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1.
Curcumin and fisetin internalization into Saccharomyces cerevisiae cells via osmoporation: impact of multiple osmotic treatments on the process efficiency.
Medeiros, FGM, Correia, RTP, Dupont, S, Beney, L, Pedrini, MRS
Letters in applied microbiology. 2018;(4):363-369
Abstract
UNLABELLED Cell osmoporation is a simple and straightforward procedure of creating food-grade biocapsules. This study proposes a new protocol of sequential cell osmoporation stages and evaluates its impact on the efficiency of curcumin and fisetin internalization into Saccharomyces cerevisiae cells. To the best of our knowledge, this is the first report in the literature regarding the subject. To assess how multiple osmoporation stages influence the encapsulation efficiency (% EE), encapsulated amount of curcumin (IC) and fisetin (IF) into S. cerevisiae cells and cell viability, the residual supernatant was used for the subsequent encapsulation stages and viability was assessed by the CFU method. Quantification was carried through direct extraction, using an ultrasonic bath and UV-Vis spectrophotometry. Experimental data demonstrated that the addition of a second osmoporation stage increases both the EE (% EE) and the amount of encapsulated curcumin and fisetin (IC and IF). As a result, the EE was considerably improved and the obtained microcapsules contained a higher amount of the targeted bioactive compounds in its internal structure. However, adding a third osmoporation stage proved to less beneficial to the process efficiency due to its lower yield and the significant negative impact to cell viability. SIGNIFICANCE AND IMPACT OF THE STUDY For the first time in the literature, a protocol of serial osmoporation stages to enhance the encapsulation efficiency of hydrophobic low molecular weight molecules (curcumin and fisetin) into Saccharomyces cerevisiae cells was determined. By increasing overall efficiency, this protocol empowers the encapsulation process and creates a rational way to reduce waste for future industrial osmoporation applications.
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2.
Effect of Lachancea thermotolerans on the Formation of Polymeric Pigments during Sequential Fermentation with Schizosaccharosmyces pombe and Saccharomyces cerevisiae.
Escott, C, Morata, A, Ricardo-da-Silva, JM, Callejo, MJ, González, MDC, Suarez-Lepe, JA
Molecules (Basel, Switzerland). 2018;(9)
Abstract
Anthocyanins in red grape musts may evolve during the winemaking process and wine aging for several different reasons; colour stability and evolution is a complex process that may depend on grape variety, winemaking technology, fermentative yeast selection, co-pigmentation phenomena and polymerization. The condensation of flavanols with anthocyanins may occur either with the flavylium ion or with the hemiacetal formation in order to produce oligomers and polymers. The kinetics of the reaction are enhanced by the presence of metabolic acetaldehyde, promoting the formation of pyranoanthocyanin-type dimers or flavanol-ethyl-anthocyanin structures. The experimental design carried out using white must corrected with the addition of malvidin-3-O-glucoside and flavanols, suggests that non-Saccharomyces yeasts are able to provide increased levels of colour intensity and larger polymeric pigment ratios and polymerization indexes. The selection of non-Saccharomyces genera, in particular Lachancea thermotolerans and Schizosaccharomyces pombe in sequential fermentation, have provided experimental wines with increased fruity esters, as well as producing wines with potential pigment compositions, even though there is an important reduction of total anthocyanins.
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3.
Postprandial Gastrointestinal Function Differs after Acute Administration of Sourdough Compared with Brewer's Yeast Bakery Products in Healthy Adults.
Polese, B, Nicolai, E, Genovese, D, Verlezza, V, La Sala, CN, Aiello, M, Inglese, M, Incoronato, M, Sarnelli, G, De Rosa, T, et al
The Journal of nutrition. 2018;(2):202-208
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Abstract
BACKGROUND Europeans consume large quantities of bakery products, although these are known as one of the food categories that potentially leads to postprandial symptoms (such as fullness and bloating). OBJECTIVE The aim of this study was to evaluate the effects of sourdough baked goods on gastric emptying and gastrointestinal fermentation and symptoms in healthy people. METHODS In a double-blind, randomized crossover study, 2 sourdough croissants (SCs) or 2 brewer's yeast croissants (BCs) were served as single meals to 17 healthy adults [9 women; age range: 18-40 y; body mass index range (in kg/m2): 18-24]. Gastric volume (GV) was evaluated by magnetic resonance to calculate gastric-emptying rate in the 3-h interval after croissant ingestion. A hydrogen breath test was performed to measure hydrogen production after SC and BC ingestion. Palatability and postprandial gastrointestinal symptoms (discomfort, nausea, fullness, and bloating) over a 4-h period after the meal were evaluated. The area under the curve (AUC) was used to evaluate the overall effects on all variables tested. RESULTS The total GV AUC was reduced by 11% during the 3 h after the consumption of SCs compared with BCs (P = 0.02). Hydrogen production during the 4-h interval after ingestion of SCs was 30% lower than after BCs (P = 0.03). SCs were rated as being >2 times as palatable as BCs (P < 0.001). The overall severity of postprandial symptoms was 36% lower during the 4 h after intake of SCs compared with BCs (P = 0.05). CONCLUSION Sourdough bakery products could promote better postprandial gastrointestinal function in healthy adults and be more acceptable than those prepared with brewer's yeast. This trial was registered at www.clinicaltrials.gov as NCT03207516.
