Littérature scientifique sur le sujet « Metschnikowia spp »

Numerous strains of an unusual asexual yeast species were isolated from flowers of morning glory (Ipomoea spp., Convolvulaceae) and associated drosophilids and sap beetles of the genus Conotelus sampled in Hawaii and in Brazil. The nutritional profile of this yeast is similar to those of Metschnikowia hawaiiensis and Metschnikowia continentalis, which share the same habitats. The cells are large, hydrophobic, and tend to remain attached after budding, causing the colonies on agar media to have a convoluted appearance, reminiscent of popcorn. The sequences of the D1/D2 domain of large subunit rDNAs of strains from three different localities confirmed that a single species is involved, and that it is related to large-spored Metschnikowia species. The type strain is UWO(PS)91-672.1 (CBS 8466).Key words: Candida ipomoeae, yeast, new species, rDNA.

The chemical characteristics of lysates obtained from yeasts belonging to Metschnikowia spp. were determined. Cell lysis was induced using saponin from Q. saponaria or 5% NaCl. The process was conducted at 50 °C for 24 for 48 h. The enzymatic profiles of the resulting lysates were analyzed. The mannose and glucose contents were also investigated, as well as the concentrations of proteins, free amino nitrogen (FAN), and free amino acids. The results were compared to the characteristics of lysates from conventional industrial strains of Saccharomyces spp. obtained under analogous conditions. The Metschnikowia lysates showed different chemical profiles and the pool of individual amino acids was generally smaller. However, the content of hydroxyproline HPro was 4 to 5 times higher. The results of this study show that yeast lysates are an attractive supplement for numerous applications.

The chemical characteristics of lysates obtained from yeasts belonging to Metschnikowia spp. were determined. Cell lysis was induced using saponin from Q. saponaria or 5% NaCl. The process was conducted at 50 °C for 24 for 48 h. The enzymatic profiles of the resulting lysates were analyzed. The mannose and glucose contents were also investigated, as well as the concentrations of proteins, free amino nitrogen (FAN), and free amino acids. The results were compared to the characteristics of lysates from conventional industrial strains of Saccharomyces spp. obtained under analogous conditions. The Metschnikowia lysates showed different chemical profiles and the pool of individual amino acids was generally smaller. However, the content of hydroxyproline HPro was 4 to 5 times higher. The results of this study show that yeast lysates are an attractive supplement for numerous applications.

The wet synthesis of uniformly sized zero-Valente iron nanoparticles (NPs) for application in nanomedicine and biology is still a challenging because of magnetic interaction, oxidation and corrosion. In this study, various Fe-containing NPs were synthesized using amino acids as their size stabilizing agents to investigate their bio-interactions with Metschnikowia spp. yeast strains. For this, D-glutamic, DL-cysteine, DL-methionine, and taurine amino acids were tested. In this way, NPs in size from several to 40 nm, composed of a-Fe0, a-FeB, Fe2O3 and lepidocrocite, g-FeOOH, were synthesized and characterized using X-ray diffraction and Mössbauer spectroscopy, and HRTEM investigations. The surprising influence of amino acid nature and DL-cysteine concentration on the NP size and composition has been revealed allowing fabrication of quite pure lepidocrocite as well as a-Fe0 NPs containing boron. As-synthesized NPs were cultivated in a YEPD growth media for research on the formation of insoluble red pigment pulcherrimin by several Metschnikowia spp. yeast strains. For comparison, the behavior of M. pulcherrima yeast with metallic iron plate and Fe0 NPs has been visualized.

