Yeast Saccharomyces Cerevisiae Research Articles

Reduction of Ferric Chloride in Yeast Growth Media, by Sugars and Aluminum

Iron compounds can be used in antimicrobial applications by exploiting the toxicity of divalent iron to living organisms due to the Fenton reaction. In this study, the growth inhibitory effects of ferrous sulfate FeSO4·7H2O and ferric chloride FeCl3·6H2O were observed on Metschnikowia clade and Saccharomyces cerevisiae yeast cells. The relatively high amount of reduced Fe3+ to Fe2+ in the growth medium determined by Mössbauer spectroscopy may contribute to the antimicrobial activity of ferric chloride. In order to test the reducing ability of sugars in the growth media of yeasts, the reaction of ferric chloride FeCl3·6H2O with sugars was investigated. In mixtures of FeCl3·6H2O and fructose, approximately two thirds of Fe3+ can be reduced to Fe2+. When the mixture of FeCl3·6H2O and fructose is placed on the surface of aluminum foil, an iron film is formed on the surface of the aluminum due to the reduction by both fructose and aluminum. The relative amount of Fe3+ which was reduced to Fe0 reached 68%.

Targeted Formation of Biofilms on the Surface of Graphite Electrodes as an Effective Approach to the Development of Biosensors for Early Warning Systems

Biofilms based on bacteria Pseudomonas veronii (Ps. veronii) and Escherichia coli (E. coli) and yeast Saccharomyces cerevisiae (S. cerevisiae) were used for novel biosensor creation for rapid biochemical oxygen demand (BOD) monitoring. Based on the electrochemical measurement results, it was shown that the endogenous mediator in the matrix of E. coli and Ps. veronii biofilms and ferrocene form a two-mediator system that improves electron transport in the system. Biofilms based on Ps. veronii and E. coli had a high biotechnological potential for BOD assessment; bioreceptors based on such biofilms had high sensitivity (the lower limits of detectable BOD5 concentrations were 0.61 (Ps. veronii) and 0.87 (E. coli) mg/dm3) and high efficiency of analysis (a measurement time 5–10 min). The maximum biosensor response based on bacterial biofilms has been observed in the pH range of 6.6–7.2. The greatest protective effect was found for biofilms based on E. coli, which has high long-term stability (151 days for Ps. veronii and 163 days for E. coli). The results of the BOD5 analysis of water samples obtained using the developed biosensors had a high correlation with the results of the standard 5-day method (R2 = 0.9820, number of tested samples is 10 for Ps. veronii, and R2 = 0.9862, number of tested samples is 10 for E. coli). Thus, biosensors based on Ps. veronii biofilms and E. coli biofilms could be a novel analytical system to give early warnings of pollution.

Screening and In Silico Analyses of the Yeast Saccharomyces cerevisiae Σ1278b Bank Mutants Using Citral as a Natural Antimicrobial

The antimicrobial function of citral, one of the main compounds of the essential oils (EO) of the Citrus genus, and widely used by the food industry toward spoilage yeast, was previously proven. In this study, the possible mode of action of citral against yeast cells was evaluated by using a global deletome approach. Firstly, the suitability of Saccharomyces cerevisiae Σ1278b to serve as model yeast was assessed by determining its sensitivity to citral (MIC = 0.5 μL/mL). Subsequently, the complete library of Σ1278b haploid mutants deleted in 4019 non-essential genes was screened to identify potential molecular targets of citral. Finally, the deleted genes in the 590 mutants showing increased citral resistance was analyzed with an in-silico approach (Gene Ontology). The significantly enriched GO Terms were “cytoplasm”, “vacuole”, and “mitochondrion” (cellular components); “catalytic activity” (molecular function); “pseudohyphal growth” (biological process). For molecular function, resistant mutants were grouped into thiosulfate sulfur transferase activity, transferase activity, and oxidoreductase activity; for cellular components, resistant mutants were grouped as: cytoplasm, intracellular organelle, membrane-bounded organelle, mitochondrion, organelle membrane, and vacuole; and finally, with regard to biological process, deleted genes were grouped as: pseudohyphal growth, mitochondrion organization, lipid metabolic process, DNA recombination and repair, and proteolysis. Interestingly, many identified genes were associated with the cellular response to oxidative stress and ROS scavenging. These findings have important implications for the development of citral-based antimicrobials and the elucidation of its mechanism of action.

