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Yeasts have been used for food processing since ancient times due to their special fermentative characteristics. In present, they represent a major group of microorganisms used in food industry as well in related domains of biotechnology. Yeasts are a rich source of proteins, vitamins (especially those from B complex) and are main producers of biocatalysts (lipases, esterases, phospholipases) used to improve aromas and flavours and of different natural additives such as food colorants. Yeasts isolated from traditional dairy products produce inulinases and β- galactosidases important for production of foods intended for weight loss or for people with lactose intolerance. Inulinases exhibit also prebiotic potential, catalysing the growth of probiotic microorganisms. Certain yeast species are used as probiotics since they not participate in horizontal antibiotic resistance genes exchanges. Recently, the yeasts with antioxidant activity are considered as attractive for development of biopreservatives, an economic alternative for classical food preservatives of chemical origin. With a great history developed in the food field, the yeasts continue to surprise the scientific world even in the 21st century through their special metabolic abilities. [ABSTRACT FROM AUTHOR]

The yeast species Pichia ohmeri has been described as far, as biocontrol agent. The present work deals with the complex characterization of a new yeast strain CMGB-ST19 isolated from the surface of jam roses (Rosa damascena) petals. The conventional taxonomy tests and the BiologMicroLog system allowed the identification of CMGB-ST19 as Pichia ohmeri. The results were confirmed using ITS-PCR, the strain being renamed as Pichia ohmeri CMGB-ST19. Various tests were performed for determination of its biotechnological properties. P. ohmeri CMGB-ST19 presented good lipolytic activity and hydrolysed tributyrin releasing the butyric acid with positive impact on human health. Moreover, the strain showed antimicrobial activity against 11 Candida and Saccharomyces strains in presence of low pH values. During the preliminary assays for bioethanol and biosurfactants synthesis, significant growth rates were recorded after 24 hours on molasses, respectively, after 72 hours on D-xylose when morphological changes were also observed related to cell stress. In conclusion, P. ohmeri CMGB-ST19 represents an interesting newly characterized yeast strain with high potential for a wide range of biotechnological applications. [ABSTRACT FROM AUTHOR]

Phytoremediation represents an ecological and economic alternative for remediation of polluted environments. The combination of plants and xenodegrading microorganisms is often used for the improvement of the remediation process. Yeast strains Yarrowia lipolytica CMGB32, Cryptococcus curvatus YR-P2 and Rhodotorula glutinis RG5 were tested for assimilation of petroleum and n-hexadecane and biosurfactant synthesis. Y. lipolytica CMGB32 grew well on n-hexadecane over two weeks, C. curvatus YR-P2 degraded petroleum during the first ten days, while R. glutinis RG5 was more active at the beginning of incubation period. All strains produced good rates of biosurfactants. Bean (Phaseolus vulgaris) seeds were sown in pots with sterilized soil and a mixture of the three yeast strains in the presence of petroleum and n-hexadecane (2:1 v:v) and observed for a month. Similar experiments were performed using oil polluted soil from oil wells (Ploiesti area, Romania) and a mixture of polluted soil, sand and gravel. The plants grew slowly on sterilized soil, with visible results only after three weeks. The presence of oil well polluted soil allowed seed germination during the first week due probably to complex interaction between soil native microorganisms-yeast mixture-plant-pollutant which provided the necessary nutrients. Although P. vulgaris has the ability to convert contaminants in less toxic compounds and to fix atmospheric nitrogen, the yeast mixture seems to enhance the plant growth, fully developed plants being observed after two weeks compared to control plants. Soil aeration was also a determinant factor, since seeds planted in soil mixture showed the most rapid growth during first week. The results suggest a positive influence over long period of time of the yeast mixture on plant growth in presence of oil compounds. Further work aims optimization of the novel yeast-plant system as basis for phytoremediation studies. [ABSTRACT FROM AUTHOR]

The probiotics strains are available in a variety of food products and supplements. Most of them are lactic acid bacteria, microorganisms considered commensal and harmless for the host organism (lactic acid bacteria are generally recognized as safe- GRAS). Despite the important progress made in the field of probiotics, the selection of probiotic strains that would be capable of performing effectively in the gastrointestinal tract and the understanding of the precise mechanism of action are still a significant challenge. The purpose of the present work was to characterize the probiotic potential of seven lactic acid bacteria strains isolated from fermented vegetables and from cereals. The study comprised bacterial growth to pH variations, antibiotic susceptibility and growth to different sodium chloride/ bile salt/ digestive enzymes concentration. Obtained results revealed that newly isolated lactic acid bacteria strains presented high resistance to different concentration of bile salt and sodium chloride and also resistance to digestive enzymes.Regarding resistance to different pH values, our studies showed that a part of tested lactic acid bacteria strains have a low resistance to acid pH values (pH 3.0; 4.0) and high resistance to alkaline pH values such as 10.0 and 12.0; antibiotic susceptibility profile was strain dependent. Our studies allowed us to select the most resistant strains in conditions similar to those from the gastrointestinal tract and to exclude the ones with potential risk for human health. [ABSTRACT FROM AUTHOR]

