SWD after exposure to treated leaves. Ion-exchange chromatography was performed to measure carbohydrates, sugar alcohols, and organic acids on leaf surfaces, while amino acids were assessed through liquid chromatography–mass-spectrometry. Additionally, the VOCs released by plants treated with H.uvarum were collected via closed-loop-stripping analysis and compared to those emitted by untreated leaves. A higher mortality was observed for adult SWDs in contact with H. uvarum containing spinosad compared to PDB containing spinosad. Generally, a decrease in the amounts of non-volatile compounds was observed over time, though numerous nutrients were still present one week after treatment. The application of the yeast-based formulation induced the emission of VOCs by the treated leaves. The concentration of 2-phenylethanol, one of the main VOCs emitted by yeasts, decreased over time. These findings describe the presence of potential phagostimulants and compounds attractive to SWD in a yeast-based attract-and-kill formulation and demonstrate the efficacy of the formulation over one week.

Zygosaccharomyces rouxii, an Aromatic Yeast Isolated From Chili Sauce, Is Able to Biosynthesize 2-Phenylethanol via the Shikimate or Ehrlich Pathways.

We isolated an aromatic strain of yeast (M2013310) from chili sauce. Assembly, annotation, and phylogenetic analysis based on genome sequencing, identified M2013310 as an allodiploid yeast that was closely related to Zygosaccharomyces rouxii. During fermentation, M2013310, produced an aromatic alcohol with a rose-honey scent; gas chromatography tandem mass spectrometry identified this alcohol as 2-phenylethanol. The concentration of 2-phenylethanol reached 3.8 mg/L, 1.79 g/L, and 3.58 g/L, in M3 (NH4+), M3 (NH4+ + Phe), and M3 (Phe) culture media, after 72 h of fermentation, respectively. The mRNA expression levels of ARO8 encoding aromatic aminotransferases I and ARO10 encoding phenylpyruvate decarboxylase by M2013310 in M3 (Phe) were the lowest of the three different forms of media tested. These results indicated that M2013310 can synthesize 2-phenylethanol via the Shikimate or Ehrlich pathways and the production of 2-phenylethanol may be significantly improved by the over-expression of these two genes. Our research identified a promising strain of yeast (M2013310) that could be used to improve the production of 2-phenylethanol.

Volatile compounds associated with growth of Asaia bogorensis and Asaia lannensis-unusual spoilage bacteria of functional beverages.

Acetic acid bacteria of the genus Asaia are recognized as common bacterial spoilage in the beverage industry. Their growth in contaminated soft drinks can be visible in the form of flocs, turbidity and flavor changes. Volatile profiles associated with the growth and metabolic activities of Asaia lannensis and As. bogorensis strains were evaluated using comprehensive gas chromatography-time of flight mass spectrometry (GC × GC-ToF MS). Based on obtained results, 33 main compounds were identified. The greatest variety of volatile metabolites was noted for As. lannensis strain W4. 2-Phenylethanol, 3-pentanone, 2-nonanol, 2-hydroxy-3-pentanone, and 2-nitro-1-butanol were detected as dominant volatile compounds. Additionally, As. lannensis strains formed 2-propenoic acid ethyl ester. As. bogorensis ISD1 was distinguished by the higher concentration of 2-hydroxy-3-pentanone and 3-methyl-1-butene but the lowest concentration of 2-phenylethanol. Based on these results, it was found that volatile profiles of Asaia spp. are unique among acetic acid bacteria. Moreover, obtained profiles depended not only on bacterial species and strains but also on the composition of culture media.

