Showing papers on "Yeast published in 2013"
TL;DR: This work demonstrates the excellent capacity for lipid production by the oleaginous yeast Y. lipolytica and the effects of metabolic engineering of two important steps of the lipid synthesis pathway, which acts to divert flux towards the cholesterol synthesis and creates driving force for TAG synthesis.
576 citations
TL;DR: It is concluded that human cells adopt unique strategies and recruit distinct trans-acting factors to carry out essential processing steps, posing fundamental implications for understanding ribosomopathies at the molecular level and developing effective therapeutic agents.
390 citations
TL;DR: Manipulation of regulators of gene expression at both transcriptional and posttranscriptional levels allows to modulate yeast life span during its biotechnological use.
Abstract: Yeast viability and vitality are essential for different industrial processes where the yeast Saccharomyces cerevisiae is used as a biotechnological tool. Therefore, the decline of yeast biological functions during aging may compromise their successful biotechnological use. Life span is controlled by a variety of molecular mechanisms, many of which are connected to stress tolerance and genomic stability, although the metabolic status of a cell has proven a main factor affecting its longevity. Acetic acid and ethanol accumulation shorten chronological life span (CLS), while glycerol extends it. Different age-related gene classes have been modified by deletion or overexpression to test their role in longevity and metabolism. Overexpression of histone deacetylase SIR2 extends CLS and reduces acetate production, while overexpression of SIR2 homolog HST3 shortens CLS, increases the ethanol level, and reduces acetic acid production. HST3 overexpression also enhances ethanol tolerance. Increasing tolerance to oxidative stress by superoxide dismutase SOD2 overexpression has only a moderate positive effect on CLS. CLS during grape juice fermentation has also been studied for mutants on several mRNA binding proteins that are regulators of gene expression at the posttranscriptional level; we found that NGR1 and UTH4 deletions decrease CLS, while PUF3 and PUB1 deletions increase it. Besides, the pub1 Δ mutation increases glycerol production and blocks stress granule formation during grape juice fermentation. Surprisingly, factors relating to apoptosis, such as caspase Yca1 or apoptosis-inducing factor Aif1, play a positive role in yeast longevity during winemaking as their deletions shorten CLS. Manipulation of regulators of gene expression at both transcriptional (i.e., sirtuins) and posttranscriptional (i.e., mRNA binding protein Pub1) levels allows to modulate yeast life span during its biotechnological use. Due to links between aging and metabolism, it also influences the production profile of metabolites of industrial relevance.
286 citations
TL;DR: This work collectively demonstrates that yeast has the potential to be a platform for the bioproduction of muconic acid and suggests an area that is ripe for future metabolic engineering efforts.
268 citations
TL;DR: It is suggested that it is necessary to understand the determinants of microbial species composition in nectar and their differential modification of floral rewards to explain the mutual benefits that plants and pollinators gain from each other.
Abstract: Mutualistic interactions are often subject to exploitation by species that are not directly involved in the mutualism. Understanding which organisms act as such ‘third-party’ species and how they d...
213 citations
TL;DR: How the secretory pathway can be engineered to ensure more efficient protein production is discussed and the involvement of directed metabolic engineering through the integration of tools from genetic engineering, systems biology and mathematical modeling is discussed.
Abstract: Production of recombinant proteins for use as pharmaceuticals, so-called biopharmaceuticals, is a multi-billion dollar industry. Many different cell factories are used for the production of biopharmaceuticals, but the yeast Saccharomyces cerevisiae is an important cell factory as it is used for production of several large volume products. Insulin and insulin analogs are by far the dominating biopharmaceuticals produced by yeast, and this will increase as the global insulin market is expected to grow from USD12B in 2011 to more than USD32B by 2018. Other important biopharmaceuticals produced by yeast are human serum albumin, hepatitis vaccines and virus like particles used for vaccination against human papillomavirus. Here is given a brief overview of biopharmaceutical production by yeast and it is discussed how the secretory pathway can be engineered to ensure more efficient protein production. The involvement of directed metabolic engineering through the integration of tools from genetic engineering, systems biology and mathematical modeling, is also discussed.
