scholarly journals Homoserine Toxicity in Saccharomyces cerevisiae and Candida albicans Homoserine Kinase (thr1Δ) Mutants

2010 ◽  
Vol 9 (5) ◽  
pp. 717-728 ◽  
Author(s):  
Joanne M. Kingsbury ◽  
John H. McCusker
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Amino Acids ◽  
Protein Synthesis ◽  
Candida Albicans ◽  
Biosynthetic Genes ◽  
Ubiquitin Pathway ◽  
Content Type ◽  
Threonine Synthase ◽  
Copy Numbers ◽  
Homoserine Kinase

ABSTRACT In addition to threonine auxotrophy, mutation of the Saccharomyces cerevisiae threonine biosynthetic genes THR1 (encoding homoserine kinase) and THR4 (encoding threonine synthase) results in a plethora of other phenotypes. We investigated the basis for these other phenotypes and found that they are dependent on the toxic biosynthetic intermediate homoserine. Moreover, homoserine is also toxic for Candida albicans thr1Δ mutants. Since increasing levels of threonine, but not other amino acids, overcome the homoserine toxicity of thr1Δ mutants, homoserine may act as a toxic threonine analog. Homoserine-mediated lethality of thr1Δ mutants is blocked by cycloheximide, consistent with a role for protein synthesis in this lethality. We identified various proteasome and ubiquitin pathway components that either when mutated or present in high copy numbers suppressed the thr1Δ mutant homoserine toxicity. Since the doa4Δ and proteasome mutants identified have reduced ubiquitin- and/or proteasome-mediated proteolysis, the degradation of a particular protein or subset of proteins likely contributes to homoserine toxicity.

scholarly journals Characterization of the Candida albicans Amino Acid Permease Family: Gap2 Is the Only General Amino Acid Permease and Gap4 Is an S-Adenosylmethionine (SAM) Transporter Required for SAM-Induced Morphogenesis

mSphere ◽  
2016 ◽  
Vol 1 (6) ◽  
Author(s):  
Lucie Kraidlova ◽  
Sanne Schrevens ◽  
Hélène Tournu ◽  
Griet Van Zeebroeck ◽  
Hana Sychrova ◽  
...  
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Amino Acids ◽  
Candida Albicans ◽  
Amino Acid ◽  
Virulence Factor ◽  
Amino Acid Transporters ◽  
Amino Acid Permease ◽  
Content Type ◽  
Important Virulence Factor ◽  
General Amino Acid Permease

ABSTRACT Candida albicans is a commensal organism that can thrive in many niches in its human host. The environmental conditions at these different niches differ quite a bit, and this fungus must be able to sense these changes and adapt its metabolism to them. Apart from glucose and other sugars, the uptake of amino acids is very important. This is underscored by the fact that the C. albicans genome encodes 6 orthologues of the Saccharomyces. cerevisiae general amino acid permease Gap1 and many other amino acid transporters. In this work, we characterize these six permeases and we show that C. albicans Gap2 is the functional orthologue of ScGap1 and that C. albicans Gap4 is an orthologue of ScSam3, an S-adenosylmethionine (SAM) transporter. Furthermore, we show that Gap4 is required for SAM-induced morphogenesis, an important virulence factor of C. albicans. Amino acids are key sources of nitrogen for growth of Candida albicans. In order to detect and take up these amino acids from a broad range of different and changing nitrogen sources inside the host, this fungus must be able to adapt via its expression of genes for amino acid uptake and further metabolism. We analyzed six C. albicans putative general amino acid permeases based on their homology to the Saccharomyces cerevisiae Gap1 general amino acid permease. We generated single- and multiple-deletion strains and found that, based on growth assays and transcriptional or posttranscriptional regulation, Gap2 is the functional orthologue to ScGap1, with broad substrate specificity. Expression analysis showed that expression of all GAP genes is under control of the Csy1 amino acid sensor, which is different from the situation in S. cerevisiae, where the expression of ScGAP1 is not regulated by Ssy1. We show that Gap4 is the functional orthologue of ScSam3, the only S-adenosylmethionine (SAM) transporter in S. cerevisiae, and we report that Gap4 is required for SAM-induced morphogenesis. IMPORTANCE Candida albicans is a commensal organism that can thrive in many niches in its human host. The environmental conditions at these different niches differ quite a bit, and this fungus must be able to sense these changes and adapt its metabolism to them. Apart from glucose and other sugars, the uptake of amino acids is very important. This is underscored by the fact that the C. albicans genome encodes 6 orthologues of the Saccharomyces. cerevisiae general amino acid permease Gap1 and many other amino acid transporters. In this work, we characterize these six permeases and we show that C. albicans Gap2 is the functional orthologue of ScGap1 and that C. albicans Gap4 is an orthologue of ScSam3, an S-adenosylmethionine (SAM) transporter. Furthermore, we show that Gap4 is required for SAM-induced morphogenesis, an important virulence factor of C. albicans.

