Search

We traced back a nationwide outbreak of human listeriosis in Switzerland to a persisting production line contamination of a factory producing baker's yeast with Listeria monocytogenes serotype 1/2a sequence type 3141. We used whole-genome sequencing to match clinical isolates to isolates from product samples.

Punicic acid (PuA), an unusual conjugated linolenic acid found in pomegranate, offers diverse health benefits and has potential applications in the food industry. Due to the limited availability of PuA from natural plant sources, there is growing interest in producing it through microbial fermentation. In this study, the yeast Saccharomyces cerevisiae , which is classified as "generally recognized as safe", was engineered to produce PuA using a results-driven approach. Genes potentially involved in PuA synthesis were integrated directly into the yeast genome, targeting Ty retrotransposon sites. Screening of the yeast transformants, followed by optimization of culture conditions, resulted in the production of 26.7% PuA within the yeast's total fatty acids. Further analysis revealed that the strain's triacylglycerol fraction contained over 22% PuA. By incorporating this health-promoting lipid into the nutritional profile of S. cerevisiae , the engineered strain could serve as a sustainable source of yeast biomass with enhanced nutritional value.

With rapid progress in the yeast fermentation industry, a comprehensive commercial yeast quality assessment approach integrating efficiency, accuracy, sensitivity, and cost-effectiveness is required. In this study, a new yeast quality assessment method based on single-cell Raman technology was developed and contrasted with traditional methods. The findings demonstrated significant associations (Pearson correlation coefficient of 0.933 on average) between the two methods in measuring physiological indicators, including cell viability and intracellular trehalose content, demonstrating the credibility of the Raman method compared to the traditional method. Furthermore, the sensitivity of the Raman method in viable but non-culturable cells was higher in measuring yeast cell viability (17.9 % more sensitive). According to the accurate quantitative analysis of metabolic activity level (MAL) of yeast cells, the cell vitality was accurately quantified at population and single-cell levels, offering a more comprehensive assessment of yeast fermentation performance. Overall, the single-cell Raman method integrates credibility, feasibility, accuracy, and sensitivity in yeast quality assessment, offering a new technological framework for quality assessments of live-cell yeast products., Competing Interests: The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (© 2024 The Authors.)

Loss of Heterozygosity (LOH) due to mitotic recombination is frequently associated with the development of various cancers (e.g. retinoblastoma). LOH is also an important source of genetic diversity, especially in organisms where meiosis is infrequent. Irc20 is a putative helicase, and E3 ubiquitin ligase involved in DNA double-strand break repair pathway. We analyzed genome-wide LOH events, gross chromosomal changes, small insertion-deletions and single nucleotide mutations in eleven S. cerevisiae mutation accumulation lines of irc20∆, which underwent 50 mitotic bottlenecks. LOH enhancement in irc20∆ was small (1.6 fold), but statistically significant as compared to the wild type. Short (≤ 1 kb) and long (> 10 kb) LOH tracts were significantly enhanced in irc20∆. Both interstitial and terminal LOH events were also significantly enhanced in irc20∆ compared to the wild type. LOH events in irc20∆ were more telomere proximal and away from centromeres compared to the wild type. Gross chromosomal changes, single nucleotide mutations and in-dels were comparable between irc20∆ and wild type. Locus based and genome-wide analysis of meiotic recombination showed that meiotic crossover frequencies are not altered in irc20∆. These results suggest Irc20 primarily regulates mitotic recombination and does not affect meiotic crossovers. Our results suggest that the IRC20 gene is important for regulating LOH frequency and distribution., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier B.V. All rights reserved.)

One of the common causes of water pollution is the presence of toxic dye-based effluents, which can pose a serious threat to the ecosystem and human health. The application of Saccharomyces cerevisiae (S. cerevisiae) for wastewater decolorization has been widely investigated due to their efficient removal and eco-friendly treatments. This review attempts to create an awareness of different forms and methods of using Saccharomyces cerevisiae (S. cerevisiae) for wastewater decolorization through a systematic approach. Overall, some suggestions on classification of dyes and related environmental/health problems, and treatment methods are discussed. Besides, the mechanisms of dye removal by S. cerevisiae including biosorption, bioaccumulation, and biodegradation and cell immobilization methods such as adsorption, covalent binding, encapsulation, entrapment, and self-aggregation are discussed. This review would help to inspire the exploration of more creative methods for applications and modification of S. cerevisiae and its further practical applications., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Inc. All rights reserved.)

Meiotic crossovers are initiated from programmed DNA double-strand breaks. The Msh4-Msh5 heterodimer is an evolutionarily conserved mismatch repair-related protein complex that promotes meiotic crossovers by stabilizing strand invasion intermediates and joint molecule structures such as Holliday junctions. In vivo studies using homozygous strains of the baker's yeast Saccharomyces cerevisiae (SK1) show that the Msh4-Msh5 complex associates with double-strand break hotspots, chromosome axes, and centromeres. Many organisms have heterozygous genomes that can affect the stability of strand invasion intermediates through heteroduplex rejection of mismatch-containing sequences. To examine Msh4-Msh5 function in a heterozygous context, we performed chromatin immunoprecipitation and sequencing (ChIP-seq) analysis in a rapidly sporulating hybrid S. cerevisiae strain (S288c-sp/YJM789, containing sporulation-enhancing QTLs from SK1), using SNP information to distinguish reads from homologous chromosomes. Overall, Msh5 localization in this hybrid strain was similar to that determined in the homozygous strain (SK1). However, relative Msh5 levels were reduced in regions of high heterozygosity, suggesting that high mismatch densities reduce levels of recombination intermediates to which Msh4-Msh5 binds. Msh5 peaks were also wider in the hybrid background compared to the homozygous strain (SK1). We determined regions containing heteroduplex DNA by detecting chimeric sequence reads with SNPs from both parents. Msh5-bound double-strand break hotspots overlap with regions that have chimeric DNA, consistent with Msh5 binding to heteroduplex-containing recombination intermediates., Competing Interests: Conflicts of interest The authors declare no conflicts of interest., (© The Author(s) 2023. Published by Oxford University Press on behalf of The Genetics Society of America. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.)

Selective transport through the nuclear pore complex (NPC) depends on the dynamic binding of FG-repeat containing nucleoporins, the FG-nups, with each other and with Karyopherins (Kaps). Here, we assessed the specificity and mechanism by which the aliphatic alcohol 1,6-hexanediol (1,6HD) disrupts the permeability barrier of NPCs in live baker's yeast cells. After a 10-minute exposure to 5% 1,6HD, no notable changes were observed in cell growth, cytosolic pH and ATP levels, or the appearance of organelles. However, effects on the cytoskeleton and Hsp104 were noted. 1,6HD clearly affected the NPC permeability barrier, allowing passive nuclear entry of a 177kDa reporter protein that is normally confined to the cytosol. Moreover, multiple Kaps were displaced from NPCs, and the displacement of Kap122-GFP correlated with the observed passive permeability changes. 1,6HD thus temporarily permeates NPCs, and in line with Kap-centric models, the mechanism includes the release of numerous Kaps from the NPCs.

Research Background: Wine production, which is considered a major sector in food industry, often involves the use of a large amount of resources. Moreover, wine making generates a large amount of grape pomace, which is generally used for low-value applications such as fertiliser and animal feed. The aim of the present research is to explore the possibility of improving the overall sustainability of traditional winemaking., Experimental Approach: A zero-waste process was developed. It includes the production of white wine and the substantial valorisation of grape pomace, which is converted into solid biofuel, tartaric acid and concentrated grape extract as feedstock for industrial baker's yeast production., Results and Conclusions: We estimate that a significant surplus of renewable energy of approx. 3 MJ/kg processed grapes can be obtained during this conversion. The suitability of grape extract as a potential substrate for industrial baker's yeast production was evaluated and the feasibility of a partial replacement of molasses (up to 30 %) was demonstrated., Novelty and Scientific Contribution: We present a circular economy approach for the conversion of winery biowaste into high-value resources such as feedstock and solid biofuel., Competing Interests: CONFLICT OF INTEREST The authors declare that they have no conflict of interest., (Authors.)

