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Single-cell proteins (SCPs) have the potential to mitigate the global pressures of food waste and protein demand. Food waste can be used as a feedstock and growth substrate for microorganisms that produce SCPs. SCPs can be produced through submerged fermentation, semisolid fermentation, or solid-state fermentation, which differ in substrate preparation and cultivation conditions, depending on the species selected (i.e., algae, bacteria, fungi, or yeast). Innovative technologies have been adopted for SCP analysis, but traditional methods mainly rely on spectrometry. The SCPs generated from food waste are nutritious and contain amino acids, vitamins, minerals, glucose, and other nutrients. Due to their high nutritional value, SCPs can replace plant- and meat-derived proteins in animal feed and also in human diet. However, SCPs may contain toxic substances, such as nucleic acids, mycotoxins, and bacterial toxins, generated during production. Therefore, further purification steps are often required. SCP production offers a potential alternative to traditional food production pathways given its economic and nutritional value.

Metabolism is one of the best studied fields of biochemistry, but its regulation involves processes on many different levels, some of which are still not understood well enough to allow for quantitative modeling and prediction. Glycolysis in yeast is a good example: although high-quality quantitative data are available, well-established mathematical models typically only cover direct regulation of the involved enzymes by metabolite binding. The effect of various metabolites on the enzyme kinetics is summarized in carefully developed mathematical formulae. However, this approach implicitly assumes that the enzyme concentrations themselves are constant, thus neglecting other regulatory levels – e.g. transcriptional and translational regulation – involved in the regulation of enzyme activities. It is believed, however, that different experimental conditions result in different enzyme activities regulated by the above mechanisms. Detailed modeling of all regulatory levels is still out of reach since some of the necessary data – e.g. quantitative large scale enzyme concentration data sets – are lacking or rare. Nevertheless, a viable approach is to include the regulation of enzyme concentrations into an established model and to investigate whether this improves the predictive capabilities. Proteome data are usually hard to obtain, but levels of mRNA transcripts may be used instead as clues for changes in enzyme concentrations. Here we investigate whether including mRNA data into an established model of yeast glycolysis allows to predict the steady state metabolic concentrations for different experimental conditions. To this end, we modified an established ODE model for the glycolytic pathway of yeast to include changes of enzyme concentrations. Presumable changes were inferred from mRNA transcript level measurement data. We investigate how this approach can be used to predict metabolite concentrations for steady-state yeast cultures at five different oxygen levels ranging from anaerobic to fully aerobic conditions. We were partly able to reproduce the experimental data and present a number of changes that were necessary to improve the modeling result.

We present a model of osmoadaptation in S. cerevisiae based on existing experimental and theoretical work. In order to investigate the impact of osmoadaptation on glycolysis, this model focuses on the interactions between glycolysis and osmoadaptation, namely the production of glycerol and its influence on flux towards pyruvate. Evaluation of this model shows that, depending on initial relations between glycerol and pyruvate production, the increased glycerol production can have a substantial negative effect on the pyruvate production rate. Existing experimental data and a detailed analysis of the model lead to the suggestion of an interaction between activated Hog1 and activators of glycolysis such as Pfk26.

Thorough knowledge of the model organism S. cerevisiae has fueled efforts in developing theories of cell ageing since the 1950s. Models of these theories aim to provide insight into the general biological processes of ageing, as well as to have predictive power for guiding experimental studies such as cell rejuvenation. Current efforts in in silico modeling are frustrated by the lack of efficient simulation tools that admit precise mathematical models at both cell and population levels simultaneously. We developed a novel hierarchical simulation tool that allows dynamic creation of entities while rigorously preserving the mathematical semantics of the model. We used it to expand a single-cell model of protein damage segregation to a cell population model that explicitly tracks mother-daughter relations. Large-scale exploration of the resulting tree of simulations established that daughters of older mothers show a rejuvenation effect, consistent with experimental results. The combination of a single-cell model and a simulation platform permitting parallel composition and dynamic node creation has proved to be an efficient tool for in silico exploration of cell behavior.