scholarly journals Cell Wall-Related Bionumbers and Bioestimates of Saccharomyces cerevisiae and Candida albicans

2013 ◽  
Vol 13 (1) ◽  
pp. 2-9 ◽  
Author(s):  
Frans M. Klis ◽  
Chris G. de Koster ◽  
Stanley Brul
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Cell Wall ◽  
Candida Albicans ◽  
Cell Size ◽  
Pathogenic Fungus ◽  
Turgor Pressure ◽  
Hyphal Growth ◽  
Biological Research ◽  
Content Type ◽  
Starting Point

ABSTRACTBionumbers and bioestimates are valuable tools in biological research. Here we focus on cell wall-related bionumbers and bioestimates of the budding yeastSaccharomyces cerevisiaeand the polymorphic, pathogenic fungusCandida albicans. We discuss the linear relationship between cell size and cell ploidy, the correlation between cell size and specific growth rate, the effect of turgor pressure on cell size, and the reason why using fixed cells for measuring cellular dimensions can result in serious underestimation ofin vivovalues. We further consider the evidence that individual buds and hyphae grow linearly and that exponential growth of the population results from regular formation of new daughter cells and regular hyphal branching. Our calculations show that hyphal growth allowsC. albicansto cover much larger distances per unit of time than the yeast mode of growth and that this is accompanied by strongly increased surface expansion rates. We therefore predict that the transcript levels of genes involved in wall formation increase during hyphal growth. Interestingly, wall proteins and polysaccharides seem barely, if at all, subject to turnover and replacement. A general lesson is how strongly most bionumbers and bioestimates depend on environmental conditions and genetic background, thus reemphasizing the importance of well-defined and carefully chosen culture conditions and experimental approaches. Finally, we propose that the numbers and estimates described here offer a solid starting point for similar studies of other cell compartments and other yeast species.

scholarly journals Single Amino Acid Substitutions in HXT2.4 from Scheffersomyces stipitis Lead to Improved Cellobiose Fermentation by Engineered Saccharomyces cerevisiae

2012 ◽  
Vol 79 (5) ◽  
pp. 1500-1507 ◽  
Author(s):  
Suk-Jin Ha ◽  
Heejin Kim ◽  
Yuping Lin ◽  
Myoung-Uoon Jang ◽  
Jonathan M. Galazka ◽  
...  
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Amino Acids ◽  
Single Amino Acid ◽  
Kinetic Properties ◽  
Wild Type ◽  
Scheffersomyces Stipitis ◽  
Content Type ◽  
Charged Amino Acids ◽  
Cellodextrin Transporter ◽  
Engineered Strain

ABSTRACTSaccharomyces cerevisiaecannot utilize cellobiose, but this yeast can be engineered to ferment cellobiose by introducing both cellodextrin transporter (cdt-1) and intracellular β-glucosidase (gh1-1) genes fromNeurospora crassa. Here, we report that an engineeredS. cerevisiaestrain expressing the putative hexose transporter geneHXT2.4fromScheffersomyces stipitisandgh1-1can also ferment cellobiose. This result suggests that HXT2.4p may function as a cellobiose transporter whenHXT2.4is overexpressed inS. cerevisiae. However, cellobiose fermentation by the engineered strain expressingHXT2.4andgh1-1was much slower and less efficient than that by an engineered strain that initially expressedcdt-1andgh1-1. The rate of cellobiose fermentation by theHXT2.4-expressing strain increased drastically after serial subcultures on cellobiose. Sequencing and retransformation of the isolated plasmids from a single colony of the fast cellobiose-fermenting culture led to the identification of a mutation (A291D) in HXT2.4 that is responsible for improved cellobiose fermentation by the evolvedS. cerevisiaestrain. Substitutions for alanine (A291) of negatively charged amino acids (A291E and A291D) or positively charged amino acids (A291K and A291R) significantly improved cellobiose fermentation. The mutant HXT2.4(A291D) exhibited 1.5-fold higherKmand 4-fold higherVmaxvalues than those from wild-type HXT2.4, whereas the expression levels were the same. These results suggest that the kinetic properties of wild-type HXT2.4 expressed inS. cerevisiaeare suboptimal, and mutations of A291 into bulky charged amino acids might transform HXT2.4p into an efficient transporter, enabling rapid cellobiose fermentation by engineeredS. cerevisiaestrains.