Invertase, an industrially significant glycoenzyme, was purified from baker's yeast using poly (2-Hydroxyethyl methacrylate) [PHema-Pba] cryogels functionalized with boronic acid. At subzero temperatures, PHema-Pba cryogels were synthesized and characterized using swelling tests, scanning electron microscopy, and Fourier-transform infrared spectroscopy. The surface area of the PHema-Pba cryogels was 14 m 2 /g with a swelling ratio of 88.3% and macroporosity of 72%. The interconnected macropores of PHema-Pba cryogels were shown via scanning electron microscopy. Invertase binding capacity of PHema-Pba cryogel was evaluated by binding studies in different pH, temperature, and interaction time conditions and the maximum Invertase binding of PHema-Pba cryogel was found as 15.2 mg/g. and 23.7 fold Invertase purification was achieved from baker's yeast using PHema-Pba cryogels. The results show that PHema-Pba cryogels have high Invertase binding capacity and may be used as an alternative method for enzyme purification via boronate affinity systems., (© 2023. The Author(s), under exclusive licence to Springer Nature B.V.)

A biohybrid therapeutic system, consisting of responsive materials and living microorganisms with inter-cooperative effects, is designed and investigated for tumor treatment. In this biohybrid system, S 2 O 3 2- -intercalated CoFe layered double hydroxides (LDH) are integrated at the surface of Baker's yeasts. Under the tumor microenvironment, functional interactions between yeast and LDH are effectively triggered, resulting in S 2 O 3 2- release, H 2 S production, and in-situ generation of highly catalytic agents. Meanwhile, the degradation of LDH in the tumor microenvironment induces the exposure of the surface antigen of yeast, leading to effective immune activation at the tumor site. By virtue of the inter-cooperative phenomena, this biohybrid system exhibits significant efficacy in tumor ablation and strong inhibition of recurrence. This study has potentially offered an alternative concept by utilizing the metabolism of living microorganisms and materials in exploring effective tumor therapeutics., (© 2023 The Authors. Advanced Science published by Wiley-VCH GmbH.)

A suitable nutrient supply, especially of vitamins, is very significant for the deep display of the inherent genetic properties of microorganisms. Here, using the chemically defined minimal medium (MM) for yeast, nicotinamide and inositol were confirmed to be more beneficial for the performance of two industrial baker's yeasts, a conventional and a high-sugar-tolerant strain. Increasing nicotinamide or inositol to proper levels could enhance the both strains on cell growth and activity and product performance, including trehalose accumulation and leavening performance. The activity of key enzymes (PCK, TPS) and the content of intermediate metabolites (G6P, UDPG) in the trehalose synthesis pathway were promoted by a moderate supply of nicotinamide and inositol. That were also proved that an appropriate amount of niacinamide promoted the transcription of longevity-related genes (PNC1, SIR2), and the proper concentration of inositol altered the phospholipid composition in cells, namely, phosphatidylinositol and phosphatidyl choline. Furthermore, the cell growth and the leavening performance of the both strains were promoted after adjusting inositol to choline to the proper ratio, resulting directly in content changes of phosphatidylinositol and phosphatidyl choline in the cells. While the two strains responded to the different proper ratio of inositol to choline probably due to their specific physiological characteristics. Such beneficial effects of increased nicotinamide levels were confirmed in natural media, molasses and corn starch hydrolyzed sugar media. Meanwhile, such adjustment of inositol to choline ratio could lessen the inhibition of excess inositol on cell growth of the two tested strains in corn starch hydrolyzed sugar media. However, in molasse, such phenomenon was not observed probably since there was higher Ca 2+ in it. The results indicated that the effects of nutrient factors, such as vitamins, on cell growth and other properties found out from the simple chemically defined minimal medium were an effective measure to use in improving the recipe of natural media at least for baker's yeast., (© 2023. The Author(s).)

Background: Saccharomyces cerevisiae (S. cerevisiae) has been demonstrated in vitro to sensitize several breast cancer cell lines and to be a safe, non-toxic drug with anti-skin cancer action in mice. Furthermore, plasmonic photothermal treatment using gold nanorods has been authorized as a novel method for in vitro and in vivo cancer therapy., Results: When compared to tumor-free rats, the treatment with S. cerevisiae conjugated to gold nanospheres (GNSs) lowered Bcl-2 levels while increasing FasL, Bax, cytochrome c, and caspases 8, 9, and 3 levels. Histopathological results showed changes reflecting the ability of nanogold conjugated heat-killed yeast to induce apoptosis is greater than heat-killed yeast alone as the nanogold conjugated with heat-killed yeast showed no tumor, no hyperplasia, no granulation tissue formation, no ulceration, and no suppuration. Nanogold conjugated with heat-killed yeast-treated breast cancer group displayed normal levels of ALT and AST, indicating relatively healthy hepatic cells., Conclusion: Our results proved that nanogold conjugated heat-killed yeast can initiate apoptosis and can be used as a safe non-invasive method for breast cancer treatment more effectively than the yeast alone. This, in turn, gives us new insight and a future hope for the first time that breast cancer can be treated by non-invasive, simple, safe, and naturally originated method and achieves a hopeful treatment and a novel method for in vivo cancer therapy., (© 2023. The Author(s).)

Introduction: Bioproduction of plant-derived triterpenoids in recombinant microbes is receiving great attention to make these biologically active compounds industrially accessible as nutraceuticals, pharmaceutics, and cosmetic ingredients. So far, there is no direct method for detecting triterpenoids under physiological conditions on a cellular level, information yet highly relevant to rationalizing microbial engineering. Methods: Here, we show in a proof-of-concept study, that triterpenoids can be detected and monitored in living yeast cells by combining coherent anti-Stokes Raman scattering (CARS) and second-harmonic-generation (SHG) microscopy techniques. We applied CARS and SHG microscopy measurements, and for comparison classical Nile Red staining, on immobilized and growing triterpenoid-producing, and non-producing reference Saccharomyces cerevisiae strains. Results and Discussion: We found that the SHG signal in triterpenoid-producing strains is significantly higher than in a non-producing reference strain, correlating with lipophile content as determined by Nile red staining. In growing cultures, both CARS and SHG signals showed changes over time, enabling new insights into the dynamics of triterpenoid production and storage inside cells., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2023 Dianat, Münchberg, Blank, Freier and Ebert.)

Background: Mitochondrial respiration is central to cellular and organismal health in eukaryotes. In baker's yeast, however, respiration is dispensable under fermentation conditions. Because yeast are tolerant of this mitochondrial dysfunction, yeast are widely used by biologists as a model organism to ask a variety of questions about the integrity of mitochondrial respiration. Fortunately, baker's yeast also display a visually identifiable Petite colony phenotype that indicates when cells are incapable of respiration. Petite colonies are smaller than their Grande (wild-type) counterparts, and their frequency can be used to infer the integrity of mitochondrial respiration in populations of cells. Unfortunately, the computation of Petite colony frequencies currently relies on laborious manual colony counting methods which limit both experimental throughput and reproducibility., Results: To address these problems, we introduce a deep learning enabled tool, petiteFinder, that increases the throughput of the Petite frequency assay. This automated computer vision tool detects Grande and Petite colonies and computes Petite colony frequencies from scanned images of Petri dishes. It achieves accuracy comparable to human annotation but at up to 100 times the speed and outperforms semi-supervised Grande/Petite colony classification approaches. Combined with the detailed experimental protocols we provide, we believe this study can serve as a foundation to standardize this assay. Finally, we comment on how Petite colony detection as a computer vision problem highlights ongoing difficulties with small object detection in existing object detection architectures., Conclusion: Colony detection with petiteFinder results in high accuracy Petite and Grande detection in images in a completely automated fashion. It addresses issues in scalability and reproducibility of the Petite colony assay which currently relies on manual colony counting. By constructing this tool and providing details of experimental conditions, we hope this study will enable larger-scale experiments that rely on Petite colony frequencies to infer mitochondrial function in yeast., (© 2023. The Author(s).)

