Auswahl der wissenschaftlichen Literatur zum Thema „Saccharomyces cerevisiae Polysaccharides“

The protectant activity of pectic polysaccharides derived from various plants was studied on Saccharomyces cerevisiae yeast-like fungi, human blood platelets and leukocytes, and the antihemolytic action of the same compounds was studied on red blood cells. The feasibility of cryopreservation of biological objects in the environment of pectic polysaccharide- containing cryoprotectant solutions was demonstrated.

To gain knowledge on the role of Saccharomyces cerevisiae yeast strains (and their hybrids) on wine sensory properties, 10 commercially available yeast strains were selected on the basis of their widespread usage and/or novel properties and used to produce Shiraz wines. Significant differences were evident post-alcoholic fermentation and after 24 months of ageing with regards to the number of wine compositional variables, in particular the concentration of tannin and polysaccharide. Strain L2323 is known for its pectinolytic activity and yielded the highest concentration of both yeast- and grape-derived polysaccharides. Wines made with the mannoprotein-producing strain Uvaferm HPS (high levels of polysaccharides) did not have elevated concentrations of yeast-derived polysaccharides, despite this observation being made for corresponding model fermentations, suggesting that mannoprotein production or retention might be limited by the wine matrix. Wine tannin concentration showed a high level of variability between strains, with L2323 having the highest, and AWRI1503 the lowest concentration. Sensory analysis of the wines after 24 months ageing revealed significant differences between the yeast strains, but only the attributes opacity (visual colour) and astringency could be predicted by partial least squares regression using the wine compositional data. Notably, the astringency attribute was associated with higher concentrations of both tannin and polysaccharide, contrary to reports in the literature which suggested that polysaccharide exerts a moderating effect on astringency. The results confirm previous reports demonstrating that the choice of yeast strain represents an opportunity to shape wine style outcomes.

Carboxymethylated derivatives were prepared from the (1→3)-β-ᴅ-glucan isolated from the cell wall of baker’s yeast Saccharomyces cerevisiae and from the chitin-glucan complex of the mycelium of the industrial filamentous fungus Aspergillus niger. The polysaccharides were applied to peritoneal mouse macrophages and after a 2-h incubation the release of TNF-α by the stimulated macrophages was measured using an enzyme-linked immunosorbent assay. As the third polysaccharide stimulant, a water-soluble derivative of chitin was assayed and the observed cytokine release was compared with the control experiment. In three concentrations of the polysaccharides applied, carboxymethyl glucan revealed a dramatic increase in the TNF-α release, while addition of carboxymethyl chitin-glucan resulted only in a moderate enhancement, and carboxymethyl chitin was inactive. The results indicate that fungal polysaccharides, especially (1→3)-β-ᴅ-glucan, are potent macrophage stimulators and activators of TNF-α release, which implies their potential application in antitumor therapy.

Residual brewing yeast is one of the main solid wastes in brewing. Using residual brewing biomass as a source of biologically active substances is an important way of recycling these brewing by-products. According to the literature S. cerevisiae is considered as the promising source of polysaccharides, particularly beta-glucans. Beta-glucans are structural polysaccharides of the yeast cell and perform immune stimulating properties. At the same time, there is too little information about the content of these polysaccharides in brewing yeast of the genus Brettanomyces. The objects of this study were yeast cultures of Saccharomyces cerevisiae and Brettanomyces bruxellensis. In this work, the cultivations of the yeasts were carried out to compare them as possible sources of beta-glucans. The yeasts were cultivated in a simple periodic culture using a laboratory fermenter (Biostat A, Sartorius). As a result, the content of beta-glucans in the yeasts S. cerevisiae and B. bruxellensis biomass was measured by enzymatic method (Megazyme, Ireland). According to the obtained data, the yeast B. bruxellensis contains a higher amount of beta-glucans than the yeast S. cerevisiae.

Traditionally, non-Saccharomyces yeasts have been considered contaminants because of their high production of metabolites with negative connotations in wine. This aspect has been changing in recent years due to an increased interest in the use of these yeasts in the winemaking process. The majority of these yeasts have a low fermentation power, being used in mixed fermentations with Saccharomyces cerevisiae due to their ability to produce metabolites of enological interest, such as glycerol, fatty acids, organic acids, esters, higher alcohols, stable pigments, among others. Additionally, existing literature reports various compounds derived from the cellular structure of non-Saccharomyces yeasts with benefits in the winemaking process, such as polysaccharides, proteins, enzymes, peptides, amino acids, or antimicrobial compounds, some of which, besides contributing to improving the quality of the wine, can be used as a source of nitrogen for the fermentation yeasts. These compounds can be produced exogenously, and later incorporated into the winemaking process, or be uptake directly by S. cerevisiae from the fermentation medium after their release via lysis of non-Saccharomyces yeasts in sequential fermentations.