Large enrichments in fatty acid 2H/1H ratios distinguish respiration from aerobic fermentation in yeast Saccharomyces cerevisiae

Shifts in the hydrogen stable isotopic composition (2H/1H ratio) of lipids relative to water (lipid/water 2H-fractionation) at natural abundances reflect different sources of the central cellular reductant, NADPH, in bacteria. Here, we demonstrate that lipid/water 2H-fractionation (2εfattyacid/water) can also constrain the relative importance of key NADPH pathways in eukaryotes. We used the metabolically flexible yeast Saccharomyces cerevisiae, a microbial model for respiratory and fermentative metabolism in industry and medicine, to investigate 2εfattyacid/water. In chemostats, fatty acids from glycerol-respiring cells were >550‰ 2H-enriched compared to those from cells aerobically fermenting sugars via overflow metabolism, a hallmark feature in cancer. Faster growth decreased 2H/1H ratios, particularly in glycerol-respiring cells by 200‰. Variations in the activities and kinetic isotope effects among NADP+-reducing enzymes indicate cytosolic NADPH supply as the primary control on 2εfattyacid/water. Contributions of cytosolic isocitrate dehydrogenase (cIDH) to NAPDH production drive large 2H-enrichments with substrate metabolism (cIDH is absent during fermentation but contributes up to 20 percent NAPDH during respiration) and slower growth on glycerol (11 percent more NADPH from cIDH). Shifts in NADPH demand associated with cellular lipid abundance explain smaller 2εfattyacid/water variations (<30‰) with growth rate during fermentation. Consistent with these results, tests of murine liver cells had 2H-enriched lipids from slower-growing, healthy respiring cells relative to fast-growing, fermenting hepatocellular carcinoma. Our findings point to the broad potential of lipid 2H/1H ratios as a passive natural tracker of eukaryotic metabolism with applications to distinguish health and disease, complementing studies that rely on complex isotope-tracer addition methods.

Effects of Mango Pectin Concentration on the Calcium Pectate Bead Properties and on the Cell Leakage of Yeast (Saccharomyces cerevisiae) Immobilized by Entrapment Technique

Immobilized yeast cells have advantages for use in industries due to their stability, viability, and productivity. As a support material, pectin is suitable because of its stability, strong mechanical attributes, and favorable absorption properties. In this study, the influence of mango pectin concentration on the CP bead characteristics and the leakage of immobilized yeast cells were determined. Results have indicated that yeast cells can be immobilized using low-methoxyl pectin (LMP) from mango peels via entrapment technique. Pectin concentration did not affect the size (3.0323 to 3.4315 mm) of the CP beads. Only 5% and 7% (w/v) pectin concentrations produced spherical beads (SF&lt;0.05). Increasing the pectin concentration from 3% to 7% (w/v) resulted in a 36.21% decrease in swelling ratio for CP beads with yeast. The pectin concentration significantly affects the cell leakage (p-value&lt;0.05). The results further indicate the feasibility of using locally available materials as a matrix for immobilization.

Species-wide quantitative transcriptomes and proteomes reveal distinct genetic control of gene expression variation in yeast

Gene expression varies between individuals and corresponds to a key step linking genotypes to phenotypes. However, our knowledge regarding the species-wide genetic control of protein abundance, including its dependency on transcript levels, is very limited. Here, we have determined quantitative proteomes of a large population of 942 diverse natural Saccharomyces cerevisiae yeast isolates. We found that mRNA and protein abundances are weakly correlated at the population gene level. While the protein coexpression network recapitulates major biological functions, differential expression patterns reveal proteomic signatures related to specific populations. Comprehensive genetic association analyses highlight that genetic variants associated with variation in protein (pQTL) and transcript (eQTL) levels poorly overlap (3%). Our results demonstrate that transcriptome and proteome are governed by distinct genetic bases, likely explained by protein turnover. It also highlights the importance of integrating these different levels of gene expression to better understand the genotype-phenotype relationship.

