scholarly journals Galacturonic Acid Inhibits the Growth of Saccharomyces cerevisiae on Galactose, Xylose, and Arabinose

2012 ◽  
Vol 78 (15) ◽  
pp. 5052-5059 ◽  
Author(s):  
Eline H. Huisjes ◽  
Erik de Hulster ◽  
Jan C. van Dam ◽  
Jack T. Pronk ◽  
Antonius J. A. van Maris
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Galacturonic Acid ◽  
Competitive Inhibition ◽  
Energy Requirement ◽  
Major Constituent ◽  
Yeast Fermentation ◽  
Substrate Uptake ◽  
Citrus Peel ◽  
Content Type ◽  
The Impact

ABSTRACTThe efficient fermentation of mixed substrates is essential for the microbial conversion of second-generation feedstocks, including pectin-rich waste streams such as citrus peel and sugar beet pulp. Galacturonic acid is a major constituent of hydrolysates of these pectin-rich materials. The yeastSaccharomyces cerevisiae, the main producer of bioethanol, cannot use this sugar acid. The impact of galacturonic acid on alcoholic fermentation byS. cerevisiaewas investigated with anaerobic batch cultures grown on mixtures of glucose and galactose at various galacturonic acid concentrations and on a mixture of glucose, xylose, and arabinose. In cultures grown at pH 5.0, which is well above the pKavalue of galacturonic acid (3.51), the addition of 10 g · liter−1galacturonic acid did not affect galactose fermentation kinetics and growth. In cultures grown at pH 3.5, the addition of 10 g · liter−1galacturonic acid did not significantly affect glucose consumption. However, at this lower pH, galacturonic acid completely inhibited growth on galactose and reduced galactose consumption rates by 87%. Additionally, it was shown that galacturonic acid strongly inhibits the fermentation of xylose and arabinose by the engineered pentose-fermentingS. cerevisiaestrain IMS0010. The data indicate that inhibition occurs when nondissociated galacturonic acid is present extracellularly and corroborate the hypothesis that a combination of a decreased substrate uptake rate due to competitive inhibition on Gal2p, an increased energy requirement to maintain cellular homeostasis, and/or an accumulation of galacturonic acid 1-phosphate contributes to the inhibition. The role of galacturonic acid as an inhibitor of sugar fermentation should be considered in the design of yeast fermentation processes based on pectin-rich feedstocks.

scholarly journals Metabolic Reprogramming ofVibrio choleraeImpaired in Respiratory NADH Oxidation Is Accompanied by Increased Copper Sensitivity

2018 ◽  
Vol 200 (15) ◽  
Author(s):  
Charlotte Toulouse ◽  
Kristina Metesch ◽  
Jens Pfannstiel ◽  
Julia Steuber
Keyword(s):  
Vibrio Cholerae ◽  
Pathogenic Bacteria ◽  
Carbon Sources ◽  
Copper Resistance ◽  
Metabolic Reprogramming ◽  
Deletion Strain ◽  
Substrate Uptake ◽  
Content Type ◽  
Nadh:Quinone Oxidoreductase ◽  
The Impact

ABSTRACTThe electrogenic, sodium ion-translocating NADH:quinone oxidoreductase (NQR) fromVibrio choleraeis frequent in pathogenic bacteria and a potential target for antibiotics. NQR couples the oxidation of NADH to the formation of a sodium motive force (SMF) and therefore drives important processes, such as flagellar rotation, substrate uptake, and energy-dissipating cation-proton antiport. We performed a quantitative proteome analysis ofV. choleraeO395N1 compared to its variant lacking the NQR using minimal medium with glucose as the carbon source. We found 84 proteins (regulation factor of ≥2) to be changed in abundance. The loss of NQR resulted in a decrease in the abundance of enzymes of the oxidative branch of the tricarboxylic acid (TCA) cycle and an increase in abundance of virulence factors AcfC and TcpA. Most unexpected, the copper resistance proteins CopA, CopG, and CueR were decreased in thenqrdeletion strain. As a consequence, the mutant exhibited diminished resistance to copper compared to the reference strain, as confirmed in growth studies using either glucose or mixed amino acids as carbon sources. We propose that the observed adaptations of thenqrdeletion strain represent a coordinated response which counteracts a drop in transmembrane voltage that challengesV. choleraein its different habitats.IMPORTANCEThe importance of the central metabolism for bacterial virulence has raised interest in studying catabolic enzymes not present in the host, such as NQR, as putative targets for antibiotics.Vibrio choleraelacking the NQR, which is studied here, is a model to estimate the impact of specific NQR inhibitors on the phenotype of a pathogen. Our comparative proteomic study provides a framework to evaluate the chances of success of compounds directed against NQR with respect to their bacteriostatic or bactericidal action.