Yeast killer toxins represent an interesting field of study not only for food preservation, but also for development of new bioproducts with biomedical applications. The yeast strain Kluyveromyces lactis CMGB 226 from dairy products was identified using PCR-RFLP on ITS1-5.8S rDNA-ITS2 region. The Hae III and Hinf I restriction profiles of the 675 bp amplicon were similar to those from reference yeast strains. The RAPD analysis using the primer M13 assured the best discriminatory inter and intraspecific characterization of our strain. Killer screening tests were positive against five Candida species, the highest response being observed against C. parapsilosis CBS 604. The 10- fold concentrated killer toxin had a good thermostability and was more active when resuspended in citrate-phosphate buffer with pH from 5.0 to 6.2. The correlation of pH with temperatures of 22, respectively, 28°C represented an important fungistatic factor. Longer treatments with the toxin caused a decline in the viability of C. parapsilosis CBS 604 sensitive cells, with an augmented effect at 28°C after 24 hours. The combination of conditions near to human body favors the killer toxin activity, representing a potential benefit for its future biomedical use against pathogenic Candida strains. [ABSTRACT FROM AUTHOR]

Objective. The main objective of this study was to select lactic acid bacteria strains with antimicrobial activity and to identify and characterize the antimicrobial compounds. Methods. In this study we tested the antimicrobial activity of 153 lactic bacteria strains by disk diffusion method against 6 microbial pathogenic strains isolated from patients with urinary and vaginal infections. Results. Antimicrobial test results revealed that most of lactic acid bacteria strains exhibited high antimicrobial activity against pathogenic microorganisms. For most of lactic bacteria strains antimicrobial activity has been correlated with the production of organic acids and only for two strains with the biosynthesis of bacteriocins. Bacteriocin produced by Lactococcus (Lc.) lactis F2a strain presented a broad spectrum of activity and high activity (51,200 AU/ml) compared with bacteriocins isolated from Lactobacillus (Lb.) paracasei ssp. paracasei JR strain (400 AU/ml). The stability tests of bacteriocin revealed that the bacteriocin produced by Lc. lactis F2a strain, it is stable at acid pH while exposure for long time to 600C causes a drastic decrease in bacteriocin activity. Conclusions. Lactic bacteria strains showed a high antimicrobial activity against both prokaryotic and eukaryotic pathogen strains. Two bacterial strains have bacteriocins. Bacteriocins isolated from Lc. lactis F2a strain showed a high activity and a broad spectrum of action. [ABSTRACT FROM AUTHOR]

Three Metschnikowia pulcherrima strains isolated from white grapes (strains designated SG1 and SG2) and cherries (strain CPM1) from Romania were tested for antagonistic activity against natural and reference yeasts, fungi and E. coli. The best results were obtained for SG2 strain against the following microbes isolated from natural environments: yeasts Candida tropicalis OT4 and Candida albicans Cc, and fungal strains Botrytis cinerea BCS and BCF1. Using 2 % sodium hydrogen carbonate and 1 or 2 % calcium chloride, antimicrobial activities of strains SG1 and SG2 were maintained or even enhanced, while strain CPM1 was less influenced. Antimicrobial tests revealed four types of colonies and halos of strains SG1, SG2 and CPM1 reflecting differences in iron immobilization under similar growth conditions. Antifungal activity and the level of pigment production increased at 25 °C, and the largest diffusible pigment area was obtained by strain SG2, which altered Botrytis conidia germination and induced modifications of mycelium. Competition for iron seems to be the major mechanism of antagonistic action of our strains, which is reduced/absent under iron chloride addition. Lowering of antifungal activity by heating or proteolytic treatment indicates that a protein might also be involved. The inhibitory activity of yeast supernatants was less important, suggesting a cell-related mechanism. When combined, strains SG1 and SG2 had synergistic activity, which was reduced in the presence of CPM1 due to possible production of an inhibitory compound. [ABSTRACT FROM AUTHOR]

The study was dedicated to investigate the effect of aspirin and piroxicam on suspension cells of different Candida albicans strais. Candida albicans is an opportunistic dimorphic fungus that inhabits various host mucosal sites. It can cause both superficial and serious systemic diseases and are now widely recognized as important agents of hospital-acquired infection. Prostaglandins are small lipid molecules and may play an important rol in fungal colonization. Nonsteroidal anti-inflammatory drugs (aspirin and piroxicam) are inhibitors of the cyclooxygenase isoenzymes. These drugs specifically block the biosynthesis of mammalian prostaglandins by inhibiting one or both of COX isoenzymes. Piroxicam drastically reduced the viability of planktonic cells to 0,94% and aspirin had reduced to the 4,45% of that of untreated control cells. Aspirin and piroxicam might improve the traditional antifungic therapies against Candida albicans. [ABSTRACT FROM AUTHOR]

