Hanseniaspora Uvarum Research Articles

Capturing yeast associated with grapes and spontaneous fermentations of the Negro Saur\xed minority variety from an experimental vineyard near Le\xf3n

‘Microbial terroir’ relates to the influence of autochthonous yeasts associated with a grape cultivar on the resultant wine. Geographic region, vineyard site and topography, climate and vintage influence the biodiversity of these microbial communities. Current research focus attempts to correlate their ‘microbial fingerprint’ to the sensorial and chemical characteristics of varietal wines from distinct geographical wine regions. This study focuses on the minor red grape variety, Negro Saurí, which has seen a resurgence in the León Appellation of Origin in Spain as a varietal wine. An experimental vineyard at Melgarajo S.A. (42° 15′ 48.68_N 5° 9′ 56.66_W) was sampled over four consecutive vintages, with autochthonous yeasts being isolated from grapes, must and pilot-scale un-inoculated fermentations, and identified by ITS sequencing. Forty-nine isolates belonging to Metschnikowia pulcherrima, Lachancea thermotolerans, Hanseniaspora uvarum and Torulaspora delbrueckii were isolated from grapes and must, and early stages of fermentation dependent on seasonal variation. Saccharomyces cerevisiae predominated throughout fermentation, as a heterogeneous and dynamic population, with seven major biotypes identified amongst 110 isolates across four consecutive vintages. Twenty-four S. cerevisiae isolates representing five strains dominated in two or more vintages. Their persistence through fermentation warrants further validation of their oenological properties as starter cultures.

Metabolic Engineering of Saccharomyces cerevisiae for Ethyl Acetate Biosynthesis

Ethyl acetate can be synthesized from acetyl-CoA and ethanol via a reaction by alcohol acetyltransferases (AATase) in yeast. In order to increase the yield of acetyl-CoA, different terminators were used to optimize the expressions of acetyl-CoA synthetase (ACS1/2) and aldehyde dehydrogenase (ALD6) to increase the contents of acetyl-CoA in Saccharomyces cerevisiae. ATF1 coding AATase was coexpressed in expression cassettes of ACS1/ACS2 and ALD6 to promote the carbon flux toward ethyl acetate from acetyl-CoA. Further to improve ethyl acetate production, four heterologous AATase including HuvEAT1 (Hanseniaspora uvarum), KamEAT1 (Kluyveromyces marxianus), VAAT (wild strawberry), and AeAT9 (kiwifruit) were introduced. Subsequently mitochondrial transport and utilization of pyruvate and acetyl-CoA were impeded to increase the ethyl acetate accumulation in cytoplasm. Under the optimal fermentation conditions, the engineered strain of PGAeΔPOR2 produced 1.69 g/L ethyl acetate, which was the highest value reported to date by metabolic engineering methods.

Influence of Hanseniasporauvarum AS27 on Chemical and Sensorial Characteristics of Aglianico Wine

In this work was evaluated the effect of sequential inoculum of Hanseniaspora uvarum AS27 strain and a commercial Saccharomyces cerevisiae yeast on the physical–chemical and organoleptic features of Aglianico, a traditional red wine of Southern Italy. Four fermentation treatments on a pilot scale were performed. In fermentation treatment A, the alcoholic fermentation was spontaneously conducted by the indigenous yeasts present in grape must. In the fermentation treatments B and C were inoculated respectively S. cerevisiae FE and H. uvarum AS27 strains, as a single starter. The fermentation treatment D was initially inoculated with H. uvarum AS27, and S. cerevisiae strain was added after 72 h (sequential inoculation). Microbiological, physical–chemical parameters and sensory profiles of the wines have been defined. The results showed that the use of H. uvarum AS27, in sequential inoculum with S. cerevisiae FE, influenced the wine composition, enriching it in polyphenolic and volatile compounds. Further, the sensory evaluation showed that the use of H. uvarum AS27 strain, in co-culture with S. cerevisiae, gives the wine more pleasant characteristics. Therefore, the results have highlighted how the use of particular non-Saccharomyces yeasts can represent a biotechnological resource in red wine production.