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Genome-wide identification of natural RNA aptamers in prokaryotes and eukaryotes.
Tapsin, S, Sun, M, Shen, Y, Zhang, H, Lim, XN, Susanto, TT, Yang, SL, Zeng, GS, Lee, J, Lezhava, A, et al
Nature communications. 2018;(1):1289
Abstract
RNAs are well-suited to act as cellular sensors that detect and respond to metabolite changes in the environment, due to their ability to fold into complex structures. Here, we introduce a genome-wide strategy called PARCEL that experimentally identifies RNA aptamers in vitro, in a high-throughput manner. By applying PARCEL to a collection of prokaryotic and eukaryotic organisms, we have revealed 58 new RNA aptamers to three key metabolites, greatly expanding the list of natural RNA aptamers. The newly identified RNA aptamers exhibit significant sequence conservation, are highly structured and show an unexpected prevalence in coding regions. We identified a prokaryotic precursor tmRNA that binds vitamin B2 (FMN) to facilitate its maturation, as well as eukaryotic mRNAs that bind and respond to FMN, suggesting FMN as the second RNA-binding ligand to affect eukaryotic expression. PARCEL results show that RNA-based sensing and gene regulation is more widespread than previously appreciated in different organisms.
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5.
The pleiotropic effects of the glutamate dehydrogenase (GDH) pathway in Saccharomyces cerevisiae.
Mara, P, Fragiadakis, GS, Gkountromichos, F, Alexandraki, D
Microbial cell factories. 2018;(1):170
Abstract
Ammonium assimilation is linked to fundamental cellular processes that include the synthesis of non-essential amino acids like glutamate and glutamine. In Saccharomyces cerevisiae glutamate can be synthesized from α-ketoglutarate and ammonium through the action of NADP-dependent glutamate dehydrogenases Gdh1 and Gdh3. Gdh1 and Gdh3 are evolutionarily adapted isoforms and cover the anabolic role of the GDH-pathway. Here, we review the role and function of the GDH pathway in glutamate metabolism and we discuss the additional contributions of the pathway in chromatin regulation, nitrogen catabolite repression, ROS-mediated apoptosis, iron deficiency and sphingolipid-dependent actin cytoskeleton modulation in S.cerevisiae. The pleiotropic effects of GDH pathway in yeast biology highlight the importance of glutamate homeostasis in vital cellular processes and reveal new features for conserved enzymes that were primarily characterized for their metabolic capacity. These newly described features constitute insights that can be utilized for challenges regarding genetic engineering of glutamate homeostasis and maintenance of redox balances, biosynthesis of important metabolites and production of organic substrates. We also conclude that the discussed pleiotropic features intersect with basic metabolism and set a new background for further glutamate-dependent applied research of biotechnological interest.
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6.
Origins, evolution, domestication and diversity of Saccharomyces beer yeasts.
Gallone, B, Mertens, S, Gordon, JL, Maere, S, Verstrepen, KJ, Steensels, J
Current opinion in biotechnology. 2018;:148-155
Abstract
Yeasts have been used for food and beverage fermentations for thousands of years. Today, numerous different strains are available for each specific fermentation process. However, the nature and extent of the phenotypic and genetic diversity and specific adaptations to industrial niches have only begun to be elucidated recently. In Saccharomyces, domestication is most pronounced in beer strains, likely because they continuously live in their industrial niche, allowing only limited genetic admixture with wild stocks and minimal contact with natural environments. As a result, beer yeast genomes show complex patterns of domestication and divergence, making both ale (S. cerevisiae) and lager (S. pastorianus) producing strains ideal models to study domestication and, more generally, genetic mechanisms underlying swift adaptation to new niches.
