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PubMed1990

[Effect of dietary concentration of Saccharomyces carlsbergensis yeast recovered from beer, in Warren male chicks].

Six groups of 1-day-old Warren chicks (seven per group) were fed for 15 days on diets with the protein supplement made of mixtures of soybean protein and dried yeast Saccharomyces carlsbergensis recovered from beer. The purpose was to establish the maximum substitution level of the soybean protein isolate by dried yeast, with the least possible related metabolic effects. Each group was fed one of the diets containing 0%, 25%, 50%, 75% and 100% of the protein supplement based on yeast protein, substituting the soybean protein isolate. In order to estimate the NPR value of the yeast protein, a group which received a protein-free diet, was also included. Protein utilization and changes in both plasma and liver total lipids, triglycerides, cholesterol and liver and kidney uric acid, were determined. In triglycerides, cholesterol and liver and kidney uric acid, were determined. In the groups fed diets with 75% and 100% of yeast protein, decreased body weight gain and PER and NPR values were observed, as well as an increment in the liver and kidney uric acid concentrations, although the diet consumption was not substantially modified. Thus, protein utilization, measured as PER and NPR, was lower in these groups. Plasma uric acid was not modified in neither group. The plasma lipids were not altered at whatever yeast concentration, while in the liver, total lipids as well as triglycerides decreased when the dietary yeast was increased. Results indicated that when using whole yeast cells recovered from beer in pre-starting rations for chicks, 50% of yeast protein is the maximum substitution level.

Amino Acids, Essential↗

PubMed1983

[Insertion of transposon Tn9 into the spinal (Escherichia coli-Saccharomyces cerevisiae) plasmids and the expression of the prokaryotic gene of chloramphenicol resistance in yeast cells].

Transposon Tn9 carrying camr gene which controls resistance to chloramphenicol has been introduced in vivo (in cells of Escherichia coli) into two chimeric shuttle plasmids pYF91 and YEp13. These plasmids consist of the different parts of the E. coli plasmid pBR322, the yeast 2mkm DNA plasmid and the yeast LEU2 structural gene. The plasmidis able to autonomously replicate in both yeast and bacterial cells. A recipient yeast strain carrying cams and leu2 markers was constructed to study the functional expression of the prokaryotic camr gene in eukaryotic yeast cells. The chimeric plasmids pYF91::Tn9 and YEp13::Tn9 were introduced into the yeast and bacterial recipient strains by transformation. The camr LEU2 yeast transformants were isolated. They were genetically unstable when grown on non-selective medium and they simultaneously lost camr and LEU2 markers with a frequency of 10 to 30%. The E. coli transformants were genetically stable under nonselective conditions and they maintain all plasmid markers. The chimeric plasmid pYF91::Tn9 was isolated from the yeast transformants and reintroduced into the cams leuB bacterial strain by transformation. The camr LEUB transformants were obtained. All these data confirm the possibility of the expression of the prokaryotic camr gene in yeast cells and present evidence for introduction of transposon Tn9 into chimeric plasmids.

Chimera↗

PubMedDate not supplied

[Group and fatty acid composition of the lipids in yeasts of the genus Candida].

The group and fatty acid composition of lipids from 62 species and strains of Candida yeast was investigated. No strict correlation between the group composition of lipids and the yeast species was found but certain consistencies were seen. For instance, C. humicola yeast showed a higher ability for biomass and lipid accumulation. In their group composition triglycerides were predominant while polar lipids + monoglycerides and sterol esters + hydrocarbons were in small quantities as compared to other yeast species. Besides, C. humicola yeast contained no pigments. The C. guilliermondii strains contained low amounts of free fatty acids. The lipid fraction of all C. tropicalis yeast studied contained pigments. The yeast with increased amounts of triglycerides showed a comparatively high content of biomass and lipids. C. guilliermondii yeast had a high content of oleic acid and a low content of linoleic acid. All the yeast contained small quantities of stearic acid.