Effects of milk proteins supplementation on muscle protein synthesis

2019 ◽  
Vol 49 (6) ◽  
pp. 1275-1286
Author(s):  
Milena Casagranda ◽  
Priscila Berti Zanella ◽  
Alexandra Ferreira Vieira ◽  
Rodrigo Cauduro Oliveira Macedo
Keyword(s):  
Amino Acids ◽  
Protein Synthesis ◽  
Muscle Protein ◽  
Muscle Protein Synthesis ◽  
Protein Biosynthesis ◽  
Nitrogen Compound ◽  
Milk Proteins ◽  
Control Group ◽  
Content Type ◽  
Protein Sources

Purpose The purpose of the study was to evaluate the acute effect of milk proteins supplementation, compared to another nitrogen compound on muscle protein synthesis. Design/methodology/approach The search was conducted on MEDLINE® (via PUBMED®), Cochrane and Embase databases, using the terms “whey proteins,” “caseins,” “milk proteins,” “protein biosynthesis,” “human” and its related entry terms. The selected outcome was fractional synthetic rate (FSR) before (0) and 3 h after consumption of milk proteins, compared to supplementation with other protein sources or isolated amino acids. Findings The results were expressed as mean difference (MD) of absolute values between treatments with confidence interval (CI) of 95 per cent. Of the 1,913 identified studies, 4 were included, with a total of 74 participants. Milk proteins generated a greater FSR (MD 0.03 per cent/h, CI 95 per cent 0.02-0.04; p < 0.00001), compared to control group. Acute consumption of milk proteins promotes higher increase in FSR than other protein sources or isolated amino acids. Originality/value This paper is a systematic review of the effects of milk proteins supplementation, which is considered an important subject because of its large consumption among athletes and physical exercise practitioners.

scholarly journals Genetic Analysis of Azole Resistance in the Darlington Strain of Candida albicans

2000 ◽  
Vol 44 (11) ◽  
pp. 2985-2990 ◽  
Author(s):  
Hiroshi Kakeya ◽  
Yoshitsugu Miyazaki ◽  
Haruko Miyazaki ◽  
Katherine Nyswaner ◽  
Brian Grimberg ◽  
...  
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Amino Acids ◽  
Candida Albicans ◽  
Amino Acid ◽  
Genetic Analysis ◽  
Expression System ◽  
Single Copy ◽  
Gene Replacement ◽  
Azole Resistance ◽  
High Level

ABSTRACT High-level azole resistance in the Darlington strain ofCandida albicans was investigated by gene replacement inC. albicans and expression in Saccharomyces cerevisiae. We sequenced the ERG11 gene, which encodes the sterol C14α-demethylase, from our copy of the Darlington strain. Both alleles contained the histidine for tyrosine substitution at position 132 (Y132H) reported in Darlington by others, but we also found a threonine-for-isoleucine substitution (I471T) not previously reported in the C. albicans ERG11. The encoded I471T change in amino acids conferred azole resistance when overexpressed alone and increased azole resistance when added to the Y132H amino acid sequence in an S. cerevisiae expression system. Replacement of one copy of ERG11 in an azole-susceptible strain of C. albicans with a single copy of the Darlington ERG11 resulted in expression of the integrated copy and a modest increase in azole resistance. The profound azole resistance of the Darlington strain is the result of multiple mutations.

Carbon source induced yeast-to-hypha transition in Candida albicans is dependent on the presence of amino acids and on the G-protein-coupled receptor Gpr1

2005 ◽  
Vol 33 (1) ◽  
pp. 291-293 ◽  
Author(s):  
M.M. Maidan ◽  
J.M. Thevelein ◽  
P. Van Dijck
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Amino Acids ◽  
Candida Albicans ◽  
Carbon Source ◽  
G Protein ◽  
High Glucose ◽  
Glucose Concentration ◽  
G Protein Coupled Receptor ◽  
Hypha Formation ◽  
G Protein Coupled

