Generation of some new mutant xylitol producing yeast strains.

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.

Probiotics--an alternative treatment for various diseases.

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.

[Biotherapeutic use of yeasts--importance of probiotic products]. / Aplicatiile bioterapeutice ale drojdiilor--importanta produselor probiotice.

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.

Effect of the yeast and bacteria biomass on the microbiota in the rumen.

This study aims at obtaining a probiotic product based on viable biomass from 6 yeast strains and 2 strains of lactic bacteria used for nutrition of animals. The strains are subjected to some resistance tests, at temperature, pH, pepsin, pancreatin and biliary salts so as to make obvious their viability. Tests were done by comparison to the witness strain and respectively a protective solution based on mucin and casein. Based on the resulted viabilities 2 products are formulated. Their effect is tested by inoculating fresh rumen content and supervising the microbic balance for a period of 12 days. After the final tests, it resulted that the product Fpl (20% Saccharomyces cerevisiae 1-29, 10% Kluyveromyces marxianus R-CS, 20% Issatchenkia orientalis R-BC, 30% Lactobacillus paracasei CMGB16, 20% Enterococcus faecium GM8) was chosen because anaerobic strains were preponderant as a consequence of the tests performed with rumen.

Preliminary identification and classification of five new yeast strains isolated from oil-polluted environment.

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.

[Molecular taxonomy techniques used for yeast identification]. / Tehnici de taxonomie moleculara utilizate în identificarea drojdiilor.

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.