Изменение климата приводит к повышению содержания сахара в виноградном сусле, снижению концентрации органических кислот, прекурсоров ароматобразующих веществ и т.д. и, как следствие, к повышение содержания алкоголя, нарушению баланса вкуса и искажению аромата вина и другие проблемы. Технологические подходы, предлагаемые для их решения, хотя и позволяют достичь цели, но часто негативно влияют на качество вина. Перспективной альтернативой является использование микроорганизмов, не относящихся к Saccharomyces , продукты метаболизма которых - глицерин, кислоты, маннопротеины, полисахариды и др. - оказывают влияние на органолептические характеристики вина. Так, использование дрожжей Candida spp., Metschnikowia spp., Lachancea spp. способствует снижению содержания этанола в винах на 1,5-2,0% об. Hansensiaspora spp., Pichia spp., Starmerella spp., Torulaspora spp. и др. отличаются высокой способностью к синтезу глицерина и полисахаридов. Использования консорциума дрожжей Saccharomyces и не- Saccharomyces для брожения сусла приводит к усилению ароматических и вкусовых характеристик вин. Отмечено, что среди не сахаромицетов присутствуют организмы, синтезирующие малые количества уксусной кислоты и ацетальдегида, что благоприятно влияет на качество получаемых вин. Настоящая работа является результатом систематизации информации, касающейся некоторых аспектов использования дрожжей несахаромицетов в винодельческой промышленности, их влияния на химический состав вин. Climate change leads to an increase in the sugar content of grape must, a decrease in the concentration of organic acids, precursors of aroma-producing substances, etc. and, as a consequence, to an increase in the alcohol content, flavor imbalance and distortion of wine aroma and other problems. Even though technological approaches proposed for solution allow to achieve the goal, they often negatively affect the quality of wine. A promising alternative is using of non- Saccharomyces microorganisms with their metabolic products - glycerin, acids, mannoproteins, polysaccharides, etc. affecting the organoleptic characteristics of wine. So, using of yeast Candida spp., Metschnikowia spp., Lachancea spp. helps to reduce ethanol content in wines by 1.5-2.0% by volume. Hansensiaspora spp., Pichia spp., Starmerella spp., Torulaspora spp. and others are distinguished by a high ability to synthesize glycerin and polysaccharides. Using of yeast consortium of Saccharomyces and non- Saccharomyces for must fermentation leads to an increase in the aroma and flavor characteristics of wines. It was noted that among the non-saccharomycetes there are organisms that synthesize small amounts of acetic acid and acetaldehyde, favorably affecting the quality of wines obtained. This work is the result of information systematization concerning some aspects of using non-Saccharomyces in winemaking industry, their effect on the chemical composition of wines.

The influence of fruit varieties on yeast ecology during spontaneous plum mash fermentation was investigated. Yeast colonies were isolated from mashes obtained from four plum varieties throughout fermentation in laboratory conditions during two consecutive years. The yeast strains were differentiated by random amplification of polymorphic DNA (RAPD-PCR) and identified by the 26S rDNA D1/D2 sequence analysis. Hanseniaspora uvarum, Metschnikowia spp. and Pichia kudriavzevii were the dominant yeasts during the early stages of plum mash fermentation, while the middle and end phases were dominated by Saccharomyces cerevisiae. The strains of Candida sake, Nakazawaea ernobii, Pichia kluyveri, Rhodotorula mucilaginosa and Wickerhamomyces anomalus were also detected in fermenting plum mashes. Metschnikowia sp. M1, H. uvarum H1 and H2 strains were detected in all samples, irrespective of the tested variety and year. Investigation of the impact of individual yeast strains on the production of volatile compounds showed the potential possibility of using them as starter cultures.

Metschnikowia pulcherrima is a highly effective biocontrol yeast due to its pigment pulcherrimin that accumulates in the cells and in the growth medium. Three different strains of M. pulcherrima were isolated from local grapes. The yeast isolates were characterized on the basis of their biochemical, physiological and ITS1-5.8 s rDNA-ITS2 region. Based on the obtained results, the M. pulcherrima isolates were identifi ed as new strains of M. pulcherrima. Strong antagonistic activities of the M. pulcherrima strains on the human pathogens Proteus vulgaris, Escherichia coli, Candida albicans, Candida parapsilosis, Candida krusei, and Trichosporon mucoides were determined. In addition, antagonistic effects of these M. pulcherrima strains were also tested against Aspergillus fl avus, Aspergillus fumigatus, Aspergillus niger, Trichoderma spp., Paecilomyces spp., and Bipolaris spp. and it was shown that the three different strains of M. pulcherrima also have an antagonistic effect on the growth of these fungal species at different extents. This study showed that all three strains of M. pulcherrima produce the same amount of the pigment pulcherrimin, but their antimicrobial activities on different microorganisms show important variations

Sour rot, a disease affecting berries of cultivated Vitis spp. worldwide, has not been clearly defined. Reported symptoms of the disease include browning of the berry skin, oozing of disintegrated berry pulp, and the smell of acetic acid, all in the presence of fruit flies (Drosophila spp.). We determined acetic acid concentrations in multiple collections of symptomatic berries, isolated and identified microbes from them, and inoculated commonly isolated organisms into healthy berries with and without concurrent exposure to wild-type or axenic Drosophila melanogaster. Coinoculations combining one of several yeasts (Metschnikowia spp., Pichia spp., and a Saccharomyces sp.) plus an acetic acid bacterium (an Acetobacter sp. and Gluconobacter spp.) reproduced sour rot symptoms, defined here as decaying berries with a loss of turgor and containing acetic acid at a minimum of 0.83 g/liter, based on observed field levels. Symptoms developed only in the presence of D. melanogaster, either wild type or axenic, indicating a nonmicrobial contribution of these insects in addition to a previously suggested microbial role. We conclude that sour rot is the culmination of coinfection by various yeasts, which convert grape sugars to ethanol, and bacteria that oxidize the ethanol to acetic acid, and that this process is mediated by Drosophila spp.