Yeast-to-hypha transition in Candida albicans can be induced by a wide variety of factors, including specific nutrients. We have started to investigate the mechanism by which some of these nutrients may be sensed. The G-protein-coupled receptor Gpr1 is required for yeast-to-hypha transition on various solid hypha-inducing media. Recently we have shown induction of Gpr1 internalization by specific amino acids, e.g. methionine. This suggests a possible role for methionine as a ligand of CaGpr1. Here we show that there is a big variation in methionine-induced hypha formation depending on the type of carbon source present in the medium. In addition high glucose concentrations repress hypha formation whereas a concentration of 0.1%, which mimics the glucose concentration present in the bloodstream, results in maximal hypha formation. Hence, it remains unclear whether Gpr1 senses sugars, as in Saccharomyces cerevisiae, or specific amino acids like methionine.

scholarly journals Put3 Positively Regulates Proline Utilization in Candida albicans

mSphere ◽  
2017 ◽  
Vol 2 (6) ◽  
Author(s):  
Walters Aji Tebung ◽  
Raha Parvizi Omran ◽  
Debra L. Fulton ◽  
Joachim Morschhäuser ◽  
Malcolm Whiteway
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Transcription Factor ◽  
Candida Albicans ◽  
Nitrogen Source ◽  
Opportunistic Pathogen ◽  
Baker's Yeast ◽  
Null Mutant ◽  
Multiple Sources ◽  
Content Type ◽  
Proline Catabolism

ABSTRACT Candida albicans poses a significant threat to the lives of immunocompromised people. Historically, knowledge has been drawn from studies on Saccharomyces cerevisiae to understand the pathogen, and many Candida albicans genes are named after their S. cerevisiae orthologs. Direct studies on the pathogen have, however, revealed differences in the roles of some orthologous proteins in the two yeasts. We show that the Put3 transcription factor allows the pathogen to completely degrade proline to usable nitrogen and carbon by evading regulatory restrictions imposed on its S. cerevisiae ortholog, which mandates conditional use of proline only as a nitrogen source in the baker’s yeast. The ability of Candida albicans to freely obtain nutrients from multiple sources may help it thrive as a commensal and opportunistic pathogen. The zinc cluster transcription factor Put3 was initially characterized in Saccharomyces cerevisiae as the transcriptional activator of PUT1 and PUT2, two genes acting early in the proline assimilation pathway. We have used phenotypic studies, transcription profiling, and chromatin immunoprecipitation with microarray technology (ChIP-chip) to establish that unlike S. cerevisiae, which only uses proline as a nitrogen source, Candida albicans can use proline as a nitrogen source, a carbon source, or a source of both nitrogen and carbon. However, a C. albicans put3 null mutant cannot grow on proline, suggesting that as in S. cerevisiae, C. albicans Put3 (CaPut3) is required for proline catabolism, and because the C. albicans put3 null mutant grew efficiently on glutamate as the sole carbon or nitrogen source, it appears that CaPut3 also regulates the early genes of the pathway. CaPut3 showed direct binding to the CaPUT1 promoter, and both PUT1 and PUT2 were upregulated in response to proline addition in a Put3-dependent manner, as well as in a C. albicans strain expressing a hyperactive Put3. CaPut3 directs proline degradation even in the presence of a good nitrogen source such as ammonia, which contrasts with S. cerevisiae Put3 (ScPut3)-regulated proline catabolism, which only occurs in the absence of a rich nitrogen source. Thus, while overall proline regulatory circuitry differs between S. cerevisiae and C. albicans, the specific role of Put3 appears fundamentally conserved. IMPORTANCE Candida albicans poses a significant threat to the lives of immunocompromised people. Historically, knowledge has been drawn from studies on Saccharomyces cerevisiae to understand the pathogen, and many Candida albicans genes are named after their S. cerevisiae orthologs. Direct studies on the pathogen have, however, revealed differences in the roles of some orthologous proteins in the two yeasts. We show that the Put3 transcription factor allows the pathogen to completely degrade proline to usable nitrogen and carbon by evading regulatory restrictions imposed on its S. cerevisiae ortholog, which mandates conditional use of proline only as a nitrogen source in the baker’s yeast. The ability of Candida albicans to freely obtain nutrients from multiple sources may help it thrive as a commensal and opportunistic pathogen.