Baker's yeast industries generate highly polluted effluents, especially the cell free broth (i.e., vinasse) characterized by high chemical oxygen demand, nitrogen, and salts. In this work, it was found that the residual by-products (i.e., ethanol and acetic acid) and salts in the vinasse severely inhibited the cell growth, which hindered the reuse of the vinasse for the production of Saccharomyces cerevisiae. Through optimizing a suitable control strategy, the productions of ethanol and acetic acid were eliminated. Then, a nanofiltration membrane (i.e., NF5) was preferred for preliminarily and simultaneously separating and concentrating valuable molecules (i.e., invertase, food grade proteins and pigments) in the vinasse, and the main fouling mechanism was cake layer formation. Subsequently, a reverse osmosis membrane (RO) was suitable to separate and concentrate salts in the NF5 permeate, where the membrane fouling was negligible. Finally, the RO permeate was successfully reused for the production of S. cerevisiae. In addition, without calculating the benefit from the recovery of the valuable molecules, the cost of the integrated process can be decreased by 59.8% compared with the sole triple effect evaporation. Meanwhile, the volume of the fresh water used in the fermentation process can be decreased by 68.8%. Thus, it is a sustainable process for the cleaner production of baker's yeast using the integrated fermentation and membrane separation process., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022 Elsevier Ltd. All rights reserved.)

The study aimed to produce instant dried baker's yeast (BY) by conventional or infrared-assisted refractance window drying (RWD or InfraRWD, respectively) and compare their bakery performance with commercial BY. According to the findings of the study, the total yeast count was higher than 9.60 log cfu/g in all dried BY samples, and the lowest viability was obtained in BY dried by InfraRWD at 50°C. In general, BY produced by RWD increased the physical quality parameters of bread such as specific volume, total cell count, and the number of cell areas of bread crumbs. Moreover, bread leavened by BY dried by RWD slowed down the staling rate of bread, while infrared assistance accelerated the staling. Sensorial analysis showed that bread produced by refractance window dried BY was more acceptable than commercial BY. In a conclusion, RWD can be an effective alternative to the production of instant baker's yeast, but the most quality features of BY has negatively affected by infrared assistance. PRACTICAL APPLICATION: In the drying of baker's yeast, promising advantages can be obtained by refractance window drying. The higher specific volume and superior bread crumb with a retarded staling rate were determined when bread was produced by the refractance window. This is the first time that RWD and InfraRWD have been used for the production of instant baker's yeast and it has several practical applications for bread quality., (© 2022 Institute of Food Technologists.)

Yeasts are reported to be rich in folates, a group of vitamers known to be involved in several biosynthetic reactions such as methylation reactions, oxidation and reduction processes, and nucleotide synthesis. Not being able to synthesize folates, humans rely on external folate supply. Here, we show the application of LC/MS-MS methods using SIDA (stable isotope dilution analysis) assays for the quantitative analysis of different folate mono- and polyglutamates during growth of Saccharomyces cerevisiae . Molecular networking (MN) was applied for detailed analysis of further folate metabolites. Highest folate contents of 13,120 μg/100 g were observed after 20 h of cultivation. The main vitamers 5-CH 3 -H 4 folate and H 4 folate decreased during cultivation, while 5-CHO-H 4 folate increased during cultivation. The hexa- and heptaglutamate of 5-CH 3 -H 4 folate accounted for >96% of the total 5-CH 3 -H 4 folate content. A shift of the major polyglutamate from hexa- to heptaglutamate was observed after 29 h. MN unraveled two groups of novel folates which could be assigned to a potentially existing C 2 -metabolism in yeast. In detail, 5,10-ethenyl-tetrahydrofolate and a further CO-substituted 5-CH 3 -H 4 folate were identified as hexa- and heptaglutamates. The latter was neither identified as 5-acetyl-tetrahydrofolate nor as EthylFox, the oxidation product of 5-ethyl-tetrahydrofolate. The structure needs to be elucidated in future studies., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2022 Schillert, Wirtz, Weber, Schaller, Striegel, Schmitt-Kopplin and Rychlik.)

Aim: This study is to investigate the use of a constitutively expressed trehalose transport protein to directly control intracellular trehalose levels and protect baker's yeast (Saccharomyces cerevisiae) cells against freeze-thaw stress in vivo., Methods and Results: We used a constitutively overexpressed Agt1 transporter to investigate the role of trehalose in the freeze-thaw tolerance of yeast cells by regulating intracellular trehalose concentrations independently of intracellular biosynthesis. Using this method, we found that increasing intracellular trehalose in yeast cells improved cell survival rate after 8 days of freezing at -80 and -20°C. We also observed that freeze-thaw tolerance promoted by intracellular trehalose only occurs in highly concentrated cell pellets rather than cells in liquid suspension., Conclusions: Trehalose is sufficient to provide freeze-thaw tolerance using our Agt1 overexpression system. Freeze-thaw tolerance can be further enhanced by deletion of genes encoding intracellular trehalose degradation enzymes., Significance and Impact of Study: These findings are relevant to improving the freeze-thaw tolerance of baker's yeast in the frozen baked goods industry through engineering strains that can accumulate intracellular trehalose via a constitutively expressed trehalose transporter and inclusion of trehalose into the growth medium., (© 2022 Society for Applied Microbiology.)

Background: Cereals are known to trigger for wheat allergy, celiac disease and non-celiac wheat sensitivity (NCWS). Inflammatory processes and intestinal barrier impairment are suspected to be involved in NCWS, although the molecular triggers are unclear., Aims: We were interested if different bread types influence inflammatory processes and intestinal barrier function in a mouse model of inflammatory bowel disease., Methods: Epithelial caspase-8 gene knockout (Casp8 ΔIEC ) and control (Casp8 fl ) mice were randomized to eight groups, respectively. The groups received different diets for 28 days (gluten-free diet, gluten-rich diet 5 g%, or different types of bread at 50 g%). Breads varied regarding grain, milling and fermentation. All diets were isocaloric., Results: Regardless of the diet, Casp8 ΔIEC mice showed pronounced inflammation in colon compared to ileum, whereas Casp8 fl mice were hardly inflamed. Casp8 fl mice could tolerate all bread types. Especially yeast fermented rye and wheat bread from superfine flour but not pure gluten challenge increased colitis and mortality in Casp8 ΔIEC mice. Hepatic expression of lipopolysaccharide-binding protein and colonic expression of tumor necrosis factor-α genes were inversely related to survival. The bread diets, but not the gluten-rich diet, also decreased colonic tight junction expression to variable degrees, without clear association to survival and inflammation., Conclusions: Bread components, especially those from yeast-fermented breads from wheat and rye, increase colitis and mortality in Casp8 ΔIEC mice highly susceptible to intestinal inflammation, whereas control mice can tolerate all types of bread without inflammation. Yet unidentified bread components other than gluten seem to play the major role., (© 2022. The Author(s).)