Candida↗

PubMed1994

Effect of addition of brewer's yeast to soy protein and casein on plasma cholesterol levels of rabbits.

The purpose of this study was to determine whether the addition of high levels of yeast to casein and soy diets could modify the well known effects of any of these proteins on plasma cholesterol. Rabbits, were fed either a diet containing soybean protein-brewer's yeast or casein-brewer's yeast (each protein source providing 50 percent of the dietary nitrogen content) and casein and soybean protein basal diets. Brewer's yeast was obtained from a local beer factory in its non-debittered form. The diets contained 20 percent protein, 9 percent coconut oil and 1 percent corn oil, with no added cholesterol. After a 22 day experimental period, rabbits fed casein developed hypercholesterolemia whereas those fed the soybean protein diet did not. The replacement of 50 percent of the soy nitrogen by brewer's yeast nitrogen, increased the total cholesterol plasma level, but significant differences were only observed between rabbits fed casein and casein-yeast and those fed soybean protein. No differences in high density lipoprotein cholesterol could be detected among the groups. However, the HDL-cholesterol/total cholesterol ratio was significantly reduced in response to soy substitution by brewer's yeast. The (low density lipoprotein + very low density lipoprotein)--cholesterol was increased in all groups with the exception of the animals fed purely soy protein. These data suggest a hypercholesterolemic activity of the dietary non-debittered brewer's yeast. Nevertheless, according to the amino acid composition, the factor responsible for the reported effects of dietary yeast was not associated with a high lysine to arginine ratio which could be due to extracellular components.

Animals↗

PubMed2001

Yeast colonization in surgical patients with intra-abdominal perforations.

A prospective study was conducted to determine (i) the degree of yeast colonization in surgical patients with intra-abdominal perforations and (ii) whether the frequency of colonization is different in patients with a complicated postoperative course than in patients recovering uneventfully. A total of 1,496 specimens taken per- and post-operatively from the mouth, stomach, feces, urine, trachea, and abdomen of 109 surgical patients with intra-abdominal perforations were examined. Yeast was recovered from 98 (90%) of the patients and from 634 (42%) of the specimens. Approximately 70% of the specimens from the mouth and stomach, 47% of fecal specimens, and 31% of abdominal specimens were positive for yeast. A total of 42 patients had a complicated postoperative course. The majority of these patients were colonized with yeast at multiple body sites: yeast was recovered on one or more occasions from two or more body sites in 90% and from three or more body sites in 71%. Many of the patients with an uncomplicated postoperative course also were colonized: yeast was recovered from two or more body sites in 69% and from three or more body sites in 34%. The results of this study indicate that treatment recommendations based on yeast colonization will expose a large number of patients to unnecessary or even harmful antifungal treatment. This does not mean that yeast colonization is insignificant; however, more accurate criteria and methods based on prospective clinical studies are needed to detect patients at risk of developing severe Candida infection.

Adolescent↗

PubMed1965

TRANSFORMATION OF MYCELIAL AND YEAST FORMS OF PARACOCCIDIOIDES BRASILIENSIS IN CULTURES AND IN EXPERIMENTAL INOCULATIONS.

Carbonell, Luis M. (Instituto Venezolano de Investigaciones Científicas, Caracas, Venezuela), and Joaquín Rodríguez. Transformation of mycelial and yeast forms of Paracoccidioides brasiliensis in cultures and in experimental inoculations. J. Bacteriol. 90:504-510. 1965.-Experimental transformations of mycelial to yeast and yeast to mycelial forms in culture, and mycelial to yeast forms in tissue, were studied. All the transitional forms that appeared in culture were also seen in tissue, but in fewer number. Most of the hyphae in culture were transformed into yeast, but only a few in tissue. Yeast appeared in testicle around the 3rd day after inoculation, but on the 10th day in subcutaneous tissue. Pathogenicity of mycelium was high, since yeast was found in almost all of the organs inoculated with mycelium. Histologically, an acute inflammation occurred first, owing to the inoculation of mycelium, followed by a giant-cell granuloma with abundant hyphae detritus. These giant cells almost disappeared about 10 days after inoculation, giving place to a second giant-cell granuloma with yeast forms.