Saccharomyces cerevisiae was used as a model to explore the preventive effect of two marine polysaccharides separately derived from Sepia esculenta ink (SIP) and Laminaria japonica (FL) as well as one terrestrial polysaccharides from Eleocharis tuberosa peel (WCPP) on toxic injury induced by acrylamide (AA). The growth of yeast was evaluated by kinetics indexes including doubling time, lag phase and maximum proliferation density. Meanwhile, intracellular redox state was determined by contents of MDA and GSH, and SOD activity. The results showed that AA inhibited yeast growth and destroyed the antioxidant defense system. Supplement with polysaccharides, the oxidative damage of cells was alleviated. According to the growth recovery of yeast, FL and WCPP had similar degree of capacity against AA associated cytotoxicity, while SIP was 1.5~2 folds as strong as FL and WCPP. SIP and FL significantly reduced production of MDA by AA administration. Moreover, SIP, FL and WCPP increased SOD activity and repressed GSH depletion caused by AA.

An algorithm for the biocatalytic conversion of polymers of subcellular structures of Saccharomyces cerevisiae 985-T has been developed. It was shown that the action of enzymes on cell wall mannoproteins and (3-glucans led to deformation of their structure and the transfer of more than 50% of polysaccharides to a soluble state with the formation of 13.4% reducing carbohydrates, 1.8% amine nitrogen and 7.7% free amino acids (biological-1). Biological-2 had an increased content of total carbohydrates (32.2%) and fiber (10.5%). It was found that the combined action of the complex of proteinases and peptidases contributed to an increase in the degree of hydrolysis of subcellular structures, which was accompanied by a growth of the content of amino nitrogen by 2.7 times, free amino acids by 3.1 times, and low-molecular peptides (up to 500 Da) by 3.5 times (biological-3). The obtained biologicals were characterized by a high content of phosphorus and potassium. It was shown that the use of enzyme systems that catalyze the hydrolysis of intracellular polymers in yeast biomass allows us to obtain products with different biochemical and structural-fractional composition, which determines their properties. Saccharomyces cerevisiae, enzymes, structural-fractional composition, functional ingredients The work was carried out at the expense of the subsidy for the implementation of the State Task.