Carbon limitation is a common feeding strategy in bioprocesses to enable an efficient microbiological conversion of a substrate to a product. However, industrial settings inherently promote mixing insufficiencies, creating zones of famine conditions. Cells frequently traveling through such regions repeatedly experience substrate shortages and respond individually but often with a deteriorated production performance. A priori knowledge of the expected strain performance would enable targeted strain, process, and bioreactor engineering for minimizing performance loss. Today, computational fluid dynamics (CFD) coupled to data-driven kinetic models are a promising route for the in silico investigation of the impact of the dynamic environment in the large-scale bioreactor on microbial performance. However, profound wet-lab datasets are needed to cover relevant perturbations on realistic time scales. As a pioneering study, we quantified intracellular metabolome dynamics of Saccharomyces cerevisiae following an industrially relevant famine perturbation. Stimulus-response experiments were operated as chemostats with an intermittent feed and high-frequency sampling. Our results reveal that even mild glucose gradients in the range of 100 μmol·L -1 impose significant perturbations in adapted and non-adapted yeast cells, altering energy and redox homeostasis. Apparently, yeast sacrifices catabolic reduction charges for the sake of anabolic persistence under acute carbon starvation conditions. After repeated exposure to famine conditions, adapted cells show 2.7% increased maintenance demands.

The protein-rich nature of Saccharomyces cerevisiae has led this yeast to the spotlight concerning the search for antimicrobial peptides. Herein, a <10 kDa peptide-rich extract displaying antibacterial activity was obtained through the autolysis of yeast biomass under mild thermal treatment with self-proteolysis by endogenous peptidases. Estimated IC 50 for the peptide pools obtained by FPLC gel filtration indicated improved antibacterial activities against foodborne bacteria and bacteria of clinical interest. Similarly, the estimated cytotoxicity concentrations against healthy human fibroblasts, alongside selective indices ≥10, indicates the fractions are safe, at least in a mixture format, for human tissues. Nano-LC-MS/MS analysis revealed that the peptides in FPLC fractions could be derived from both induced-proteolysis and proteasome activity in abundant proteins, up-regulated under stress conditions during S. cerevisiae biomass manufacturing, including those coded by TDH1/2/3 , HSP12 , SSA1/2 , ADH1/2 , CDC19 , PGK1 , PPI1 , PDC1 , and GMP1 , as well as by other non-abundant proteins. Fifty-eight AMP candidate sequences were predicted following an in silico analysis using four independent algorithms, indicating their possible contribution to the bacterial inactivation observed in the peptides pool, which deserve special attention for further validation of individual functionality. S. cerevisiae -biomass peptides, an unconventional but abundant source of pharmaceuticals, may be promissory adjuvants to treat infectious diseases that are poorly sensitive to conventional antibiotics.

Studying protein complexes in vitro requires the production of a relatively pure sample that maintains the full complement, native organization, and function of that complex. This can be particularly challenging to achieve for large, multi-component, membrane embedded complexes using the traditional recombinant expression and reconstitution methodologies. However, using affinity capture from native cells, suitable whole endogenous protein complexes can be isolated. Here we present a protocol for the affinity isolation of baker's yeast (S. cerevisiae) nuclear pore complexes, which are ~50 MDa assemblies made up of 552 distinct proteins and embedded in a double-membraned nuclear envelope. Producing this sample allowed us for the first time to perform analyses to characterize the mass, stoichiometry, morphology, and connectivity of this complex and to obtain its integrative structure with ~9 Å precision. We believe this methodology can be applied to other challenging protein complexes to produce similar results., (© 2022. Springer Science+Business Media, LLC, part of Springer Nature.)

Despite being widely available, Saccharomyces cerevisiae has not been widely explored for direct extraction of chitosan biopolymer for antimicrobial applications. In our study, S. cerevisiae from Baker's yeast and Aspergillus niger from moldy onion extracts are studied as alternative sources of chitosan; and S cerevisiae chitosan tested for antimicrobial efficacy. The properties of S. cerevisiae chitosan are compared with moldy onion chitosan and shrimp chitosan extracted from shrimp shells. Chitosan extracted from S. cerevisiae is tested for antimicrobial efficacy against Staphylococcus Aureus. The maximum yields of fungal chitosan are 20.85 ± 0.35 mg/g dry S. cerevisiae biomass at 4th day using a culture broth containing sodium acetate, and 16.15 ± 0.95 mg/g dry A. niger biomass at 12th day. The degree of deacetylation (DD%) of the extracted fungal chitosan samples from S. cerevisiae and A. niger is found to be 63.4%, and 61.2% respectively, using Fourier Transform Infrared Spectroscopy. At a concentration of 2 g/L, S. cerevisiae chitosan shows the maximum inhibition zone diameter of 15.48 ± 0.07 mm. Baker's yeast S cerevisiae biomass and A. niger from moldy onions has not been previously explored as a source of extractible fungal chitosan. This study gives insight that S. cerevisiae and A. niger from agricultural or industrial wastes could be a potential biomass source for production of the chitosan biopolymer. The S. cerevisiae chitosan displayed effective antimicrobial properties against S aureus, indicating the viablitiy of S cerevisae as a resource for extraction of high-quality chitosan., (© 2021. The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature.)

Iron is a vital micronutrient that functions as an essential cofactor in multiple biological processes, including oxygen transport, cellular respiration, and metabolic pathways, such as sterol biosynthesis. However, its low bioavailability at physiological pH frequently leads to nutritional iron deficiency. The yeast Saccharomyces cerevisiae is extensively used to study iron and lipid metabolisms, as well as in multiple biotechnological applications. Despite iron being indispensable for yeast ergosterol biosynthesis and growth, little is known about their interconnections. Here, we used lipid composition analyses to determine that changes in the pattern of sterols impair the response to iron deprivation of yeast cells. Yeast mutants defective in ergosterol biosynthesis display defects in the transcriptional activation of the iron-acquisition machinery and growth defects in iron-depleted conditions. The transcriptional activation function of the iron-sensing Aft1 factor is interrupted due to its mislocalization to the vacuole. These data uncover novel links between iron and sterol metabolisms that need to be considered when producing yeast-derived foods or when treating fungal infections with drugs that target the ergosterol biosynthesis pathway.

Usage of sprouted grains is an increasing trend in thermally processed foods. Sprouting alters the composition of sugars and amino acids, which are Maillard reaction precursors. Free asparagine, total free amino acids, and sugars were monitored during sprouting and yeast and sourdough fermentations. Acrylamide and 5-hydroxymethylfurfural (HMF) were analyzed in heated samples. The asparagine concentration decreased up to 40% after 24-36 h of sprouting, except for buckwheat, and then increased to the initial concentration after 48 h and several folds after 72 h. The increased amount of reducing sugars after sprouting caused higher acrylamide and HMF formation even if the asparagine concentration was lower. Acrylamide and HMF formation decreased after fermentation of sprouted wholemeal because sugars and asparagine were consumed by yeast. A pH drop of 3 units by sourdough fermentation decreased acrylamide formation but increased HMF formation. Results indicated that sprouted cereal products should be produced under controlled conditions to be used in heated foods.

Immunoreceptors expressed on osteoclast precursor cells modify osteoclast differentiation and bone resorption activity. Dectin-1 is a lectin receptor of β-glucan and is specifically expressed in osteoclast precursor cells. In this study, we evaluated the bioactivity of β-glucan on receptor activator of nuclear factor-kappa B ligand (RANKL)-induced osteoclastogenesis and observed that glucan from baker's yeast inhibited this process in mouse bone marrow cells and dectin-1-overexpressing RAW264.7 (d-RAW) cells. In conjunction, RANKL-induced nuclear factor of activated T cell c1 expression was suppressed, subsequently downregulating TRAP and Oc-stamp. Additionally, nuclear factor-kappa B activation and the expression of c-fos and Blimp1 were reduced in d-RAW cells. Furthermore, glucan from baker's yeast induced the degradation of Syk protein, essential factor for osteoclastogenesis. These results suggest that glucan from baker's yeast suppresses RANKL-induced osteoclastogenesis and can be applied as a new treatment strategy for bone-related diseases., (© 2020 Wiley Periodicals LLC.)

