Abstract

The work deals with lipid modifications of pigment-forming yeasts Rhodotorula and Sporobolomyces growing under presence of selenium. This metal in the medium significantly prolonged lag-phase of all cultures and enlarged yeast cells. Total, neutral, and membrane yeast lipids (phosphatidylcholine, phosphatidylethanolamine, phosphatidylserine, and phosphatidylinositol) consisted of predominantly palmitic, palmitoleic, stearic, oleic, linoleic, and linolenic acids. Selenium activated fatty acid unsaturation mainly in phosphatidylcholine due to elevated levels of linoleic and linolenic acids. Because biosynthesis of C18 unsaturated fatty acids in Rhodotorula and Sporobolomyces species may be associated with phosphatidylcholine moieties, selenium might be involved to the induction of membrane bound fatty acid Δ12 and Δ15 desaturases in red yeasts. Oppositely, neutral lipids (primarily triacylglycerols) did not show such intensive changes in fatty acid composition as their polar counterparts. These observations could be applied for preparation of selenized red yeasts containing carotenoid pigments with enhanced accumulation of linoleic and linolenic acids.

Abstract

Rhodotorula glutinis CCY 20-2-26 when grown under controlled stress of either NaCl (1–5 %) or H₂O₂ (1–5 mM) on basal media exhibited a twofold increase in its total phenolic contents. The radical scavenging capacities (RSCs) as determined by ABTS test were found to be highest in 4 mM H₂O ₂ (1.44 mM TEAC mg^-1) and 4% NaCl (1.13 mM TEAC mg^-1) as compared to control samples (0.41 mM TEAC mg^-1). Similarly, the RSCs as determined by DPPH test were also highest in 4 % NaCl (1.83 mM TEAC mg^-1) and4 mM H₂O₂ (1.78 mM TEAC mg^-1) compared to control (0.48 TEAC mg^-1). The relative RSCs from EPR spin-trapping assay for H₂O₂-stressed cultures were highest in 1 mM H₂O₂ (56.1 µM TEAC g^-1) whereas in NaCl-stressed cultures it was highest in 5 % NaCl (44.6 µM TEAC g^-1) as compared to control (30.9 µM TEAC g^-1). Five phenolic compounds (gallic acid, benzoic acid, catechin, caffeic acid and ferulic acid) were detected for the first time in R. glutinis CCY 20-2-26.

Abstract

Yeasts form a significant and diverse part of the phyllosphere microbiota. Some yeasts that inhabit plants have been found to exhibit extracellular enzymatic activities. The aim of the present study was to investigate the ability of yeasts isolated from leaves, fruits, and blossoms of fruit trees cultivated in Southwest Slovakia to produce extracellular enzymes, and to discover whether the yeasts originating from these plant organs differ from each other in their physiological properties. In total, 92 strains belonging to 29 different species were tested for: extracellular protease, beta-glucosidase, lipase, and polygalacturonase activities; fermentation abilities; the assimilation of xylose, saccharose and alcohols (methanol, ethanol, glycerol); and for growth in a medium with 33% glucose. The black yeast Aureobasidium pullulans showed the largest spectrum of activities of all the species tested. Almost 70% of the strains tested demonstrated some enzymatic activity, and more than 90% utilized one of the carbon compounds tested. Intraspecies variations were found for the species of the genera Cryptococcus and Pseudozyma. Interspecies differences of strains exhibiting some enzymatic activities and utilizing alcohols were also noted. The largest proportion of the yeasts exhibited beta-glucosidase activity and assimilated alcohols independently of their origin. The highest number of strains positive for all activities tested was found among the yeasts associated with leaves. Yeasts isolated from blossoms assimilated saccharose and D-xylose the most frequently of all the yeasts tested. The majority of the fruit-inhabiting yeasts grew in the medium with higher osmotic pressure.

Abstract

Many different yeast species have been isolated from grapes and musts worldwide. The diversity and frequency of yeasts depend on a number of factors such as the grape variety, the physical damage of the grapes, the weather conditions and the chemical composition of must. A total of 366 isolates were associated with the three grape cultivars: Blue Frankish, Green Veltliner and Sauvignon Blanc over four consecutive years. Yeast cultures were isolated from the grapes and from the fermenting musts after first and seventh days. The ascomycetous yeasts of the genera Aureobasidium, Candida, Hanseniaspora, Metschnikowia, Pichia, Saccharomyces and Saccharomycopsis together with basidiomycetous yeasts of the genera Cryptococcus, Dioszegia, Filobasidium, Rhodotorula and Sporidiobolus were associated with the three grape varieties.Hanseniaspora uvarum, Metschnikowia pulcherrima, Pichia kluyveri, Pichia kudriavzevii and Sporidiobolus pararoseus were found on the berries in significant amounts. Pichia kluyveri and P. kudriavzevii were more associated with the damaged grapes, whereas Sp. pararoseus with intact ones. Hanseniaspora uvarum and M. pulcherrima were present on both types of grapes almost equally. The yeast composition and quantitative representation of yeast species varied over the grape varieties and the years examined. Although the basidiomycetous species formed a significant proportion of the yeast population in some individual grape variety/year combinations, the ascomycetous species were dominant.