Design of hybrid systems with in-situ product removal from fermentation broth: Case study for 2-phenylethanol production

Many natural compounds used as flavours and aromas, such as 2-phenylethanol, can be produced both synthetically and biotechnologically. Large amounts of cheap product can be synthesised, however, a substance to be used in food and pharmaceutical industry or perfumery has to be produced from natural precursors. Biotechnologically, this can be accomplished in a classic batch process - by transforming L-phenylalanine into 2-phenylethanol using Saccharomyces cerevisiae as a production strain followed by the product separation. The major downside of the configuration is the inhibition effect of the product on the production strain – concentration of 2-phenylethanol above 4 g L−1 is fatal for the yeasts. One way of solving the problem is to combine the fermentation and separation processes and continuously remove the product from the bioreactor during fermentation. This process configuration is called hybrid system. In this work, two batch configurations and three hybrid systems are presented and compared considering overall production rate, cost of operation units, raw materials and energy consumption. It has been shown that hybrid systems in which microfiltration is not present during in-situ product removal perform better than traditional batch systems or hybrid system with microfiltration.

Volatile compounds flavoring obtained from Brazilian and Mexican spirit wastes by yeasts.

Vinasse is a waste obtained from the production of beverages, such as tequila and cachaça. The presence of acids, alcohols, sugars, minerals, amino acids, peptides, and nitrogen salts make vinasse a hazardous liquid waste to the environment, affecting the fauna, flora, and microbiota of rivers and lagoons. This study used biological treatment concomitant to volatile compound production. The yeasts used in the study were Saccharomyces cerevisiae (CCMA 0187 and CCMA 0188), Candida parapsilosis (CCMA 0544), and Pichia anomala (CCMA 0193). A higher percentage reduction in chemical and biochemical oxygen demand was observed in the tequila vinasse than in the cachaça vinasse. However, a higher production of volatile compounds was observed in the cachaça vinasse. C. parapsilosis CCMA 0544 produced the highest concentration of 2-phenylethanol (162mgL-1). These results indicated that the environmental damage of vinasse can be reduced by treating vinasse with yeasts, and this treatment produces aroma compounds. This biological treatment has high economic potential, especially for the tequila industry.

Contribution of a BrazilianTorulaspora delbrueckiiisolate and a commercialSaccharomyces cerevisiaeto the aroma profile and sensory characteristics of Moscato Branco wines

Background and Aims Moscato Branco is the most important cultivar used in the production of Brazilian muscat sparkling wines and is responsible for their sensory characteristics. The aim of this work was to evaluate the effect of monoculture and co-fermentations by Torulaspora delbrueckii (TPI-4) and Saccharomyces cerevisiae (EC1118) on the physicochemical, aromatic composition and sensory characteristics of Moscato Branco wines. Methods and Results Wines inoculated with axenic and co-inoculated with S. cerevisiae and T. delbrueckii were elaborated and subjected to physicochemical, chromatographic and sensory analysis. The monoculture fermentation with T. delbrueckii, and co-fermentation with 25%EC1118/75%TPI-4 showed the lowest concentration of volatile fatty acids, considered as undesirable compounds and the highest concentration of 2-phenylethanol, acetates and ethyl esters, with fruity and flowery descriptors. Based on odour activity values, the main positive contribution of T. delbrueckii was on the concentration of isoamyl acetate, 2-phenylethanol, 2-phenylethyl acetate, ethyl hexanoate and linalyl acetate. Conclusions Wines produced by co-fermentation with 25%EC1118/75%TPI-4 obtained the highest general quality, aroma quality and flavour intensity scores in the sensory evaluation, reflecting the positive contribution of T. delbrueckii on the sensory attributes of Moscato Branco wines. Significance of the Study This work showed that co-inoculation with T. delbrueckii and S. cerevisiae improves the quality of muscat wines.

Investigations on the Aroma of Cocoa Pulp ( Theobroma cacao L.) and Its Influence on the Odor of Fermented Cocoa Beans.