In 2014, the EFSA NDA Panel concluded that UV-treated baker's yeast containing up to 3.5 Mio IU of vitamin D/100 g, is safe under the proposed conditions of use for yeast-leavened breads, rolls and fine bakery wares, and food supplements. Following a request from the European Commission, the EFSA Panel on Nutrition, Novel Foods and Food Allergens (NDA) was asked to deliver an opinion on an application for an extension of the use of UV-treated baker's yeast as a novel food (NF) pursuant to Regulation (EU) 2015/2283. In this extension of use, the applicant proposed a broad range of food categories to which the NF can be added. On the basis of the proposed uses and maximum use levels, the Panel estimated the potential exposure to vitamin D from the NF and the potential combined exposure to vitamin D including also exposure from the background diet and food supplements. The Panel notes that the upper level (UL) for one age group, i.e. children aged 4-10 years, is exceeded by 4%, when summing up the highest P95 estimate for the background diet (including food supplements) and the highest P95 estimate for vitamin D from the NF under the proposed uses and maximum use levels. The Panel notes, however, the highly conservative approach for estimating the potential intake of vitamin D from the NF, given that the applicant has proposed 34 FoodEx2 level 2 food categories. Thus, the Panel considers that the UL for children aged between 4 and 10 years is highly unlikely to be exceeded. The Panel concludes that the NF is safe under the proposed conditions of use., (© 2021 European Food Safety Authority. EFSA Journal published by John Wiley and Sons Ltd on behalf of European Food Safety Authority.)

Lactic acid bacteria (LAB) decisively influence the technological, nutritional, organoleptic and preservation properties of bakery products. Therefore, their use has long been considered an excellent strategy to improve the characteristics of those goods. The aim of this study was the evaluation of microbial diversity in different doughs used for the production of a typical Apulian flatbread, named focaccia. Leavening of the analyzed doughs was obtained with baker's yeast or by applying an innovative "yeast-free" protocol based on a liquid sourdough obtained by using Leuconostoc citreum strain C2.27 as a starter. The microbial populations of the doughs were studied by both a culture-dependent approach and metagenetic analyses. The flours used for dough preparation were also subjected to the same analyses. The metagenetic analyses were performed by sequencing the V5-V6 hypervariable regions of the 16S rRNA gene and the V9 hypervariable region of the 18S rRNA gene. The results indicate that these hypervariable regions were suitable for studying the microbiota of doughs, highlighting a significant difference between the microbial community of focaccia dough with baker's yeast and that of the dough inoculated with the bacterial starter. In particular, the dough made with baker's yeast contained a microbiota with a high abundance of Proteobacteria (82% of the bacterial population), known to be negatively correlated with the biochemical properties of the doughs, while the Proteobacteria in dough produced with the L. citreum starter were about 43.5% lower than those in flour and dough prepared using baker's yeast. Moreover, the results show that the L. citreum C2.27 starter was able to dominate the microbial environment and also reveal the absence of the genus Saccharomyces in the dough used for the production of the "yeast-free" focaccia . This result is particularly important because it highlights the suitability of the starter strain for obtaining an innovative "yeast-free" product.

The aim of this study was to compare the effect of consumption of ancient grain "Verna" bread obtained by two different leavening agents, sourdough (SD) and baker's yeast (BY), on inflammatory parameters and cardiometabolic risk factors. Seventeen clinically healthy subjects were included to consume SD or BY bread for 4 weeks each, and blood analyses were carried out. The consumption of "Verna" bread obtained with both leavening agents led to a significant improvement of LDL cholesterol. A reduction of -10.6% and -8.53% was observed after replacement with SD and BY bread, respectively. A significant increase in fasting blood glucose (+6%) was observed only after the intervention with BY bread. A 10.7% decrease of vascular endothelial growth factor was found after the SD bread replacement period. The consumption of "Verna" bread resulted significantly associated with an improvement in the cardiometabolic and inflammatory profile. However, only consumption of BY bread determined a significant increase in blood glucose levels.

This research aimed to explore the feasibility of fortifying bread with cooked Vitelotte potato powder and Citrus albedo, comparing the use of baker's yeast or sourdough as leavening agents. Breads obtained were thus subjected to physico-chemical and sensory characterizations. The replacement of part of the wheat flour with purple potato and albedo determined a significant enhancement of the phenolic profile and antioxidant status of fortified breads, as well as a longer shelf life. Thanks to its acidity and antimicrobial activity, sourdough improved the levels of health-promoting compounds and stability. Both the fortification and the leavening agent deeply affected the organoleptic, expression, and the aroma profile, of the fortified bread. Interestingly, albedo addition, despite its effectiveness in boosting the phenolic profile, determined a higher perception of aftertaste and bitterness, irrespective of the leavening agent. Based on these results, the use of purple potatoes and Citrus albedo, if properly formulated, could represent a valuable strategy for the development of high-quality products, with longer shelf-life.

The industrial currants finishing generates a considerable amount of side-stream (FSS) with great potential for biotechnological exploitation. The chemical composition of FSS generated from the premium quality Vostitsa currants was studied. Its use for wine making (at low temperatures, using both free and immobilized yeast) combined with baker's yeast production (with minor nutrient supplementation), is also proposed. Analysis showed that FSS has a rich volatilome (including Maillard reaction/lipid degradation products), increased antioxidant capacity, and total lipid and phenolic contents, compared to the marketable product (currants). However, acidity levels and the presence of specific volatiles (such as acetate esters and higher alcohols) may be indicative of microbial spoilage. The wines made from FSS were methanol free and contained higher levels of terpenes (indicating hydrolysis of bound forms) and fermentation-derived volatiles, compared to FSS. A preliminary technoeconomic analysis for integrated wine/baker's yeast industrial production, showed that the investment is realistic and worthwhile., (Copyright © 2020 Elsevier Ltd. All rights reserved.)

Cadaverine, 1,5-diaminopentane, is one of the most promising chemicals for biobased-polyamide production and it has been successfully produced up to molar concentration. Pyridoxal 5'-phosphate (PLP) is a critical cofactor for inducible lysine decarboxylase (CadA) and is required up to micromolar concentration level. Previously the regeneration of PLP in cadaverine bioconversion has been studied and salvage pathway pyridoxal kinase (PdxY) was successfully introduced; however, this system also required a continuous supply of adenosine 5'-triphosphate (ATP) for PLP regeneration from pyridoxal (PL) which add in cost. Herein, to improve the process further a method of ATP regeneration was established by applying baker's yeast with jhAY strain harboring CadA and PdxY, and demonstrated that providing a moderate amount of adenosine 5'-triphosphate (ATP) with the simple addition of baker's yeast could increase cadaverine production dramatically. After optimization of reaction conditions, such as PL, adenosine 5'-diphosphate, MgCl 2 , and phosphate buffer, we able to achieve high production (1740 mM, 87% yield) from 2 M L-lysine. Moreover, this approach could give averaged 80.4% of cadaverine yield after three times reactions with baker's yeast and jhAY strain. It is expected that baker's yeast could be applied to other reactions requiring an ATP regeneration system.

As is widely accepted, the quality decay of freshly baked bread that affects product shelf life is the result of a complex multifactorial process that involves physical staling, together with microbiological, chemical and sensorial spoilage. In this context, this paper provides a critical review of the recent literature about the main factors affecting shelf life of bread during post-baking. An overview of the recent findings about the mechanism of bread staling is firstly provided. Afterwards, the effect on staling induced by baker's yeasts and sourdough as well as by the extra ingredients commonly utilized for bread fortification is also addressed and discussed. As inclusion/exclusion criteria, only papers dealing with wheat bread and not with long-life bread or gluten-free bakery products are taken into consideration. Despite recent developments in international scientific literature, the whole mechanism that induces bread staling is far from being completely understood and the best analytical methods to be adopted to measure and/or describe in depth this process appear still debated. In this topic, the effects induced on bread shelf life by the use of biological leavening agents (baker's yeasts and sourdough) as well as by some extra ingredients included in the bread recipe have been individuated as two key issues to be addressed and discussed in terms of their influence on the kinetics of bread staling. © 2020 Society of Chemical Industry., (© 2020 Society of Chemical Industry.)

