Yeast proteins do not practice social distancing as species hybridize.

With the current COVID-19 pandemic, we all realized how important interactions are. Interactions are everywhere. At the cellular level, protein interactions play a key role and their ensemble, also called interactome, is often referred as the basic building blocks of life. Given its importance, the maintenance of the integrity of the interactome is a real challenge in the cell. Many events during evolution can disrupt interactomes and potentially result in different characteristics for the organisms. However, the molecular underpinnings of changes in interactions at the cellular level are still largely unexplored. Among the perturbations, hybridization puts in contact two different interactomes, which may lead to many changes in the protein interaction network of the hybrid, including gains and losses of interactions. We recently investigated the fate of the interactomes after hybridization between yeast species using a comparative proteomics approach. A large-scale conservation of the interactions was observed in hybrids, but we also noticed the presence of proteostasis-related changes. This suggests that, despite a general robustness, small differences may accumulate in hybrids and perturb their protein physiology. Here, we summarize our work with a broader perspective on the importance of interactions.

Frozen-dough baking potential of psychrotolerant Saccharomyces species and derived hybrids.

Despite Saccharomyces cerevisiae being a synonym for baker's yeast, the species does not perform well in all baking-related conditions. In particular, dough fermentation, or proofing, is compromised by the species' sensitivity to the low and freezing temperatures that are often used in modern bakeries. Here, screening trials that included representatives of all known Saccharomyces species, showed that S. cerevisiae was generally the most sensitive member of the genus with respect to cold and freezing conditions. We hypothesized therefore that the superior cold tolerance of the non-S. cerevisiae yeast would enable their use as frozen-dough baking strains. To test this, the different yeast species were incorporated into doughs, flash frozen and kept in a frozen state for 14 days. During the proofing stage, dough development was lower in doughs that had been frozen, relative to fresh doughs. This reduction in fermentation performance was however most pronounced with S. cerevisiae. The psychrotolerant yeasts S. eubayanus, S. jurei and S. arboricola showed a strong capacity for post-freeze proofing in terms of dough development and duration of lag phase prior to fermentation. The superior proofing power of these species resulted in breads that were significantly softer and less dense than those prepared with S. cerevisiae. A sensory panel could distinguish the S. cerevisiae and non-S. cerevisiae breads based on their physical properties, but aroma and taste were unaffected by the species employed. To further improve frozen dough baking properties, S. eubayanus, S. jurei and S. arboricola were crossed with baker's yeast through rare mating, and hybrids with improved proofing capacities in both fresh and frozen doughs relative to the parents were created. The use of S. jurei and S. arboricola in baking represents the first potential technological application of these species.

Purification and characterization of Saccharomyces eubayanus killer toxin: Biocontrol effectiveness against wine spoilage yeasts.

Microbiological contamination by spoilage yeasts species are frequent during winemaking, and biological control using antagonistic yeasts is considered a more beneficial alternative to conventional synthetic antimicrobials. Saccharomyces eubayanus killer toxin (SeKT) was produced and purified in a synthetic optimized medium. Purification procedure allowed the identification of SeKT as protein with an apparent molecular mass of 70 kDa and activity at physicochemical conditions suitable for winemaking process. Purified SeKT reduced the levels of volatile phenols produced by the spoilage yeasts Brettanomyces bruxellensis, Pichia membranifaciens, Meyerozyma guilliermondii and Pichia manshurica in wine-like medium. The putative mode of action of SeKT on sensitive yeast strains comprises cell wall disruption through ß-glucanase and chitinase activities as well as necrotic and apoptotic death in a toxin dose dependent manner. Thus, SeKT appears to be a promising biocontrol agent against spoilage yeasts during wine aging and storing.

Saccharomyces cerevisiae and S. pastorianus species and strain differentiation by direct analysis in real time time-of-flight mass spectrometry.