Animals↗

PubMed1995

Three-dimensional structure of tubular networks, presumably Golgi in nature, in various yeast strains: a comparative study.

BACKGROUND: In the yeast Saccharomyces cerevisiae, the Golgi apparatus consists of discrete units distributed throughout the cytoplasm. When such units are examined in three dimensions, in relatively thick sections prepared for the electron microscope, they usually appear as small tubular networks with a stained material accumulating in dilations located at the junctions of membranous tubules. To see whether such tubular networks are observed in other yeast species, the three-dimensional structure of organelles in eight additional yeast strains, endowed with diverse biological properties, are examined. METHODS: Yeast strains were grown at 24 degrees C in YPD medium (2% Bactopeptone, 1% Bactoyeast extract, and 2% glucose). Cells that were examined by electron microscopy came from exponentially growing cultures grown in a shaking water bath and maintained at a OD 600 (optical density at 600 nm) of 0.5. Cells were fixed in a fixative containing 2% glutaraldehyde in 0.1 M cacodylate buffer pH 7.4 and 0.8 M sorbitol. They were then treated for 15 min in 1% sodium metaperiodate and postfixed for 1 hr in potassium ferrocyanide-osmic acid. They were preembedded in agarose prior to dehydration and finally embedded in Epon. In these conditions, the preservation of cell organelles was improved and the cytoplasmic retraction from the cell wall was minimized. Photographs of sections tilted at +/- 15 degrees from the 0 degrees position of the goniometric stage were used to prepare stereopairs from which the three-dimensional configuration of the organelles was visualized. RESULTS: In all yeast strains, tubular networks appeared as separate elements or units disperse throughout the cytoplasm. Each unit consisted of anastomosed membranous tubules. In some strains such as Saccharomyces cerevisiae, Zygosaccharomyces rouxii, or Saccharomyces pombe, such units appeared mainly as polygonal networks of intensely stained membranous tubules. Along these networks, distensions filled with stained material were similar in size to nearby secretory granules, suggesting that the latter formed by fragmentation of the tubular networks. In Hansenula polymorpha, Pichia pastoris, and Debaryomyces hansenii, networks of anastomosed tubules were closely superposed to each other and formed parallel arrays reminiscent of the stacks of Golgi saccules seen in mammalian cells. However, in contrast to what is usually found in the latter, the layers making up the parallel arrays in yeasts, were clearly continuous to each other. In other strains, i.e., Kluyveromyces lactis, Candida albicans, and Candida parapsilosis, the situation was intermediate and their cytoplasm contained only arrays of small size with two or at most three superposed layers of membranous tubules. Small vesicles in the 30-50 nm range were rarely encountered in most yeast strains. CONCLUSIONS: It is therefore concluded that tubular networks, presumably Golgi in nature, are present in all yeasts examined so far. Yet, in some strains, these tubular networks may be arranged in parallel arrays or stacks.

Cell Membrane↗

PubMed1988

Utilization of phenol by hydrocarbon assimilating yeasts.

77 Ascomycetous, basidiomycetous as well as imperfect yeast strains of 46 different species and 20 genera were tested for growth with the substrates n-octane, n-hexadecane, and phenol. Of 59 yeast strains with ascomycetous cell wall structure 33 grew on hydrocarbons and 32 on phenol. No yeast strain out of 26 which are unable to use n-alkanes as a source of carbon and energy grew on phenol. In comparison with the latter 32 out of 33 n-hexadecane assimilating yeasts were also capable of using phenol. All n-octane utilizing yeasts of this group also assimilate phenol as a carbon source for growth. The correlation of the hydrocarbon assimilation with the phenol assimilation seems to be not so strong in the basidiomycetous yeasts. 7 out of 18 strains from this group grew on n-hexadecane and 13 on phenol. Furthermore, it could be shown that the use of hydrocarbons and phenol (as well as methanol) is strongly correlated with the coenzyme Q structure of the respective yeast strain. The results are discussed with respect to the particular chemical properties of the substrates used and the fact that coenzyme Q structure is considered to be an important marker of evolutionary relationships among yeasts.