scholarly journals Identification of the Aldo-Keto Reductase Responsible for d-galacturonic Acid Conversion to l-galactonate in Saccharomyces cerevisiae

2021 ◽  
Vol 7 (11) ◽  
pp. 914
Author(s):  
Dorthe Rippert ◽  
Federica Linguardo ◽  
Andreea Perpelea ◽  
Mathias Klein ◽  
Elke Nevoigt
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Galacturonic Acid ◽  
Homology Search ◽  
Cell Factory ◽  
Citrus Peel ◽  
Beet Pulp ◽  
By Products ◽  
Sequence Similarities

d-galacturonic acid (d-GalUA) is the main constituent of pectin, a complex polysaccharide abundant in several agro-industrial by-products such as sugar beet pulp or citrus peel. During several attempts to valorise d-GalUA by engineering the popular cell factory Saccharomyces cerevisiae, it became obvious that d-GalUA is, to a certain degree, converted to l-galactonate (l-GalA) by an endogenous enzymatic activity. The goal of the current work was to clarify the identity of the responsible enzyme(s). A protein homology search identified three NADPH-dependent unspecific aldo-keto reductases in baker’s yeast (encoded by GCY1, YPR1 and GRE3) that show sequence similarities to known d-GalUA reductases from filamentous fungi. Characterization of the respective deletion mutants and an in vitro enzyme assay with a Gcy1 overproducing strain verified that Gcy1 is mainly responsible for the detectable reduction of d-GalUA to l-GalA.

scholarly journals Engineering cofactor supply and NADH-dependent d-galacturonic acid reductases for redox-balanced production of l-galactonate in Saccharomyces cerevisiae

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Simon Harth ◽  
Jacqueline Wagner ◽  
Tamina Sens ◽  
Jun-yong Choe ◽  
J. Philipp Benz ◽  
...  
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Galacturonic Acid ◽  
Major Constituent ◽  
Sugar Alcohol ◽  
Catabolic Pathway ◽  
Efficient Utilization ◽  
Yeast Strains ◽  
Potential Applications ◽  
Agricultural Byproduct ◽  
Sorbitol Metabolism

Abstract d-Galacturonic acid (GalA) is the major constituent of pectin-rich biomass, an abundant and underutilized agricultural byproduct. By one reductive step catalyzed by GalA reductases, GalA is converted to the polyhydroxy acid l-galactonate (GalOA), the first intermediate of the fungal GalA catabolic pathway, which also has interesting properties for potential applications as an additive to nutrients and cosmetics. Previous attempts to establish the production of GalOA or the full GalA catabolic pathway in Saccharomyces cerevisiae proved challenging, presumably due to the inefficient supply of NADPH, the preferred cofactor of GalA reductases. Here, we tested this hypothesis by coupling the reduction of GalA to the oxidation of the sugar alcohol sorbitol that has a higher reduction state compared to glucose and thereby yields the necessary redox cofactors. By choosing a suitable sorbitol dehydrogenase, we designed yeast strains in which the sorbitol metabolism yields a “surplus” of either NADPH or NADH. By biotransformation experiments in controlled bioreactors, we demonstrate a nearly complete conversion of consumed GalA into GalOA and a highly efficient utilization of the co-substrate sorbitol in providing NADPH. Furthermore, we performed structure-guided mutagenesis of GalA reductases to change their cofactor preference from NADPH towards NADH and demonstrated their functionality by the production of GalOA in combination with the NADH-yielding sorbitol metabolism. Moreover, the engineered enzymes enabled a doubling of GalOA yields when glucose was used as a co-substrate. This significantly expands the possibilities for metabolic engineering of GalOA production and valorization of pectin-rich biomass in general.

scholarly journals Metabolic Impact of Redox Cofactor Perturbations on the Formation of Aroma Compounds in Saccharomyces cerevisiae

2015 ◽  
Vol 82 (1) ◽  
pp. 174-183 ◽  
Author(s):  
Audrey Bloem ◽  
Isabelle Sanchez ◽  
Sylvie Dequin ◽  
Carole Camarasa
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Volatile Compounds ◽  
Carbon Metabolism ◽  
Isoamyl Alcohol ◽  
Redox Status ◽  
Central Carbon Metabolism ◽  
Ethyl Esters ◽  
Content Type ◽  
Central Carbon ◽  
The Impact

