Recent advances in applying omic technologies for studying acetic acid bacteria in industrial vinegar production: A comprehensive review

Vinegar and related bioproducts containing acetic acid as the main component are among the most appreciated fermented foodstuffs in numerous European and Asian countries because of their exceptional organoleptic and bio-healthy properties. Regarding the acetification process and obtaining of final products, there is still a lack of knowledge on fundamental aspects, especially those related to the study of biodiversity and metabolism of the present microbiota. In this context, omic technologies currently allow for the massive analysis of macromolecules and metabolites for the identification and characterization of these microorganisms working in their natural media without the need for isolation. This review approaches comprehensive research on the application of omic tools for the identification of vinegar microbiota, mainly acetic acid bacteria, with subsequent emphasis on the study of the microbial diversity, behavior, and key molecular strategies used by the predominant groups throughout acetification. The current omics tools are enabling both the finding of new vinegar microbiota members and exploring underlying strategies during the elaboration process. The species Komagataeibacter europaeus may be a model organism for present and future research in this industry; moreover, the development of integrated meta-omic analysis may facilitate the achievement of numerous of the proposed milestones. This work might provide useful guidance for the vinegar industry establishing the first steps towards the improvement of the acetification conditions and the development of new products with sensory and bio-healthy profiles adapted to the agri-food market.

Latest Trends in Industrial Vinegar Production and the Role of Acetic Acid Bacteria: Classification, Metabolism, and Applications-A Comprehensive Review

Vinegar is one of the most appreciated fermented foods in European and Asian countries. In industry, its elaboration depends on numerous factors, including the nature of starter culture and raw material, as well as the production system and operational conditions. Furthermore, vinegar is obtained by the action of acetic acid bacteria (AAB) on an alcoholic medium in which ethanol is transformed into acetic acid. Besides the highlighted oxidative metabolism of AAB, their versatility and metabolic adaptability make them a taxonomic group with several biotechnological uses. Due to new and rapid advances in this field, this review attempts to approach the current state of knowledge by firstly discussing fundamental aspects related to industrial vinegar production and then exploring aspects related to AAB: classification, metabolism, and applications. Emphasis has been placed on an exhaustive taxonomic review considering the progressive increase in the number of new AAB species and genera, especially those with recognized biotechnological potential.

Combining omics tools for the characterization of the microbiota of diverse vinegars obtained by submerged culture: 16S rRNA amplicon sequencing and MALDI-TOF MS

Vinegars elaborated in southern Spain are highly valued all over the world because of their exceptional organoleptic properties and high quality. Among the factors which influence the characteristics of the final industrial products, the composition of the microbiota responsible for the process and the raw material used as acetification substrate have a crucial role. The current state of knowledge shows that few microbial groups are usually present throughout acetification, mainly acetic acid bacteria (AAB), although other microorganisms, present in smaller proportions, may also affect the overall activity and behavior of the microbial community. In the present work, the composition of a starter microbiota propagated on and subsequently developing three acetification profiles on different raw materials, an alcohol wine medium and two other natural substrates (a craft beer and fine wine), was characterized and compared. For this purpose, two different "omics" tools were combined for the first time to study submerged vinegar production: 16S rRNA amplicon sequencing, a culture-independent technique, and matrix-assisted laser desorption/ionization-time of flight mass spectrometry (MALDI-TOF MS), a culture-dependent method. Analysis of the metagenome revealed numerous taxa from 30 different phyla and highlighted the importance of the AAB genus Komagataeibacter, which was much more frequent than the other taxa, and Acetobacter; interestingly, also archaea from the Nitrososphaeraceae family were detected by 16S rRNA amplicon sequencing. MALDI-TOF MS confirmed the presence of Komagataeibacter by the identification of K. intermedius. These tools allowed for identifying some taxonomic groups such as the bacteria genera Cetobacterium and Rhodobacter, the bacteria species Lysinibacillus fusiformis, and even archaea, never to date found in this medium. Definitely, the effect of the combination of these techniques has allowed first, to confirm the composition of the predominant microbiota obtained in our previous metaproteomics approaches; second, to identify the microbial community and discriminate specific species that can be cultivated under laboratory conditions; and third, to obtain new insights on the characterization of the acetification raw materials used. These first findings may contribute to improving the understanding of the microbial communities' role in the vinegar-making industry.