Abstract

Yeasts are common inhabitants of the phyllosphere, but our knowledge of their diversity in various plant organs is still limited. This study focused on the diversity of yeasts and yeast-like organisms associated with matured fruits and fully open blossoms of apple, plum, and pear trees, during 2 consecutive years at 3 localities in southwest Slovakia.

The occurrence of yeasts and yeast-like organisms in fruit samples was 2½ times higher and the yeast community more diverse than that in blossom samples. Only 2 species (Aureobasidium pullulans and Metschnikowia pulcherrima) occurred regularly in the blossom samples, whereas Galactomyces candidus, Hanseniaspora guilliermondii, Hanseniaspora uvarum, M. pulcherrima, Pichia kluyveri, Pichia kudriavzevii, and Saccharomyces cerevisiae were the most frequently isolated species from the fruit samples. The ratio of the number of samples where only individual species were present to the number of samples where 2 or more species were found (consortium) was counted.

The occurrence of individual species in comparison with consortia was much higher in blossom samples than in fruit samples. In the latter, consortia predominated. Aureobasidium pullulans, M.pulcherrima, and S. cerevisiae, isolated from both the fruits and blossoms, can be considered as resident yeast species of various fruit tree species cultivated in southwest Slovakia localities.

Abstract

The effect of nine different pesticides on the growth of yeasts isolated from the leaves of fruit and forest trees was investigated. Four insecticides (with the active ingredients: thiacloprid, deltamethrin, lambdacyhalothrin, and thiamethoxam) and five fungicides (with the effective substances: bitertanol, kresoxim-methyl, mancozeb, trifloxystrobin, and cupric oxychloride) were tested. The concentrations of chemicals were those recommended by the manufacturers for the spraying of trees. The yeast strains isolated from the leaves of fruit trees were not sensitive to any of the insecticides. The majority of yeast strains isolated from the leaves of forest trees were either not sensitive or only to a small extent. WhileRhodotorula mucilaginosa and Pichia anomala were not affected by any insecticide, the strains of Cryptococcus laurentii and Rhodotorula glutinis showed the highest sensitivity.

The effects of fungicides on the growth of isolated yeasts were more substantial. The fungicide Dithane® DG (mancozeb) completely inhibited the growth of all yeasts. All strains isolated from fruit tree leaves were more resistant to the tested fungicides than those isolated from the leaves of forest trees. The most resistant strains from the leaves of fruit trees belonged to the speciesMetschnikowia pulcherrima, Pichia anomala, and Saccharomyces cerevisiae, whereas Cryptococcus albidus and C. laurentii, originating from the leaves of forest trees, showed the highest sensitivity to fungicides.

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Abstract

The aim of this study is to compare the production of biomass enriched with carotenoids and ergosterol by yeast strain Rhodotorula glutinis CCY 20-2-26 grown under optimal growth conditions and in the presence of exogenous stress factors. R. glutinis cells were exposed to UV irradiation, oxidative stress (2–10 mmol/L H₂O₂) and osmotic stress (2–10 % NaCl).

During the experiment, growth characteristics and the production of biomass, carotenoids and ergosterol were evaluated. Experiments were carried out in Erlenmeyer flasks and in laboratory fermentor. First, R. glutinis cells were exposed to higher concentration of stress factors added into the production medium. Further, low concentrations of NaCl and H₂O₂ were added to the inoculum medium or to both inoculum and production media. Exposure of red yeast cells to all tested stress factors resulted in higher production of carotenoids as well as ergosterol, while biomass production was changed only slightly. Under high stress, 2–3 times increase of β-carotene was observed.