The odor-active constituents of cocoa pulp have been analyzed by aroma extract dilution analysis (AEDA) for the first time. Pulps of three different cocoa varieties have been investigated. The variety CCN51 showed low flavor intensities, in terms of flavor dilution (FD) factors, in comparison to varieties FSV41 and UF564, for which floral and fruity notes were detected in higher intensities. To gain first insights on a molecular level of how the cocoa pulp odorants affected the odor quality of cocoa beans during fermentation, quantitative measurements of selected aroma compounds were conducted in pulp and bean at different time points of the fermentation. The results showed significantly higher concentrations of 2-phenylethanol and 3-methylbutyl acetate in pulp than in the bean during the different time steps of the fermentation, whereas the reverse could be observed for the odorants linalool and 2-methoxyphenol. The findings of this study constitute a basis for further investigations on the aroma formation of cocoa during fermentation.

Volatile Compound Profiling in Commercial Lager Regular Beers and Derived Alcohol-Free Beers After Dealcoholization by Vacuum Distillation

Alcohol-free beers are characterized by less aroma and body than regular ones. Seven flavor compounds were chosen as indicators in dealcoholization experiments at 102 and 200 mbar. Compounds were analyzed by headspace (HS)-solid phase microextracion (SPME)-gas chromatography–mass spectrometry (GC-MS). Also, contents of aroma-related compounds were compared between commercial regular and alcohol-free beers. In dealcoholization experiments by vacuum distillation, most of the compounds were shown to be evaporated in the first vapor fraction. The compounds that mainly remained in alcohol-free beers were amyl alcohols and 2-phenylethanol; this might explain their characteristic sweet and, to a lesser extent, fruity and flowery flavors. Regular beers were mainly characterized by 1-butanol, amyl alcohols, and ethyl acetate. Beers dealcoholized at 102 mbar are characterized by a high concentration of 2-phenylethanol. Beers dealcoholized at 200 mbar and commercial non-alcoholic beers had a similar flavor profile, which is characterized by low concentrations of the compounds used as indicators.

Volatile flavour profile of reduced alcohol wines fermented with the non-conventional yeast species Metschnikowia pulcherrima and Saccharomyces uvarum

Production of quality wines with decreased alcohol concentration continues to be one of the major challenges facing wine producers. Therefore, there is considerable interest in the isolation or generation of wine yeasts less efficient at transforming grape sugars into ethanol. We recently demonstrated that Metschnikowia pulcherrima AWRI1149 and Saccharomyces uvarum AWRI2846 were both able to produce reduced alcohol wine when used in sequential inoculation with Saccharomyces cerevisiae. This effect is additive when both strains are co-inoculated in grape must. Here we describe the volatile flavour profile of Chardonnay and Shiraz wines produced with these two strains. Wines fermented with M. pulcherrima showed concentrations of ethyl acetate likely to affect negatively wine aroma. Wines fermented with S. uvarum and with a combination of M. pulcherrima and S. uvarum were characterised by increased concentrations of 2-phenyl ethanol and 2-phenylethyl acetate, both associated with positive sensory attributes.

Isolation, Identification, and Quantification of Lichenysin, a Novel Nonvolatile Compound in Chinese Distilled Spirits

Nonvolatile components influence overall flavor volatility and perception in alcoholic beverages. However, little information has been reported about the nonvolatile compounds in Chinese distilled spirits. For the first time, we isolated and identified a cyclic lipopeptide "lichenysin" as a novel nonvolatile compound in Chinese liquors, using preparative high performance liquid chromatography coupled with quadrupole-time-of-flight mass spectrometer and nuclear magnetic resonance. The concentrations of lichenysin were quantified in 14 main types of bottled Chinese liquors by using ultra performance liquid chromatography coupled with triple quadrupole mass spectrometer. The concentrations of lichenysin in Chinese liquor ranged from 0.01 to 111.74 μg/L, where the concentration was the highest in Dongjiu liquor. Furthermore, we found that lichenysin selectively affected aroma volatility in the Chinese liquor, using the headspace solid-phase microextraction coupled with gas chromatography-mass spectrometry. The headspace concentrations of 2-phenylethanol, phenol, and 4-methylphenol significantly decreased by respectively 58%, 76%, and 59% in 3 Chinese commercial liquors with an increase in lichenysin. These results indicated that lichenysin could be a novel nonvolatile compound that selectively affected aroma volatility in Chinese liquors. This was the first report that lichenysin was isolated, identified, and quantified as a nonvolatile compound in traditional Chinese liquors. Lichenysin selectively affected the volatility of the aroma compounds in Chinese liquors. So far, there is no report on lichenysin in other alcoholic beverages. It would give a new insight into flavoromics in food and help to improve aroma quality of Chinese liquors.