RATIONALE: Seventeen different dried yeast strains, including twelve strains of Saccharomyces cerevisiae and five strains of S. pastorianus, were analyzed using direct analysis in real time (DART) time-of-flight mass spectrometry. The resulting mass spectra were used for rapid species and strain differentiation based upon small-molecule metabolomic profiles. METHODS: Yeast strains purchased from local shops were suspended in a 1:1 water-methanol solution. Solutions were sampled by dipping the sealed end of a melting point capillary into each vial. Six replicates were measured in positive-ion and negative-ion mode for each strain using an automated linear rail with the DART source operated with helium gas and a gas heater temperature of 350°C. Averaged and centroided mass spectra were exported for analysis with chemometric software. RESULTS: Negative-ion DART mass spectra exhibited less chemical background and more distinctive components than positive-ion DART mass spectra. An on-line search of the Yeast Metabolome Database provided candidate metabolites for selection as features for chemometric analysis. Negative-ion DART mass spectra could distinguish both species and all strains. The DART analysis was also able to identify potential metabolomic differences between top-fermenting and bottom-fermenting yeast, between beer and baking yeast, and between red wine and champagne yeast. CONCLUSIONS: All strains could be distinguished by their negative-ion DART mass spectra with 97.7% validation accuracy. Clear differences were observed between dry and liquid forms and Saccharomyces strains with different applications to baking or beverage fermentation. Possible differences in metabolite profiles were suggested, but not confirmed, by accurate mass data.

The tripartite architecture of the eukaryotic integral membrane protein zinc metalloprotease Ste24.

Ste24 enzymes, a family of eukaryotic integral membrane proteins, are zinc metalloproteases (ZMPs) originally characterized as "CAAX proteases" targeting prenylated substrates, including a-factor mating pheromone in yeast and prelamin A in humans. Recently, Ste24 was shown to also cleave nonprenylated substrates. Reduced activity of the human ortholog, HsSte24, is linked to multiple disease states (laminopathies), including progerias and lipid disorders. Ste24 possesses a unique "α-barrel" structure consisting of seven transmembrane (TM) α-helices encircling a large intramembranous cavity (~14 000 Å3 ). The catalytic zinc, coordinated via a HExxH…E/H motif characteristic of gluzincin ZMPs, is positioned at one of the cavity's bases. The interrelationship between Ste24 as a gluzincin, a long-studied class of soluble ZMPs, and as a novel cavity-containing integral membrane protein protease has been minimally explored to date. Informed by homology to well-characterized soluble, gluzincin ZMPs, we develop a model of Ste24 that provides a conceptual framework for this enzyme family, suitable for development and interpretation of structure/function studies. The model consists of an interfacial, zinc-containing "ZMP Core" module surrounded by a "ZMP Accessory" module, both capped by a TM helical "α-barrel" module of as yet unknown function. Multiple sequence alignment of 58 Ste24 orthologs revealed 38 absolutely conserved residues, apportioned unequally among the ZMP Core (18), ZMP Accessory (13), and α-barrel (7) modules. This Tripartite Architecture representation of Ste24 provides a unified image of this enzyme family.

Administration of dietary prebiotics improves growth performance and reduces pathogen colonization in broiler chickens.

Dietary prebiotics are thought to be potentially important alternatives to antibiotic growth promoters in poultry production because of their beneficial performance and health effects. The administration of dietary prebiotics has been demonstrated to improve animal health, growth performance, and microbial food safety in poultry production. In this study, we evaluated the effects of Saccharomyces-derived prebiotic refined functional carbohydrates (RFC) with yeast culture on growth performance and gastrointestinal and environmental microbiota when administered in-feed and through drinking water to broiler chickens. Broilers were administered 2 doses of prebiotic in-feed through 42 d of production and prebiotic-treated water in the final 72 h. Administration of prebiotic RFC improved ADG and decreased cecal Campylobacter counts, while the high dose also increased final BW. Additionally, significant main effects of prebiotic RFC dose were observed with the high dose improving ADG and ADFI over the finisher phase and final BW. Although the effects were not significant, the prevalence of Campylobacter in the cecum after feed withdrawal was 17% lower when broilers were administered the high prebiotic dose, and recovery of Campylobacter from litter was up to 50% lower when broilers were administered prebiotic RFC. Our results suggest that co-administration of RFC with yeast culture as a prebiotic can be used to improve growth performance and reduce human foodborne pathogens in poultry.

Toward a rapid method for the study of biodiversity in cold environments: the characterization of psychrophilic yeasts by MALDI-TOF mass spectrometry.

To investigate the potential of matrix-assisted laser desorption ionization mass spectrometry (MALDI-TOF/MS) as a platform to support biodiversity and phylogenetic studies of psychrophilic yeasts in cold environments, the technique was employed to rapidly characterize and distinguish three psychrophilic yeasts (Rhodotorula mucilaginosa, Naganishia vishniacii, and Dioszegia cryoxerica) from three mesophilic counterparts (Saccharomyces cerevisiae Cry Havoc, S. cerevisiae California V Ale, and S. pastorianus). A detailed workflow for providing reproducible mass spectral fingerprints of low molecular weight protein/peptide features specific to the organisms studied is presented. The potential of this approach as a tool in the study of biodiversity, systematics, and phylogeny of psychrophilic microorganisms is highlighted.