197 citations
TL;DR: Thirteen new oleaginous yeast species were discovered, representing multiple ascomycete and basidiomycete clades, and fatty acid profiles varied with the growth conditions regardless of taxonomic affiliation.
193 citations
TL;DR: A current overview of the canonical protein secretion pathway in the model yeast Saccharomyces cerevisiae is provided, highlighting differences to mammalian cells as well as currently unresolved questions, and a genomic comparison of the S. cerevisae pathway to seven other yeast species where secretion has been investigated due to their attraction as protein production platforms, or for their relevance as pathogens.
Abstract: Protein secretion is an essential process for living organisms. In eukaryotes, this encompasses numerous steps mediated by several hundred cellular proteins. The core functions of translocation through the endoplasmic reticulum membrane, primary glycosylation, folding and quality control, and vesicle-mediated secretion are similar from yeasts to higher eukaryotes. However, recent research has revealed significant functional differences between yeasts and mammalian cells, and even among diverse yeast species. This review provides a current overview of the canonical protein secretion pathway in the model yeast Saccharomyces cerevisiae, highlighting differences to mammalian cells as well as currently unresolved questions, and provides a genomic comparison of the S. cerevisiae pathway to seven other yeast species where secretion has been investigated due to their attraction as protein production platforms, or for their relevance as pathogens. The analysis of Candida albicans, Candida glabrata, Kluyveromyces lactis, Pichia pastoris, Hansenula polymorpha, Yarrowia lipolytica, and Schizosaccharomyces pombe reveals that many - but not all - secretion steps are more redundant in S. cerevisiae due to duplicated genes, while some processes are even absent in this model yeast. Recent research obviates that even where homologous genes are present, small differences in protein sequence and/or differences in the regulation of gene expression may lead to quite different protein secretion phenotypes.
182 citations
TL;DR: The results suggest that ethanol fermentation evolved progressively, involving several successive molecular events that have gradually remodeled the yeast carbon metabolism.
Abstract: When fruits ripen, microbial communities start a fierce competition for the freely available fruit sugars. Three yeast lineages, including baker's yeast Saccharomyces cerevisiae, have independently developed the metabolic activity to convert simple sugars into ethanol even under fully aerobic conditions. This fermentation capacity, named Crabtree effect, reduces the cell-biomass production but provides in nature a tool to out-compete other microorganisms. Here, we analyzed over forty Saccharomycetaceae yeasts, covering over 200 million years of the evolutionary history, for their carbon metabolism. The experiments were done under strictly controlled and uniform conditions, which has not been done before. We show that the origin of Crabtree effect in Saccharomycetaceae predates the whole genome duplication and became a settled metabolic trait after the split of the S. cerevisiae and Kluyveromyces lineages, and coincided with the origin of modern fruit bearing plants. Our results suggest that ethanol fermentation evolved progressively, involving several successive molecular events that have gradually remodeled the yeast carbon metabolism. While some of the final evolutionary events, like gene duplications of glucose transporters and glycolytic enzymes, have been deduced, the earliest molecular events initiating Crabtree effect are still to be determined.
179 citations
TL;DR: In this article, a prion formed by the Mot3 transcription factor, [MOT3 + ], governs the acquisition of facultative multicellularity in the budding yeast Saccharomyces cerevisiae.
167 citations
TL;DR: The majority of the surface communities before and after harvest comprised organisms with no known link to wine fermentations and a near-absence of spoilage-related organisms, suggesting that winery surfaces do not overtly vector wine spoilage microbes under normal operating conditions.