Modification of the endoplasmic reticulum morphology enables improved recombinant antibody expression in Saccharomyces cerevisiae

The yeast Saccharomyces cerevisiae is a versatile cell factory used for manufacturing of a wide range of products, among them recombinant proteins. Protein folding is one of the rate-limiting processes and this shortcoming is often overcome by the expression of folding catalysts and chaperones in the endoplasmic reticulum (ER). In this work, we aimed to establish the impact of ER structure on cellular productivity. The reticulon proteins Rtn1p and Rtn2p, and Yop1p are membrane curvature inducing proteins that define the morphology of the ER and depletion of these proteins creates yeast cells with a higher ER sheet-to-tubule ratio. We created yeast strains with different combinations of deletions of Rtn1p, Rtn2p, and Yop1p coding genes in cells with a normal or expanded ER lumen. We identified strains that reached up to 2.2-fold higher antibody titres compared to the control strain. The expanded ER membrane reached by deletion of the lipid biosynthesis repressor OPI1 was essential for the increased productivity. The improved specific productivity was accompanied by an up to 2-fold enlarged ER surface area and a 1.5-fold increased cross-sectional cell area. Furthermore, the strains with enlarged ER displayed an attenuated unfolded protein response. These results underline the impact that ER structures have on productivity and support the notion that reprogramming subcellular structures belongs into the toolbox of synthetic biology.

Metabolomics combined with chemometric analysis to identify α-glucosidase inhibitors in Phaleria macrocarpa fruit extracts and its molecular docking simulation

Phaleria macrocarpa is a medicinal plant widely available in Malaysia. The plant parts have been traditionally used as an antidiabetic remedy. This study aimed to identify the putative inhibitors of the α-glucosidase enzyme from P. macrocarpa using a gas chromatography-mass spectrometry (GC–MS)-based metabolomics approach and further subjected them to in silico molecular docking analysis to elucidate the possible mechanism of action. This study assessed the inhibitory potential of P. macrocarpa fruit extracts (aqueous, 20 %, 40 %, 60 %, 80 %, and 100 % ethanol) against the α-glucosidase enzyme using GC–MS and chemometric analysis. Orthogonal partial least squares (OPLS) combined with GC–MS analysis were applied to correlate the inhibition of enzyme activity to the metabolites profile of P. macrocarpa. All the potential inhibitors identified were further docked to the yeast (Saccharomyces cerevisiae) protein crystal structure (PDB3A4A). The generated score scatter plot of OPLS showed a recognizable separation of all the extracts into six different clusters. GC–MS, incorporated with multivariate data analysis techniques, was used to identify significant chemical markers. Methyl α-d-glucopyranoside, squalene, palmitic acid, myo-inositol and isoquinoline metabolites were identified as putative inhibitors against α-glucosidase activity from P. macrocarpa. In conclusion, the GC–MS-based metabolomics approach identified potential chemical markers of P. macrocarpa that could be utilized in the development of herbal based medicine.

Production of liquid organic fertilizer using residual yeast (Saccharomycescerevisiae) from the brewing process

The goal of the researchwas to re-evaluate the yeast (Saccharomyces cerevisiae) from the brewing process to obtain liquid organic fertilizer. The experiment was conductedin two stages: in the field by collecting raw material; and,in the laboratory by determining the moisture percentage and the microbiological, physicochemical, and agronomic analyses. A complete randomized design (CRD) with a 4x4 factorial arrangement withthree replications wasperformed. The yeast characterization was pH: 6.52, EC: 3.60 dS/m;relative RH: 84.94%;and,organic matter in solution: 66.64%; while, the liquid organic fertilizer characterization was pH: 3.96;EC: 21.40 dS/m;total solids: 183.30 g/L;and,organic matter in solution: 146.40 g/L.Lactic acid fermentation carried out by lactic acid bacteria of the microbial consortium (B-lac) is an option for producing liquid organic fertilizer using residual yeast from the brewing process. Through yeast characterization, it was shownthat the concentration of organic matter, macronutrient and micronutrient content of the residual yeast is high in certain elements, such as nitrogen (9681 mg/L), phosphorus (2203.70 mg/L), and potassium (3850 mg/L), resulting in a product of agronomic quality.