The addition of low salt or peroxide concentration into the inoculation media led to about 2-fold increase of carotenoid production. In Erlenmeyer flasks the best effect on the carotenoid and ergosterol production (3- to 4-fold increase) was exhibited by the combined stress: the addition of low amount of NaCl (2 mmol/L) into the inoculum medium, followed by the addition of H₂O₂ (5 mmol/L) into the production medium. The production of ergosterol in most cases increased simultaneously with the production of carotenoids. Cultivation of R. glutinis carried out in a 2-litre laboratory fermentor was as follows: under optimal conditions about 37 g/L of yeast biomass were obtained containing approx. 26.30 mg/L of total carotenoids and 7.8 mg/L of ergosterol. After preincubation with a mild stress factor, the yield of biomass as well as the production of carotenoids and ergosterol substantially increased.

The best production of enriched biomass was obtained in the presence of peroxide in the inoculation medium (52.7 g/L of biomass enriched with 34 mg/L of carotenoids) and also under combined salt/peroxide or salt/salt stress (about 30–50 g/L of biomass enriched with 15–54 mg/L of total carotenoids and about 13–70 mg/L of ergosterol). R. glutinis CCY 20-2-26 could be used as a potential biotechnological producer of carotenoid-rich biomass.

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Abstract

Yeasts were isolated from leaf surfaces of five species of fruit trees located in southwest Slovakia. One hundred and fifty five yeast strains belonging to 11 genera were isolated from 300 samples of leaves. Seventeen yeast species were identified, but only three occurred regularlyAureobasidium pullulans, Cryptococcus laurentii, and Metschnikowia pulcherrima. Species such as Hanseniaspora uvarum, Pichia anomala, Rhodotorula glutinis, and Saccharomyces cerevisiae, were isolated less frequently.

We found only few differences in the yeast community isolated from leaves of different tree species although dominant species occurred regularly on the majority of leaves. Furthermore, yeast species varied throughout years. In spite of the fact that the yeast community occupying the leaves of the fruit trees was studied in the samples harvested in three localities, which are distanced from each other some kilometers, the qualitative representation of the most isolated yeasts was identical. The differences were only in the frequency of the incidence of individual species in the samples.

Abstract

The fungi Thamnidium elegans, as a producer of γ-linolenic acid (GLA), and Mortierella alpina, as a producer of dihomo-γ-linolenic acid (DGLA), arachidonic acid (AA) and eicosapentaenoic acid (EPA), and the yeasts Rhodotorula glutinis and Sporobolomyces roseus, as producers of ß-carotene, torulene and torularhodin, were tested for their ability to utilize cereal substrates during solid state fermentations (SSF). Depending on the strain and conditions, the cereal materials were effectively enriched with polyunsaturated fatty acids (PUFAs) or carotenoids. These naturally prepared bioproducts could find applications in food, feed, biomedical, pharmaceutical and veterinary fields.

Abstract

The yeasts were isolated from the leaf surfaces of ten species of trees. The study site was a forest park (Železná Studnička) of the Small Carpathians mountain range. One hundred and thirty seven yeast strains belonging to 13 genera were isolated from 320 samples of leaves and needles. Seventeen yeast species were isolated, but only seven occurred regularly: Aureobasidium pullulans, Cryptococcus laurentii, Pichia anomala, Metschnikowia pulcherrima, Saccharomyces sp., Lachancea thermotolerans, and Rhodotorula glutinis. The remaining species were isolated from the leaves and needles of three or less tree species. A. pullulans, Cr. laurentii, and P. anomala were the most frequently found species and they occurred on leaves and needles of all ten tree species. Saccharomyces sp. occurred in leaf samples collected from eight kinds of trees. M. pulcherrima and L. thermotolerans were found in samples collected from six species of trees. Both these species occurred almost always on the leaves of deciduous trees. Rh. glutinis was the most frequently isolated carotenoids producing species. We have found out that the ascomycetous and basidiomycetous species were present in the leaf samples in approximately equal frequency, contrary to the soil samples taken from this forest park, where the ascomycetous species were found rarely.

Abstract

The tolerance of seventy yeast strains belonging to 15 species, isolated from water and soil environments as well as from tree leaves, to four heavy metals – copper, zinc, nickel and cadmium were studied. We have found that the interspecific and intraspecific variations in metal tolerance among studied strains were considerable. The highest interspecific variations were observed toward copper and cadmium.

The strains of the species Sporobolomyces salmonicolor, Cryptococcus albidus, Cystofilobasidium capitatum, Saccharomyces cerevisiae, and Candida maltosa belonged to the most sensitive ones. In general ascomycetous yeasts were more tolerant to heavy metals than basidiomycetous ones. The differences among strains that came from various natural sources were also found. The most sensitive yeast population originated from untilled soil whereas the most tolerant population was isolated from tree leaves.