The release of xenobiotic compounds as petroleum and its derivatives still represents a problematic and not fully manageable consequence of various anthropogenic activities. Thus, endogenous microbial communities facing such pollutants are constantly adapting to new conditions, their evaluation being an important asset for environmental preservation. This study analyzes structural and metabolic shifts in a soil microbial community following kerosene pollution. Metabolic profiles from Biolog EcoPlate, analyzed as a guild grouping, Shannon diversity index (H index) and functional divergence revealed a significant reorganization followed by specialization in communities' metabolic function, also being supported by molecular profiles from ribosomal RNA (rRNA) intergenic spacer analysis (RISA) fingerprinting. Highly intense metabolic activity and structural changes are suggested by the increase in alkB and rRNA genes copy number, having similar trends. Thus, alkB gene copy number increased in 70 days from 5.53x109 to 1.67x1011 copies. In this study we managed to report the changes that occur in a soil microbial community facing kerosene pollution using a significant number of complementary techniques, resulting in a complex characterization that can be of great use when facing kerosene-type pollutants. [ABSTRACT FROM AUTHOR]

Objective. The main goal of our study was to determine the effect that association of nonsteroidal anti-inflammatory drugs (NSAIDs) with antifungal drugs on viability of Candida (C.) albicans and C. krusei species. Materials and methods. Six yeast strains were isolated from pharyngeal and vaginal secretions (C. albicans and C. krusei). Tests (diffusion and serial microdilutions methods) were carried out in the presence of some NSAIDs by using different concentrations (0.25mg/ml and 1 mg/ml). Antifungal drugs were used in lower concentrations than the MIC (1 µg/ml). Results. Cell viability of C. krusei strain was of 82% for NSAIDs used and association of these with ketoconazole led to decrease of cell viability of C. krusei strain to 60% as compared to the cells treated with antifungal drugs. In the presence of NSAIDs, cell viability of C. albicans strains, decreased between 6 to 18% for diclofenac and ibuprofen. In the case of simultaneous use of the two classes of drugs, there was observed an increase of antimicrobial activity, especially for diclofenac association, cell viability was reduced up to 60% and respectively 70% as compared to the cells treated only with ketoconazole and fluconazole. Conclusion. We observed a synergistic action of certain NSAIDs with two antifungal drugs used on some Candida species. [ABSTRACT FROM AUTHOR]

Candida albicans is an opportunistic dimorphic fungus that inhabits various host mucosal sites. It can cause both superficial and serious systemic disease. Conversion from the yeast to the hyphal form has been associated with increased virulence and mucosal invasiveness. The aim of this study was to investigate the effect of sodium diclofenac and aspirin on germs tube formation of different Candida albicans strains. Prostaglandins may play an important role in fungal colonization. Nonsteroidal anti-inflammatory drugs are inhibitors of the cyclooxygenase isoenzymes. These drugs specifically block the biosynthesis of mammalian prostaglandins by inhibiting one or both of cyclooxygenase isoenzymes. In tests for germ tube formation sodium diclofenac reduced the filamentation to the 12.5%- 5.1%. In the presence of aspirin the filamentation was reduced up to 85-45% depending on the tested strain. Our results suggest that cyclooxygenase-depending synthesis of fungal prostaglandins is important for morphogenesis and fungal virulence. Inhibitors of cyclooxygenase isoensymes (aspirin and diclofenac) are effective in decreasing germ tube formation of Candida albicans.

In order to establish an infection, pathogenic microorganisms have to colonize, survive, multiply, evade the immune system and spread to other tissues [1, 2, 3]. Although some Candida species are normally commensal in humans, in the last decades the frequency and the severity of nosocomial diseases due to Candida strains have increased dramatically [4]. The aim of the present study was to characterize some Candida strains isolated from vulvovaginal infections by determining the virulence and pathogenicity profile. The assessment of the in vitro expression of virulence cell wall associated factors (hyphal formation, adherence to HeLa cell line, biofilm development), soluble secreted enzymes (aspartyl protease, lipase, phospholipase, DN-ase) and Fe3+ accumulation was achieved by phenotypic methods on 13 yeast strains belonging to five Candida (C.) species (C. albicans, C. krusei, C. parapsilopsis, C. catenulata and C. kefyr). Candida sp. strains isolated from vulvovaginal infections showed species/ strain specific virulence profile.