Production of a novel killer toxin from Saccharomyces eubayanus using agro-industrial waste and its application against wine spoilage yeasts.

The juicing industry generates large amounts of waste that mostly lack commercial value and, in the absence of waste treatment policies, produces environmental pollution. Also, microbiological spoilage is a major concern in the wine industry and control tools are limited. Taking these challenges into account, agro-industrial waste coming from ultrafiltrated apple and pear juice were used to grow Saccharomyces eubayanus and to produce its killer toxin (SeKT). A Plackett-Burman screening was performed in order to optimize SeKT production in ultrafiltrated apple and pear juice. The optimized medium was characterized: 75% v/v WUJ, 0.5% m/v KH2PO4, 0.5% m/v MgSO4, 0.5% m/v (NH4)SO4, 0.5% g/L urea, 10% v/v glycerol and 0.1% v/v Triton X-100. SeKT produced in WUJ optimised medium was used to perform killer assays against wine spoilage yeasts and showed antagonistic activity against Brettanomyces bruxellensis, Pichia guilliermondii, Pichia manshurica and Pichia membranifaciens. Different inhibition percentages against spoilage species in a wine environment (49-69%) were detected and preserved for at least 48 h. For the first time, this work reports the ability of S. eubayanus to produce a killer toxin with potential use as a biocontrol tool in winemaking. Producing SeKT using agro-industrial waste as an alternative medium to cultivate S. eubayanus would have industrial, economic and ecological benefits.

A highly stable laccase obtained by swapping the second cupredoxin domain.

The robustness of a high-redox potential laccase has been enhanced by swapping its second cupredoxin domain with that from another fungal laccase, which introduced a pool of neutral mutations in the protein sequence without affecting enzyme functionality. The new laccase showed outstanding stability to temperature, pH (2-9) and to organic solvents, while maintaining the ability to oxidize high-redox potential substrates. By engineering the signal peptide, enzyme secretion levels in Saccharomyces cerevisiae were increased, which allowed to purify the engineered enzyme for further characterization. The purified domain-swap laccase presented higher activity in the presence of ethanol or methanol, superior half-lives at 50-70 °C, improved stability at acidic pH, and similar catalytic efficiency for DMP albeit a lower one for ABTS (due to a shift in optimum pH). A new N-glycosylation site and a putative new surface salt-bridge were evaluated as possible determinants for the improved stability by site-directed mutagenesis. Although neither seemed to be strictly responsible for the improved thermostability, the new salt bridge was found to notably contribute to the high stability of the swapped enzyme in a broad pH range. Finally, the application potential of the new laccase was demonstrated with the enzymatic treatment of kraft lignin, an industrially relevant lignin stream, at high temperature, neutral pH and short incubation times.

Measuring interactions between yeast cells and a micro-sized air bubble via atomic force microscopy.

A method for the determination of interactions between yeast cells and air bubbles using the atomic force microscope was developed, in which a bubble acts as probe on immobilised living cells. The experimental setup and influencing parameters like bubble size, dwell time and maximum contact force on force-distance curves and maximum adhesion forces are explained. Also, interactions between bubble and yeast cells under variation of pH, ethanol concentration, salt concentration, ionic strength and influence of storage time in Yeast Malt Broth and phosphate buffered saline are investigated and discussed.

Comparison of integrated sustainable biodiesel and antibacterial nano silver production by microalgal and yeast isolates.

Microalgal isolates (Chlorella sp. and Spirulina sp.) and yeast isolates (Candida albicans and Saccharomyces sp.) were employed as the resources of biodiesel production and silver nanoparticle synthesis. The prominent peaks of the FTIR spectrum accustomed the efficient lipid property. The developed profile containing fatty acid methyl ester (FAME) displayed the elevated amount of both saturated (C15:0, C17:0, C21:0) and unsaturated (C17:1, C18:2, C20:4) fatty acids. The physicochemical properties analyzed by using Biodiesel analyzer V1.1.software, confirmed the competency of the isolates for sustainable biodiesel production. Biosynthesis of silvernanoparticles (AgNPs) were accomplished extracellularly by using supernatant of microalgal and yeast culture. The maximum absorbance at 420 and 421 nm under UV-visible spectra showed the presence of nanoparticles. The purity of the synthesized AgNPs were analyzed by XRD analysis. The elemental silver presence was affirmed by EDAX, SEM and AFM, the results revealed spherical crystalline shaped nanoparticles of size ranging from 2.0 to 7.3 nm. The antimicrobial efficacy of the silver nanoparticles (AgNPs) against various clinical pathogens which includes Bacillus sp., E. coli, Klebsiella sp., Proteus sp. and Staphylococcus aureus were observed. However, enhanced antimicrobial activity was displayed by the AgNPs, produced by Candida albicans (12 mm) against Bacillus sp., and E.coli, the nanoparticle produced by Chlorella sp. showed the least antagonistic activity (07 mm).