The baker's yeast Saccharomyces (S.) cerevisiae is a single-celled eukaryotic model organism widely used in research on life sciences. Being a unicellular organism, S. cerevisiae has some evident limitations in application to neuroscience. However, yeast prions are extensively studied and they are known to share some hallmarks with mammalian prion protein or other amyloidogenic proteins found in the pathogenesis of Alzheimer's, Parkinson's, or Huntington's diseases. Therefore, the yeast S. cerevisiae has been widely used for basic research on aggregation properties of proteins in cellulo and on their propagation. Recently, a yeast-based study revealed that some regions of mammalian prion protein and amyloid β 1-42 are capable of induction and propagation of yeast prions. It is one of the examples showing that evolutionarily distant organisms share common mechanisms underlying the structural conversion of prion proteins making yeast cells a useful system for studying mammalian prion protein. S. cerevisiae has also been used to design novel screening systems for anti-prion compounds from chemical libraries. Yeast-based assays are cheap in maintenance and safe for the researcher, making them a very good choice to perform preliminary screening before further characterization in systems engaging mammalian cells infected with prions. In this review, not only classical red/white colony assay but also yeast-based screening assays developed during last year are discussed. Computational analysis and research carried out using yeast prions force us to expect that prions are widely present in nature. Indeed, the last few years brought us several examples indicating that the mammalian prion protein is no more peculiar protein - it seems that a better understanding of prion proteins nature-wide may aid us with the treatment of prion diseases and other amyloid-related medical conditions., Competing Interests: None

Background: The accumulation of intracellular fat depots is a polygenic trait. Therefore, the extent of lipid storage in the individuals of a species covers a broad range and is determined by many genetic factors. Quantitative trait loci analysis can be used to identify those genetic differences between two strains of the same species that are responsible for the differences in a given phenotype. We used this method and complementary approaches to identify genes in the yeast Saccharomyces cerevisiae that are involved in neutral lipid storage., Results: We selected two yeast strains, the laboratory strain BY4741 and the wine yeast AWRI1631, with a more than two-fold difference in neutral lipid content. After crossing, sporulation and germination, we used fluorescence activated cell sorting to isolate a subpopulation of cells with the highest neutral lipid content from the pool of segregants. Whole genome sequencing of this subpopulation and of the unsorted pool of segregants implicated several loci that are involved in lipid accumulation. Three of the identified genes, PIG1, PHO23 and RML2, were investigated in more detail. Deletions of these genes and the exchange of the alleles between the two parental strains confirmed that the encoded proteins contribute to neutral lipid storage in S. cerevisiae and that PIG1, PHO23 and RML2 are the major causative genes. Backcrossing of one of the segregants with the parental strains for seven generations revealed additional regions in the genomes of both strains with potential causative genes for the high lipid accumulation phenotype., Conclusions: We identified several genes that contribute to the phenotype of lipid accumulation in an allele-specific manner. Surprisingly, no allelic variations of genes with known functions in lipid metabolism were found, indicating that the level of storage lipid accumulation is determined by many cellular processes that are not directly related to lipid metabolism.

Several studies showed that products made with ancient wheat genotypes have beneficial health properties compared to those obtained with modern wheat varieties, even though the mechanisms responsible for the positive effects are not clear. Ancient durum wheat genotypes are being currently used for the production of pasta, bread and other typical bakery products but the consumption is strictly local. In this work 15 genotypes of Triticum turgidum subsp. durum, including 10 ancient and 5 modern, were characterized for their technological traits through the determination of different parameters: protein content, dry gluten, gluten index, yellow index, ash, P/L, W and G. In addition, the baking aptitude of all genotypes was evaluated. All semolinas were subjected to leavening by commercial baker's yeast and the experimental breads were subjected to the qualitative characterization (weight loss, height, firmness, colour, volatile organic compounds, image and sensory analysis). The results obtained showed that protein content of grains and semolinas was higher in ancient rather than modern genotypes. Dry gluten ranged from 6.7% of the modern variety Simeto to 13.6% of the ancient genotype Scorsonera. Great differences were found for the yellow index which reached the highest value in Saragolla variety. The P/L and W ratios were significantly higher for the modern genotypes. On average, weight loss was about 14 g, while bread height varied significantly between the trials. Bread consistency varied between 12.6 and 31.3 N. Differences were observed for the yellow of the crumb (higher for modern genotypes) and for the redness of the crust (higher for ancient genotypes). The sensory evaluation displayed a high variability among the breads from the 10 ancient genotypes, while the control breads received scores closed to those of the modern genotypes. This study revealed that the modern durum wheat varieties showed a certain uniformity of behaviour, while the ancient genotypes exhibited a great variability of the final attributes of breads., (Copyright © 2020 Elsevier Ltd. All rights reserved.)

Yeasts are rich source of proteins, antioxidants, vitamins, and other bioactive compounds. The main drawback in their utilization as valuable ingredients in functional foods and dietary supplements production is the thick, indigestible cell wall, as well as the high nucleic acid content. In this study, we evaluated the feasibility of pulsed electric field (PEF) treatment as an alternative method for extraction of proteins and other bioactive intracellular compounds from yeasts. Baker's yeast water suspensions with different concentration (12.5-85 g dry cell weight per liter) were treated with monopolar rectangular pulses using a continuous flow system. The PEF energy required to achieve irreversible electropermeabilization was significantly reduced with the increase of the biomass concentration. Upon incubation of the permeabilized cells in water, only relatively small intracellular compounds were released. Release of 90% of the free amino acids and low molecular UV absorbing compounds, 80% of the glutathione, and ∼40% of the total phenol content was achieved about 2 h after pulsation and incubation of the suspensions at room temperature. At these conditions, the macromolecules (proteins and nucleic acids) were retained largely inside. Efficient protein release (∼90% from the total soluble protein) occurred only after dilution and incubation of the permeabilized cells in buffer with pH 8-9. Protein concentrates obtained by ultrafiltration (10 kDa cut off) had lower nucleic acid content (protein/nucleic acid ratio ∼100/4.5) in comparison with cell lysates obtained by mechanical disintegration. The obtained results allowed to conclude that PEF treatment can be used as an efficient alternative approach for production of yeast extracts with different composition, suitable for application in food, cosmetics and pharmaceutical industries., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2020 Ganeva, Angelova, Galutzov, Goltsev and Zhiponova.)

Indanols are a family of chemical compounds that have been widely studied due to their broad range of biological activity. They are also important intermediates used as synthetic precursors to other products with important applications in pharmacology. Enantiomerically pure chloroindanol derivatives exhibiting antifungal activity against the phytopathogenic fungus Botrytis cinerea were prepared using biocatalytic methods. As a result of the biotransformation of racemic 6-chloroindanol ( 1 ) and 5-chloroindanol ( 2 ) by the fungus B. cinerea , the compounds anti -(+)-6-chloroindan-1,2-diol ( anti -(+)- 7 ), anti -(+)-5-chloroindan-1,3-diol ( anti -(+)- 8 ), syn -(+)-5-chloroindan-1,3-diol ( syn -(+)- 8 ), syn -(-)-5-chloroindan-1,3-diol ( syn -(-)- 8 ), and anti -(+)-5-chloroindan-1,2-diol ( anti -(+)- 9 ) were isolated for the first time. These products were characterized by spectroscopic techniques and their enantiomeric excesses studied by chromatographic techniques. The results obtained in the biotransformation seem to suggest that the fungus B. cinerea uses oxidation reactions as a detoxification mechanism.