Abstract: During the transformation of grapes to wine, wine fermentations are exposed to a large area of specialized equipment surfaces within wineries, which may serve as important reservoirs for two-way transfer of microbes between fermentations. However, the role of winery environments in shaping the microbiota of wine fermentations and vectoring wine spoilage organisms is poorly understood at the systems level. Microbial communities inhabiting all major equipment and surfaces in a pilot-scale winery were surveyed over the course of a single harvest to track the appearance of equipment microbiota before, during, and after grape harvest. Results demonstrate that under normal cleaning conditions winery surfaces harbor seasonally fluctuating populations of bacteria and fungi. Surface microbial communities were dependent on the production context at each site, shaped by technological practices, processing stage, and season. During harvest, grape- and fermentation-associated organisms populated most winery surfaces, acting as potential reservoirs for microbial transfer between fermentations. These surfaces harbored large populations of Saccharomyces cerevisiae and other yeasts prior to harvest, potentially serving as an important vector of these yeasts in wine fermentations. However, the majority of the surface communities before and after harvest comprised organisms with no known link to wine fermentations and a near-absence of spoilage-related organisms, suggesting that winery surfaces do not overtly vector wine spoilage microbes under normal operating conditions.
TL;DR: Phenolic compounds were strong inhibitors of enzyme hydrolysis and fermentation of concentrated filtrates by Saccharomyces cerevisiae wine yeast NRRL Y-1536 or xylose fermenting yeast 424A (LNH-ST).
TL;DR: Yeast 25S rRNA was reported to contain a single cytosine methylation (m5C), but it was discovered that instead of one, yeast contains two m5C residues at position 2278 and 2870, and two putative methyltransferases, Rcm1 and Nop2, were identified and characterized to be responsible for these two cytOSine methylations.
Abstract: Yeast 25S rRNA was reported to contain a single cytosine methylation (m(5)C). In the present study using a combination of RP-HPLC, mung bean nuclease assay and rRNA mutagenesis, we discovered that instead of one, yeast contains two m(5)C residues at position 2278 and 2870. Furthermore, we identified and characterized two putative methyltransferases, Rcm1 and Nop2 to be responsible for these two cytosine methylations, respectively. Both proteins are highly conserved, which correlates with the presence of two m(5)C residues at identical positions in higher eukaryotes, including humans. The human homolog of yeast Nop2, p120 has been discovered to be upregulated in various cancer tissues, whereas the human homolog of Rcm1, NSUN5 is completely deleted in the William's-Beuren Syndrome. The substrates and function of both human homologs remained unknown. In the present study, we also provide insights into the significance of these two m(5)C residues. The loss of m(5)C2278 results in anisomycin hypersensitivity, whereas the loss of m(5)C2870 affects ribosome synthesis and processing. Establishing the locations and enzymes in yeast will not only help identifying the function of their homologs in higher organisms, but will also enable understanding the role of these modifications in ribosome function and architecture.
TL;DR: This study characterised the change in the bacterial population within the rumen of cattle fed supplemental live yeast and showed that the analysis of short V1 region of 16s rRNA gene could give as much phylogenetic information as a longer read (454 pyrosequencing of 250 bp).
Abstract: It has been suggested that the ability of live yeast to improve milk yield and weight gain in cattle is because the yeast stimulates bacterial activity within the rumen. However it remains unclear if this is a general stimulation of all species or a specific stimulation of certain species. Here we characterised the change in the bacterial population within the rumen of cattle fed supplemental live yeast. Three cannulated lactating cows received a daily ration (24 kg/d) of corn silage (61% of DM), concentrates (30% of DM), dehydrated alfalfa (9% of DM) and a minerals and vitamins mix (1% of DM). The effect of yeast (BIOSAF SC 47, Lesaffre Feed Additives, France; 0.5 or 5 g/d) was compared to a control (no additive) in a 3×3 Latin square design. The variation in the rumen bacterial community between treatments was assessed using Serial Analysis of V1 Ribosomal Sequence Tag (SARST-V1) and 454 pyrosequencing based on analysis of the 16S rRNA gene. Compared to the control diet supplementation of probiotic yeast maintained a healthy fermentation in the rumen of lactating cattle (higher VFA concentration [high yeast dose only], higher rumen pH, and lower Eh and lactate). These improvements were accompanied with a shift in the main fibrolytic group (Fibrobacter and Ruminococcus) and lactate utilising bacteria (Megasphaera and Selenomonas). In addition we have shown that the analysis of short V1 region of 16s rRNA gene (50–60 bp) could give as much phylogenetic information as a longer read (454 pyrosequencing of 250 bp). This study also highlights the difficulty of drawing conclusions on composition and diversity of complex microbiota because of the variation caused by the use of different methods (sequencing technology and/or analysis).