Evaluation of indigenous non-Saccharomyces cider yeasts for use in brewing

The non-Saccharomyces yeasts represent a great richness for the production of new and different types of beers. In this study, the role of eight yeast strains (Saccharomycodes ludwigii, Metchnikowia pulcherrima, Hanseniaspora uvarum, Hanseniaspora osmophila and Brettanomyces bruxellensis) isolated from Asturian cider and belonging to five unconventional species was evaluated. None of the strains could ferment the main wort sugars (maltose and maltotriose). Beers produced by S. ludwigii strains showed the highest ethanol content (21.6 g/L) and interestingly high levels of fusel alcohols, fatty esters and isoamyl acetate. Strains of B. bruxellensis were the only ones that produced ethyl phenols and they also generated the highest concentration of fatty acids and their ethyl esters. Sucrose was not utilised by Metschnikowia and Hanseniaspora strains, resulting in low ethanol formation (4.7 g/L), although these yeasts differed in terms of their synthesis of volatile compounds. Larger amounts of fatty acid esters were detected in beers fermented by H. osmophyla 10, while H. uvarum 62 produced more 2-phenylethyl acetate and ethyl acetate. M. pulcherrima 301 stands out for its low fermentative capacity and production of volatile compounds. These results show the interest of non-Saccharomyces strains in the production of beers with low alcohol content and their potential use in developing new beer styles in sequential or mixed inoculations with S. cerevisiae strains.

Volatilome and Bioaccessible Phenolics Profiles in Lab-Scale Fermented Bee Pollen.

Bee-collected pollen (BCP) is currently receiving increasing attention as a dietary supplement for humans. In order to increase the accessibility of nutrients for intestinal absorption, several biotechnological solutions have been proposed for BCP processing, with fermentation as one of the most attractive. The present study used an integrated metabolomic approach to investigate how the use of starter cultures may affect the volatilome and the profile of bioaccessible phenolics of fermented BCP. BCP fermented with selected microbial starters (Started-BCP) was compared to spontaneously fermented BCP (Unstarted-BCP) and to unprocessed raw BCP (Raw-BCP). Fermentation significantly increased the amount of volatile compounds (VOC) in both Unstarted- and Started-BCP, as well as modifying the relative proportions among the chemical groups. Volatile free fatty acids were the predominant VOC in Unstarted-BCP. Started-BCP was differentiated by the highest levels of esters and alcohols, although volatile free fatty acids were always prevailing. The profile of the VOC was dependent on the type of fermentation, which was attributable to the selected Apilactobacillus kunkeei and Hanseniaspora uvarum strains used as starters, or to the variety of yeasts and bacteria naturally associated to the BCP. Started-BCP and, to a lesser extent, Unstarted-BCP resulted in increased bioaccessible phenolics, which included microbial derivatives of phenolic acids metabolism.

Yeasts associated with aerial parts of Theobroma cacao L. in southern Bahia, Brazil, as prospective biocontrol agents against Moniliophthora perniciosa

The cacao tree surface is a substrate for various microorganisms. However, the species which live on the surface have hardly been described. The aims of this study were to evaluate the diversity of native cacao yeasts and to investigate their possible interaction with Moniliophthora perniciosa. A total of 225 yeast strains were isolated from the surface of leaves, fruits, and flowers of 20 cacao genotypes selected as carriers of resistance genes to M. perniciosa and M. roreri, which are the causal agents of witches’ broom (WB) and frosty pod rot diseases (FPR), respectively. The yeast isolates were molecularly identified based on sequences of the D1/D2 and ITS1/ITS4 regions of the rDNA. A total of 20 taxa distributed into 11 genera was found: Hannaella (23), Cryptococcus (9), Candida (11), Hanseniaspora (4), Kwoniella (1), Occultifur (3), Rhodotorula (17), Pichia (2), Sporobolomyces (1), Wicherhamomyces (1), and Yamadazyma (1). Phylloplane tissues showed the greatest richness: 55% of species and 81.82% of identified genera. Six yeast strains (Candida orthopsilosis—LEV 225; Hanseniaspora uvarum—LEV 162, 210, 211; and Rhodotorula paludigena—LEV 166, 168) exhibited the desired traits for a BCA agent: antibiosis in cocultivation, antibiosis by volatile compounds, germination inhibition, and production of killer toxins. This study is the first to show the great diversity of yeasts found in the cocoa phytobiome and the discovery of at least six microorganisms with excellent potential as BCA against cocoa witches’ broom disease.