Unraveling the Role of Acetic Acid Bacteria Comparing Two Acetification Profiles From Natural Raw Materials: A Quantitative Approach in Komagataeibacter europaeus

The industrial production of vinegar is carried out by the activity of a complex microbiota of acetic acid bacteria (AAB) working, mainly, within bioreactors providing a quite specific and hard environment. The “omics” sciences can facilitate the identification and characterization analyses of these microbial communities, most of which are difficult to cultivate by traditional methods, outside their natural medium. In this work, two acetification profiles coming from the same AAB starter culture but using two natural raw materials of different alcoholic origins (fine wine and craft beer), were characterized and compared and the emphasis of this study is the effect of these raw materials. For this purpose, the composition and natural behavior of the microbiota present throughout these profiles were analyzed by metaproteomics focusing, mainly, on the quantitative protein profile of Komagataeibacter europaeus. This species provided a protein fraction significantly higher (73.5%) than the others. A submerged culture system and semi-continuous operating mode were employed for the acetification profiles and liquid chromatography with tandem mass spectrometry (LC-MS/MS) for the protein analyses. The results showed that neither of two raw materials barely modified the microbiota composition of the profiles, however, they had an effect on the protein expression changes in different biological process. A molecular strategy in which K. europaeus would prevail over other species by taking advantage of the different features offered by each raw material has been suggested. First, by assimilating the excess of inner acetic acid through the TCA cycle and supplying biosynthetic precursors to replenish the cellular material losses; second, by a previous assimilation of the excess of available glucose, mainly in the beer medium, through the glycolysis and the pentose phosphate pathway (PPP); and third, by triggering membrane mechanisms dependent on proton motive force to detoxify the cell at the final moments of acetification. This study could complement the current knowledge of these bacteria as well as to expand the use of diverse raw materials and optimize operating conditions to obtain quality vinegars.

Functional metaproteomic analysis of alcohol vinegar microbiota during an acetification process: A quantitative proteomic approach

Vinegar is elaborated using a semi-continuous submerged culture of a complex microbiota of acetic acid bacteria. The genus Komagataeibacter provides much of the proteins of the metaproteome, being K. europaeus the main species working in this environment. In this work, the protein profile of the vinegar microbiota, obtained by means of liquid chromatography-tandem mass spectrometry (LC-MS/MS) in samples from different cycle times of an acetification process using an alcohol medium, has been used to describe the functional metaproteome throughout the process. The analysis was focused on Komagataeibacter species which supplied about 90% of the metaproteome and particularly K. europaeus which accounts for more than 70%. According to these results, the natural behaviour of a microbial community in vinegar has been predicted at a quantitative proteomic level. The results revealed that most of the identified proteins involved in the metabolism of amino acids, biosynthesis of proteins, and energy production related-metabolic pathways increased their expression throughout the cycle loading phase and afterwards experimented a decrease coming into play other proteins acting against acetic acid stress. These findings may facilitate a better understanding of the microbiota's role and contributing to obtain a quality product.

Metaproteomics of microbiota involved in submerged culture production of alcohol wine vinegar: A first approach

Acetic acid bacteria form a complex microbiota that plays a fundamental role in the industrial production of vinegar through the incomplete oxidation reaction from ethanol to acetic acid. The organoleptic properties and the quality of vinegar are influenced by many factors, especially by the raw material used as acetification substrate, the microbial diversity and the technical methods employed in its production. The metaproteomics has been considered, among the new methods employed for the investigation of microbial communities, since it may provide information about the microbial biodiversity and behaviour by means of a protein content analysis. In this work, alcohol wine vinegar was produced through a submerged culture of acetic acid bacteria using a pilot acetator, operated in a semi-continuous mode, where the main system variables were monitored and the cycle profile throughout the acetification was obtained. Through a first approach, at qualitative level, of a metaproteomic analysis performed at relevant moments of the acetification cycle (end of fast and discontinuous loading phases and just prior to unloading phase), it is aimed to investigate the microbiota existent in alcohol wine vinegar as well as its changes during the cycle; to our knowledge, this is the first metaproteomics report carried out in this way on this system. A total of 1723 proteins from 30 different genera were identified; 1615 out of 1723 proteins (93.73%) belonged to the four most frequent (%) genera: Acetobacter, Gluconacetobacter, Gluconobacter and Komagataeibacter. Around 80% of identified proteins belonged to the species Komagataeibacter europaeus. In addition, GO Term enrichment analysis highlighted the important role of catalytic activity, organic cyclic compound binding, metabolic and biosynthesis processes throughout acetic acid fermentation. These findings provide the first step to obtain an AAB profile at omics level related to the environmental changes produced during the typical semi-continuous cycles used in this process and it would contribute to the optimization of operating conditions and improving the industrial production of vinegar.