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7.
Strategies for microbial synthesis of high-value phytochemicals.
Li, S, Li, Y, Smolke, CD
Nature chemistry. 2018;(4):395-404
Abstract
Phytochemicals are of great pharmaceutical and agricultural importance, but often exhibit low abundance in nature. Recent demonstrations of industrial-scale production of phytochemicals in yeast have shown that microbial production of these high-value chemicals is a promising alternative to sourcing these molecules from native plant hosts. However, a number of challenges remain in the broader application of this approach, including the limited knowledge of plant secondary metabolism and the inefficient reconstitution of plant metabolic pathways in microbial hosts. In this Review, we discuss recent strategies to achieve microbial biosynthesis of complex phytochemicals, including strategies to: (1) reconstruct plant biosynthetic pathways that have not been fully elucidated by mining enzymes from native and non-native hosts or by enzyme engineering; (2) enhance plant enzyme activity, specifically cytochrome P450 activity, by improving efficiency, selectivity, expression or electron transfer; and (3) enhance overall reaction efficiency of multi-enzyme pathways by dynamic control, compartmentalization or optimization with the host's metabolism. We also highlight remaining challenges to - and future opportunities of - this approach.
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8.
The yeast replicative aging model.
He, C, Zhou, C, Kennedy, BK
Biochimica et biophysica acta. Molecular basis of disease. 2018;(9 Pt A):2690-2696
Abstract
It has been nearly three decades since the budding yeast Saccharomyces cerevisiae became a significant model organism for aging research and it has emerged as both simple and powerful. The replicative aging assay, which interrogates the number of times a "mother" cell can divide and produce "daughters", has been a stalwart in these studies, and genetic approaches have led to the identification of hundreds of genes impacting lifespan. More recently, cell biological and biochemical approaches have been developed to determine how cellular processes become altered with age. Together, the tools are in place to develop a holistic view of aging in this single-celled organism. Here, we summarize the current state of understanding of yeast replicative aging with a focus on the recent studies that shed new light on how aging pathways interact to modulate lifespan in yeast.
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9.
Lipids and lipid domains of the yeast vacuole.
Tsuji, T, Fujimoto, T
Biochemical Society transactions. 2018;(5):1047-1054
Abstract
The membrane raft has been a focus of intensive research for the past two decades. Liquid-ordered domains form in artificial liposomes containing sterol and saturated lipids, but their presence in living cell membranes has been controversial. The yeast vacuole is exceptional in that micron-sized raft-like domains form in the stationary phase and under several other conditions. The sterol content of the vacuole in the log phase is much lower than that of liposomes showing liquid-ordered domains, suggesting that sterols may need to be supplied to the vacuole for the raft-like domain formation. We will discuss how lipids and lipid domains are organized in the vacuolar membrane and examine whether evidence is strong enough to conclude that the observed micron-sized domains are rafts.
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10.
Bifurcations and limit cycles in cytosolic yeast calcium.
Fan, G, Huff, R, Muir, J, Nektalova, Z, Kruchowsky, J, Kepler, JL, Wang, H, Marshall, PA, Solis, FJ
Mathematical biosciences. 2018;:58-70
Abstract
Calcium homeostasis is a fundamental cellular process in yeast. The regulation of the cytosolic calcium concentration is required for volume preservation and to regulate many vital calcium dependent processes such as mating and response to stress. The homeostatic mechanism is often studied by applying calcium pulses: sharply changing the calcium concentration in the yeast environment and observing the cellular response. To address these experimental investigations, several mathematical models have been proposed to describe this response. In this article we demonstrate that a previously studied model for this response predicts the presence of limit point instabilities and limit cycles in the dynamics of the calcium homeostasis system. We discuss the ways in which such dynamic characteristics can be observed with luminometric techniques. We contrast these predictions with experimentally observed responses and find that the experiments reveal a number of features that are consistent with modeling predictions. In particular, we find that equilibrium cytosolic concentrations have a sharp change in behavior as pulse size changes in the micromolar range. We show that such change is consistent with the presence of limit point instabilities. Additionally, we find that the response of synchronized yeast cells to millimolar range pulses is non-monotonic in its late stages. This response has characteristics similar to those associated with limit cycles.