The sun is the only source of renewable energy available to us, if geothermal energy is not taken into account. In the form of radiation (UV light, visible light, infrared light, Section 1.1) it sends us annually 178,000 terawatts (1 TW = 10¹² W; unit of power 1 W = 1 J s^–1 = 859.85 calories per hour), that is to say 15,000 times the energy consumed annually by humanity. Only 0.1% of the solar energy received by planet Earth is converted into plant biomass, i.e. 100 × 10⁹ tons per year which corresponds to ca. 180 × 10⁹ tons per year of CO₂ captured from the atmosphere. This CO₂ returns to the biosphere after the death of the plants. Consumption of fossil carbon emits ca. 35 × 10⁹ tons of CO₂ yearly. Biomass is the material produced by all living organisms (plants, animals, microorganisms, fungi)…

Moulds and yeasts are frequently referred as microbial contaminants of feed meals used in intensive animal production. Most of the sanitary risks that are present in milk, eggs and meat are related with the safety of animal feeds. In this study, 75 samples of swine feed, being 10 feed meals and 65 granulated, were tested for mycological characterisation, using conventional methods (NP-3277-2; 2002). Only two granulated feed were negative (2.7%). Out of 75 samples, 73 (97.3%) were positive. Mean count of fungi has been 6.6 × 10² cfu/g ranging from 2.7 × 10¹ to 2.7 × 10³ cfu/g; yeasts were present in 69.9% of the positive samples. Potential toxigenic moulds (Fusarium spp., Aspergillus flavus and Penicillium spp.) were present in all the positive samples with mean levels of 3.2 log₁₀ cfu/g, 2.8 log₁₀ cfu/g and 3.0 log₁₀ cfu/g, respectively. Other genera found were Phoma, Rhizopus and Paecillomyces, with low levels of contamination (32.9%, 35.6% and 47.9%, respectively). It was concluded that the levels and frequency of mycobiota contamination are decreasing judging the results obtained in the last ten years, in Portugal.

An important aspect to consider in the modulation of gene expression with biotechnological purposes is mRNA stability. The KlCYC1 gene has a long (1.2 kb) 3′-UTR region that can be used to modulate gene expression in yeast by the alternative use of its proximal or distal 3′-Untranslated Region [1, 2]. The stability of the two KlCYC1 transcripts was analysed in Saccharomyces cerevisiae puf3 and rpb1-1 mutants. When the puf3 mutant and the deletion of the UGUR element at positions (131-135) were combined, there was a two-fold increase in total KlCYC1 levels mainly due to the increase in the long transcript signal. After a cease of transcription (rpb1-1 mutant), the long transcript was stable for more than two hours while the short one for less than one. When the gene was expressed in the yeast Kluyveromyces lactis under hypoxic conditions, both transcripts were degraded faster than in the rpb1-1 mutant. These findings suggest the presence of different mRNA turnover mechanisms able to operate on KlCYC1 transcripts under different physiological conditions.

The gene HIS4 from Kluyveromyces lactis is transcriptionally activated in complete synthetic respect to rich media and in an independent mechanism related to carbon source. This regulation was not previously described for Saccharomyces cerevisiae HIS4. The EMSA assay carried out with F7 showed a specific band, Fc1, in YPG, and two bands, Fc2 and Fc3, in complete medium. The Fc2 and Fc3 bands were dependent on the carbon source present in the medium, since their intensities were higher in glycerol than in glucose. The protein or proteins causing the Fc1 band seem to be involved in the different regulation mechanisms between rich and synthetic complete media because the Fc1 band was detected in cells grown in synthetic medium. Therefore, the promoter region (-200 to -173) is responsible for two independent regulatory mechanisms.