Effect of endogenous CO2 overpressure on the yeast "stressome" during the "prise de mousse" of sparkling wine

Sparkling wines elaboration by the "Champenoise" method involves a second fermentation of a base wine in hermetically sealed bottles and a subsequent aging period. The whole process is known as "prise de mousse". The endogenous CO₂ pressure produced during the second fermentation by the yeast Saccharomyces cerevisiae could modify the sub-proteome involved in the response to different stresses, or "stressome", and cell viability thus affecting the wine organoleptic properties. This study focuses on the stressome evolution along the prise de mousse under CO₂ overpressure conditions in an industrial S. cerevisiae strain. The results reveal an important effect of endogenous CO₂ overpressure on the stress sub-proteome, cell viability and metabolites such as glycerol, reducing sugars and ethanol. Whereas the content of glycerol biosynthesis-related proteins increased in sealed bottle, those involved in the response to toxic metabolites like ROS, ethanol, acetaldehyde and acetic acid, decreased in content. Proteomic profile obtained in this study may be used to select suitable wine yeast strains for sparkling wine elaboration and improve their stress tolerance.

New insights on yeast and filamentous fungus adhesion in a natural co-immobilization system: proposed advances and applications in wine industry

Fungi possess extraordinary strength in attachment to biotic and abiotic surfaces. This review focuses on adhesion mechanisms of yeast and filamentous fungi and the proposed combination of the adhesive forces of both organisms in an immobilization system called yeast biocapsules, whereby Saccharomyces cerevisiae cells are attached to the hyphae of Penicillium chrysogenum. The natural adherent properties of each organism, one multicellular and another unicellular, allow yeast to be fixated securely on the filamentous fungi and complete alcoholic fermentation. Following alcoholic fermentation, the hyphae become an inert support for yeast cells while maintaining shape and integrity. Biocapsules have been used successfully in both wine and bioethanol production. Investigation of the potential genes involved in fungal-yeast fusion suggests that natural hydrophobic interactions of both organisms play a major role. Analysis of the possible mechanisms involved in fungus and yeast adhesion, future perspectives on improving yeast immobilization, and proposed applications of the biocapsules are explored.

Comparative analysis of intracellular metabolites, proteins and their molecular functions in a flor yeast strain under two enological conditions

Flor yeasts confer a wide range of organoleptic properties to Sherry-type wines during a process called "biological aging" that takes place after alcoholic fermentation. These kinds of yeasts adapt to a biological aging condition by forming a biofilm known as "flor velum" and by changing from fermentative to oxidative metabolism. It has been reported that some functions such as increase of cell surface hydrophobicity or changes to lipid metabolism are enhanced when yeasts switch to biofilm lifestyle. Here, we attempt to reveal intracellular metabolites and protein molecular functions not documented before that are relevant in biofilm formation and in fermentation by an endometabolome and proteome screening. We report that at early stages of biofilm formation, flor yeasts accumulate mannose, trehalose, glycerol, oleic and stearic acids and synthesize high amounts of GTPases, glycosylases and lipoproteins. On the other hand, in early fermentation, flor yeasts rapidly consume glucose and phosphoric acid; and produce abundant proteins related to chromatin binding, transcription factors and methyl transferases.

FLO1, FLO5 and FLO11 Flocculation Gene Expression Impacts Saccharomyces cerevisiae Attachment to Penicillium chrysogenum in a Co-immobilization Technique

A reoccurring flaw of most yeast immobilization systems that limits the potential of the technique is leakage of the cells from the matrix. Leakage may be due to weakly adherent cells, deterioration of the matrix, or to new growth and loss of non-adherent daughter cells. Yeast biocapsules are a spontaneous, cost effective system of immobilization whereby Saccharomyces cerevisiae cells are attached to the hyphae of Penicillium chrysogenum, creating hollow spheres that allow recovery and reutilization. This attachment is based on naturally occurring adherent properties of the yeast cell surface. We hypothesized that proteins associated with flocculation might play a role in adherence to fungal hyphae. To test this hypothesis, yeast strains with overexpressed and deleted flocculation genes (FLO1, FLO5, and FLO11) were evaluated for biocapsule formation to observe the impact of gene expression on biocapsule diameter, number, volume, dry mass, and percent immobilized versus non-immobilized cells. Overexpression of all three genes enhanced immobilization and resulted in larger diameter biocapsules. In particular, overexpression of FLO11 resulted in a five fold increase of absorbed cells versus the wild type isogenic strain. In addition, deletion of FLO1 and FLO11 significantly decreased the number of immobilized yeast cells compared to the wild type BY4742. These results confirm the role of natural adherent properties of yeast cells in attachment to fungal hyphae and offer the potential to create strongly adherent cells that will produce adherent progeny thereby reducing the potential for cell leakage from the matrix.