Consumption of fructan-containing cereal products is considered beneficial for most people, but not for those suffering from irritable bowel syndrome (IBS), as they should avoid the consumption of fermentable oligosaccharides, disaccharides, monosaccharides and polyols (acronym: FODMAP). Controlling fructan levels in cereal products is not trivial. However, controlling yeast invertase-mediated hydrolysis of fructan during dough fermentation might offer a handle to modulate fructan concentrations. In this work, the variability in invertase activity and substrate specificity in an extensive set of industrial Saccharomyces cerevisiae strains is investigated. Analysis showed a high variability in the capacity of these strains to hydrolyse sucrose and fructo-oligosaccharides. Industrial yeast strains with a high activity towards fructo-oligosaccharides efficiently reduced wheat grain fructans during dough fermentation to a final fructan level of 0.3% dm, whereas strains with a low invertase activity yielded fructan levels around 0.6% dm. The non-bakery strains produced lower levels of CO 2 in fermenting dough resulting in lower loaf volumes. However, CO 2 production and loaf volume could be increased by the addition of 3% glucose. In conclusion, this study shows that variation in yeast invertase activity and specificity can be used to modulate the fructan content in bread, allowing the production of low FODMAP breads, or alternatively, breads with a higher soluble dietary fibre content., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020 Elsevier B.V. All rights reserved.)

Yeast autolysis refers to the process in which cells degrade and release intracellular contents under specific conditions by endogenous enzymes such as proteases, nucleases and lipid enzymes. Protein-rich baker's yeast is widely used to produce yeast extract in food industry, however, the molecular mechanism related to baker's yeast autolysis is still unclear. In this study, RNA-seq technology and biochemical analysis were performed to analyze the autolysis processes in baker's yeast. The differentially expressed genes (DEGs), 27 autolysis-related euKaryotic Ortholog Groups (KOG) and three types of autolysis-induced Gene Ontology (GO) were identified and analyzed in detail. A total of 143 Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways under autolysis were also assigned. Interestingly, the DEGs were significantly enriched in the mitogen-activated protein kinase (MAPK) signaling pathways and metabolic pathways, and key genes MID2, MTL1, SLT2, PTP2, HKR1 and GPD1 may play important roles in autolysis. Further quantitative PCR was performed to verify the expression pattern in baker's yeast autolysis. Together, all these results indicated that MAPK pathways might play an essential role during autolysis process through inhibiting the metabolism and disrupting cell wall in baker's yeast. This result may provide important clues for the in-depth interpretation of the yeast autolysis mechanism., (© FEMS 2020.)

Folates are a group of B 9 vitamins playing an important role in many metabolic processes such as methylation reactions, nucleotide synthesis or oxidation and reduction processes. However, humans are not able to synthesize folates de novo and thus rely on external sources thereof. Baker's yeast ( Saccharomyces cerevisiae ) has been shown to produce high amounts of this vitamin but extensive identification of its folate metabolism is still lacking. Therefore, we optimized and compared different sample preparation and purification procedures applying solid phase extraction (SPE). Strong anion exchange (SAX), C18 and hydrophilic-lipophilic-balanced (HLB) materials were tested for their applicability in future metabolomics studies. SAX turned out to be the preferred material for the quantitative purification of folates. Qualification of several folate vitamers was achieved by ultra-high pressure liquid chromatography quadrupole time of flight mass spectrometry (UHPLC-Q-ToF-MS) measurements and quantification was performed by liquid chromatography tandem mass spectrometry (LC-MS/MS) applying stable isotope dilution assays (SIDAs). The oxidation product s -pyrazino-triazine (MeFox) was included into the SIDA method for total folate determination and validation. Applying the best protocol (SAX) in regard to folate recovery, we analyzed 32 different vitamers in different polyglutamate states up to nonaglutamates, of which we could further identify 26 vitamers based on tandem-MS (MS 2 ) spectra. Total folate quantification revealed differences in formyl folate contents depending on the cartridge chemistry used for purification. These are supposedly a result of interconversion reactions occurring during sample preparation due to variation in pH adjustments for the different purification protocols. The occurrence of interconversion and oxidation reactions should be taken into consideration in sample preparation procedures for metabolomics analyses with a focus on folates.

The use of cadmium sulphide quantum dot (CdS QD)-enabled products has become increasingly widespread. The prospect of their release in the environment is raising concerns. Here we have used the yeast model Saccharomyces cerevisiae to determine the potential impact of CdS QD nanoparticles on living organisms. Proteomic analyses and cell viability assays performed after 9 h exposure revealed expression of proteins involved in oxidative stress and reduced lethality, respectively, whereas oxidative stress declined, and lethality increased after 24 h incubation in the presence of CdS QDs. Quantitative proteomics using the iTRAQ approach (isobaric tags for relative and absolute quantitation) revealed that key proteins involved in essential biological pathways were differentially regulated over the time course of the experiment. At 9 h, most of the glycolytic functions increased, and the abundance of the number of heat shock proteins increased. This contrasts with the situation at 24 h where glycolytic functions, some heat shock proteins as well as oxidative phosphorylation and ATP synthesis were down-regulated. It can be concluded from our data that cell exposure to CdS QDs provokes a metabolic shift from respiration to fermentation, comparable to the situation reported in some cancer cell lines.

L-Theanine, found in green tea leaves has been shown to positively affect immunity and relaxation in humans. There have been many attempts to produce L-theanine through enzymatic synthesis to overcome the limitations of traditional methods. Among the many genes coding for enzymes in the L-theanine biosynthesis, glutamylmethylamide synthetase (GMAS) exhibits the greatest possibility of producing large amounts of production. Thus, GMAS from Methylovorus mays No. 9 was overexpressed in several strains including vectors with different copy numbers. BW25113(DE3) cells containing the pET24ma:: gmas was selected for strains. The optimal temperature, pH, and metal ion concentration were 50°C, 7, and 5 mM MnCl 2 , respectively. Additionally, ATP was found to be an important factor for producing high concentration of L-theanine so several strains were tested during the reaction for ATP regeneration. Bakers yeast was found to decrease the demand for ATP most effectively. Addition of potassium phosphate source was demonstrated by producing 4-fold higher L-theanine. To enhance the conversion yield, GMAS was additionally overexpressed in the system. A maximum of 198 mM L-theanine was produced with 16.5 mmol/l/h productivity. The whole-cell reaction involving GMAS has greatest potential for scale-up production of L-theanine.

Glucose-6-phosphate dehydrogenase (G6PD) is a key enzyme of the oxidative part of the pentose phosphate pathway and serves as the major source of NADPH for metabolic reactions and oxidative stress response in pro- and eukaryotic cells. We here report on a strain of the model yeast Saccharomyces cerevisiae which lacks the G6PD-encoding ZWF1 gene and displays distinct growth retardation on rich and synthetic media, as well as a strongly reduced chronological lifespan. This strain was used as a recipient to introduce plasmid-encoded heterologous G6PD genes, synthesized in the yeast codon usage and expressed under the control of the native PFK2 promotor. Complementation of the hypersensitivity of the zwf1 mutant towards hydrogen peroxide to different degrees was observed for the genes from humans ( HsG6PD1 ), the milk yeast Kluyveromyces lactis ( KlZWF1 ), the bacteria Escherichia coli ( EcZWF1 ) and Leuconostoc mesenteroides ( LmZWF1 ), as well as the genes encoding three different plant G6PD isoforms from Arabidopsis thaliana ( AtG6PD1, AtG6PD5, AtG6PD6 ). The plastidic AtG6PD1 isoform retained its redox-sensitive activity when produced in the yeast as a cytosolic enzyme, demonstrating the suitability of this host for determination of its physiological properties. Mutations precluding the formation of a disulfide bridge in AtG6PD1 abolished its redox-sensitivity but improved its capacity to complement the yeast zwf1 deletion. Given the importance of G6PD in human diseases and plant growth, this heterologous expression system offers a broad range of applications., Competing Interests: The authors declare no conflicts of interest.