scholarly journals Utilization of the Mating Scaffold Protein in the Evolution of a New Signal Transduction Pathway for Biofilm Development

mBio ◽  
2011 ◽  
Vol 2 (1) ◽  
Author(s):  
Song Yi ◽  
Nidhi Sahni ◽  
Karla J. Daniels ◽  
Kevin L. Lu ◽  
Guanghua Huang ◽  
...  
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Candida Albicans ◽  
Scaffold Protein ◽  
White Cell ◽  
Pheromone Response ◽  
Content Type ◽  
Pheromone Response Pathway ◽  
Protein Map ◽  
Mitogen Activated Protein ◽  
Kinase Cascade

ABSTRACTAmong the hemiascomycetes, onlyCandida albicansmust switch from the white phenotype to the opaque phenotype to mate. In the recent evolution of this transition, mating-incompetent white cells acquired a unique response to mating pheromone, resulting in the formation of a white cell biofilm that facilitates mating. All of the upstream components of the white cell response pathway so far analyzed have been shown to be derived from the ancestral pathway involved in mating, except for the mitogen-activated protein (MAP) kinase scaffold protein, which had not been identified. Here, through binding and mutational studies, it is demonstrated that in both the opaque and the white cell pheromone responses, Cst5 is the scaffold protein, supporting the evolutionary scenario proposed. Although Cst5 plays the same role in tethering the MAP kinases as Ste5 does inSaccharomyces cerevisiae, Cst5 is approximately one-third the size and has only one rather than four phosphorylation sites involved in activation and cytoplasmic relocalization.IMPORTANCECandida albicansmust switch from white to opaque to mate. Opaque cells then release pheromone, which not only induces cells to mate but also in a unique fashion induces mating-incompetent white cells to form biofilms that facilitate opaque cell mating. All of the tested upstream components of the newly evolved white cell pheromone response pathway, from the receptor to the mitogen-activated protein (MAP) kinase cascade, are the same as those of the conserved opaque cell response pathway. One key element, however, remained unidentified, the scaffold protein for the kinase cascade. Here, we demonstrate that Cst5, a homolog of theSaccharomyces cerevisiaescaffold protein Ste5, functions as the scaffold protein in both the opaque and the white cell pheromone responses. Pheromone induces Cst5 phosphorylation, which is involved in activation and cytoplasmic localization of Cst5. However, Cst5 contains only one phosphorylation site, not four as in theS. cerevisiaeortholog Ste5. These results support the hypothesis that the entire upper portion of the newly evolved white cell pheromone response pathway is derived from the conserved pheromone response pathway in the mating process.

scholarly journals The Evolutionary Rewiring of Ubiquitination Targets Has Reprogrammed the Regulation of Carbon Assimilation in the Pathogenic Yeast Candida albicans

mBio ◽  
2012 ◽  
Vol 3 (6) ◽  
Author(s):  
Doblin Sandai ◽  
Zhikang Yin ◽  
Laura Selway ◽  
David Stead ◽  
Janet Walker ◽  
...  
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Fatty Acids ◽  
Candida Albicans ◽  
Isocitrate Lyase ◽  
Carbon Sources ◽  
Carbon Assimilation ◽  
Pathogenic Yeast ◽  
Content Type ◽  
Catabolite Inactivation ◽  
Accelerated Degradation

ABSTRACTMicrobes must assimilate carbon to grow and colonize their niches. Transcript profiling has suggested thatCandida albicans, a major pathogen of humans, regulates its carbon assimilation in an analogous fashion to the model yeastSaccharomyces cerevisiae, repressing metabolic pathways required for the use of alterative nonpreferred carbon sources when sugars are available. However, we show that there is significant dislocation between the proteome and transcriptome inC. albicans. Glucose triggers the degradation of theICL1andPCK1transcripts inC. albicans, yet isocitrate lyase (Icl1) and phosphoenolpyruvate carboxykinase (Pck1) are stable and are retained. Indeed, numerous enzymes required for the assimilation of carboxylic and fatty acids are not degraded in response to glucose. However, when expressed inC. albicans,S. cerevisiaeIcl1 (ScIcl1) is subjected to glucose-accelerated degradation, indicating that likeS. cerevisiae, this pathogen has the molecular apparatus required to execute ubiquitin-dependent catabolite inactivation.C. albicansIcl1 (CaIcl1) lacks analogous ubiquitination sites and is stable under these conditions, but the addition of a ubiquitination site programs glucose-accelerated degradation of CaIcl1. Also, catabolite inactivation is slowed inC. albicans ubi4cells. Ubiquitination sites are present in gluconeogenic and glyoxylate cycle enzymes fromS. cerevisiaebut absent from theirC. albicanshomologues. We conclude that evolutionary rewiring of ubiquitination targets has meant that following glucose exposure,C. albicansretains key metabolic functions, allowing it to continue to assimilate alternative carbon sources. This metabolic flexibility may be critical during infection, facilitating the rapid colonization of dynamic host niches containing complex arrays of nutrients.IMPORTANCEPathogenic microbes must assimilate a range of carbon sources to grow and colonize their hosts. Current views about carbon assimilation in the pathogenic yeastCandida albicansare strongly influenced by theSaccharomyces cerevisiaeparadigm in which cells faced with choices of nutrients first use energetically favorable sugars, degrading enzymes required for the assimilation of less favorable alternative carbon sources. We show that this is not the case inC. albicansbecause there has been significant evolutionary rewiring of the molecular signals that promote enzyme degradation in response to glucose. As a result, this major pathogen of humans retains enzymes required for the utilization of physiologically relevant carbon sources such as lactic acid and fatty acids, allowing it to continue to use these host nutrients even when glucose is available. This phenomenon probably enhances efficient colonization of host niches where sugars are only transiently available.