Influence of yeast strain on aromatic profile of Gewürztraminer wine

Three selected autochthonous and one commercial Saccharomyces cerevisiae strains used as starters for fermentation of the same Gewürztraminer must were compared in terms of their influence on primary and secondary aroma of wine. At the same testing conditions, each strain S. cerevisiae produced individual metabolites in different concentrations and combinations which significantly influenced resulting wine flavour. Higher concentrations of 2-phenylethanol and cis-rose oxide, associated with S. cerevisiae TC-NAX-A, considerably distinguished this strain from the others. Occurrence of these VOCs has important influence on sweet rose-like flavour typical for Gewürztraminer wine. This paper deals with the characterization of chemical substances that directly affect the primary varietal aroma of Gewürztraminer wine, while looking for a tool to produce an original and attractive product in form of suitable autochthonous strain S. cerevisiae.

Intensive 2-phenylethanol production in a hybrid system combined of a stirred tank reactor and an immersed extraction membrane module

AbstractBioconversion of l-phenylalanine to 2-phenylethanol using Saccharomyces cerevisiae is connected with the growth of biomass strongly limited by product inhibition. Therefore, fermentation can proceed only at low conversions of l-phenylalanine with very low yield of the desired product, which allows reaching the maximum concentration of 2-phenylethanol, 4 g L−1, in an ordinary batch, fed-batch, or chemostat bioreactor. To minimize capital and operating costs in the bioproduction of chemical specialties where the product inhibits the bioreaction, using a hybrid system based on the application of membrane extraction integrated in the bioreactor to remove the product is a suitable solution. Integration can be done by an external module for membrane extraction or, as a more efficient solution, by an extraction membrane module immersed directly in the bioreactor. Such a hybrid system can be used to remove 2-phenylethanol from the fermentation media and thus to overcome the product inhibition of the biotransformation process. In this paper, a hybrid system consisting of a stirred tank bioreactor (3.5 L) and an immersed extraction hollow fiber membrane module was studied. In the proposed system, the kinetics of 2-phenylethanol extraction from a water solution with and without biomass in the bioreactor to alkanes at different operational conditions was measured. Extraction kinetics was compared with the predictions obtained by a mathematical model. In the hybrid system, two extractive biotransformation experiments were performed and compared with that without product removal. Experimental data were also mathematically predicted with good accuracy between the simulation and the experiment.

Airlift reactor — membrane extraction hybrid system for aroma production

AbstractIn recent times, environmental production methods and organic products are increasingly sought after in food, perfume, and cosmetic industries, where the products are consumed or come into direct contact with humans. One such additive is 2-phenylethanol, an alcoholic aromatic rose like smell compound, mainly used as a flavor and aroma. 2-Phenylethanol can be produced by bioconversion from l-phenylalanine using Saccharomyces cerevisiae. This type of biotransformation is strongly limited by product inhibition which allows reaching the maximum concentration of 2-phenylethanol, 4 g L−1, in an ordinary batch, fed-batch, or chemostat bioreactor. The main aim of the presented work was to study the possible yield increase of 2-phenylethanol in a hybrid system consisting of membrane extraction performed by a hollow fiber membrane module immersed in the downcomer of an airlift reactor. Such hybrid system can be used to remove 2-phenylethanol from the fermentation medium and thus to overcome the product inhibition of biotransformation. In this paper, the influence of biomass on membrane extraction of 2-phenylethanol from aqueous solution in an airlift reactor to alkanes at different operational conditions was studied. The measured extraction kinetics was compared with the predictions obtained by a mathematical model. Hydrodynamics of the hybrid system was also studied.