TL;DR: Functional expression of Rubisco in a heterotrophic eukaryote is demonstrated and incorporation of CO2 as a co-substrate in metabolic engineering ofheterotrophic industrial microorganisms can be used to improve product yields.
Abstract: Background
Redox-cofactor balancing constrains product yields in anaerobic fermentation processes. This challenge is exemplified by the formation of glycerol as major by-product in yeast-based bioethanol production, which is a direct consequence of the need to reoxidize excess NADH and causes a loss of conversion efficiency. Enabling the use of CO2 as electron acceptor for NADH oxidation in heterotrophic microorganisms would increase product yields in industrial biotechnology.
TL;DR: The intracellular signaling pathways involved in the cross-talk of pro-survival and pro-death pathways underlying the importance of understanding fundamental aspects of yeast cell homeostasis to improve the performance of a given yeast strain in biotechnological applications are elaborated.
Abstract: Beyond its classical biotechnological applications such as food and beverage production or as a cell factory, the yeast Saccharomyces cerevisiae is a valuable model organism to study fundamental mechanisms of cell response to stressful environmental changes. Acetic acid is a physiological product of yeast fermentation and it is a well-known food preservative due to its antimicrobial action. Acetic acid has recently been shown to cause yeast cell death and aging. Here we shall focus on the molecular mechanisms of S. cerevisiae stress adaptation and programmed cell death in response to acetic acid. We shall elaborate on the intracellular signaling pathways involved in the cross-talk of pro-survival and pro-death pathways underlying the importance of understanding fundamental aspects of yeast cell homeostasis to improve the performance of a given yeast strain in biotechnological applications.
TL;DR: Despite never being the dominant yeast species at any stage of fermentation, the un-conched chocolates produced from the two inoculated fermentations were judged by sensory analysis to differ in flavour profile compared to the spontaneously fermented control, which could indicate that yeasts have a greater impact on the sensory qualities of cocoa than previously assumed.
TL;DR: This review presents detailed protocols for the use of yeast surface display to isolate de novo binding proteins from combinatorial libraries, and subsequent biophysical characterization of binders.
TL;DR: The results demonstrate that the calcineurin pathway orchestrates the yeast-hyphal and spore size dimorphic transitions that contribute to virulence of this common zygomycete fungal pathogen.
Abstract: Many pathogenic fungi are dimorphic and switch between yeast and filamentous states. This switch alters host-microbe interactions and is critical for pathogenicity. However, in zygomycetes, whether dimorphism contributes to virulence is a central unanswered question. The pathogenic zygomycete Mucor circinelloides exhibits hyphal growth in aerobic conditions but switches to multi-budded yeast growth under anaerobic/high CO2 conditions. We found that in the presence of the calcineurin inhibitor FK506, Mucor exhibits exclusively multi-budded yeast growth. We also found that M. circinelloides encodes three calcineurin catalytic A subunits (CnaA, CnaB, and CnaC) and one calcineurin regulatory B subunit (CnbR). Mutations in the latch region of CnbR and in the FKBP12-FK506 binding domain of CnaA result in hyphal growth of Mucor in the presence of FK506. Disruption of the cnbR gene encoding the sole calcineurin B subunit necessary for calcineurin activity yielded mutants locked in permanent yeast phase growth. These findings reveal that the calcineurin pathway plays key roles in the dimorphic transition from yeast to hyphae. The cnbR yeast-locked mutants are less virulent than the wild-type strain in a heterologous host system, providing evidence that hyphae or the yeast-hyphal transition are linked to virulence. Protein kinase A activity (PKA) is elevated during yeast growth under anaerobic conditions, in the presence of FK506, or in the yeast-locked cnbR mutants, suggesting a novel connection between PKA and calcineurin. cnaA mutants lacking the CnaA catalytic subunit are hypersensitive to calcineurin inhibitors, display a hyphal polarity defect, and produce a mixture of yeast and hyphae in aerobic culture. The cnaA mutants also produce spores that are larger than wild-type, and spore size is correlated with virulence potential. Our results demonstrate that the calcineurin pathway orchestrates the yeast-hyphal and spore size dimorphic transitions that contribute to virulence of this common zygomycete fungal pathogen.