Basidiomycota↗

PubMed1993

Kinetics of growth and sugar consumption in yeasts.

An overview is presented of the steady- and transient state kinetics of growth and formation of metabolic byproducts in yeasts. Saccharomyces cerevisiae is strongly inclined to perform alcoholic fermentation. Even under fully aerobic conditions, ethanol is produced by this yeast when sugars are present in excess. This so-called 'Crabtree effect' probably results from a multiplicity of factors, including the mode of sugar transport and the regulation of enzyme activities involved in respiration and alcoholic fermentation. The Crabtree effect in S. cerevisiae is not caused by an intrinsic inability to adjust its respiratory activity to high glycolytic fluxes. Under certain cultivation conditions, for example during growth in the presence of weak organic acids, very high respiration rates can be achieved by this yeast. S. cerevisiae is an exceptional yeast since, in contrast to most other species that are able to perform alcoholic fermentation, it can grow under strictly anaerobic conditions. 'Non-Saccharomyces' yeasts require a growth-limiting supply of oxygen (i.e. oxygen-limited growth conditions) to trigger alcoholic fermentation. However, complete absence of oxygen results in cessation of growth and therefore, ultimately, of alcoholic fermentation. Since it is very difficult to reproducibly achieve the right oxygen dosage in large-scale fermentations, non-Saccharomyces yeasts are therefore not suitable for large-scale alcoholic fermentation of sugar-containing waste streams. In these yeasts, alcoholic fermentation is also dependent on the type of sugar. For example, the facultatively fermentative yeast Candida utilis does not ferment maltose, not even under oxygen-limited growth conditions, although this disaccharide supports rapid oxidative growth.

Acetaldehyde↗

PubMed1994

Yeast communities of the cactus Pilosocereus arrabidae as resources for larval and adult stages of Drosophila serido.

The feeding behavior of Drosophila serido on the yeast communities of necrotic stem tissue of Pilosocereus arrabidae were studied in a sand dune ecosystem of Rio de Janeiro, Brazil. The prevalence of cactophilic yeasts including Pichia barkeri, Candida sonorensis and Geotrichum sp. in the crops and external surfaces of D. serido reflected its association with the cactus habitat. The effective number of yeasts vectored on the surface of flies was higher than that in the crops. Also overlap between the yeasts from stems and from crops was partial suggesting selective feeding by the flies in the substrates visited. The females had a higher effective number of yeast species and a lower similarity than males with the yeast community of P. arrabidae. This was probably related to the search for oviposition sites by females. The presence of Pichia thermotolerans-like and Pichia amethionina var pachycereana in the flies, but not in P. arrabidae stems, indicated that D. serido was not limited to this cactus species. The larvae and adults lived in different patches with the adults feeding in patches with higher yeast species richness. The larvae had a narrower feeding niche and higher overlap with P. arrabidae, and preferred P. barkeri and Pichia cactophila as food. Adult flies fed on patches with the most frequent yeasts except for P. cactophila. Pichia caribaea was found in higher frequency in the adult crops than in the stems. Our data suggested that there was food selection and diet partitioning between adult and larval stages of D. serido.

Animals↗

PubMed1988

Exudate polymorphonuclear leukocytes isolated from skin chambers are primed for enhanced response to subsequent stimulation with chemoattractant f-Met-Leu-Phe and C3-opsonized yeast particles.