Grain by-products and Saccharomyces cerevisiae application in paper packaging material: impact on physical–mechanical and barrier properties

AbstractRenewable materials and material circularity are key priorities for the coming decades. While paper is the most utilized material in the packaging sector, its applications in food packaging are limited due to low barrier properties. Coating it with petroleum-based polymer barrier coatings renders it unrecyclable both mechanically and biologically. Bio-coated paper packaging, made from agricultural waste or by-products, presents environmentally favorable solutions that can benefit the biological cycle of the circular economy. The main objective of this study is to assess the applicability of grain and beer production by-products in wood pulp food packaging materials. It examines the effects of different grain by-products (industrial wheat grain processing residues and wheat bran) particles and concentrations (15 wt% and 40 wt%), as well as the impact of brewer’s yeast (Saccharomyces cerevisiae) at a concentration of 10 wt%, on the physical–mechanical and barrier properties of Northern bleached softwood kraft (NBSK) and chemithermomechanical (CTMP) pulps. Material composites were fabricated using a standard sheet forming method. Physical–mechanical properties were analyzed through tensile strength, strain at break, tear resistance, and bending stiffness tests. Barrier-related properties were analyzed through roughness, air permeance, and water contact angle tests. Results revealed that the vast majority of physical–mechanical properties decreased with the increase of both types of grain production fillers. Industrial wheat grain processing residues had a lower impact on physical–mechanical properties than wheat bran filler. A higher percentage of property decrease was absorbed in NBSK pulp than in CTMP. Roughness of CTMP can be improved by adding both industrial wheat grain processing residues and wheat bran. Wheat bran particles can increase hydrophobicity. CTMP pulp strength properties can be increased with the addition of yeast; however, the yeast additive’s effect on air permeance demonstrated a negative impact. In the case of NBSK pulp, which has higher primary strength properties, the addition of yeast does not make any significant changes. The conducted experiments demonstrated that, overall, the addition of these fillers resulted in a decline in physical–mechanical properties such as tensile strength, strain at break, tear resistance, and bending stiffness. This decline was more pronounced with higher concentrations of fillers. In the case of CTMP pulp, both types of fillers exhibited similar trends in affecting properties, whereas for NBSK pulp, wheat bran had a more significant impact compared to wheat grain processing residues. The addition of yeast generally led to a reduction in physical–mechanical properties, particularly in tensile strength and tear resistance. However, samples containing yeast displayed increased flexibility compared to controls. The influence on barrier properties varied: while yeast increased air permeability, it also enhanced surface hydrophobicity, thereby reducing the paper’s receptivity to liquids.

Investigation of metabolic processes of alcohol yeast during the fermentation of buckwheat-corn wort

To expand the range of competitive alcoholic beverages with original organoleptic properties, it is promising to study the use of new types of plant raw materials in grain distillate technologies. The purpose of this work was to establish the influence of the characteristics of the composition of grain wort prepared with the joint use of an alternative raw material source — buck- wheat and corn, which is widely used in alcohol production, on the metabolic processes of the yeast Saccharomyces cerevisiae 985-T and alcoholic fermentation. The objects of the study were buckwheat and corn; enzyme preparations — sources of amylases, xylanases, β-glucanases and proteases; samples of grain wort, mash and mash distillates. The prospects of introducing mixed grain media prepared using non-traditional buckwheat raw materials into the technology of original alcoholic bever- ages are substantiated. It was shown that the use of buckwheat as a source of biocomplete protein, essential amino acids and minerals together with corn containing a high level of starch and a low level of non-starch polysaccharides contributed both to an increase in the yield of alcohol and a change in the quantitative content of secondary metabolites in the composition of volatile impurities. It was found that an increase in the concentration of soluble carbohydrates in the wort and a decrease in its viscosity by 15.5–40.3% occurred due to the inclusion of corn in the composition of the grain mixture, and the enrichment of the wort with nitrogen assimilated by yeast by 19.0–41.8% — as a result adding buckwheat. The optimal ratio of corn and buckwheat in the composition of the grain mixture (7:3) was selected, which made it possible to improve the biochemical and technological parameters of grain must, increase the efficiency of the vital processes of yeast and alcoholic fermentation, ensure an increase in the yield of alcohol by 1.8%, reduce the formation of side metabolites, especially higher alcohols, and change their composition in the direction of increasing the proportion of aldehydes and esters, which can have a positive effect on the organoleptic characteristics of the distillate.

Glutathionylation of a glycolytic enzyme promotes cell death and vigor loss during aging of elm seeds.