TL;DR: Gene co-expression analysis confirmed the presence of candidate P450s whose gene expression correlated highly with that of β-amyrin synthase (bAS) and identified CYP716A12 and CYP93E2 as key enzymes in hemolytic and non-hemolytic sapogenin biosynthetic pathways.
Abstract: Triterpenoid saponins are a diverse group of specialized (secondary) metabolites with many biological properties. The model legume Medicago truncatula has an interesting profile of triterpenoid saponins from which sapogenins are differentiated into hemolytic and non-hemolytic types according to the position of their functional groups and hemolytic properties. Gene co-expression analysis confirmed the presence of candidate P450s whose gene expression correlated highly with that of b-amyrin synthase (bAS). Among these, we identified CYP716A12 and CYP93E2 as key enzymes in hemolytic and non-hemolytic sapogenin biosynthetic pathways. The other candidate P450s showed no b-amyrin oxidation activity. However, among the remaining candidate P450s, CYP72A61v2 expression highly correlated with that of CYP93E2, and CYP72A68v2 expression highly correlated with that of CYP716A12. These correlation values were higher than occurred with bAS expression. We generated yeast strains expressing bAS, CPR, CYP93E2 and CYP72A61v2, and bAS, CPR, CYP716A12 and CYP72A68v2. These transgenic yeast strains produced soyasapogenol B and gypsogenic acid, respectively. We were therefore able to identify two CYP72A subfamily enzymes: CYP72A61v2, which modifies 24-OH-b-amyrin, and CYP72A68v2, which modifies oleanolic acid. Additionally, P450s that seemed not to work together in planta were combinatorially expressed in transgenic yeast. The yeast strains (expressing bAS, CPR, CYP72A63 and CYP93E2 or CYP716A12) produced rare triterpenoids that do not occur in M. truncatula. These results show the potential for combinatorial synthesis of diverse triterpenoid structures and enable identification of the enzymes involved in their biosynthesis.
TL;DR: A strategy for lowering ethanol production during grape must fermentation by taking advantage of the differences in energy metabolism among ascomycetous wine yeast species is proposed, hypothesize that using carefully selected yeast strains the available oxygen would be taken up by yeast cells for the respiration of a significant fraction of the hexoses present in grape must.
Abstract: The increasing ethanol content is a major challenge imposed by climate change on the production of quality wines. We propose a strategy for lowering ethanol production during grape must fermentation by taking advantage of the differences in energy metabolism among ascomycetous wine yeast species. We hypothesize that using carefully selected yeast strains the available oxygen would be taken up by yeast cells for the respiration of a significant fraction of the hexoses present in grape must. The actual degree of sugar consumption by this pathway, and the concomitant reduction in the final ethanol yield, would depend among other factors on the amount of available oxygen, in turn depending on standard winemaking practices or ad hoc aeration regimes. Setting up this strategy would involve the birth of a new research field, integrating topics like quantitative analysis of the energy and overall metabolism of non-Saccharomyces yeast species under winemaking conditions, interactions between yeast strains of different species in the grape must environment, or the impact of eventual ad hoc oxygenation treatments on must and wine constituents.
TL;DR: This was a systematical investigation of yeast community structure dynamics in the Maotai-flavor liquor fermentation process, finding that yeast population was much larger in the upper layer than that in the middle and bottom layers in liquor fermentation, which was in accordance with the profile of reducing sugar consumption and ethanol production.
TL;DR: Three superior industrial S. cerevisiae strains are constructed that combine efficient D-xylose utilization with high inhibitor tolerance and have strong potential for direct application in industrial bioethanol production.