ABSTRACTRedox homeostasis is a fundamental requirement for the maintenance of metabolism, energy generation, and growth inSaccharomyces cerevisiae. The redox cofactors NADH and NADPH are among the most highly connected metabolites in metabolic networks. Changes in their concentrations may induce widespread changes in metabolism. Redox imbalances were achieved with a dedicated biological tool overexpressing native NADH-dependent or engineered NADPH-dependent 2,3-butanediol dehydrogenase, in the presence of acetoin. We report that targeted perturbation of the balance of cofactors (NAD+/NADH or, to a lesser extent, NADP+/NADPH) significantly affected the production of volatile compounds. In most cases, variations in the redox state of yeasts modified the formation of all compounds from the same biochemical pathway (isobutanol, isoamyl alcohol, and their derivatives) or chemical class (ethyl esters), irrespective of the cofactors. These coordinated responses were found to be closely linked to the impact of redox status on the availability of intermediates of central carbon metabolism. This was the case for α-keto acids and acetyl coenzyme A (acetyl-CoA), which are precursors for the synthesis of many volatile compounds. We also demonstrated that changes in the availability of NADH selectively affected the synthesis of some volatile molecules (e.g., methionol, phenylethanol, and propanoic acid), reflecting the specific cofactor requirements of the dehydrogenases involved in their formation. Our findings indicate that both the availability of precursors from central carbon metabolism and the accessibility of reduced cofactors contribute to cell redox status modulation of volatile compound formation.

scholarly journals Identification of a glucose-insensitive variant of Gal2 from Saccharomyces cerevisiae exhibiting a high pentose transport capacity

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Sebastian A. Tamayo Rojas ◽  
Virginia Schadeweg ◽  
Ferdinand Kirchner ◽  
Eckhard Boles ◽  
Mislav Oreb
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Competitive Inhibition ◽  
Cellular Membrane ◽  
Major Constituent ◽  
Transport Capacity ◽  
Xylose Consumption ◽  
Fermentation Time ◽  
Renewable Feedstocks ◽  
Engineered Yeast ◽  
Pentose Transport

AbstractAs abundant carbohydrates in renewable feedstocks, such as pectin-rich and lignocellulosic hydrolysates, the pentoses arabinose and xylose are regarded as important substrates for production of biofuels and chemicals by engineered microbial hosts. Their efficient transport across the cellular membrane is a prerequisite for economically viable fermentation processes. Thus, there is a need for transporter variants exhibiting a high transport rate of pentoses, especially in the presence of glucose, another major constituent of biomass-based feedstocks. Here, we describe a variant of the galactose permease Gal2 from Saccharomyces cerevisiae (Gal2N376Y/M435I), which is fully insensitive to competitive inhibition by glucose, but, at the same time, exhibits an improved transport capacity for xylose compared to the wildtype protein. Due to this unique property, it significantly reduces the fermentation time of a diploid industrial yeast strain engineered for efficient xylose consumption in mixed glucose/xylose media. When the N376Y/M435I mutations are introduced into a Gal2 variant resistant to glucose-induced degradation, the time necessary for the complete consumption of xylose is reduced by approximately 40%. Moreover, Gal2N376Y/M435I confers improved growth of engineered yeast on arabinose. Therefore, it is a valuable addition to the toolbox necessary for valorization of complex carbohydrate mixtures.

scholarly journals Engineering Saccharomyces cerevisiae for co-utilization of d-galacturonic acid and d-glucose from citrus peel waste

2018 ◽  
Vol 9 (1) ◽  
Author(s):  
Ryan J. Protzko ◽  
Luke N. Latimer ◽  
Ze Martinho ◽  
Elise de Reus ◽  
Tanja Seibert ◽  
...  
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Galacturonic Acid ◽  
Citrus Peel

The More Control, the Better?

2014 ◽  
Vol 26 (2) ◽  
pp. 81-91 ◽  
Author(s):  
Jeeyun Oh ◽  
Mun-Young Chung ◽  
Sangyong Han
Keyword(s):  
Mixed Design ◽  
Negative Effects ◽  
Story Structure ◽  
Content Type ◽  
High User ◽  
User Control ◽  
Rigorous Research ◽  
Control Versus ◽  
The Media ◽  
The Impact

Despite of the popularity of interactive movie trailers, rigorous research on one of the most apparent features of these interfaces – the level of user control – has been scarce. This study explored the effects of user control on users’ immersion and enjoyment of the movie trailers, moderated by the content type. We conducted a 2 (high user control versus low user control) × 2 (drama film trailer versus documentary film trailer) mixed-design factorial experiment. The results showed that the level of user control over movie trailer interfaces decreased users’ immersion when the trailer had an element of traditional story structure, such as a drama film trailer. Participants in the high user control condition answered that they were less fascinated with, absorbed in, focused on, mentally involved with, and emotionally affected by the movie trailer than participants in the low user control condition only with the drama movie trailer. The negative effects of user control on the level of immersion for the drama trailer translated into users’ enjoyment. The impact of user control over interfaces on immersion and enjoyment varies depending on the nature of the media content, which suggests a possible trade-off between the level of user control and entertainment outcomes.