Yeast Immobilization Systems for Alcoholic Wine Fermentations: Actual Trends and Future Perspectives

Yeast immobilization is defined as the physical confinement of intact cells to a region of space with conservation of biological activity. The use of these methodologies for alcoholic fermentation (AF) offers many advantages over the use of the conventional free yeast cell method and different immobilization systems have been proposed so far for different applications, like winemaking. The most studied methods for yeast immobilization include the use of natural supports (e.g., fruit pieces), organic supports (e.g., alginate), inorganic (e.g., porous ceramics), membrane systems, and multi-functional agents. Some advantages of the yeast-immobilization systems include: high cell densities, product yield improvement, lowered risk of microbial contamination, better control and reproducibility of the processes, as well as reuse of the immobilization system for batch fermentations and continuous fermentation technologies. However, these methods have some consequences on the behavior of the yeasts, affecting the final products of the fermentative metabolism. This review compiles current information about cell immobilizer requirements for winemaking purposes, the immobilization methods applied to the production of fermented beverages to date, and yeast physiological consequences of immobilization strategies. Finally, a recent inter-species immobilization methodology has been revised, where yeast cells are attached to the hyphae of a Generally Recognized As Safe fungus and remain adhered following loss of viability of the fungus. The bio-capsules formed with this method open new and promising strategies for alcoholic beverage production (wine and low ethanol content beverages).

Influence of two yeast strains in free, bioimmobilized or immobilized with alginate forms on the aromatic profile of long aged sparkling wines

Production of sparkling wines involve a second alcoholic fermentation and contact with yeast less over an extended period of time, which influences the aroma composition and sensory quality of the resulting wines. Sparkling wines obtained with two yeast strains inoculated as free cells, immobilized in alginate bed and bioimmobilized as biocapsules, were aged during 32 months. Among the volatile compounds, high Odor Activity Values were obtained with isoamyl acetate, ethyl propanoate, ethyl butanoate, ethyl 3-methylbutanoate, ethyl hexanoate, ethyl octanoate, hexanol, 2-methoxy-4-vinylphenol, decanal, octanoic acid, decanoic acid and TDN. Taken together these contribute more than 70% of the overall aromatic series value. Although some results rely more on the yeast strain than the inoculation format, specific aroma compounds were associated with the immobilization format, allowing the classification of sparkling wines by PCA. As a result the aroma quality of sparkling wines could be improved using immobilized yeasts.

Biotechnologically relevant features of gluconic acid production by acetic acid bacteria

The many uses of gluconic acid and some of its salts are arousing increasing interest in these compounds and in their production levels. Although gluconic acid and gluconates can be obtained chemically, they are currently almost exclusively biotechnologically produced, mostly by fungus based methods. There is, however, an ongoing search for alternative microorganisms to avoid the problems of using fungi for this purpose and to improve the productivity of the process. Especially promising in this respect are acetic acid bacteria, particularly Gluconobacter strains. This paper discusses the main variables and operating conditions to be considered in optimizing gluconic acid production by Gluconobacter.

Flor Yeast: New Perspectives Beyond Wine Aging

The most important dogma in white-wine production is the preservation of the wine aroma and the limitation of the oxidative action of oxygen. In contrast, the aging of Sherry and Sherry-like wines is an aerobic process that depends on the oxidative activity of flor strains of Saccharomyces cerevisiae. Under depletion of nitrogen and fermentable carbon sources, these yeast produce aggregates of floating cells and form an air–liquid biofilm on the wine surface, which is also known as velum or flor. This behavior is due to genetic and metabolic peculiarities that differentiate flor yeast from other wine yeast. This review will focus first on the most updated data obtained through the analysis of flor yeast with -omic tools. Comparative genomics, proteomics, and metabolomics of flor and wine yeast strains are shedding new light on several features of these special yeast, and in particular, they have revealed the extent of proteome remodeling imposed by the biofilm life-style. Finally, new insights in terms of promotion and inhibition of biofilm formation through small molecules, amino acids, and di/tri-peptides, and novel possibilities for the exploitation of biofilm immobilization within a fungal hyphae framework, will be discussed.

Changes in the intracellular concentrations of the adenosine phosphates and nicotinamide adenine dinucleotides ofSaccharomyces cerevisiae during batch fermentation

Significant changes in the intracellular concentrations of adenosine phosphates and nicotinamide adenine dinucleotides were observed during fermentation of grape must by three different strains ofSaccharomyces cerevisiae: S. cerevisiae var.cerevisiae, a typical fermentative yeast strain and two flor-veil-forming strains,S. cerevisiae var.bayanus andS. cerevisiae var.capensis. The intracellular concentration of ATP was always higher inS. cerevisiae var.cerevisiae than in the flor-veil-forming strains. NAD(+) and NADP(+) concentrations decreased at faster rates in the flor-veil-forming yeasts than in the other yeast but NADH concentration was the same in all yeasts for the first 10 days of fermentation. NADPH concentration was always lower inS. cerevisiae var.cerevisiae than in the other yeasts and this yeast also showed higher rates of growth and fermentation during the early stages of the fermentation and the presence of non-viable cells at the end of fermentation. In contrast, the flor-veil-forming strains maintained growth and fermentation capabilities for a relatively long time and viable cells were present throughout the entire fermentation process (31 days).