The population dynamics of yeasts in oleic ecosystems in the Castilla la Mancha region (Spain) was analysed for two consecutive years (2007 to 2008) in two different varieties (Cornicabra and Arbequina respectively). Yeasts were isolated from of fresh olives (Olea europaea L.) fruits, olive pomace (solid waste) and olive paste (crush olives). All yeast species were identified by RFLPs of their rDNA but in some species sequence analysis of the 5.8S rDNA gene was necessary. This study allowed to identify 108 yeast isolated which belonging to seven different genera (Zygosaccharomyces, Pichia, Lachancea, Kluyveromyces, Saccharomyces, Candida, Torulaspora) and fourteen species. The most representative species were Pichia caribbica, Zygosaccharomyces fermentati and Pichia holstii. The yeast characterization was studied by means of several enzymes how β-glucosidase, β-glucanase, carboxymethylcellulase, polygalacturonase, peroxydase and lipase and was observed that the mayority of them presented β-glucanase, β-glucosidase and peroxidase activities, a few had cellulase and polygalacturonase activities and none of species showed lipase activity.

We have developed a 2-day lab-practice to present microbiology and biotechnology to science secondary school students. This initiative seeks to familiarize students with microbial physiology and fermentation technology and to stimulate debate between students and researchers. This project has strengthened the relationship between secondary school science (students and teachers) and university teachers and researchers.

The YARE (Yeast AP1-Recognition Element) is the DNA binding site for YAp1 and YAp2 transcriptional activators in the presence of cadmium. The roles of three sequences matching the YARE consensus on the KlHIS4 promoter are analysed to determine their implication in cadmium transcriptional regulation. A specific band, Cd2, is characterised by EMSA in the region encompassing positions -283 to -276, which disappears in the presence of cadmium or when the YARE consensus is mutated. The factor causing Cd2 is named CSP1 (Cadmium Sensitive Protein 1). The binding of a second factor (P3) producing the band Cd3, also dependent on the YARE consensus, but insensitive to cadmium, is also characterised in the same region. The gel-shift pattern of region -384 to -323 with no YARE consensus is also altered by cadmium, thus, the cadmium transcriptional response of KlHIS4 appears to be modulated by multiple promoter elements. The presence of YARE regulatory elements is not a guarantee of a specific cadmium transcriptional regulation in K. lactis.

Two genomic fragments containing the KlADE2 and the KlPUT2 genes were isolated from Kluyveromyces lactis genomic library by functional complementation of the corresponding ade2 and put2 mutations in Saccharomyces cerevisiae. The deduced KlAde2p and KlPut2p amino acid sequences displayed strong similarities to their counterparts in Saccharomyces cerevisiae (75% and 72% identity respectively) with highly conserved domains. Thus, we report the isolation and characterization of ADE2 and PUT2 genes from Kluyveromyces lactis, including their protein structure, flanking sequence regions, and transcriptional gene regulation by different nutrients in the medium.

Cell membranes have the ability to bend and curve, thus providing clathrine-coated pits and plasmalemma caveolae, and facilitating many cell functions such as receptor-mediated endocytosis. On the other hand all intracellular membranes are highly deformable, producing cargo vesicles destined to organelles and plasma membrane. Generation of membrane curvature is currently believed to involve the penetration of amphipathic helix into the cytosolic face of the membrane bilayer, producing an asymmetry between the two membrane leaflets and generating bending and curvature towards the cytosol. Here we show, using thin section and freeze-fracture electron microscopy, that ethidium bromide is able to produce negative curvature toward the cytosol in Candida utilis yeast cells. The curvatures were produced in grooves area, resulting in cup-shaped structures with centrally located groove or in polymorph structures with laterally located grooves; these structures were termed "nanocups". Apparently the curvatures were not able to generate vesicles and tubules, suggesting that they were not involved in intracellular trafficking. Thus besides mechanically- or biologically-produced curvature, we can add chemically-produced curvature the function of which remains to be elucidated.