scholarly journals Specific Phenotypic Traits ofStarmerella bacillarisRelated to Nitrogen Source Consumption and Central Carbon Metabolite Production during Wine Fermentation

2018 ◽  
Vol 84 (16) ◽  
Author(s):  
Vasileios Englezos ◽  
Luca Cocolin ◽  
Kalliopi Rantsiou ◽  
Anne Ortiz-Julien ◽  
Audrey Bloem ◽  
...  
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Amino Acids ◽  
Fermentation Process ◽  
Nitrogen Sources ◽  
Starter Cultures ◽  
Wine Fermentation ◽  
Phenotypic Traits ◽  
Mixed Fermentation ◽  
Content Type ◽  
Central Carbon

ABSTRACTOver the last few years, the potential of non-Saccharomycesyeasts to improve the sensory quality of wine has been well recognized. In particular, the use ofStarmerella bacillarisin mixed fermentations withSaccharomyces cerevisiaewas reported as an appropriate way to enhance glycerol formation and reduce ethanol production. However, during sequential fermentation, many factors, such as the inoculation timing, strain combination, and physical and biochemical interactions, can affect yeast growth, the fermentation process, and/or metabolite synthesis. Among them, the availability of yeast-assimilable nitrogen (YAN), due to its role in the control of growth and fermentation, has been identified as a key parameter. Consequently, a comprehensive understanding of the metabolic specificities and the nitrogen requirements would be valuable to better exploit the potential ofStarm. bacillarisduring wine fermentation. In this study, marked differences in the consumption of the total and individual nitrogen sources were registered between the two species, while the twoStarm. bacillarisstrains generally behaved uniformly.Starm. bacillarisstrains are differentiated by their preferential uptake of ammonium compared with amino acids that are poorly assimilated or even produced (alanine). Otherwise, the non-Saccharomycesyeast exhibits low activity through the acetaldehyde pathway, which triggers an important redistribution of fluxes through the central carbon metabolic network. In particular, the formation of metabolites deriving from the two glycolytic intermediates glyceraldehyde-3-phosphate and pyruvate is substantially increased during fermentations byStarm. bacillaris. This knowledge will be useful to better control the fermentation process in mixed fermentation withStarm. bacillarisandS. cerevisiae.IMPORTANCEMixed fermentations using a controlled inoculation ofStarmerella bacillarisandSaccharomyces cerevisiaestarter cultures represent a feasible way to modulate wine composition that takes advantage of both the phenotypic specificities of the non-Saccharomycesstrain and the ability ofS. cerevisiaeto complete wine fermentation. However, according to the composition of grape juices, the consumption byStarm. bacillarisof nutrients, in particular of nitrogen sources, during the first stages of the process may result in depletions that further limit the growth ofS. cerevisiaeand lead to stuck or sluggish fermentations. Consequently, understanding the preferences of non-Saccharomycesyeasts for the nitrogen sources available in grape must together with their phenotypic specificities is essential for an efficient implementation of sequential wine fermentations withStarm. bacillarisandS. cerevisiaespecies. The results of our study demonstrate a clear preference for ammonium compared to amino acids for the non-Saccharomycesspecies. This finding underlines the importance of nitrogen sources, which modulate the functional characteristics of inoculated yeast strains to better control the fermentation process and product quality.

Sign in / Sign up

Export Citation Format

Share Document