Sweet wine production by two osmotolerant Saccharomyces cerevisiae strains

The use of Saccharomyces cerevisiae to produce sweet wine is difficult because yeast is affected by a hyperosmotic stress due to the high sugar concentrations in the fermenting must. One possible alternative could be the coimmobilization of the osmotolerant yeast strains S. cerevisiae X4 and X5 on Penicillium chrysogenum strain H3 (GRAS) for the partial fermentation of raisin musts. This immobilized has been, namely, as yeast biocapsules. Traditional sweet wine (that is, without fermentation of the must) and must partially fermented by free yeast cells were also used for comparison. Partially fermented sweet wines showed higher concentration of the volatile compounds than traditionally produced wines. The wines obtained by immobilized yeast cells reached minor concentrations of major alcohols than wines by free cells. The consumption of specific nitrogen compounds was dependent on yeast strain and the cellular immobilization. A principal component analysis shows that the compounds related to the response to osmotic stress (glycerol, acetaldehyde, acetoin, and butanediol) clearly differentiate the wines obtained with free yeasts but not the wines obtained with immobilized yeasts.

Free amino acids, urea and ammonium ion contents for submerged wine vinegar production: influence of loading rate and air-flow rate

The nitrogen source for acetic acid bacteria is important during the vinegar making process. There can be great variation in the final result according to the specific source, the total nitrogen availability and the operational conditions. These bacteria use L-proline, L-leucine and ammonium ion as their main source of nitrogen from white wine. The effect of loading and air-flow rates on the changes in amino acids, urea and ammonium ion contents have been studied for a semi-batch submerged wine vinegar controlled production. Experiments were carried out in a Frings 8L fermenter working in a semi-batch mode. Amino acid contents were determined from their dansyl derivatives on an HPLC furnished with a C18 reversed-phase column. Urea and ammonium ion contents were quantified with an enzymatic kit. Specific nitrogen consumption is given for 25 amino acids and ammonium ion. In addition, profiles for main system variables as well as the three main nitrogen sources (ammonium ion, L-leucine and L-proline) are given. Type of loading and air-flow rates seemed to have a strong impact on the consumption of the nitrogen compounds tested. An increased loading rate and decreased air-flow rate resulted in greater overall consumption of available nitrogen due to different causes. Nitrogen requirement of the bacteria is proportional to the time spent in the acetification process. An acetification procedure involving relatively sudden changes in the fermentation medium may be desirable in order to reduce the formation of urea.

Relationship between changes in the total concentration of acetic acid bacteria and major volatile compounds during the acetic acid fermentation of white wine

BACKGROUND

In the scope of the wine vinegar production, this paper provides comprehensive information about the evolution of some volatile compounds during the biological acetification cycle. These data were compared with the acidity, cell concentration and ethanol concentration. Such information may allow a better understanding of the complex biological processes involved.

RESULTS

The volatile compounds 2-phenylethanol, diethyl succinate (diethyl butanedioate), meso-2,3-butanediol (meso-butane-2,3-diol), levo-2,3-butanediol (levo-butane-2,3-diol), methanol and ethyl acetate exhibited no significant changes between the starting wine and produced vinegar, whereas the rest [acetoin (3-hydroxybutan-2-one) excepted] ethyl lactate (ethyl 2-hydroxypropanoate), isoamyl alcohols (3-methylbutan-1-ol and 2-methylbutan-1-ol), isobutanol (2-methylpropan-1-ol), 1-propanol (propan-1-ol), and acetaldehyde were consumed in substantial amounts during the process. Additionally, their specific evolution patterns alongside bacterial cell concentrations, acidity and ethanol concentration are shown.

CONCLUSION

Concentrations of acetic acid bacteria at the end of the acetification cycle were found to vary because of cell lysis, a result of the high acidity and low ethanol concentration of the medium. Variations were similar to those in some volatile compounds, which suggests their involvement in the metabolism of acetic bacteria. The results testify to the usefulness of this pioneering study and suggest that there should be interest in similar, more detailed studies for a better knowledge of the presence of certain volatile compounds and metabolic activity in cells effecting the acetification of wine.