Yeasts are present throughout the spontaneous fermentation of table olives, and can have a great influence on the final product. For this reason, yeasts could be used as starter cultures in order to improve the quality of table olives. The aim of the present work was to study the effect of the growth conditions on the behaviour of yeast isolated from table olives. In this study, 17 yeast strains obtained from table olives, and belonging to various species of the Candida, Debaryomyces, Kluyveromyces, Pichia and Saccharomyces genera, were characterized by their behaviour in different culture conditions (NaCl and pH). Moreover, the flocculation capacity was studied, and interactions between yeasts and lactic acid bacteria were analyzed. Significant differences were found when yeasts were grown in culture media with salt concentrations between 7% and 12%, and pH between 3.5 and 7. Most of the yeasts analyzed could be useful as starter cultures to enhance the control of table olive fermentation, and hence obtain a high quality final product.

The effect was studied of several yeast strains of the genera Saccharomyces, Pichia, and Kluyveromyces on the persistence of four pesticides (pyraclostrobin, dimethoate, oxamyl, and pymetrozine) in brine during the fermentation process of vegetable products. The growth of yeast strains in a synthetic brine in the presence of the pesticides was recorded with a Bioscreen C kinetic growth reader and compared with their growth in a control brine without pesticides. After incubation for 7 days with the yeast strains, the concentration of pesticides in the synthetic brine was determined. Prior to this pesticide assay, the brines were centrifuged to removing the yeast pellets. The pesticides were determined in both yeast-free brine and yeast pellets and compared with the control consisting of sterile brine with pesticides. A modified QuEChERS (quick, easy, cheap, effective, rugged, and safe) method was used to extract the pesticides, which were assayed by LC-MS. The effect of the yeasts on the concentration of the four pesticides in synthetic brine depended on the yeast strain, and was clearest on pymetrozine and pyraclostrobin.

This paper present the Tropical Culture Collection CCT to show how it is and the areas it is involved: Applied microbiology, Culture and preservation methods, Environmental protection, Industrial microbiology, Fermentation, Freeze drying and so on, and also about the services and training courses it offers: Management of a culture collection, Culture and preservation methods, Propagation, Preservation, Storage services (Bacteria, Yeasts, Fungi), Distribution (Bacteria, Yeasts, Fungi).

The new Saccharomyces cerevisiae killer toxin (Klus) killed all the previously known S. cerevisiae killer strains, in addition to other yeast species. The Klus phenotype is encoded by a medium-size dsRNA virus, ScV-Mlus, whose genome size ranged from 2.1 to 2.3 kb. Its genome structure is similar to those of M1, M2, or M28 dsRNAs with a 5’ terminal coding region followed by two internal A-rich sequences and a 3’ terminal region without coding capacity. Mlus positive strands carry cis acting signals at their 5’ and 3’ termini for transcription and replication similar to those of killer viruses. The ORF at the 5’ portion codes for a putative preprotoxin with an N-terminal secretion signal, potential Kex2p/Kexlp processing sites and N-glycosylation sites. No sequence homology was found either between the Mlus dsRNA and M1, M2, or M28 dsRNAs, or between Klus and K1, K2, or K28 toxins. The Klus amino acid sequence showed a significant degree of conservation with the host chromosomally-encoded ORF YFR020W of unknown function.

Among the four types of Saccharomyces killer yeasts already described (K1, K2, K28, and Klus), we found K2 and Klus killer yeasts in south-western Spain. The K2 yeasts were found in all the wine producing sub-areas during all the vintages analyzed, while the Klus yeasts were found in the warmest locations and mostly in the warmest vintages. The killer yeasts were present in most spontaneous fermentations. Most were K2 with Klus being the minority. The proportion of killer yeasts increased during fermentation, while the proportion of sensitive yeasts decreased. The fermentation speed, malic acid, ethanol yield, and wine organoleptic quality decreased in those fermentations where the killer yeasts replaced at least 15% of a dominant population of sensitive yeasts.