RNA-seq based transcriptomic analysis of the non-conventional yeast Spathaspora passalidarum during Melle-boinot cell recycle in xylose-glucose mixtures
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ABSTRACT:
ORGANISM(S): Spathaspora passalidarum
PROVIDER: GSE178100 | GEO | 2021/06/15
REPOSITORIES: GEO
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Project description:Creating Saccharomyces yeasts capable of efficient fermentation of pentoses such as xylose remains a key challenge in the production of ethanol from lignocellulosic biomass. Metabolic engineering of industrial Saccharomyces cerevisiae strains has yielded xylose-fermenting strains, but these strains have not yet achieved industrial viability due largely to xylose fermentation being prohibitively slower than that of glucose. Recently, it has been shown that naturally occurring xylose-utilizing Saccharomyces species exist. Uncovering the genetic architecture of such strains will shed further light on xylose metabolism, suggesting additional engineering approaches or possibly even the development of xylose-fermenting yeasts that are not genetically modified. We previously identified a hybrid yeast strain, the genome of which is largely Saccharomyces uvarum, which has the ability to grow on xylose as the sole carbon source. Despite the sterility of this hybrid strain, we were able to develop novel methods to genetically characterize its xylose utilization phenotype, using bulk segregant analysis in conjunction with high-throughput sequencing. We found that its growth in xylose is governed by at least two genetic loci: one of the loci maps to a known xylose-pathway gene, a novel allele of the aldo-keto reductase gene GRE3, while a second locus maps to an allele of APJ1, a chaperonin gene not previously connected to xylose metabolism. Our work demonstrates that the power of sequencing combined with bulk segregant analysis can also be applied to a non-genetically-tractable hybrid strain that contains a complex, polygenic trait, and it identifies new avenues for metabolic engineering as well as for construction of non-genetically modified xylose-fermenting strains.
2012-07-19 | GSE35528 | GEO
Project description:The modification of the The modification of the tolerance of xylose-fermenting yeast is an urgent issue for improving ethanol production. In this study, multiple genes involving in superoxide dismutase, glutathione biosynthesis, NADPH regeneration and acetic acid degradation were overexpressed using stress-induced promoters, which is selected from the transcriptome data. Stress-induced promoters were used to realize the feedback control of the tolerant genes, which can ultimately improve the tolerance and ethanol production. We reported the stress-induced promoters for overexpressing tolerant genes and increasing yeast tolerance in a feedback manner
2022-01-01 | GSE140075 | GEO
Project description:xylose fermenting yeast for ethanol production
| PRJNA827654 | ENA
Project description:Background: Lignocellulosic biomass is a promising renewable feedstock for the microbial production of fuels. To release the major fermentable sugars such as glucose and xylose, pretreatment and enzymatic hydrolysis of biomass feedstock are needed. During this process, many toxic compounds are produced or introduced which subsequently inhibit microbial growth and eventually the production rate and yield. Acetate is one of the major inhibitors liberated from hemicelluloses during dilute acid pretreatment. An understanding of the toxic effects of acetate on the fermentation microorganism is critical to improving biofuel yields in the process. In addition, the efficient utilization of mixed sugars of glucose and xylose in the presence of hydrolysate inhibitors is crucial for economic biofuel production. Results: We have observed previously that some pretreatment inhibitors affect growth and performance in Zymomonas mobilis 8b differently when different sugars (e.g. glucose or xylose) are used as substrate. To investigate this phenomenon at the cellular level, microarray technology was used to investigate the acetate stress responses of Z. mobilis 8b when using single carbon sources of glucose or xylose, and mixed sugars of glucose and xylose. We designed a microarray based on the most up-to-date genome annotation for both coding sequences and intergenic regions. In the presence of acetate, 8b still can utilize all the glucose (though xylose utilization was inhibited) with similar ethanol yield although the growth, final biomass, and ethanol production rate were reduced. The presence of acetate caused genes related to biosynthesis, flagellar system, and glycolysis to be downregulated, and genes related to stress responses and energy metabolism to be