Use of a Schizosaccharomyces pombe mutant to reduce the content in gluconic acid of must obtained from rotten grapes

Schizosaccharomyces pombe YGS-5 and Saccharomyces cerevisiae G1 strains were used in order to develop an effective method for reducing the gluconic acid content of musts without altering the development of alcoholic fermentation or detracting from quality in the resulting wines. The best results in synthetic media were obtained by using a temperature of 24 degrees C and a sulfur dioxide rate below 100 mg/L under semiaerobic conditions. Sequential inoculation of the musts with YGS-5 first and fermentative G1 yeasts then reduced their gluconic acid content by 85% within 43 h; by contrast, simultaneous inoculation with YGS-5 and G1 provided a reduction of only 40%. The wines with the best sensory and analytical properties were obtained by sequentially inoculating the musts with YGS-5 and, once gluconic acid was removed, G1. The wine obtained by sequential inoculation without removing YGS-5 was that exhibiting the highest odorant activity value (OAV) for the volatile compounds in the floral odor series. A protocol for treating musts containing gluconic acid was developed and tested at the pilot plant scale. The treatment reduced the gluconic acid content by 70% within 46 h with no adverse effect on the analytical or sensory quality of the resulting wines.

Relationship between ethanol tolerance, H+ -ATPase activity and the lipid composition of the plasma membrane in different wine yeast strains

Ethanol tolerance, ATPase activity and the lipid composition of the plasma membrane to study potential relationship among them were examined in five different wine yeast strains. Yeast cells were subjected to ethanol stress (4% v/v). Principal component analysis of the results revealed that the wine yeasts studied can be distinguished in terms of ATPase activity and oleic acid (C18:1), and palmitoleic acid (C16:1), in plasma membrane. Multiple regression analysis was used to identify a potential influence of some components of the plasma membrane on ethanol tolerance and ATPase activity. Based on the results, the ergosterol, oleic acid and palmitoleic acid are highly correlated with ATPase activity and ethanol tolerance. Ethanol tolerance and the ATPase activity of the plasma membrane were correlated at the 96.64% level with the oleic acid and ergosterol in plasma membrane. The Saccharomyces cerevisiae var. capensis flor yeast strain, which exhibited the highest ergosterol concentration in plasma membrane when grown in the presence of 4% v/v ethanol, was found to be the most ethanol-tolerant.

Use of a Novel Immobilization Yeast System for Winemaking

Penicillium was used to immobilize Saccharomyces cerevisiae, without using physico-chemical external supports, to form yeast biocapsules. The biocapsules, once the Penicillium was killed by the ethanol produced, were used in a grape must fermentation. Must fermentation was carried out for 160 h with the biocapsules and for 300 h with free yeast cells. Acetaldehyde (84 vs. 63 mg/l), isobutanol (217 vs. 194 mg/l), L: -proline (7.7 vs. 6.5 mM: ) and aspartic acid (0.42 vs. 0 mM: ) in final wine were higher with the biocapsules than with free cells.

Potential application of a glucose-transport-deficient mutant of Schizosaccharomyces pombe for removing gluconic acid from grape must

Musts from rotten grapes typically contain high levels of gluconic acid, which can raise severe problems in winemaking processes. In this work, the ability of the glucose-transport-deficient mutant YGS-5 of Schizosaccharomyces pombe to completely or partly remove gluconic acid from a synthetic glucose-containing medium and the potential use of this yeast strain for the same purpose in musts and wines were examined. Surprisingly, the S. pombe YGS-5 strain successfully removed 93% of the initial gluconic acid (2.5 gL(-1)) and 80% of the initial malic acid (1.0 gL(-1)) within 30 h after inoculation. Also, the yeast strain produced no volatile compounds other than those obtained in fermentations conducted with the wine yeast Saccharomyces cerevisiae. S. pombe YGS-5 could thus be used to remove gluconic acid present in musts from rotten grapes. On the basis of these results, various ways of using S. pombe YGS-5 to treat musts containing gluconic acid in order to solve the problems due to the high gluconic acid concentrations in botrytized grape must are proposed.

Changes in volatile compounds and aromatic series in sherry wine with high gluconic acid levels subjected to aging by submerged flor yeast cultures

Volatile compounds of sherry wine containing gluconic acid under aging by submerged flor yeast cultures were analyzed. The aroma profile was obtained by grouping the compounds in nine aromatic series. The balsamic, fatty, herbaceous and empyreumatic series increased significantly as consequence of the increase of pantolactone, acids (butanoic, 2-methylbutanoic and 3-methylbutanoic), methionol and gamma-butyrolactone compounds, respectively. The decrease of higher alcohols promoted solvent series diminished. These changes are consistent with those observed in the production of commercial sherry wine using traditional biological aging.