Abstract: In addition to efficient pentose utilization, high inhibitor tolerance is a key trait required in any organism used for economically viable industrial bioethanol production with lignocellulose biomass. Although recent work has succeeded in establishing efficient xylose fermentation in robust industrial Saccharomyces cerevisiae strains, the resulting strains still lacked sufficient inhibitor tolerance for efficient sugar fermentation in lignocellulose hydrolysates. The aim of the present work was to combine high xylose fermentation activity and high inhibitor tolerance in a single industrial yeast strain. We have screened 580 yeast strains for high inhibitor tolerance using undetoxified acid-pretreated spruce hydrolysate and identified a triploid industrial baker’s yeast strain as having the highest inhibitor tolerance. From this strain, a mating competent diploid segregant with even higher inhibitor tolerance was obtained. It was crossed with the recently developed D-xylose fermenting diploid industrial strain GS1.11-26, with the Ethanol Red genetic background. Screening of 819 diploid segregants from the tetraploid hybrid resulted in two strains, GSF335 and GSF767, combining high inhibitor tolerance and efficient xylose fermentation. In a parallel approach, meiotic recombination of GS1.11-26 with a haploid segregant of Ethanol Red and screening of 104 segregants resulted in a similar inhibitor tolerant diploid strain, GSE16. The three superior strains exhibited significantly improved tolerance to inhibitors in spruce hydrolysate, higher glucose consumption rates, higher aerobic growth rates and higher maximal ethanol accumulation capacity in very-high gravity fermentation, compared to GS1.11-26. In complex medium, the D-xylose utilization rate by the three superior strains ranged from 0.36 to 0.67 g/g DW/h, which was lower than that of GS1.11-26 (1.10 g/g DW/h). On the other hand, in batch fermentation of undetoxified acid-pretreated spruce hydrolysate, the three superior strains showed comparable D-xylose utilization rates as GS1.11-26, probably because of their higher inhibitor tolerance. They produced up to 23% more ethanol compared to Ethanol Red. We have successfully constructed three superior industrial S. cerevisiae strains that combine efficient D-xylose utilization with high inhibitor tolerance. Since the background strain Ethanol Red has a proven record of successful industrial application, the three new superior strains have strong potential for direct application in industrial bioethanol production.
TL;DR: This review highlights recent advances in metabolic engineering of yeasts for producing value-added chemical compounds including alcohols, sugar derivatives, organic acids, fats, terpenes, aromatics, and polyketides.
TL;DR: The results show a trend to increased butanol production in strains engineered for increased cytosolic acetyl-CoA levels, with the best-producing strains having maximal butanol titers of 16.3 mg/l, which represents a 6.5-fold improvement compared to previous values reported for yeast.
Abstract: Recently, butanols (1-butanol, 2-butanol and iso-butanol) have generated attention as alternative gasoline additives. Butanols have several properties favorable in comparison to ethanol, and strong interest therefore exists in the reconstruction of the 1-butanol pathway in commonly used industrial microorganisms. In the present study, the biosynthetic pathway for 1-butanol production was reconstructed in the yeast Saccharomyces cerevisiae. In addition to introducing heterologous enzymes for butanol production, we engineered yeast to have increased flux toward cytosolic acetyl-CoA, the precursor metabolite for 1-butanol biosynthesis. This was done through introduction of a plasmid-containing genes for alcohol dehydrogenase (ADH2), acetaldehyde dehydrogenase (ALD6), acetyl-CoA synthetase (ACS), and acetyl-CoA acetyltransferase (ERG10), as well as the use of strains containing deletions in the malate synthase (MLS1) or citrate synthase (CIT2) genes. Our results show a trend to increased butanol production in strains engineered for increased cytosolic acetyl-CoA levels, with the best-producing strains having maximal butanol titers of 16.3 mg/l. This represents a 6.5-fold improvement in butanol titers compared to previous values reported for yeast and demonstrates the importance of an improved cytosolic acetyl-CoA supply for heterologous butanol production by this organism.
TL;DR: Monitoring of the fermentation process of watery kimchi revealed an increase in bacterial abundance during the early fermentation period and the pH values concurrently decreased rapidly without any initial pH increase, suggesting that bacteria and Saccharomyces have a direct antagonistic relationship.
TL;DR: In this article, the authors investigated how the aroma of wheat bread crumb is influenced by yeast fermentation by comparing the aroma formation of bread fermented by seven commercial baker's yeasts, and concluded that use of the seven commercial yeast for bread fermentation resulted in significantly different bread aroma profiles.