Xylitol, a sugar alcohol with various utilisations in food, pharmaceutical and cosmetics industry can be produced by yeasts via biotechnologies far more economically efficient and environmentally friendly than chemical separation from natural sources. The present paper reports on a successful attempt to identify high performance xylitol producers among the representatives of the Candida and Rhodotorula genera, followed by the enhancement of their capacities by mutagenesis. The strain designated as C. boidinii ICCF-UV10 was finally selected as the best xylitol producer from the parental and mutant strains.

Modulating the microbiota of the gastrointestinal tract through probiotics is an alternative to the conventional treatment of various diseases, based on synthetic drugs. The lifestyle, nutrition and stress of the present modern society could be among the factors responsible for modifications in the intestinal microbiota, correlated with specific diseases. The present study describes the positive effects of probiotics use, with special reference to the yeasts use in several frequently encountered diseases, such as hypercholesterolemia, the irritable bowel syndrome, gastritis and several uro-genital disorders.

Yeast biodiversity represents a dynamic scientific domain characterized by permanent emerging theories and accumulation of new data. Identification of genome structure for a number of yeast species and elucidation of regulatory pathways for species-specific metabolic networks, lead to development of numerous applications of yeasts in industry, biotechnology, therapeutics and bioremediation. The studies of the scientific community were long time focused on Saccharomyces cerevisae due mainly to its use in food production. Therefore, the species belonging to Saccharomyces genus became reference points for genomics and biodiversity studies. During last decades there is a growing interest for yeast species able to produce biomass by assimilating or degrading various compounds such as methanol, hydrocarbons, wood hydrolisates and other residues or by-products from different industries.

Prokaryotes are the most abundant living organisms and also most diverse from genetically and metabolically point of view, being responsible for the majority of biogeochemical processes playing the most important role in life cycle on the planet. Considering this, there is a general agreement among taxonomists, that there is a very small number of bacterial species recognized and described today, mostly because of controversial issues concerning bacterial species concept. One of the most accepted approaches, even today, is the polyphasic taxonomy because it is based on diverse information, obtained from classic taxonomy but also from molecular level. The development of new molecular techniques, especially sequencing rRNA genes conducted to an improved concept, that we intended to evaluate in this review, and even more, to reconstruction of group specific phylogenetic tree.

Besides their important biotechnological and industrial applications, yeasts have been used during the last years, in obtaining probiotic products, along with lactic acid bacteria and various enzymes. Our study deals with some aspects regarding the use of yeasts as animal and human probiotics, and their possible mechanisms of action. Also, we present information on probiotic products synthesized by international and national companies. Finally, there are described future prospective of research concerning the applications of recombinant yeast strains as basis for obtaining new bio-drugs. In conclusion, the data comprised in this paper, presents an interesting argument for using yeasts as biotherapeutic agents, an alternative to conventional treatments.

Bioremediation is a very interesting alternative for restoring the oil-polluted ecosystems. Many studies concerning the possibility of using microorganisms (bacteria and yeasts) in the degradation of oil compounds have as starting point the isolation and taxonomical identification of new species and strains with degradative abilities. Our study focusses on the preliminary classification of five yeast strains (D1, D2, D3, D4 and D6) isolated from oil-polluted environments. The strains were characterized by conventional taxonomical techniques: microscopical and macroscopical appearance, fermentation abilities, assimilation of various carbon or nitrogen compounds, growth under stress conditions (non-permissive temperatures, high glucose concentration) and urea degradation. According to these tests, D1, D2 and D4 showed great similarity to Rhodotorula glutinis, D3 to Candida parapsilosis and D6 to Candida tropicalis. Further supplementary tests were performed in order to establish their ability to degrade hydrocarbons, by observing growth in media with n-alkanes (n-decane, n-dodecane, n-tetradecane, n-hexadecane). Thus, D1, D2 and D4 were the best alkane-consuming strains, presenting possible similar degrading abilities and pathways, which correlates well to our identification as Rhodotorula strains. For D3 and D6 the growth was not so spectacular as for D1, D2 and D4, but continuous along the entire experiment. The resemblance between the curves profiles confirms the idea that both belong to the same genus, Candida.

Due to the major impact of yeasts in human life based on the existence of pathogen yeast species and of species with biotechnological abilities, in the last few years new molecular techniques are performed for an accurate identification of natural isolates. Our study is aimed to review some of these techniques such as electrokariotyping by PFGE (Pulsed Field Gel Electrophoresis), estimation of the molar percentage of guanine and cytosine, the applications of PCR reaction in yeast identification using RAPD (Random amplified polymorphic DNA), UP-PCR (Universally Primed Polymerase Chain Reaction), MLST (Multilocus sequence typing) techniques, mtDNA and rDNA homology studies. Such molecular techniques complete the phenotypical characterization based on classical taxonomical tests allowing thus the polyphasic identification of the microorganisms.