The ability to respond metabolically to stimulation with both soluble and particulate substances was investigated in human polymorphonuclear leukocytes (PMNLs) isolated from an aseptic inflammatory reaction. Exudate PMNLs isolated from skin chambers (E-PMNLs) and blood PMNLs isolated from the peripheral blood (B-PMNLs) of the same individual were investigated in parallel. E-PMNLs were primed, resulting in an increased chemiluminescence (CL) response to subsequent stimulation with the chemotactic peptide formyl-methionyl-leucyl-phenylalanine (FMLP) (334%) and serum-opsonized yeast particles (C3 yeast) (201%), as compared to B-PMNLs. Phorbol myristate acetate (PMA) on the other hand, induced a CL response in E-PMNLs that was only 70% of the response obtained in B-PMNLs. A similar primed state resulting in enhancement of the CL response to FMLP and C3 yeast could be induced in B-PMNLs by pretreatment with a bacterial culture filtrate. Pretreatment of E-PMNLs with the bacterial culture filtrate, however, did not increase the CL response to FMLPs any further. The enhanced functional response to FMLPs in E-PMNLs was accompanied by an increased binding of the peptide, demonstrated by a doubling of the amount of bound f-Met-Leu-[3H]Phe (209%), as compared to B-PMNLs. The increased C3-yeast-induced CL generation in E-PMNLs was accompanied by an increased ingestion and attachment of C3-opsonized yeast particles. The enhancement of phagocytosis in E-PMNLs was, however, dependent upon the opsonin used, since IgG-opsonized yeast particles were phagocytosed to the same extent by E-PMNLs and B-PMNLs, thereby indicating that selective receptor modulation is also involved in the priming of E-PMNLs for an enhanced response to C3-yeast. These results show that exudate cells isolated from skin chambers are modulated with respect to receptor-mediated functions resulting in an increased metabolic response to FMLP coupled with an increased binding of the peptide and an increased phagocytosis of C3-coated yeast particles. Receptor modulation during exudation may be an important mechanism in regulating the inflammatory response by PMNLs.

Chemotaxis, Leukocyte↗

PubMed1995

Differential and enrichment media for selective culture and recognition of yeast species from clinical material.

An enrichment medium was developed and evaluated for isolation of fluconazole-resistant minority yeast species in a hospital setting. The enrichment medium was made by adding fluconazole (10 micrograms/ml) to yeast nitrogen base/glucose broth. Under laboratory conditions the broth permitted detection of 20 of 20 Candida krusei isolates and 20 of 20 Candida glabrata isolates in mixtures with Candida albicans even when the Candida albicans cells outnumbered those of the other species by 1000:1. Results of culture on the enrichment medium were compared with those obtained on routine agar media and on a yeast differential agar which facilitates detection of mixed yeast species by their colony colours. Only one Candida glabrata isolate was detected on the enrichment broth but not found on routine culture of 68 yeast-positive clinical specimens. However, bacterial over-growth in some broths may have retarded the appearance of other yeast isolates. On the yeast differential agar, 20 clinical specimens were found to contain mixtures of yeast species compared with only 2 on routine culture.

Antifungal Agents↗

PubMed1994

Comparison of media for enumerating osmotolerant yeasts in orange juice concentrates.

Enumeration of osmotolerant yeasts in high-sugar food products can be improved by using diluents and recovery media formulated to closely resemble their natural environment. Heat and freeze-stressed yeasts often exhibit decreased tolerance to acetic pH and selective agents, thus requiring optimum recovery conditions for enumeration. The study reported here was done to evaluate three methods for their suitability to enumerate osmotolerant yeasts from fifty Venezuelan orange juice concentrates. Yeasts were enumerated by surface plating serially diluted samples on plate count agar containing 52% (w/w) sucrose (PCAS 52) and incubating at 32 degrees C for 6 days; pour plating in yeast extract malt extract agar containing 52% (w/w) sucrose (YEMS 52) and incubating at 32 degrees C for 6 days and pour plating in potato dextrose agar (PDA), pH 3.5, and incubating at 25 degrees C for 5 days. Mean populations of yeasts recovered were: 4.2 x 10(5), 5.3 x 10(4) and 7.5 x 10(3) cfu/ml, respectively, on PCAS 52, YEMS 52 and PDA. High recovery on PCAS 52 is attributed to avoidance of osmotic shock and possible secondary lethal effects of high temperature, which may be associated with pour plating techniques. Significantly (P < 0.05) higher population were recovered on PCAS 52 than on YEMS 52 and PDA. Predominant osmotolerant yeasts were Saccharomyces bisporus var. mellis, recently named Zygosacharomyces rouxii (Kreger-van Rij W.J.W. (1984) The Yeasts: A Taxonomic Study).