Microbial and Chemical Analysis of Non-Saccharomyces Yeasts from Chambourcin Hybrid Grapes for Potential Use in Winemaking

Native microorganisms present on grapes can influence final wine quality. Chambourcin is the most abundant hybrid grape grown in Pennsylvania and is more resistant to cold temperatures and fungal diseases compared to Vitis vinifera. Here, non-Saccharomyces yeasts were isolated from spontaneously fermenting Chambourcin must from three regional vineyards. Using cultured-based methods and ITS sequencing, Hanseniaspora and Pichia spp. were the most dominant genus out of 29 fungal species identified. Five strains of Hanseniaspora uvarum, H. opuntiae, Pichia kluyveri, P. kudriavzevii, and Aureobasidium pullulans were characterized for the ability to tolerate sulfite and ethanol. Hanseniaspora opuntiae PSWCC64 and P. kudriavzevii PSWCC102 can tolerate 8–10% ethanol and were able to utilize 60–80% sugars during fermentation. Laboratory scale fermentations of candidate strain into sterile Chambourcin juice allowed for analyzing compounds associated with wine flavor. Nine nonvolatile compounds were conserved in inoculated fermentations. In contrast, Hanseniaspora strains PSWCC64 and PSWCC70 were positively correlated with 2-heptanol and ionone associated to fruity and floral odor and P. kudriazevii PSWCC102 was positively correlated with a group of esters and acetals associated to fruity and herbaceous aroma. Microbial and chemical characterization of non-Saccharomyces yeasts presents an exciting approach to enhance flavor complexity and regionality of hybrid wines.

Separate and combined Hanseniaspora uvarum and Metschnikowia pulcherrima metabolic volatiles are attractive to Drosophila suzukii in the laboratory and field

Drosophila suzukii flies cause economic losses to fruit crops globally. Previous work shows various Drosophila species are attracted to volatile metabolites produced by individual fruit associated yeast isolates, but fruits naturally harbour a rich diversity of yeast species. Here, we report the relative attractiveness of D. suzukii to yeasts presented individually or in combinations using laboratory preference tests and field trapping data. Laboratory trials revealed four of 12 single yeast isolates were attractive to D. suzukii, of which Metschnikowia pulcherrima and Hanseniaspora uvarum were also attractive in field trials. Four out of 10 yeast combinations involving Candida zemplinina, Pichia pijperi, M. pulcherrima and H. uvarum were attractive in the laboratory. Whilst a combination of M. pulcherrima + H. uvarum trapped the greatest number of D. suzukii in the field, the efficacy of the M. pulcherrima + H. uvarum combination to trap D. suzukii was not significantly greater than traps primed with volatiles from only H. uvarum. While volatiles from isolates of M. pulcherrima and H. uvarum show promise as baits for D. suzukii, further research is needed to ascertain how and why flies are attracted to certain baits to optimise control efficacy.

PCR-RFLP ITS-based analysis of wine yeast autochthonous strains isolated from different grape cultivars in Taman subregion

The studies present the results of morphological, cultural and genetic analysis of the ITS1-ITS4 region of the autochthonous yeast strains genome by using the HaeIII restriction enzyme. On the red and white grapes varieties, based on the morphology of the cells, autochthonous strains belonging to the genus Saccharomyces prevail – 83.3%, what is confirmed by genetic analysis of rDNA ITS region. Restriction analysis showed that all strains of the genus Saccharomyces belong to the species Saccharomyces cerevisiae / S. paradoxus. The percentage of Saccharomyces isolated on the Pervenets Magaracha variety is 86.7%, Krasnostop Anapsky - 80%. The non-Saccharomyces yeast had a product size of 750 bp, presumably of the species Hanseniaspora uvarum.

Endophytic microorganisms of apple fruit (Malus domestica)

The plant-associated microorganisms are of key importance in ensuring the quality and safety of plant products. This paper focuses on the study and composition of endophytic microorganisms inautumn apple varieties from domestic selection intended for long-term storage: Bessemyanka Barantseva, Orlovsky Pioner, Alesya and Verbnoe.It was discovered that the internal tissues of fruits are richly populated with microorganisms, the number of which depends on the plant variety and the stage of fruit development. The dominant group is yeast (up to 107 CFU/g). The most common speciesis Hanseniaspora uvarum (26,0%). The number of bacteria averages 102-104 CFU/g, the dominant species–Lactobacillus sp. (52,0%) and Pantoea agglomerans(34,2%). The soft tissue of the fruits of all studied apple varieties contains mycelial fungi, the number of which, as a rule, does not exceed 102 CFU/g. The dominant species is Cladosporium aggregatocicatricatum (33,3%). The microorganisms - producers of biologically active compounds, promising for agrobiotechnologies, have been identified.