Seed deterioration during storage is a major problem in agricultural and forestry production and for germplasm conservation. Our previous studies have shown that a mitochondrial outer membrane protein VOLTAGE-DEPENDENT ANION CHANNEL (VDAC) is involved in programmed cell death (PCD)-like viability loss during the controlled deterioration treatment (CDT) of elm (Ulmus pumila L.) seeds, but its underlying mechanism remains unclear. In this study, we demonstrate that the oxidative modification of GLYCERALDEHYDE-3-PHOSPHATE DEHYDROGENASE (GAPDH) is functioned in the gate regulation of VDAC during the CDT of elm seeds. Through biochemical and cytological methods and observations of transgenic material [Arabidopsis (Arabidopsis thaliana), Nicotiana benthamiana, and yeast (Saccharomyces cerevisiae)], we demonstrate that cysteine S-glutathionylated UpGAPDH1 interacts with UpVDAC3 during seed aging, which leads to a mitochondrial permeability transition and aggravation of cell death, as indicated by the leakage of the mitochondrial pro-apoptotic factor cytochrome c and the emergence of apoptotic nucleus. Physiological assays and inductively coupled plasma mass spectrometry (ICP-MS) analysis revealed that GAPDH glutathionylation is mediated by increased glutathione, which might be caused by increases in the concentrations of free metals, especially Zn. Introduction of the Zn-specific chelator TPEN [(N, N, N', N'-Tetrakis (2-pyridylmethyl)ethylenediamine)] significantly delayed seed aging. We conclude that glutathionylated UpGAPDH1 interacts with UpVDAC3 and serves as a pro-apoptotic protein for VDAC-gating regulation and cell death initiation during seed aging.

How does active yeast supplementation reduce the deleterious effects of aflatoxins in Wistar rats? A radiolabeled assay and histopathological study

The aim of this study was to investigate the mechanisms by which yeasts (Saccharomyces cerevisiae) control the toxic effects of aflatoxins, which are not yet fully understood. Radiolabeled aflatoxin B1 (AFB13H) was administered by gavage to Wistar rats fed with aflatoxin (AflDiet) and aflatoxin supplemented with active dehydrated yeast Y904 (AflDiet + Yeast). The distribution of AFB13H and its metabolites were analyzed at 24, 48 and 72 h by tracking back of the radioactivity. No significant differences were observed between the AflDiet and AflDiet + Yeast groups in terms of the distribution of labeled aflatoxin. At 72 h, for the AflDiet group the radiolabeled aflatoxin was distributed as following: feces (79.5%), carcass (10.5%), urine (1.7%), and intestine (7.4%); in the AflDiet + Yeast the following distribution was observed: feces (76%), carcass (15%), urine (2.9%), and intestine (4.9%). These values were below 1% in other organs. These findings indicate that even after 72 h considerable amounts of aflatoxins remains in the intestines, which may play a significant role in the distribution and metabolism of aflatoxins and its metabolites over time. The presence of yeast may not significantly affect this process. Furthermore, histopathological examination of hepatic tissues showed that the presence of active yeast reduced the severity of liver damage caused by aflatoxins, indicating that yeasts control aflatoxin damage through biochemical mechanisms. These findings contribute to a better understanding of the mechanisms underlying the protective effects of yeasts against aflatoxin toxicity.Graphical abstract

Acetic Fermentation of Cagaita Pulp: Technological and Chemical Characteristics

The Brazilian Cerrado region has a rich plant diversity, with fruits that have peculiar and unique sensory characteristics. For these reasons, using these fruits for biotechnological production is a promising alternative, mainly to protect this biome from deforestation and degradation. The production of fermented acetic acid is an option to add value to native fruits and offer the market beverages with better nutritional quality and bioactive compounds. This work aimed to characterize fruits and to develop cagaita (Eugenia dysenterica DC.) acetic fermented beverage. The fruits were subjected to physical-chemical analyses in the first part. Subsequently, different treatments for fermentation were tested using two types of enzymes (amylase and pectinase), two subspecies of Saccharomyces cerevisiae yeast (UFLA CA11 and thermoresistant LNF Angel), and the chaptalization of the must with sucrose (16 °Brix). Alcoholic fermentation was carried out in an incubator with temperature control at 34 ± 1 °C. The pH, total soluble solids, titratable acidity, alcohol content, and density of the fermented products were monitored daily. The chaptalized must with amylase addition and thermoresistant yeast had the best performance during alcoholic fermentation, demonstrating that thermoresistant yeast is an economically advantageous and efficient alternative for the cagaita juice fermentation process. Subsequently, acetic fermentation was carried out using the slow method. Heat-resistant yeast without added enzymes was used to produce cagaita acetic fermented beverages within the parameters of the Brazilian legislation. Furthermore, phenolic compounds and antioxidant activity in the final product were observed. The work demonstrated the possibility of using cagaita fruits in biotechnological processes to produce new food products.