Effect of Schizosaccharomyces pombe on aromatic compounds in dry sherry wines containing high levels of gluconic acid

Volatile compounds have been determined in control dry sherry wines and those supplemented with gluconic acid, which were inoculated with the Schizosaccharomyces pombe 1379 (ATCC 26760) yeast strain. These compounds were grouped, according to volatiles exhibiting the identical odor quality, into nine groups of the same odor character (aromatic series) as a way of establishing the aroma profile for the studied wines. Control and supplemented wines showed changes in the balsamic, spicy, roasty, and fruity aromatic series, and tasters judged the aroma as typical of wines subjected to biological aging. This fission yeast may be used as a treatment to reduce gluconic acid contents in wines obtained from rotten grapes, making feasible the incorporation of these wines into the biological aging process. In addition, this procedure may also help to accelerate the traditional biological aging in sherry winemaking due to the contribution of some specific compounds by S. pombe to the wine.

Influence of blending on the content of different compounds in the biological aging of sherry dry wines

Principal components analysis to examine the effect of blending (viz. the mixing and transfer of wine between cask rows in a "criaderas and solera" system) on metabolic activity in flor yeasts during biological aging of sherry dry wines was carried out. The variables used in the analysis were the wine compounds most deeply involved in the flor yeast metabolism, namely ethanol, acetaldehyde, glycerol, acetic acid, and l-proline. The greatest blending effect was found to be on the third and second "criadera", which are the stages where the yeasts show a high metabolic activity. The stages holding the oldest wine (viz. the first criadera and the solera) exhibited no differences before and after blending; therefore, the yeasts have a decreased biological activity in them and physical-chemical aging processes seemingly prevail over it.

Changes in gluconic acid, polyols and major volatile compounds in sherry wine during aging with submerged flor yeast cultures

The traditional biological process by which sherry wines are aged can be accelerated by using submerged Saccharomyces cerevisiae var. capensis (G1) strain cultures previously grown in glycerol. The used controlled shaking conditions raise the acetaldehyde, acetoin, and meso 2,3-butanediol contents in the wine, and increases the consumption of gluconic acid by flor yeast relative to traditional biological aging under flor yeast velum.

Gluconic acid consumption in wines by Schizosaccharomyces pombe and its effect on the concentrations of major volatile compounds and polyols

Schizosaccharomyces pombe 1379 (ATCC 26760) yeast strain in wine substantially increases acetaldehyde and 1,1-diethoxyethane concentrations and to decreases levo-2,3-butanediol, glycerol, acetoin, and gluconic acid concentrations. In this study, S. pombe has been used for the first time to reduce gluconic acid in wine under aerobic conditions. Only acetaldehyde and acetoin exhibited significantly higher levels in the wines containing gluconic acid. The high in vitro specific activity of alcohol dehydrogenase observed may be directly related to the high production of acetaldehyde by the studied fission yeast.

Effect of gluconic acid consumption during simulation of biological aging of sherry wines by a flor yeast strain on the final volatile compounds

Flor yeast Saccharomyces cerevisiae (capensis G1) strain assimilates gluconic acid during the aerobic biological aging process of sherry wines and exerts significant changes on the final volatile compounds of wines, especially a decrease in volatile acidity and butanoic, isobutanoic, 2-methylbutanoic, and 3-methylbutanoic acids. This decrease may have a favorable effect on the quality of sherry wines.

Influence of aeration on the physiological activity of flor yeasts

The effect of periodic aeration on the physiological activity of a strain of Saccharomyces cerevisiae yeast during development of velum (flor) and biological aging of Sherry wine of the Fino type was investigated. L-Proline amino acid was the main nitrogen source for yeasts cells during the biological aging, and its exhaustion may be the cause of the production and consumption of other compounds that are involved in the aroma of wines. Aeration was found to increase adenylate energy charge, growth, and viability of the yeast cells. Also, it affected the intracellular redox equilibrium and the consumption and production of compounds including acetoin, acetaldehyde, higher alcohols, ethanol, glycerol, and acetic acid. Acetaldehyde reached its highest level after the second aeration, which coincided with the exhaustion of the nitrogen source in the medium. The enzyme activity of alcohol dehydrogenases I and II decreased immediately after each aeration, subsequently increasing once all of the dissolved oxygen in the wine had been consumed by yeast cells. Aldehyde dehydrogenase activity was detected only after the first aeration, and it may be related to the production and consumption of acetic acid in the wine.

Changes in nitrogen compounds in must and wine during fermentation and biological aging by flor yeasts

Urea, ammonium, and free amino acid contents were quantified in a must from Vitis vinifera cv. Pedro Ximenez grapes and in fermented wine and after a short aging of this wine by Saccharomyces cerevisiae race capensis yeast under variable oxygen availability conditions. The previous compounds were also determined in a wine in which the nitrogen source was depleted by the same race of flor yeast (old wine) and also following the addition of ammonium ion, L-glutamic acid, and L-proline. Under specific conditions such as low oxygen level and the absence of some nutrients, the yeasts release some amino acids including L-threonine, L-tryptophan, L-cysteine, and L-methionine to the medium. These amino acids must originate primarily in a de novo synthesis from ethanol that regenerates NAD(P)+. On the basis of these results, the yeasts may be able to use amino acids not only as nitrogen sources but also as redox agents to balance the oxidation-reduction potential under conditions of restricted oxygen, when electron transport along the respiratory chain may be hindered or limited.