Control of Penicillium glabrum by Indigenous Antagonistic Yeast from Vineyards.

Biocontrol is one of the most promising alternatives to synthetic fungicides for food preservation. Botrytis cinerea, Alternaria alternata, and Aspergillus section Nigri are the most concerning pathogens for grape development. However, frequently, other species, such as Penicillium glabrum in this study, are predominant in spoiled bunches. In this work, 54 native yeasts from vineyards were screened by direct confrontation in potato dextrose agar plates as antagonists against P. glabrum. Isolates of Pichia terricola, Aureobasidium pullulans, and Zygoascus meyerae were selected for their antagonist activity in vitro, plus isolates of Pichia kudriavzevii, Hormonema viticola, and Hanseniaspora uvarum were used as negative controls. However, in vivo, confrontations in wounded grapes showed disagreement with direct confrontation in vitro. P. terricola, P. kudriavzevii, H. viticola, Z. meyerae, and H. uvarum significantly reduced the incidence of P. glabrum on grapes. Nevertheless, P. terricola, H. viticola, and H. uvarum themselves spoiled the wounded grapes. Inhibitions were associated with different mechanisms such as the production of volatile organic compounds (VOCs), lytic enzymes, biofilm formation, and competition for nutrients. The isolates of P. kudriavzevii L18 (a producer of antifungal VOCs which completely inhibited the incidence of P. glabrum) and Z. meyerae L29 (with pectinase, chitinase and β-glucanase activity and biofilm formation which reduced 70% of the incidence of P. glabrum) are proposed as suitable biocontrol agents against P. glabrum.

Aroma characteristics of bread made using <i>Hanseniaspora uvarum</i> isolated from fruit

Aroma characteristics of bread made using <i>Hanseniaspora uvarum</i> isolated from fruit

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.

Revalorization of untreated Brewer’s spent grain: novel and versatile feedstock to produce cellulases, lipases, and yeast biomass in a biorefinery approach

Brewer’s spent grain (BSG) is the main by-product of the beer production industry. BSG is rich in valuable compounds, so it can be used as feedstock for the production of high value-added products. BSG was revalorized as a cost-effective, versatile, and novel media to produce lipases, cellulases, and yeast biomass. The microorganisms used were the yeasts Yarrowia lipolytica, Saccharomyces cerevisiae, Rhodotorula mucilaginosa, Hanseniaspora uvarum, and two recently isolated fungi identified as Aspergillus fumigatus and Penicillium sp. The BSG-based media allowed the production of both enzymes and yeast biomass. Y. lipolytica strains displayed similar or better lipase activity with the BSG-based media, showing that BSG can be used as carbon and nitrogen source and lipid inducer in lipases production. The highest cellulase activity on submerged fermentation was 0.354 ± 0.046 and 0.232 ± 0.004 U/mL with BSGw medium for A. fumigatus and Penicillium sp., respectively, after 72 h. On solid-state fermentation, the cellulase activity was 7.5 ± 0.039 (11 days) and 8.3 ± 0.278 (14 days) U/g BSGw for A. fumigatus and Penicillium sp., respectively. In yeast biomass production, S. cerevisiae had a better response in the BSG syrup production medium than R. mucilaginosa and H. uvarum, since these two strains were highly dependent on nitrogen supplementation. These results demonstrate that BSG can be used without pretreatment, as substrate for the growth of various microorganisms and as potential raw material for biorefineries, allowing the production of enzymes and single-cell biomass.

Combination of pre-fermentative and fermentative strategies to produce Malbec wines of lower alcohol and pH, with high chemical and sensory quality