Inhibition of Yeast Growth by Tryptamine and Recovery with Tryptophan

2020 ◽  
Vol 16 (1) ◽  
pp. 48-52 ◽  
Author(s):  
Chandrika Kadkol ◽  
Ian Macreadie
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Carbon Source ◽  
Competitive Inhibition ◽  
Yeast Species ◽  
Inhibitory Effect ◽  
The Body ◽  
Inhibitory Effects ◽  
Trna Synthetases ◽  
Fermentative Growth ◽  
Biogenic Monoamine

Background: Tryptamine, a biogenic monoamine that is present in trace levels in the mammalian central nervous system, has probable roles as a neurotransmitter and/or a neuromodulator and may be associated with various neuropsychiatric disorders. One of the ways tryptamine may affect the body is by the competitive inhibition of the attachment of tryptophan to tryptophanyl tRNA synthetases. Methods: This study has explored the effects of tryptamine on growth of six yeast species (Saccharomyces cerevisiae, Candida glabrata, C. krusei, C. dubliniensis, C. tropicalis and C. lusitaniae) in media with glucose or ethanol as the carbon source, as well as recovery of growth inhibition by the addition of tryptophan. Results: Tryptamine was found to have an inhibitory effect on respiratory growth of all yeast species when grown with ethanol as the carbon source. Tryptamine also inhibited fermentative growth of Saccharomyces cerevisiae, C. krusei and C. tropicalis with glucose as the carbon source. In most cases the inhibitory effects were reduced by added tryptophan. Conclusion: The results obtained in this study are consistent with tryptamine competing with tryptophan to bind mitochondrial and cytoplasmic tryptophanyl tRNA synthetases in yeast: effects on mitochondrial and cytoplasmic protein synthesis can be studied as a function of growth with glucose or ethanol as a carbon source. Of the yeast species tested, there is variation in the sensitivity to tryptamine and the rescue by tryptophan. The current study suggests appropriate yeast strains and approaches for further studies.

Perceived workplace gender-bias and psychological impact

2019 ◽  
Vol 43 (3/4) ◽  
pp. 339-353 ◽  
Author(s):  
Siham Lekchiri ◽  
Cindy Crowder ◽  
Anna Schnerre ◽  
Barbara A.W. Eversole
Keyword(s):  
Gender Bias ◽  
Critical Incident ◽  
Psychological Impact ◽  
Working Women ◽  
Content Type ◽  
Treatment Bias ◽  
Male Dominated ◽  
The Impact ◽  
Organizational Mechanisms ◽  
Practical Implications

Purpose The purpose of this paper is to explore the experiences of working women in a male-dominated country (Morocco) and unveil the unique challenges and everyday gender-bias they face, the psychological impact of the perceived gender-bias and, finally, identify a variety of coping strategies or combatting mechanisms affecting their motivation and retention in the workplace. Design/methodology/approach Empirical evidence was obtained using a qualitative research method. The Critical Incident Technique (CIT) was used to collect incidents recalled by women in the select institution reflecting their perceptions of their managers’ ineffective behaviors towards them and the impact of these behaviors. The critical incidents were inductively coded, and behavioral statements were derived from the coded data. Findings The qualitative data analysis led them to structure the data according to two theme clusters: The perceived gender-bias behaviors (Covert and evident personal and organizational behaviors) and Psychological impacts resulting from the perceived bias. These behavioral practices included abusive behaviors, unfair treatment, bias and lack of recognition. The psychological impact elements involved decreased productivity, depression, anxiety and low self-esteem. Practical implications Understanding these experiences can facilitate the identification of strategies geared towards the retention of women in the workforce, and Moroccan organizations can develop and implement strategies and policies that are geared towards eliminating gender-bias in the workplace and to retaining and motivating women who remain ambitious to work in male-dominated environments and cultures. Originality/value This paper provides evidence that sufficient organizational mechanisms to support women in male-dominated environments are still unavailable, leaving them to find the proper coping mechanisms to persevere and resist.

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