The total diversity of bacterial and fungal communities associated with the phyllosphere (fruits and leaves) of the ‘Williams’ pear variety was analyzed in two phenological stages during fruit development and maturation. The antagonistic potential of autochthonous bacterial and yeast isolates against phytopathogenic fungi was also evaluated. A metabarcoding approach revealed Pantoea, Sphingomonas, Hymenobacter, Massilia, and Pseudomonas as dominant bacterial constituents of the pear phyllosphere, whilst most abundant among the fungal representatives identified were Metschnikowia, Filobasidium, Aureobasidiumpullulans, Botrytis cinerea, and Taphrina. The traditional culturable approach revealed that the Pseudomonas genus with P. graminis, P. putida, and P. congelans was most prevalent. The most frequently cultivated fungal representatives belonged to the genus Fusarium with six identified species. A broad range of the antagonistic activity was detected for the Hannaella luteola and Metschnikowia pulcherrima yeasts, significantly affecting the growth of many fungal isolates in the range of 53–70%. Fusarium sporotrichioides was the most susceptible fungal isolate. The autochthonous antagonistic yeasts H. luteola and M. pulcherrima might be powerful biological control agents of postharvest diseases caused by Fusarium spp. and common pathogens like Monilinia laxa, Botrytis cinerea, Alternaria tenuissima, and Cladosporium cladosporioides.

The yeast Metschnikowia fructicola, ethanol, and sodium bicarbonate (SBC), alone or in combinations, were applied to table grapes on vines 24 h before harvest to control the incidence of postharvest diseases. In four experiments, all significantly reduced the total number of decayed berries caused by Botrytis cinerea, Alternaria spp., or Aspergillus niger after storage for 30 days at 1°C followed by 2 days at 20°C. In three experiments, a mean gray mold incidence (caused by B. cinerea) of 34.2 infected berries per kilogram among untreated grape was reduced by Metschnikowia fructicola at 2 × 107 CFU/ml, ethanol at 50% (vol/vol), or SBC at 2% (wt/vol) to 12.9, 8.1, or 10.6 infected berries per kilogram, respectively. Ethanol, SBC, and SO2 generator pads were similarly effective. M. fructicola effectiveness was not improved when combined with ethanol or SBC treatments. Ethanol and yeast treatments did not harm the appearance of the grapes. M. fructicola and SBC left noticeable residues, and SBC caused some visible phytotoxicity to the rachis and berries. Ethanol applied at 50% (vol/vol) reduced epiphytic fungal and bacterial populations by about 50% compared with controls. M. fructicola populations persisted on berries during storage when applied alone or after ethanol treatments, whereas SBC reduced its population significantly.

The optimized use of the grape environment indigenous microbiota has been proposed as an innovative tool to mimic the complexity of the spontaneous fermentation process, without taking the risks of having poor-quality wines due to the uncontrolled growth of spoilage organisms or having a “standardized” product lacking originality caused by the inoculation of a single starter culture of Saccharomyces cerevisiae exhaustively employed worldwide. With the aim of exploring new alternatives for the improvement of wine quality, it was proposed the screening of innovative yeasts to be used on mixed fermentations together with S. cerevisiae. After the mining of more than 400 yeasts isolates in samples coming from multiple Italian wine-producing regions, a collection of non-Saccharomyces yeasts was thoroughly described morphologically and identified. About one quarter of them belonging to three more interesting and prevalent oenological species, namely Starmerella bacillaris, Lachancea thermotolerans and Metschnikowia spp., were picked for an in-depth molecular and physiological characterization. After the genotyping, stress tolerance assays, enzymatic activity trials and single inoculum fermentations, important differences were acknowledged between the strains and species, allowing for the selection of a reduced number of isolates showing potentially positive oenological traits. Furthermore, the isolates of S. bacillaris and L. thermotolerans were also submitted to a safety assessment of virulence factor related to human pathogenicity and were challenged to inhibit the growth of the phytopathogen Botrytis cinerea, responsible for massive quantitative and qualitative losses on the wine industry, across in vitro and in vivo assays, in order to become candidates for an integrated vitivinicultural strategy of biocontrol and mixed fermentation. The chosen isolates from the preliminary selection steps were then applied in sequential inoculations with a commercial S. cerevisiae in natural grape must. The physicochemical analysis and the aromatic profile confirmed the great potential of all three species to a successful winemaking routine, mainly focused on the glycerol increase and reduction of acetaldehyde concentration for S. bacillaris, limitation of acetic acid and boosted aromatic complexity for Metschnikowia spp., and diminution on ethanol content and enhanced natural acidity by lactic acid production for L. thermotolerans. This last feature was intriguingly highly variable among the strains and thus received a more detailed attention, revealing that sequence mutations and transcriptional regulatory mechanisms could be involved in the strong variance of a very relevant metabolic pathway. Indeed, many of the distinctive features of alternative yeasts are species- or strain-dependent and the efficient selection of a new generation of starter cultures could provide satisfactory answers to multiple challenges of modern winemaking.