Beverages↗

PubMed1996

Enumeration of xerophilic yeasts in the presence of xerophilic moulds: a collaborative study.

A collaborative study was undertaken to compare the performance of Dichloran 18% Glycerol agar (DG18) with three other media widely used in food mycology, for the enumeration of xerophilic yeasts in the presence of xerophilic moulds. Oxytetracycline Glucose Yeast extract agar, (OGY), Dichloran Rose Bengal Chloramphenicol agar (DRBC) and Malt extract Yeast extract 50% Glucose agar (MY50G) were evaluated. Three reference samples (A, B, C) were prepared using skimmed milk powder inoculated with mixed lyophilized cultures of selected xerophilic yeasts and moulds, at levels around 10(4) to 10(5) CFU/g. Yeast species used were Candida glucosophila, C. versatilis, Zygosaccharomyces bailii and Z. rouxii, together with Eurotium spp. and some other moulds. Collaborators were asked to examine each sample twice, by dilution plating on the four media. Colonies were counted after 3, 5 and 7 days incubation at 25 degrees C. Fourteen participants from seven laboratories in six countries collaborated in this study. The ability of collaborators to detect and count yeasts after 5 and 7 days on DG18, DRBC and OGY varied depending on the sample. Few participants were able to count yeasts even after 7 days on MY50G. The overall results demonstrated that DG18 incubated 5 days at 25 degrees C was superior to the other three media tested for the enumeration of xerophilic yeasts in the presence of xerophilic moulds.

Candida↗

PubMed2004

Carbon, nitrogen and phosphorus mineralization in two soils amended with distillery yeast.

The possibility of using yeast from alcohol distilleries as a source of nutrients in soil was investigated. The following treatments were used: no fertilization (control), 0.5% (w/w) yeast, 1% (w/w) yeast, and NPK. The decomposition of yeast was monitored for 90 days in two soils. The CO2 production and the microbial biomass were increased by an average of 1- to 3-fold by yeast incorporation compared to control. Protease activity also was enhanced 3- to 8-fold in the soils supplemented with yeast compared to control. The phosphatase activities were higher than control only during the first days. While nitrate contents increased in all treatments compared to control, available P only increased in the soils amended with 1% yeast or NPK by 45-119% and 309-489%, respectively. These results indicate that there exists an excellent potential for the use of yeast in the soil as a source of nitrate and available P for plant nutrition.

Analysis of Variance↗

PubMed2006

Metabolite production of yeasts on a strawberry-agar during storage at 7 degrees C in air and low oxygen atmosphere.