Saccharomyces cerevisiae is the best studied eukaryote and a valuable tool for most aspects of basic research on eukaryotic organisms. This is due to its unicellular nature, which often simplifies matters, offering the combination of the facts that nearly all biological functions found in eukaryotes are also present and well conserved in S . cerevisiae . In addition, it is also easily amenable to genetic manipulation. Moreover, unlike other model organisms, S . cerevisiae is concomitantly of great importance for various biotechnological applications, some of which date back to several thousands of years. S . cerevisiae 's biotechnological usefulness resides in its unique biological characteristics, i.e., its fermentation capacity, accompanied by the production of alcohol and CO 2 and its resilience to adverse conditions of osmolarity and low pH. Among the most prominent applications involving the use of S . cerevisiae are the ones in food, beverage -especially wine- and biofuel production industries. This review focuses exactly on the function of S . cerevisiae in these applications, alone or in conjunction with other useful microorganisms involved in these processes. Furthermore, various aspects of the potential of the reservoir of wild, environmental, S . cerevisiae isolates are examined under the perspective of their use for such applications., Competing Interests: Conflict of interest: All authors declare no conflicts of interest in this paper., (© 2020 the Author(s), licensee AIMS Press.)

It is known, that Saccharomycetes can accumulate mineral substances with targeted enrichment of the growth medium. However, the influence of the genetic affiliation of the culture and the technological factors of yeast strains, the composition of growth media on the efficiency of essential trace elements incorporation into the biomass and on the change of theirs intracellular components content have hardly been investigated. In this regard, the aims of this work was to select promising races of yeast Saccharomyces cerevisiae, develop a biotechnological method for obtaining food ingredients enriched with selenium and chromium on their basis, and study their trace element composition. Material and methods . Industrial strains of baker's yeast (Saccharomyces cerevisiae) were used: RCAM 01137, Y-3439 and Y-581. Yeast were grown on malt wort (pH 4.6) with a dry matter content of 12% with the addition of mineral salts in stationary conditions at a temperature of 30 °C for 18 h, after which the yeast biomass was separated by centrifugation. A method for enriching yeast with trace elements has been selected, which consists in the process of culturing cells on malt growth media containing chromium chloride or selenium dioxide in various concentrations. The total protein content was determined by the Kjeldahl method, polysaccharides and ergosterol - by spectrofluorometric method, selenium - by fluorimetric method. The content of trace elements in yeast biomass enriched with chromium was studied by mass spectrometric method with inductively coupled plasma. Results . It was shown that the highest specific growth rate was demonstrated by the yeast strains RCAM 01137 and Y-3439, and the highest level of maltase activity was in the Y-581 strain. It was found that the amount of biomass after cultivation of the yeast S. cerevisiae RCAM 01137 and Y-3439 was 6.00 и 5.42 g/100 cm 3 , respectively. It was noted, that the yeast S. cerevisiae Y-581 had capability of high synthesis of ergosterol (1.08±0.04%), the level of which was 2 fold higher than other strains. S. cerevisiae RCAM 01137 yeast showed the greatest ability to selenium enrichment, its content in biomass increased 137 fold and amounted to 2740 μg% when cultivated on a medium containing 800 μg/dm 3 . S. cerevisiae Y-581 yeast strain showed the highest capability to chromium sorption. The chromium concentration in its biomass was 8340 μg% in case of cultivating on a medium containing 750 μg/dm 3 . The usage of about 2.7 g of selenium enriched yeast biomass, or 1.0 g chromium enriched one, satisfies the daily requirement for these trace elements. Conclusion . Cultivation of S. cerevisiae cells on growth media containing trace elements makes it possible to obtain yeast biomass samples that can be used to obtain food ingredients for creating food products that contribute to the maintaining human health and improve the quality and duration of life., Competing Interests: The authors declare no overt and potential conflict of interest related to the publication of this article., (Copyright© GEOTAR-Media Publishing Group.)

A yeast expression plasmid was constructed containing a cardenolide biosynthetic module, referred to as CARD II, using the AssemblX toolkit, which enables the assembly of large DNA constructs. The genes cloned into the vector were (a) a Δ 5 -3β-hydroxysteroid dehydrogenase gene from Digitalis lanata, (b) a steroid Δ 5 -isomerase gene from Comamonas testosteronii, (c) a mutated steroid-5β-reductase gene from Arabidopsis thaliana, and (d) a steroid 21-hydroxylase gene from Mus musculus. A second plasmid bearing an ADR/ADX fusion gene from Bos taurus was also constructed. A Saccharomyces cerevisiae strain bearing these two plasmids was generated. This strain, termed "CARD II yeast", was capable of producing 5β-pregnane-3β,21-diol-20-one, a central intermediate in 5β-cardenolide biosynthesis, starting from pregnenolone which was added to the culture medium. Using this approach, five consecutive steps in cardenolide biosynthesis were realized in baker's yeast., (© 2019 The Authors. MicrobiologyOpen published by John Wiley & Sons Ltd.)

Global outbreaks of drug-resistant fungi such as Candida auris are thought to be due at least in part to excessive use of antifungal drugs. Baker's yeast Saccharomyces cerevisiae has gained importance as an emerging opportunistic fungal pathogen that can cause infections in immunocompromised patients. Analyses of over 1000 S. cerevisiae isolates are providing rich resources to better understand how fungi can grow in human environments. A large percentage of clinical S. cerevisiae isolates are heterozygous across many nucleotide sites, and a significant proportion are of mixed ancestry and/or are aneuploid or polyploid. Such features potentially facilitate adaptation to new environments. These observations provide strong impetus for expanding genomic and molecular studies on clinical and wild isolates to understand the prevalence of genetic diversity and instability-generating mechanisms, and how they are selected for and maintained. Such work can also lead to the identification of new targets for antifungal drugs., (Copyright © 2019 Elsevier Ltd. All rights reserved.)

The feasibility of baker's yeast production using fruits and peels of Opuntia ficus indica (OFI) as carbohydrate feedstock was investigated. Two response surface methodologies involving central composite face centered design (CCFD) were successfully applied. The effects of four independent variables on baker's yeast production from OFI fruit juice was evaluated using the first CCFD. The best results were obtained with 24 H of inoculum age, 30 °C temperature, 200 rpm of agitation, and 10% inoculum size. At the maximum point, the biomass concentration reached 9.29 g/L. A second CCFD was performed to optimize the sugar extraction from OFI fruit peels. The potential of these latter as a fermentation substrate was determined. From the experimental results, the OFI fruit peel is an appropriate carbon source for the production of baker's yeast. The maximum biomass concentration was 12.51 g/L. Different nitrogen supplements were added to promote the yields of baker's yeast. Corn steep liquor was found to be the best alternative nutrient source of casein hydrolysate and yeast extract for baker's yeast production., (© 2019 International Union of Biochemistry and Molecular Biology, Inc.)

Baker's yeast has a finite lifespan and ages in two ways: a mother cell can only divide so many times (its replicative lifespan), and a non-dividing cell can only live so long (its chronological lifespan). Wild and laboratory yeast strains exhibit natural variation for each type of lifespan, and the genetic basis for this variation has been generalized to other eukaryotes, including metazoans. To date, yeast chronological lifespan has chiefly been studied in relation to the rate and mode of functional decline among non-dividing cells in nutrient-depleted batch culture. However, this culture method does not accurately capture two major classes of long-lived metazoan cells: cells that are terminally differentiated and metabolically active for periods that approximate animal lifespan (e.g. cardiac myocytes), and cells that are pluripotent and metabolically quiescent (e.g. stem cells). Here, we consider alternative ways of cultivating Saccharomyces cerevisiae so that these different metabolic states can be explored in non-dividing cells: (i) yeast cultured as giant colonies on semi-solid agar, (ii) yeast cultured in retentostats and provided sufficient nutrients to meet minimal energy requirements, and (iii) yeast encapsulated in a semisolid matrix and fed ad libitum in bioreactors. We review the physiology of yeast cultured under each of these conditions, and explore their potential to provide unique insights into determinants of chronological lifespan in the cells of higher eukaryotes., Competing Interests: Conflict of interest: The authors declare no conflict of interest.