Enantiomeric separation of triacylglycerols containing very long chain fatty acids.

Enantiomers of triacylglycerols (TAGs) containing any combination of very long chain fatty acids (VLCFAs) and/or very long chain polyunsaturated fatty acids (VLCPUFAs) with diolein, dilinolein and didocosahexaenoin were synthesized. Gradient non-aqueous reversed-phase high-performance liquid chromatography/high resolution atmospheric pressure chemical ionization-tandem mass spectrometry (NARP-HPLC/HRMS2-APCI) and chiral liquid chromatography were used for the separation and identification of molecular species of these TAGs. Further, NARP-LC and chiral LC were used to separate natural mixtures of TAGs obtained from four natural sources, i.e. ximenia oil (Ximenia americana), green alga (Botryococcus braunii), brewers yeast (Saccharomyces pastorianus) and a dinoflagellate (Amphidinium carterae). The ratio of regioisomers and enantiomers in individual samples was determined and a hypothesis has been confirmed on the biosynthetic pathway of natural TAGs, which is based on the preferential representation of VLCFAs and VLCPUFAs in the sn-1 position of the glycerol backbone.

Bioprospecting microbes for single-cell oil production from starchy wastes.

Production of lipid from oleaginous yeast using starch as a carbon source is not a common practice; therefore, the purpose of this investigation was to explore the capability of starch assimilating microbes to produce oil, which was determined in terms of biomass weight, productivity, and lipid yield. Saccharomyces pastorianus, Rhodotorula mucilaginosa, Rhodotorula glutinis, and fungal isolate Ganoderma wiiroense were screened for the key parameters. The optimization was also performed by one-factor-at-a-time approach. Considering the specific yield of lipid and cell dry weight yield, R. glutinis and R. mucilaginosa showed superiority over other strains. G. wiiroense, a new isolate, would also be a promising strain for starch waste utilization in terms of extracellular and intracellular specific yield of lipids. Extracellular specific yield of lipid was highest in R. glutinis culture (0.025 g g-1 of biomass) followed by R. mucilaginosa (0.022 g g-1 of biomass) and G. wiiroense (0.020 g g-1 of biomass). Intracellular lipid was again highest in R. glutinis (0.048 g g-1 of biomass). The most prominent fatty acid methyl esters among the lipid as detected by GC-MS were saturated lipids mainly octadecanoic acid, tetradecanoate, and hexadecanoate. Extracellular lipid produced on starch substrate waste would be a cost-effective alternative for energy-intensive extraction process in biodiesel industry.

Biosorption of Cd(II) and Cs(I) from aqueous solution by live and dead cells of Saccharomyces carlsbergensis PTCC 5051.

The biosorption characteristics of Cd(II) and Cs(I) using live and dead cells of Saccharomyces carlsbergensis PTCC 5051 as biosorbents have been investigated in the present research. The influence of different experimental parameters such as initial pH (pHi), shaking rate, sorption time and initial metal concentration was evaluated. The optimum pH was obtained as 4 for Cd(II) and 7 for Cs(I). The experimental adsorption data were fitted to the Langmuir linear equation adsorption model. The highest metal uptake values of 0.593 and 0.473 mmol g-1 were calculated for Cd(II) and Cs(I), respectively. The results of Fourier transform infrared analysis suggested the involvement of amine, carboxyl and hydroxyl groups during the biosorption process and also indicated that more functional groups were involved in the biosorption process of live adsorbents, compared with those linked to dead biomass. The results showed that the biomass of S. carlsbergensis PTCC 5051 is a suitable biosorbent for the removal of Cd(II) and Cs(I) from the aqueous solutions.

Crystal structure of Mdm12 and combinatorial reconstitution of Mdm12/Mmm1 ERMES complexes for structural studies.