Unraveling the Anti-Aging Properties of Phycocyanin from the Cyanobacterium Spirulina (Arthrospira platensis).

In recent years, marine natural products have become one of the most important resources of novel lead compounds for critical diseases associated with age. Spirulina, a dietary supplement made from blue-green algae (cyanobacteria: scientific name Arthrospira platensis), is particularly rich in phycocyanin, a phycobiliprotein, which accounts for up to 20% of this cyanobacterium's dry weight and is considered responsible for its anti-cancer, anti-inflammatory and antioxidant activities. Although the anti-aging activity of phycocyanin has been investigated, how exactly this compound works against aging remains elusive. The aim of our research is to use the yeast Saccharomyces cerevisiae as a model organism to investigate the anti-aging properties of phycocyanin from A. platensis. Our results show that phycocyanin has a powerful anti-aging effect, greatly extending the chronological life span of yeast cells in a dose-dependent way, as the effect was also pronounced when cells were grown in SD medium under calorie restriction conditions (0.2% glucose). Both ROS and accumulation of dead cells were followed by staining chronologically aged cells with dihydrorhodamine 123 (DHR123) and propidium iodide (PI). Interestingly, we found that most of the aged phycocyanin-treated cells, which were unable to form colonies, were actually ROS+/PI-. Finally, we show that the moment in which phycocyanin is added to the culture does not substantially influence its effectiveness in counteracting chronological aging.

Regulation of translation in response to iron deficiency in human cells

Protein synthesis is a highly energy-consuming process that is downregulated in response to many environmental stresses or adverse conditions. Studies in the yeast Saccharomyces cerevisiae have shown that bulk translation is inhibited during adaptation to iron deficiency, which is consistent with its requirement for ribosome biogenesis and recycling. Although iron deficiency anemia is the most common human nutritional disorder, how iron modulates translation in mammals is poorly understood. Studies during erythropoiesis have shown that iron bioavailability is coordinated with globin synthesis via bulk translation regulation. However, little is known about the control of translation during iron limitation in other tissues. Here, we investigated how iron depletion affects protein synthesis in human osteosarcoma U-2 OS cells. By adding an extracellular iron chelator, we observed that iron deficiency limits cell proliferation, induces autophagy, and decreases the global rate of protein synthesis. Analysis of specific molecular markers indicates that the inhibition of bulk translation upon iron limitation occurs through the eukaryotic initiation factor eIF2α and mechanistic target of rapamycin (mTOR) pathways. In contrast to other environmental and nutritional stresses, iron depletion does not trigger the assembly of messenger ribonucleoprotein stress granules, which typically form upon polysome disassembly.

Improvement of cell growth in green algae Chlamydomonas reinhardtii through co-cultivation with yeast Saccharomyces cerevisiae.

CO2 fixation methods using green algae have attracted considerable attention because they can be applied for the fixation of dilute CO2 in the atmosphere. However, green algae generally exhibit low CO2 fixation efficiency under atmospheric conditions. Therefore, it is a challenge to improve the CO2 fixation efficiency of green algae under atmospheric conditions. Co-cultivation of certain microalgae with heterotrophic microorganisms can increase the growth potential of microalgae under atmospheric conditions. The objective of this study was to determine the culture conditions under which the growth potential of green algae Chlamydomonas reinhardtii is enhanced by co-culturing with the yeast Saccharomyces cerevisiae, and to identify the cause of the enhanced growth potential. When C. reinhardtii and S. cerevisiae were co-cultured with an initial green algae to yeast inoculum ratio of 1:3, the cell concentration of C. reinhardtii reached 133 × 105cells/mL on day 18 of culture, which was 1.5 times higher than that of the monoculture. Transcriptome analysis revealed that the expression levels of 363 green algae and 815 yeast genes were altered through co-cultivation. These included genes responsible for ammonium transport and CO2 enrichment mechanism in green algae and the genes responsible for glycolysis and stress responses in yeast. We successfully increased C. reinhardtiigrowth potential by co-culturing it with S. cerevisiae. The main reasons for this are likely to be an increase in inorganic nitrogen available to green algae via yeast metabolism and an increase in energy available for green algae growth instead of CO2 enrichment.

Protracted Exposure to a Sub-background Radiation Environment Negatively Impacts the Anhydrobiotic Recovery of Desiccated Yeast Sentinels.