The climatic conditions in some wine regions imply in many cases the important delay in the harvest date to achieve an appropriate phenolic maturity in red grape varieties, leading to wines with high pH and alcohol content. This problem, associated with low acceptation for some consumers and chemical/microbial instability, can be addressed from a viticultural, oenological, or microbiological level. The present study aimed to provide a technological alternative, combining vintages blending and inoculation of native yeasts, for reducing simultaneously the alcohol content and the pH of Malbec wines without altering the chemical and sensory quality. Sauvignon blanc grapes harvested at the beginning of ripening (2017 season) were employed to obtain a wine with high acidity and low alcohol content (LW), that was blending with Malbec grapes of full phenolic maturity. Malbec grapes were harvested at two different moments (1H, 13.0 % v/v; 2H, 14.5 % v/v, probable alcohol), and elaborated following a standard protocol. From 2H, a part of the grape juice was removed and replaced with LW as a strategy for alcohol reduction (2RW). Consequently, it was obtained nine wines by triplicate combining 1H, 2H, 2RW musts with three fermentative strategies: CI, co-inoculation of Hanseniaspora uvarum BHu9/Saccharomyces cerevisiae BSc114 native yeasts; NS, S. cerevisiae BSc114 native yeast; and CS, S. cerevisiae EC 1118 commercial yeast. We found that 2RW wines, fermented with different yeast strains, showed similar levels of total phenols, tannins, anthocyanins, and polymeric pigments concerning control wines (2H). In all cases, those wines presented greater phenolic potential compared to wines from 1H. At the same time, the pre-fermentative strategy of vintages blending produced wines with 1.4 % v/v less alcohol than 2H wines, also achieving a pH decrease of 0.3 units. Combined treatments with native strains, especially as single inoculum (2RW–NS), were the most efficient in reducing both parameters, showed higher tannins, anthocyanins levels, and colour saturation, without affecting the sensory quality, in terms of aromas and mouthfeel. In conclusion, the strategies proposed could be simple and economic tools, for red wines production with low alcohol content, and high chemical and organoleptic quality, capable of competing and satisfying market needs.

Metschnikowia pulcherrima represses aerobic respiration in Saccharomyces cerevisiae suggesting a direct response to co-cultivation

The use of non-Saccharomyces species as starter cultures together with Saccharomyces cerevisiae is becoming a common practice in the oenological industry to produce wines that respond to new market demands. In this context, microbial interactions with these non-Saccharomyces species must be considered for a rational design of yeast starter combinations. Previously, transcriptional responses of S. cerevisiae to short-term co-cultivation with Torulaspora delbrueckii, Candida sake, or Hanseniaspora uvarum was compared. An activation of sugar consumption and glycolysis, membrane and cell wall biogenesis, and nitrogen utilization was observed, suggesting a metabolic boost of S. cerevisiae in response to competing yeasts. In the present study, the transcription profile of S. cerevisiae was analyzed after 3 h of cell contact with Metschnikowia pulcherrima. Results show an over-expression of the gluco-fermentative pathway much stronger than with the other species. Moreover, a great repression of the respiration pathway has been found in response to Metschnikowia. Our hypothesis is that there is a direct interaction stress response (DISR) between S. cerevisiae and the other yeast species that, under excess sugar conditions, induces transcription of the hexose transporters, triggering glucose flow to fermentation and inhibiting respiration, leading to an increase in both, metabolic flow and population dynamics.

Microbiological and biochemical performances of six yeast species as potential starter cultures for wet fermentation of coffee beans

This study investigated the microbiological and biochemical characteristics of six endogenous yeast species isolated from spontaneous wet coffee fermentation for their potential as starter cultures. The yeasts were cultured under elevated temperature, osmotic pressure, ethanol and acid concentrations to assess their tolerance to these coffee fermentation-related stress conditions. Their ability to produce hydrolytic enzymes for pectin, protein, cellulose and starch were evaluated using plate assays. Hanseniaspora uvarum and Pichia kudriavzevii were the most stress-tolerant species and also exhibited high pectinase, amylase, cellulase and protease activities compared with P. fermentans, Candida railenensis, C. xylopsoci and Wickerhamomyces anomalus. When the yeasts were inoculated in a synthetic coffee pulp extract medium all the isolates grew and produced several important aromatic compounds, including isoamyl alcohol, 2-phenylethyl alcohol, ethanol, ethyl acetate, acetaldehyde, and 2-propanone. The concentrations of these volatiles produced by the yeast species differed significantly. H. uvarum and P. kudriavzevii produced significantly higher concentration of total alcohols (42.5, 57.6 mg/l), esters (31.0, 33.7 mg/l) and aldehydes (0.7, 1.9 mg/l). Overall, H. uvarum and P. kudriavzevii demonstrated the strongest potential as starter cultures for wet coffee fermentation.