Membrane contact sites between organelles serve as molecular hubs for the exchange of metabolites and signals. In yeast, the Endoplasmic Reticulum - Mitochondrion Encounter Structure (ERMES) tethers these two organelles likely to facilitate the non-vesicular exchange of essential phospholipids. Present in Fungi and Amoebas but not in Metazoans, ERMES is composed of five distinct subunits; among those, Mdm12, Mmm1 and Mdm34 each contain an SMP domain functioning as a lipid transfer module. We previously showed that the SMP domains of Mdm12 and Mmm1 form a hetero-tetramer. Here we describe our strategy to diversify the number of Mdm12/Mmm1 complexes suited for structural studies. We use sequence analysis of orthologues combined to protein engineering of disordered regions to guide the design of protein constructs and expand the repertoire of Mdm12/Mmm1 complexes more likely to crystallize. Using this combinatorial approach we report crystals of Mdm12/Mmm1 ERMES complexes currently diffracting to 4.5 Å resolution and a new structure of Mdm12 solved at 4.1 Å resolution. Our structure reveals a monomeric form of Mdm12 with a conformationally dynamic N-terminal ß-strand; it differs from a previously reported homodimeric structure where the N-terminal ß strands where swapped to promote dimerization. Based on our electron microscopy data, we propose a refined pseudo-atomic model of the Mdm12/Mmm1 complex that agrees with our crystallographic and small-angle X-ray scattering (SAXS) solution data.

Inheritance of brewing-relevant phenotypes in constructed Saccharomyces cerevisiae × Saccharomyces eubayanus hybrids.

BACKGROUND: Interspecific hybridization has proven to be a potentially valuable technique for generating de novo lager yeast strains that possess diverse and improved traits compared to their parent strains. To further enhance the value of hybridization for strain development, it would be desirable to combine phenotypic traits from more than two parent strains, as well as remove unwanted traits from hybrids. One such trait, that has limited the industrial use of de novo lager yeast hybrids, is their inherent tendency to produce phenolic off-flavours; an undesirable trait inherited from the Saccharomyces eubayanus parent. Trait removal and the addition of traits from a third strain could be achieved through sporulation and meiotic recombination or further mating. However, interspecies hybrids tend to be sterile, which impedes this opportunity. RESULTS: Here we generated a set of five hybrids from three different parent strains, two of which contained DNA from all three parent strains. These hybrids were constructed with fertile allotetraploid intermediates, which were capable of efficient sporulation. We used these eight brewing strains to examine two brewing-relevant phenotypes: stress tolerance and phenolic off-flavour formation. Lipidomics and multivariate analysis revealed links between several lipid species and the ability to ferment in low temperatures and high ethanol concentrations. Unsaturated fatty acids, such as oleic acid, and ergosterol were shown to positively influence growth at high ethanol concentrations. The ability to produce phenolic off-flavours was also successfully removed from one of the hybrids, Hybrid T2, through meiotic segregation. The potential application of these strains in industrial fermentations was demonstrated in wort fermentations, which revealed that the meiotic segregant Hybrid T2 not only didn't produce any phenolic off-flavours, but also reached the highest ethanol concentration and consumed the most maltotriose. CONCLUSIONS: Our study demonstrates the possibility of constructing complex yeast hybrids that possess traits that are relevant to industrial lager beer fermentation and that are derived from several parent strains. Yeast lipid composition was also shown to have a central role in determining ethanol and cold tolerance in brewing strains.

iTRAQ-based proteome profiling of Saccharomyces cerevisiae and cryotolerant species Saccharomyces uvarum and Saccharomyces kudriavzevii during low-temperature wine fermentation.