Determination of the relative ploidy in different Saccharomyces cerevisiae strains used for fermentation and 'flor' film ageing of dry sherry-type wines

The full chromosomal karyotype of six enological Saccharomyces cerevisiae strains used for fermentation and biological ageing of sherry-type wines was studied. A genetic method based on the analysis of segregation frequencies of auxotrophic markers, among random spore progeny of hybrids, constructed between laboratory and industrial wine strains (Bakalinsky and Snow, 1990) was used. This method was combined with the analysis of strains by pulsed-field gel electrophoresis. The results obtained clearly indicate the presence of two, three or four copies of a chromosome in the industrial strains examined, and thus confirm that aneuploidy/polyploidy is not uncommon in these strains. In all strains examined, chromosome XIII polysomy is observed. This chromosome contains the ADH2 and ADH3 loci, that code for the ADHII and ADHIII isoenzymes of alcohol dehydrogenase, which are involved in ethanol oxidative utilization during biological ageing of wines. Tetrad analysis for the 'flor formation' character suggest two possibilities: this character is either regulated by at least a digenic system, or by only one gene present on a chromosome which is, at least, disomic.

[CT (high-resolution) in 60 cases of stapediovestibular otosclerosis with surgical indications]

Sixty patients with stapediovestibular otosclerosis (OEV) were studied by CT-scan (target program). These patients had stapedectomy indication because they had a conductive hearing loss in which one had an A/B gap of > 25 dB. The leading principle of this study was how to know the main indications of the CT-scan which makes it possible for morphologic and densitometric evaluation of the extension and probable activity of the stapedial, fenestral and fissural labyrinthine otosclerotic foci. A correlation between the CT pattern of otosclerosis and the pure or mixed hearing loss had been tried. The conclusion is that CT should be a routine examination of OEV clinical study.

Influence of fermentation conditions on specific activity of the enzymes alcohol and aldehyde dehydrogenase from yeasts

The effects of anaerobic, semi-aerobic and short aeration fermentation conditions and the addition of ergosterol and oleic acid to musts on the specific activity of alcohol and aldehyde dehydrogenase (ADH and ALDH) from two yeast species, Saccharomyces cerevisiae and Torulaspora delbrueckii, were studied. ADH I biosynthesis only occurred during the first few hours of fermentation. ADH II from S. cerevisiae and ALDH-NADP+ from the two yeast species behaved as constitutive enzymes under all fermentation conditions. ADH II from T. delbrueckii was only synthesized in small amounts, and its activity was always lower than in S. cerevisiae, where it was responsible for the termination of alcoholic fermentation during the steady growth phase.

[Semiologic considerations and clinical significance of magnetic resonance in 11 intracranial aneurysms]

The author's experience with high-field Magnetic Resonance (Signa, 1.5 T, G.E.) in 11 cases of intracranial aneurysms (6 presenting as space lesion and 5 with symptoms of rupture) is reported. Spin-echo, gradient-echo and GRASS (fast-scan or flip-angle) sequences have been used and results compared with those of CT-scan and angiography. Magnetic Resonance findings, relating to blood flow and oxidation of haemoglobin (within the lumen, in the wall and at the periphery of the aneurysm) were interpreted from the point of diagnosis and surgical planning. The authors concluded that Magnetic Resonance should be considered as a routine investigation for intracranial aneurysms particularly when it is suspected that they might be voluminous and/or thrombosed.

Psychosomatic factors in patients with hyperprolactinemia and/or galactorrhea

A biographic and clinical investigation of 101 patients with hyperprolactinemia and/or galactorrhea is reported. Fifty-one patients were reared without their fathers and 18 with an alcoholic, violent one. These situations were uncommon in the control population, and the differences were statistically significant. There was a high frequency of complaints of obesity, headaches, frigidity, lightheadedness, and fullness of the abdomen, limbs, or face. There was a significant temporal correlation of external events in the natural history with onset or worsening of the symptoms. It is concluded that exposure during childhood to an environment characterized by an absent or alcoholic, violent father conditions some women to develop hyperprolactinemia and/or galactorrhea later in life as a response to specific environmental changes. These conclusions apply similarly to patients with prolactinoma, idiopathic hyperprolactinemia, and euprolactinemic galactorrhea, suggesting a close relationship among the 3 entities.