Experiments that examine the impacts of subnatural background radiation exposure provide a unique approach to studying the biological effects of low-dose radiation. These experiments often need to be conducted in deep underground laboratories in order to filter surface-level cosmic radiation. This presents some logistical challenges in experimental design and necessitates a model organism with minimal maintenance. As such, desiccated yeast (Saccharomyces cerevisiae) is an ideal model system for these investigations. This study aimed to determine the impact of prolonged sub-background radiation exposure in anhydrobiotic (desiccated) yeast at SNOLAB in Sudbury, Ontario, Canada. Two yeast strains were used: a normal wild type and an isogenic recombinational repair-deficient rad51 knockout strain (rad51Δ). Desiccated yeast samples were stored in the normal background surface control laboratory (68.0 nGy h-1) and in the sub-background environment within SNOLAB (10.1 nGy h-1) for up to 48 wk. Post-rehydration survival, growth rate, and metabolic activity were assessed at multiple time points. Survival in the sub-background environment was significantly reduced by a factor of 1.39 and 2.67 in the wild type and rad51∆ strains, respectively. Post-rehydration metabolic activity measured via alamarBlue reduction remained unchanged in the wild type strain but was 26% lower in the sub-background rad51∆ strain. These results demonstrate that removing natural background radiation negatively impacts the survival and metabolism of desiccated yeast, highlighting the potential importance of natural radiation exposure in maintaining homeostasis of living organisms.

Synergistic Effect of a Combination of Proteasome and Ribonucleotide Reductase Inhibitors in a Biochemical Model of the Yeast Saccharomyces cerevisiae and a Glioblastoma Cell Line.

Proteasome inhibitors are used in the therapy of several cancers, and clinical trials are underway for their use in the treatment of glioblastoma (GBM). However, GBM becomes resistant to chemotherapy relatively rapidly. Recently, the overexpression of ribonucleotide reductase (RNR) genes was found to mediate therapy resistance in GBM. The use of combinations of chemotherapeutic agents is considered a promising direction in cancer therapy. The present work aimed to evaluate the efficacy of the combination of proteasome and RNR inhibitors in yeast and GBM cell models. We have shown that impaired proteasome function results in increased levels of RNR subunits and increased enzyme activity in yeast. Co-administration of the proteasome inhibitor bortezomib and the RNR inhibitor hydroxyurea was found to significantly reduce the growth rate of S. cerevisiae yeast. Accordingly, the combination of bortezomib and another RNR inhibitor gemcitabine reduced the survival of DBTRG-05MG compared to the HEK293 cell line. Thus, yeast can be used as a simple model to evaluate the efficacy of combinations of proteasome and RNR inhibitors.

Aflatoxin M1 mitigation by novel biological agents and evaluation of bioaccessibility with enzymatic digestion in milk

Aflatoxin M1 (AFM1) is a metabolite of AFB1 that is formed in the liver and excreted in the mammary glands of ruminants who fed an AFB1-contaminated feed. This study focused on the AFM1 binding ability of biological agents including lactic acid bacteria (Leuconostoc mesenteroides) and yeast (Saccharomyces cerevisiae), chitosan as a biopolymer, and inulin as a prebiotic besides their effects on the AFM1 bioaccessibility in milk. Bioaccessibility refers to the amount of a contaminant in food that can reach the systemic circulation and exert its toxic effects on the body. In vitro gastrointestinal digestion model developed by RIVM for specifically mycotoxins was employed for assessing AFM1 bioaccessibility. Moreover, the colon phase was enzymatically simulated to evaluate the state of bound and unbound AFM1 that passed from the intestine to the colon and excreted from the body. Unbound AFM1 levels were determined by high-performance liquid chromatography (HPLC). The bound AFM1 percentages after incubation varied between 26.7% and 50.9%, and the best binder was found as S. cerevisiae while chitosan showed the lowest binding level. Following in vitro digestion practice, the lowest bioaccessibility after small intestine (29.30 ± 2.29%) digestion was acquired with S. cerevisiae, however; the lowest bioaccessibility after the colon phase (51.55 ± 3.38%) was acquired with L. mesenteroides. On the other hand, L. mesenteroides and chitosan were found more stable binders through the gastrointestinal tract (GIT). The present results showed that the bound AFM1 levels in food and absorbed from the gastrointestinal tract were affected by natural binders.