Thesis (PhD (Microbiology))--University of Stellenbosch, 2005.
Biomass is the sole foreseeable sustainable source of organic fuels, chemicals and materials. It is a rich and renewable energy source, which is abundant and readily available. Primary factors motivating the use of renewable enrgy sources include the growing concern over global climate change and the drastic depletion of non-renewable resources. Among various forms of biomass, cellulosic feedstocks have the greatest potential for energy production from. The biggest technological obstacle to large-scale utilisation of cellulosic feedstocks for the production of bioethanol as a cost-effective alternative to fossil fuels is the general absence of low-cost technology for overcoming the recalcitrance of cellulosic biomass. A promising strategy to overcome this impediment involves the production of cellulolytic enzymes, hydrolysis of biomass and fermentation of resulting sugars to ethanol in a single process step via a single microorganism or consortium. Such “consolidated bioprocessing” (CBP) offers very large cost reductions if microorganisms, such as the yeast Saccharomyces cerevisiae, can be developed that possess the required combination of efficient cellulose utilisation and high ethanol yields. Cellulose degradation in nature occurs in concert with a large group of bacteria and fungi. Cellulolytic microorganisms produce a battery of enzyme systems called cellulases. Most cellulases have a conserved tripartite structure with a large catalytic core domain linked by an O-glycosylated peptide to a cellulose-binding domain (CBD) that is required for the interaction with crystalline cellulose. The CBD plays a fundamental role in cellulose hydrolysis by mediating the binding of the cellulases to the substrate. This reduces the dilution effect of the enzyme at the substrate surface, possibly by helping to loosen individual cellulose chains from the cellulose surface prior to hydrolysis. Most information on the role of CBDs has been obtained from their removal, domain exchange, site-directed mutagenesis or the artificial addition of the CBD. It thus seems that the CBDs are interchangeable to a certain degree, but much more data are needed on different catalytic domain-CBD combinations to elucidate the exact functional role of the CBDs. In addition, the shortening, lengthening or deletion of the linker region between the CBD and the catalytic domain also affects the enzymatic activity of different cellulases. Enzymes such as the S. cerevisiae exoglucanases, namely EXG1 and SSG1, and the Saccharomycopsis fibuligera β-glucosidase (BGL1) do not exhibit the same architectural domain organisation as shown by most of the other fungal or bacterial cellulases. EXG1 and SSG1 display β-1,3-exoglucanase activities as their major activity and exhibit a significant β- 1,4-exoglucanase side activity on disaccharide substrates such as cellobiose, releasing a free glucose moiety. The BGL1 enzyme, on the other hand, displays β-1,4-exoglucanase activity on disaccharides. In this study, the domain engineering of EXG1, SSG1 and BGL1 was performed to link these enzymes to the CBD2 domain of the Trichoderma reesei CBHII cellobiohydrolase to investigate whether the CBD would be able to modulate these non-cellulolytic domains to function in cellulose hydrolysis. The engineered enzymes were constructed to display different modular organisations with the CBD, either at the N terminus or the C terminus, in single or double copy, with or without the synthetic linker peptide, to mimic the multi-domain organisation displayed by cellulases from other microorganisms. The organisation of the CBD in these recombinant enzymes resulted in enhanced substrate affinity, molecular flexibility and synergistic activity thereby improving their ability to act and hydrolyse cellulosic substrates, as characterised by adsorption, kinetics, thermostability and scanning electron microscopic (SEM) analysis. The chimeric enzyme of CBD2-BGL1 was also used as a reporter system for the development and efficient screening of mutagenised S. cerevisiae strains that overexpress CBD-associated enzymes such as T. reesei cellobiohydrolase (CBH2). A mutant strain WM91 was isolated showing up to 3-fold more cellobiohydrolase activity than that of the parent strain. The increase in the enzyme activity in the mutant strain was found to be associated with the increase in the mRNA expression levels. The CBH2 enzyme purified from the mutant strain did not show a significant difference in its characteristic properties in comparison to that of the parent strain. In summary, this research has paved the way for the improvement of the efficiency of the endogenous glucanases of S. cerevisiae, and the expression of heterologous cellulases in a hypersecreting mutant of S. cerevisiae. However, this work does not claim to advance the field closer to the goal of one-step cellulose processing in the sense of technological enablement; rather, its significance hinges on the fact that this study has resulted in progress towards laying the foundation for the possible development of efficient cellulolytic S. cerevisiae strains that could eventually be optimised for the one-step bioconversion of cellulosic materials to bioethanol.

Les polysaccharides sécrétés dans les milieux fermentés par Saccharomyces cerevisiae et Pediococcus sp. Ont été peu étudiés. L'objet de ces travaux est une meilleure connaissance de la nature chimique et des propriétés de ces macromolécules glucidiques qui interviennent dans la structure colloïdale des vins. La mise au point d'une méthode analytique rapide et reproductible de dosage chromatographique des polysaccharides a permis d'établir des cinétiques de production en milieu modèle et dans les vins au cours de la fermentation alcoolique et de la conservation sur biomasse levurienne. La quantité de polysaccharides sécrétés (plusieurs centaines de milligrammes par litre) dépend de la souche de levure, de la température de fermentation, des conditions d'agitation du milieu et de la durée de conservation sur lies. La précipitation par un sel d'ammonium quaternaire ou la chromatographie d'affinité permettent de séparer une mannoprotéine majoritaire d'un complexe glucomannoprotéine. La mannoprotéine exocellulaire possède une structure moléculaire analogue à celle de la mannoprotéine constitutive de la paroi. La libération des polysaccharides levuriens peut être expliquée par les activités β -(1→3) - glucanase pariétales de la levure. L'application pratique de ces résultats concerne l'élevage des vins blancs secs de garde en barrique sur lies totales. Les polysaccharides sécrétés par certaines souches de bactéries lactiques appartenant au genre Pediococcus, responsables d'une augmentation de viscosité, sont des β-D-glucanes. Les quantités libérées dépendent de la nature et de la concentration de la source carbonée choisie comme substrat énergétique. Ces polysaccharides ont un poids moléculaire moyen de 800 000. Leur structure moléculaire a été étudiée par perméthylation, spectrométrie de masse, résonance magnétique nucléaire du carbone 13, dégradation de Smith et hydrolyse enzymatique spécifique par une exo β - (1→3) - glucanase. L'hypothèse de structure proposée est celle d'un β - (1→3 : 1→2) - glucane.