Abstract

The production of individual form of extracellular polygalacturonase by Aureobasidium pullulans from forest soil was found to depend on the pH of cultivation medium as well as on the nitrogen source in the precultivation or cultivation medium. Polygalacturonases were purified and characterized. The pH optima of polygalacturonases produced in the first phases of cultivation (24 or 48 h) and after 10 days as well as their molecular masses, isoelectric points, action pattern and ability to cleave polymeric and oligomeric substrates were different. Generally, polygalacturonases with random action pattern (EC 3.2.1.15) were produced only in the first phases of cultivation in acidic medium. The function of these enzymes for A.pullulans in the colonization of plant material rather than in the destruction of plant was hypothesized in physiological conditions. Exopolygalacturonases (EC 3.2.1.67) with terminal action pattern were produced in later phases of growth. Oligogalacturonate hydrolase as well as strongly basic polygalacturonase with unusual action pattern on substrates were found.

Abstract

Free radical scavenging and antioxidant activities of metabolites produced by carotenogenic yeasts of Rhodotorula sp. and Sporobolomyces sp. grown under heavy metal presence were studied using various EPR experiments. The thermally initiated decomposition of K₂S₂O ₈ coupled with EPR spin trapping was shown to be the best choice to characterize antioxidant properties of yeast's samples. EPR spectroscopy revealed that yeast walls showed higher ability to scavenge free radicals than those from inside the cells. Since carotenogenic yeast differ to each other in resistance against the heavy metals due to their individual protective system, quenching properties and antioxidant activities of carotenogenic yeasts were modulated by Ni²⁺ or Zn²⁺ ions variously.

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Abstract

The effect of six various pesticides on the growth of yeasts isolated from agricultural soil was investigated. Two herbicides (with the effective substances lactofen and metazachlor), two fungicides (with the effective substances fluquinconazole and prochloraz), and two insecticides (with the effective substances cypermethrin + chlorpyrifos and triazamate) were tested. It is evident that there are considerable differences in inhibition effects of studied pesticides. The fungicide with the effective substance prochloraz inhibited the growth of majority of yeast strains. The insecticide triazamate at concentration 0.6 mM restricted or inhibited growth of all tested strains. The strains of the genus Cryptococcus were the most sensitive to pesticides, while the strains of the species Cystofilobasidium capitatum, Debaryomyces occidentalis var. occidentalis, and Trichosporon cutaneum were the most resistant.

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Abstract

One hundred and eleven yeast strains were isolated from 60 agricultural soil samples. The samples were taken from four various fields located in the southwest of Slovakia. Cryptococcus laurentii, Candida maltosa, Metschnikowia pulcherrima, and Sporobolomyces salmonicolor were the predominant species in the samples collected from all four types of fields. These species represented 78.4–86.6% of the total yeast counts.

The results obtained enabled comparisons to be made between forest and agricultural soil yeast population. We have found out that the yeast population in tilled soils was significantly reduced. The number of yeasts in the tilled soils ranged from 40 to 6.8 × 10³ CFU/g soil and the average number reached approximately 1.12 × 10³. This number is more than ten times lower in comparison with the forest soils.

Abstract

One hundred and fifty six yeast strains were isolated from 160 grass-grown samples collected in four different localities in Bratislava, Slovakia. The collection of soil took place in March, May, August, and October. Cryptococcus laurentii, C. albidus, Cystofilobasidium capitatum, Sporobolomyces salmonicolor, and Trichosporon cutaneum were the most frequently isolated species from the samples taken in unpolluted localities Rusovce and Dúbravka. These species represented 92.1% of total yeast counts found in these soil samples.Cryptococcus laurentii, C.albidus, Cystofilobasidium capitatum, Debaryomyces castellii, and Rhodotorula glutinis were the most frequently isolated species from the samples taken in the polluted localities Polianky and Mlynská Dolina. These species represented 93.3% of total yeast counts there. Yeast densities ranged from 400 to 80.000 CFU/g soil. We found that yeasts occurred unevenly in soils during the year. The lowest average number of yeasts was found in August and the highest one in May.

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Abstract

One hundred and eighty one yeast strains were isolated from 180 soil samples collected in three types of forest. The samples were taken during one year. The yeast species found were similar in spite of distinct forest types. Cryptococcus laurentii, Cystofilobasidium capitatum, Leucosporidium scottii, Rhodotorula aurantiaca, and Trichosporon cutaneum were the predominant species in both deciduous and coniferous forests. The number of yeasts ranged from 1.5 × 10³ to 1.1 × 10⁴ CFU/g soil. We found that yeasts occurred unevenly in soils during the year. The lowest number of yeasts was ascertained in December and the highest one in May.