Changes of different quality factors of strawberries have been described until now from a physiological point of view. Possible effects on quality caused by yeast proliferation have not been described. To elucidate the metabolic activity of yeasts (i.e. Debaryomyces melissophilus, Rhodotorula glutinis, Cryptococcus laurentii), isolated from strawberries, they were inoculated on a simulation medium of strawberries (strawberry-agar). Their activity was measured by analysing and correlating microbiological counts, metabolite concentration in the headspace as well as in the medium, and sugar consumption. The isolated yeasts from strawberries could grow on the strawberry-agar, both under air conditions and modified atmosphere (MA) conditions. The maximum count for the yeasts reached 7.5-8.5 log cfu cm(-2) (air conditions) and 5.6-6.4 log cfu cm(-2) (MA conditions). Production or consumption of a number of compounds could be detected when microbial counts reached levels between 4.7 log cfu cm(-2) and 8.5 log cfu cm(-2) depending on species and atmospheric conditions. A range of volatile organic compounds, produced by the yeasts, was detected: acetone, ethyl acetate, ethanol, isopropyl acetate, ethyl butyrate, 1-propanol, 2-methyl-1-propanol, 1-butanol, 2-methyl-1-butanol, 3-methyl-1-butanol, 1-hexanol and hexyl acetate. These compounds are able to influence the sensory properties of strawberries. A simultaneous decrease in sugar concentrations (sucrose, glucose, fructose) was observed. When ethanol reached high concentrations, ethyl acetate and ethyl butyrate were produced. This production can be attributed to a detoxification of ethanol by yeasts. The fermentative metabolism of yeasts during aerobic conditions could be explained by the Crabtree effect. As the detected volatile organic compounds produced by yeasts are also found in fresh strawberries, it can be concluded that these compounds are produced both by microbiological and physiological processes.

Colony Count, Microbial↗

PubMed2005

Identification of yeasts associated with milk products using traditional and molecular techniques.

An integrated approach including phenotypic (morphological, biochemical and physiological characterization) and genotypic (RAPD-PCR, sequencing of D1/D2 domain of 26S rRNA encoding gene) methods was used for the identification of yeasts isolated from different milk products. There were 513 isolates in all, 460 ascomycetous and 53 basidiomycetous yeasts. The yeast isolates were characterized on the basis of their biochemical and physiological properties, and the D1/D2 domain of 26S rDNA was sequenced in selected strains. Relying on the obtained results from both the data-sets, corresponding type strains were selected and compared with the respective yeast isolates from milk products by RAPD fingerprinting. The strains showing a degree of similarity >80% were considered conspecific. By means of the applied techniques it was possible to identify 92% yeast isolates at species level. Debaryomyces hansenii, Geotrichum candidum, Kluyveromyces marxianus, Yarrowia lipolytica and Candida zeylanoides are the most frequently isolated species. The majority of the yeasts were isolated from fresh and sour curd cheese. A comparison of the results obtained by phenotypic and genotypic investigation revealed that the identification based on classical methods was supported by genotypic characterization in only 54% of examined isolates. The results described in this work show that the applied molecular identification is a reliable approach to the identification of yeasts associated with milk products in contrast to the conventional biochemical and physiological tests. The identification of new yeast species requires additional genetic markers such as sequencing of different genes or DNA:DNA hybridization.

Colony Count, Microbial↗

PubMed2004

An inter-laboratory evaluation of selective media for the detection and enumeration of yeasts from blue-veined cheese.

Five countries representative of laboratories 1-5 evaluated 11 different selective media, designed to suppress mould and bacterial growth and support yeasts growth, for the recovery of yeast populations from blue veined cheeses. In addition, qualitative results were also incorporated. The yeast enumeration values were subjected to statistical analysis using analysis of variance (ANOVA) and the Tukey-Kramer multiple comparison test. With the exception of Laboratory 3, none of the other laboratories was successful in recovering yeasts on all the media. Six of the media proved inadequate for the enumeration of yeasts in the mould invested environment and were therefore omitted from statistical analysis. No significant differences in quantitative data obtained on Rose-Bengal Chloramphenicol Agar (RBCA), Dichloran Rose-Bengal Chloramphenicol Agar (DRBC), Dichloran 18% Glycerol Agar (DG18), and Malt extract agar supplemented with NaCl and oxytetracycline (MES) were detected by four of the collaborating laboratories whereas one laboratory found RBCA to be superior for yeast enumeration. DG18 and Malt Extract Agar with Biphenyl (MEB), however, were ranked superior based on qualitative results compared to the other media, attributed to distinctive individual yeast colonies and mould inhibition. RBCA, DRBC, DG18, and MES on the other hand, all proved to be adequate in supporting yeast colony development for quantitative analysis in samples obtained from blue veined cheeses.

Agar↗