UNLABELLED: Temperature is one of the most important parameters to affect the duration and rate of alcoholic fermentation and final wine quality. Some species of the Saccharomyces genus have shown better adaptation at low temperature than Saccharomyces cerevisiae, which was the case of cryotolerant yeasts Saccharomyces uvarum and Saccharomyces kudriavzevii. In an attempt to detect inter-specific metabolic differences, we characterized the proteomic landscape of these cryotolerant species grown at 12°C and 28°C, which we compared with the proteome of S. cerevisiae (poorly adapted at low temperature). Our results showed that the main differences among the proteomic profiling of the three Saccharomyces strains grown at 12°C and 28°C lay in translation, glycolysis and amino acid metabolism. Our data corroborate previous transcriptomic results, which suggest that S. kudriavzevii is better adapted to grow at low temperature as a result of enhanced more efficient translation. Fitter amino acid biosynthetic pathways can also be mechanisms that better explain biomass yield in cryotolerant strains. Yet even at low temperature, S. cerevisiae is the most fermentative competitive species. A higher concentration of glycolytic and alcoholic fermentation enzymes in the S. cerevisiae strain might explain such greater fermentation activity. BIOLOGICAL SIGNIFICANCE: Temperature is one of the main relevant environmental variables that microorganisms have to cope with and it is also a key factor in some industrial processes that involve microorganisms. However, we are still far from understanding the molecular and physiological mechanisms of adaptation at low temperatures. The results obtained in this study provided a global atlas of the proteome changes triggered by temperature in three different species of the genus Saccharomyces with different degree of cryotolerance. These results would facilitate a better understanding of mechanisms for how yeast could adapt at the low temperature of growth.

Rapid sensory-directed methodology for the selection of high-quality aroma wines.

BACKGROUND: The present work contributes by developing a rapid sensory-directed methodology for the screening and selection of high-quality wines with different sensory profiles. Verdejo and Tempranillo musts were fermented with 50 different yeasts each under controlled laboratory conditions. Resulting samples were firstly categorised according to five levels of quality by a panel of wine professionals. Higher quality samples were described by flash profiling by a semi-trained panel and most distinctive samples were screened by gas chromatography-olfactometry (GC-O). RESULTS: Seven Verdejo and five Tempranillo samples were classified in the highest quality category, presenting different aroma profiles such as citrus, fruit in syrup, boxtree/vegetal, tropical or wet grain aromas for Verdejo and red fruit or fruit in syrup for Tempranillo. ß-Damascenone, 3-mercaptohexyl acetate and ethyl butyrate appeared as distinctive quality compounds linked to dried, tropical and red fruit aromas, respectively. CONCLUSIONS: The categorisation task followed by flash profiling and GC-O analysis was shown to be a rapid and effective sensory-directed methodology for the screening of distinctive and quality wine aroma profiles in a case study of yeast selection. The wine industry could benefit from the use of this methodology as a complementary tool for optimising different technical processes. © 2016 Society of Chemical Industry.

A multivariate approach using attenuated total reflectance mid-infrared spectroscopy to measure the surface mannoproteins and ß-glucans of yeast cell walls during wine fermentations.

Yeast cells possess a cell wall comprising primarily glycoproteins, mannans, and glucan polymers. Several yeast phenotypes relevant for fermentation, wine processing, and wine quality are correlated with cell wall properties. To investigate the effect of wine fermentation on cell wall composition, a study was performed using mid-infrared (MIR) spectroscopy coupled with multivariate methods (i.e., PCA and OPLS-DA). A total of 40 yeast strains were evaluated, including Saccharomyces strains (laboratory and industrial) and non-Saccharomyces species. Cells were fermented in both synthetic MS300 and Chardonnay grape must to stationery phase, processed, and scanned in the MIR spectrum. PCA of the fingerprint spectral region showed distinct separation of Saccharomyces strains from non-Saccharomyces species; furthermore, industrial wine yeast strains separated from laboratory strains. PCA loading plots and the use of OPLS-DA to the data sets suggested that industrial strains were enriched with cell wall proteins (e.g., mannoproteins), whereas laboratory strains were composed mainly of mannan and glucan polymers.

Oral Intake of Carboxymethyl-Glucan (CM-G) from Yeast (Saccharomyces uvarum) Reduces Malondialdehyde Levels in Healthy Men.

Carboxymethyl-glucan (CM-G) is a water-soluble derivative of ß(1 → 3)(1 → 6) glucan, a well-known immunostimulant and antioxidant compound. In this experimental, randomized and placebo-controlled study, the effects of oral CM-G intake over a 60-day period on the peripheral blood, cholesterol, glycemic index and malondialdehyde (MDA) levels of healthy men was assessed. The CM-G was obtained from spent brewer's yeast (S. uvarum) with DS 0.8 and molecular weight of 2.2 × 10(5) Da. Following CM-G administration, no changes were observed in red and white blood cell, hematocrit, hemoglobin and platelet counts, or in cholesterol and glycemic indices. After 30 days of CM-G administration, the MDA levels decreased significantly (p ≤ 0.05) in men receiving CM-G. The results showed for the first time that CM-G may act as an adjuvant in preventing oxidative damage in healthy humans.