TL;DR: Results from enzymes production at low/moderate temperatures revealed that the Antarctic environment contains metabolically diverse cultivable yeasts, which could be considered as a target for biotechnological applications.
Abstract: The aim of the present study was to investigate the taxonomic identity of yeasts isolated from the Antarctic continent and to evaluate their ability to produce enzymes (lipase, protease and xylanase) at low and moderate temperatures. A total of 97 yeast strains were recovered from marine and terrestrial samples collected in the Antarctica. The highest amount of yeast strains was obtained from marine sediments, followed by lichens, ornithogenic soils, sea stars, Salpa sp., algae, sea urchin, sea squirt, stone with lichens, Nacella concinna, sea sponge, sea isopod and sea snail. Data from polyphasic taxonomy revealed the presence of 21 yeast species, distributed in the phylum Ascomycota (n = 8) and Basidiomycota (n = 13). Representatives of encapsulated yeasts, belonging to genera Rhodotorula and Cryptococcus were recovered from 7 different Antarctic samples. Moreover, Candida glaebosa, Cryptococcus victoriae, Meyerozyma (Pichia) guilliermondii, Rhodotorula mucilaginosa and R. laryngis were the most abundant yeast species recovered. This is the first report of the occurrence of some species of yeasts recovered from Antarctic marine invertebrates. Additionally, results from enzymes production at low/moderate temperatures revealed that the Antarctic environment contains metabolically diverse cultivable yeasts, which could be considered as a target for biotechnological applications. Among the evaluated yeasts in the present study 46.39, 37.11 and 14.43 % were able to produce lipase (at 15 °C), xylanase (at 15 °C) and protease (at 25 °C), respectively. The majority of lipolytic, proteolytic and xylanolytic strains were distributed in the phylum Basidiomycota and were mainly recovered from sea stars, lichens, sea urchin and marine sediments.
TL;DR: The synergism between main representatives of water kefir yeasts and lactobacilli was studied in a co-culture model system and it was revealed that co-cultivation induced the yeast to release arginine, which was essential for Lb.
TL;DR: Phlorotannins inhibited the dimorphic transition of Candida albicans, leading to the formation of pseudohyphae with diminished capacity to adhere to epithelial cells and can be potentially interesting for combined antifungal therapy, namely for the control of invasive candidiasis.
Abstract: In the last few decades, fungal infections, particularly nosocomial, increased all around the world. This increment stimulated the search for new antifungal agents, especially those derived from nature. Among natural products, those from marine sources have gained prominence in the last years. Purified phlorotannins extracts from three brown seaweeds (Cystoseira nodicaulis (Withering) M. Roberts, Cystoseira usneoides (Linnaeus) M. Roberts and Fucus spiralis Linnaeus) were screened for their antifungal activity against human pathogenic yeast and filamentous fungi. The purified phlorotannins extracts from the studied seaweeds displayed fungistatic and fungicidal activity against yeast and dermatophytes, respectively, pointing to their interest as anti-dermatophyte agent. C. albicans ATCC 10231 was the most susceptible among yeast, while Epidermophyton floccosum and Trichophyton rubrum were the most susceptible among dermatophytes. Since the antifungal mechanism constitutes an important strategy for limiting the emergence of resistance to the commercially available agents, the mechanism of action of purified phlorotannins extracts was approached. C. nodicaulis and C. usneoides seem to act by affecting the ergosterol composition of the cell membrane of yeast and dermatophyte, respectively. F. spiralis influenced the dermatophyte cell wall composition by reducing the levels of chitin. Phlorotannins also seem to affect the respiratory chain function, as all of the studied species significantly increased the activity of mitochondrial dehydrogenases and increased the incorporation of rhodamine 123 by yeast cells. Phlorotannins from F. spiralis inhibited the dimorphic transition of Candida albicans, leading to the formation of pseudohyphae with diminished capacity to adhere to epithelial cells. This finding is associated with a decrease of C. albicans virulence and capacity to invade host cells and can be potentially interesting for combined antifungal therapy, namely for the control of invasive candidiasis.