Abstract

One hundered and sixty seven yeast strains belonging to 27 species were isolated from 57 water samples of the river Morava of the Slovak Republic taken during one year. Sporobolomyces roseus, Candida maltosa, and Aureobasidium pullulans were found to be the most frequent species, from nearly 50% of all samples, and together with Saccharomyces cerevisiae, Rhodotorula glutinis, Cystofilobasidium capitatum, and Cryptococcus laurentii represented more than 80% of the total yeast population. Yeast densities of the river water ranged from 100-37,800 CFU per litre. The highest yeast population density was observed in samples taken in April, when Sacch. cerevisiae, Cr. laurentii and Cys. capitatum occurred the most frequently. The yeast community was characterized by a broad assimilation activity with xylose, cellobiose, and trehalose, which are widespread in nature, being assimilated by nearly 90% of population.

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Abstract

Six yeast extracellular glycoproteins were isolated from different cultivation media containing higher concentration of NaCl (4%, 8%) or without NaCl. The glycoproteins produced under NaCl stress and physiological conditions differ mainly in the higher content of mannose in carbohydrate moiety and glutamic acid in the protein moiety. The correlation between osmotic stress and the composition and structure of the produced glycoproteins was observed. Chemical analysis and FT-IR spectroscopy was applied to investigation of these stress glycoproteins that are known to be associated with ability of binding water and protection of water-regime of cells.

Abstract

One hundred and seventy yeast strains belonging to 14 genera and 29 species were isolated from 112 water samples of the river Danube in the area of Bratislava. The samples were collected through the year from April to March. Saccharomyces cerevisiae, Candida maltosa,Aureobasidium pullulans, Cystofilobasidium capitatum, Rhodotorula glutinis,Geotrichum candidum, and Candida krusei were the most frequent. The basidiomycetous yeasts and yeast-like organisms with oxidative metabolism were present in approximately equal numbers to those with fermentative metabolism. Saccharomyces cerevisiae was the dominant yeast and was isolated from 50% of all samples examined and represented approximately one quarter of the yeast community. Yeast densities ranged from 100 to 21,100 CFU per litre. The highest population density was observed in October. Cryptococcus albidus, Saccharomyces cerevisiae, Rhodotorula glutinis, and Aureobasidium pullulans formed the main part of the yeast population in this month.

Abstract

The killer activity of 46 strains belonging to 12 yeast and yeast-like species isolated from water or sediment samples was studied. Only two strains of the genus Cryptococcus did not show killer activity. Killer activity of yeast-like species Aureobasidium pullulans,Hyphopichia burtonii and Geotrichum candidum, and yeast species Candida krusei and Candida lambica was low. Sporobolomyces salmonicolor, Cryptococcus laurentii and Cryptococcus albidus had better activity against basidiomycetous than ascomycetous species. Hansenula anomala strains showed good activity against Geotrichum candidum strains, Cryptococcus albidus, and Sporobolomyces salmonicolor. Rhodotorula species showed activity against the majority of both ascomycetous and basidiomycetous species.

Abstract

Eighteen yeast strains were tested for their ability to survive the freeze-thaw process while being cryoprotected. Cryoprotection was accomplished by combining penetrating and nonpenetrating cryoagents. Four nonpenetrating (two extracellular polysaccharides of yeast and two extracellular glycoproteins of yeast) and two penetrating agents were used together with the nutritive-rich medium. Eight different mixtures were tested. The highest survival rate was obtained with glycoproteins of Rhodosporidium toruloides together with DMSO and nutritive-rich medium.

Abstract

Fourteen genera and 29 species of yeasts were found in the water of three artificial fresh lakes. The lakes, used for recreational purposes and located in the area of the Lowland Záhorie (Slovakia), were sampled in summer and autumn. Aureobasidium, Hansenula, Candida, and Rhodotorula species occurred the most frequently. The composition of yeast species was more heterogeneous in summer than in autumn. Relatively high population levels of fermentative and pellicle-forming yeasts were found, especially of Candida krusei and Hansenula anomala. The "black yeast" Aureobasidium pullulans was frequently isolated in autumn in high counts in contrast with the numbers of other species.

Abstract

Five strains of Malassezia pachydermatis isolated from small animals in Bratislava were subcultured, maintained under sterile paraffin oil and preserved in liquid nitrogen. Morphological and physiological characteristics as well as the analysis of long chain fatty acids of the cell mass were determined. The results showed that the maintenance in liquid nitrogen is the most satisfactory method of preservation of pure cultures of Malassezia pachydermatis.