Cryoprotective effects of yeast extracellular polysaccharides and glycoproteins.

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.

Malassezia pachydermatis: properties and storage.

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.

Storage of Candida albicans, C. tropicalis and related species in liquid nitrogen.

Storage in liquid nitrogen of a collection of C. albicans, C. tropicalis and related species checked by numerical and classical taxonomy is described. Strains stored for 3 years in liquid nitrogen were thawed and their survival was tested. After adaptation and regeneration, their fermentation and assimilation spectra, production of chlamydospores and pseudomycelia, appearance and radial growth rate of giant colonies were investigated and compared with the properties of cultures stored under paraffin oil. It follows from the results obtained that two different media--with an increased content of a nitrogen source and with an increased carbon source content--should be used for the post-heating adaptation and regeneration of yeast cells. In some strains it is useful to store them at 4 degrees C for additional time intervals in order to increase survival of the cells. The above strains can be successfully stored in liquid nitrogen.

A contribution to the quantitative evaluation of yeast cultures stored in liquid nitrogen.

Different ways of the evaluation of viability of cultures stored in liquid nitrogen are compared. The streaking technique is recommended for a rapid evaluation. It is sufficient to determine the suitability of the medium, of cryopreservatives and of the whole procedure. On storage of melted cultures for 1-7 d at 4 degrees C it was found that the cultures could be transported directly in a suitable package maintaining the low temperature on the condition that the transportation would not last longer than 5 d.

Liquid nitrogen storage of yeast cultures. II. Stability of characteristics of stored strains.

Nineteen strains of yeasts possessing different characteristics were stored in liquid nitrogen and after 5 years phenotypic characters were evaluated and compared with equivalent strains preserved under paraffin oil. All qualitative characters tested remained stable, and quantitative characters varied only within the range of natural variability.

Long-term preservation of yeast cultures in liquid nitrogen.

Nineteen strains of taxonomically diverse yeast species tested survived freezing and subsequent five-year storage in liquid nitrogen at - 196 degrees C, using a medium M 2 composed of malt extract, yeast extract, peptone, calf serum and dimethyl sulfoxide. Viability of the yeast cultures after long-term storage ranged from 5 to 97% (average 62%) compared with the viability of the cultures prior to freezing. The use of liquid nitrogen refrigeration for preserving yeast cultures is strongly advocated.

Torulopsis ethanolitolerans n. sp. and T. ethanolitolerans var. minor n. var.

A new yeast, Torulopsis ethanolitolerans and its variety minor, both isolated from industrial sulphite fodder yeast cultivated on synthetic ethanol as the only source of carbon, originally designated R 5, R 6 and the variety R 7, are described. This species differs from all recently accepted Torulopsis species (resp., Candida species), which do not assimilate nitrate, not ferment any sugars, not produce urease, by the assimilation of maltose, but not of sucrose, lactose and D-xylose.

Mannan-hydrolyzing enzymes of yeasts and yeast-like organism.

The ability to degrade mannan in the yeast Saccharomyces cerevisiae, i.e. the ability to produce an enzyme of the alpha-mannosidase type was tested in 57 representatives of various genera and species of yeasts and yeast-like organisms. Their growth was simultaneously monitored on soluble mannan and on 4-nitrophenyl-alpha-D-mannopyradnoside. The majority of strains produced alpha-mannosidase (EC 3.2.1.24).

Candida ethanolica n. sp.

A new yeast, Candida ethanolica, isolated from industrial fodder yeast cultivated on synthetic ethanol as the only source of carbon, originally designated III-5 and III-6, is described. This species differs from all recently accepted Candida species in not assimilating nitrate, not producing urease and not fermenting sugars.

Morphological changes during the life cycle of Aureobasidium pullulans (de Bary) Arnaud.

Aureobasidium pullulans (de Bary) Arnaud was isolated from different natural materials plant blossoms in particular. Elements of vegetative multiplication, structure of colonies and cultures in liquid media were analyzed in detail, leading to construction of the life cycle of this organism. Morphological polymorphism was found to be combined with the production of melanin and the polysaccharide pullulan. Morphological analysis served for a directed selection for studies of physiological properties of this organism and its practical application.

Biochemical similarities among strains of Aureobasidium pullulans (de Bary) Arnaud.

Seventy-seven properties of Aureobasidium pullulans including utilization of various carbon sources, decomposition of the lignin-cellulose complex and the respective enzymes were checked in the present communication. According to these properties the group of 43 strains was separated in three parts, out of which two groups were found to belong to varieties A. pullulans var. pullulans and A. pullulans var. melanigenum. The third group formed a marginal part. The two varieties differed in numerous biochemical markers, particularly in the absence of monophenol monooxygenase in the variety A. pullulans var. pullulans.

Production of alpha-amylase by yeasts and yeast-like organisms.

Of a total of 177 strains of yeasts and yeast-like organisms only 8 were capable of producing alpha-amylase; most strains were able to utilize 1,4-alpha-glucans by means of enzymes acting on the non-reducing ends of the outer glucan chains.

Liquid nitrogen storage of yeast cultures. I. Survival, and literature review of the perservation of fungi at ultralow temperatures.

All 20 yeast strains of 17 species tested survived 75 days (the length of the experimental period) in liquid nitrogen at -196 C. The components of the more protective of the two freezing media used were (w/v) malt extract 2.5%, yeast extract 0.25%, peptone 0.5%, calf serum 15% (v/v) and dimethyl sulfoxide 10% (v/v). Viability of the cells in this medium after rapid uncontrolled freezing and thawing in selaed plastic ampoules ranged from 2% to 98% (average 67%) compared with the viability of the cultures before freezing. In only 4 strains was survival lower than 50%. (90 references).

Xylan-degrading activity in yeasts: growth on xylose, xylan and hemicelluloses.

The ability to grow in liquid media with D-xylose, xylan from decidous trees, and hemicelluloses from conifers was tested in 95 strains of 35 genera of yeasts and yeast-like organisms. Of 54 strains thriving on xylose, only 13 (genera Aureobasidium, Cryptococcus and Trichosporon) utilized xylan and hemicelluloses as growth substrates. The árowth media of these strains were found to contain xylan-degrading enzymes splitting the substrate to xylose and a mixture of xylose oligosaccharides. The ability of these yeasts to utilize the wood components (hitherto unknown in the genus Crytococcus) makes them potential producers of microbial proteins from industrial wood wastes containing xylose oligosaccharides, xylan, and hemicelluloses as the major saccharide components without previous saccharification.