Evaluating the effect of using non-Saccharomyces on Oenococcus oeni and wine malolactic fermentation

Interest in using non-Saccharomyces yeasts in winemaking has increased in recent years due to their ability to improve wine quality. However, little information has been published regarding the possible effect on malolactic fermentation (MLF), carried out mostly by Oenococcus oeni. The aim of this paper is therefore to evaluate the effect of the most representative non-Saccharomyces species on O. oeni and wine MLF. Different strains of Torulaspora delbrueckii, Metschnikowia pulcherrima, Hanseniaspora uvarum, Hanseniaspora vineae and Starmerella bacillaris (syn. Candida zemplinina) were used in sequential alcoholic fermentation with Saccharomyces cerevisiae. The resulting wines were inoculated with four O. oeni strains. The action of non-Saccharomyces affected the final wine composition and the later role of O. oeni. Some of its strains could not perform MLF in H. uvarum wine due to high SO2 concentrations. In some cases, MLF was inhibited in wines inoculated with S. bacillaris. All the H. uvarum and H. vineae strains notably increased acetic acid concentrations, thus threatening wine quality. The best conditions for MLF were provided by some T. delbruecckii and M. pulcherrima strains, which showed increased concentrations of mannoproteins – compounds described as MLF activators –, no production of SO2, and low consumption of L-malic acid. In conclusion, non-Saccharomyces yeasts have diverse effects on O. oeni and MLF depending on the species, with T. delbrueckii and M. pulcherrima being those that showed the best compatibility with MLF development.

Isolation and Investigation of Potential Non-Saccharomyces Yeasts to Improve the Volatile Terpene Compounds in Korean Muscat Bailey A Wine.

The Muscat Bailey A (MBA) grape, one of the most prominent grape cultivars in Korea, contains considerable amounts of monoterpene alcohols that have very low odor thresholds and significantly affect the perception of wine aroma. To develop a potential wine starter for Korean MBA wine, nine types of non-Saccharomyces yeasts were isolated from various Korean food materials, including nuruk, Sémillon grapes, persimmons, and Muscat Bailey A grapes, and their physiological, biochemical, and enzymatic properties were investigated and compared to the conventional wine fermentation strain, Saccharomyces cerevisiae W-3. Through API ZYM analysis, Wickerhamomyces anomalus JK04, Hanseniaspora vineae S7, Hanseniaspora uvarum S8, Candida railenensis S18, and Metschnikowia pulcherrima S36 were revealed to have β-glucosidase activity. Their activities were quantified by culturing in growth medium composed of different carbon sources: 2% glucose, 1% glucose + 1% cellobiose, and 2% cellobiose. W. anomalus JK04 and M. pulcherrima S36 showed the highest β-glucosidase activities in all growth media; thus, they were selected and utilized for MBA wine fermentation. MBA wines co-fermented with non-Saccharomyces yeasts (W. anomalus JK04 or M. pulcherrima S36) and S. cerevisiae W-3 showed significantly increased levels of linalool, citronellol, and geraniol compared to MBA wine fermented with S. cerevisiae W-3 (control). In a sensory evaluation, the flavor, taste, and overall preference scores of the co-fermented wines were higher than those for the control wine, suggesting that W. anomalus JK04 and M. pulcherrima S36 are favorable wine starters for improving Korean MBA wine quality.

How gut microbiome interactions affect nutritional traits of Drosophila melanogaster.

Most research on the impact of the gut microbiome on animal nutrition is designed to identify the effects of single microbial taxa and single metabolites of microbial origin, without considering the potentially complex network of interactions among co-occurring microorganisms. Here, we investigated how different microbial associations and their fermentation products affect host nutrition, using Drosophila melanogaster colonized with three gut microorganisms (the bacteria Acetobacter fabarum and Lactobacillus brevis, and the yeast Hanseniaspora uvarum) in all seven possible combinations. Some microbial effects on host traits could be attributed to single taxa (e.g. yeast-mediated reduction of insect development time), while other effects were sex specific and driven by among-microbe interactions (e.g. male lipid content determined by interactions between the yeast and both bacteria). Parallel analysis of nutritional indices of microbe-free flies administered different microbial fermentation products (acetic acid, acetoin, ethanol and lactic acid) revealed a single consistent effect: that the lipid content of both male and female flies is reduced by acetic acid. This effect was recapitulated in male flies colonized with both yeast and A. fabarum, but not for any microbial treatment in females or males with other microbial complements. These data suggest that the effect of microbial fermentation products on host nutritional status is strongly context dependent, with respect to both the combination of associated microorganisms and host sex. Taken together, our findings demonstrate that among-microbe interactions can play a critically important role in determining the physiological outcome of host-microbiome interactions in Drosophila and, likely, in other animal hosts.