upregulated. Our result indicates that Z. mobilis utilized different mechanism for xylose utilization compared to that of glucose, with even more dramatic results than those caused by treatment of the culture with the inhibitor acetate. Our study also suggests that redox imbalance caused by stressful conditions may trigger a metabolic reaction that leads to the accumulation of toxic intermediates such as xylitol, but Z. mobilis appears to be capable of managing its carbon and energy metabolism through the control of individual reactions to overcome the inhibition caused by stressful conditions. Several target gene candidates based on transcriptomic result have been selected for genetic manipulation and a TonB-dependent receptor knockout mutant was confirmed to have advantage on acetate tolerance. Conclusions: We have gained insights into the molecular responses of the model ethanologenic bacterium Z. mobilis to the inhibitor acetate when grown in different sugar sources. These insights will facilitate future metabolic modeling studies and help further strain metabolic engineering efforts for better xylose utilization and acetate tolerance. Two series of microarray studies using total RNA extracted from Zymomonas mobilis subsp mobilis 8b (an xylose-utilizing recombinant) were carried out to investigate the effect of carbon source and acetate on Z. mobilis. One study compared the acetate effect in either glucose or xylose at exponential phase and another study investigated the acetate effect in mixed sugar of glucose and xylose at three growth phases of exponential, transition, and stationary. Tthree biological replicates were used for each condition.
2014-09-08 | E-GEOD-57553 | biostudies-arrayexpress
Project description:We previously reported that a recombinant Candida utilis strain expressing a Candida shehatae xylose reductase K275R/N277D, a C. shehatae xylitol dehydrogenase, and xylulokinase from Pichia stipitis produced ethanol from xylose. However, its productivity was low. In this study, metabolomic (CE-TOF MS) and transcriptomic (microarray) analyses were performed to characterize xylose metabolism by the engineered C. utilis and to identify key genetic changes contributing to efficient xylose utilization. Metabolomic analysis revealed that the xylose-fermenting strain accumulated more pentose phosphate pathway intermediates, more NADH, and more glycolytic intermediates upstream of glyceraldehyde 3-phosphate than wild-type. Transcriptomic analysis of the strain grown on xylose indicated a significant increase in expression of genes encoding tricarboxylic acid cycle enzymes, respiratory enzymes, and enzymes involved in ethanol oxidation. To decrease the NADH/NAD+ ratio and increase ethanol yield from the fermentation of xylose, ADH1 encoding NADH-dependent alcohol dehydrogenase was overexpressed. The resultant strain exhibited a 17% increase in ethanol production and a 22% decrease in xylitol accumulation relative to the control.
2014-01-01 | GSE43514 | GEO
Project description:Background Lignocellulosic biomass is a promising renewable feedstock for biofuel production. Acetate is one of the major inhibitors liberated from hemicelluloses during hydrolysis. An understanding of the toxic effects of acetate on the fermentation microorganism and the efficient utilization of mixed sugars of glucose and xylose in the presence of hydrolysate inhibitors is crucial for economic biofuel production. Results A new microarray was designed including both coding sequences and intergenic regions to investigate the acetate stress responses of Zymomonas mobilis 8b when using single carbon sources of glucose or xylose, or mixed sugars of both glucose and xylose. With the supplementation of exogenous acetate, 8b can utilize all the glucose with a similar ethanol yield, although the growth, final biomass, and ethanol production rate were reduced. However, xylose utilization was inhibited in both media containing xylose or a mixed sugar of glucose and xylose, although the performance of 8b was better in mixed sugar than xylose-only media. The presence of acetate caused genes related to biosynthesis, the flagellar system, and glycolysis to be downregulated, and genes related to stress responses and energy metabolism to be upregulated. Unexpectedly, xylose seems to pose more stress on 8b, recruiting more genes for xylose utilization, than does acetate. Several gene candidates based on transcriptome results were selected for genetic manipulation, and a TonB-dependent receptor knockout mutant was confirmed to have a slight advantage regarding acetate tolerance. Conclusions Our results indicate Z. mobilis utilized a different mechanism for xylose utilization, with an even more severe impact on Z. mobilis than that caused by acetate treatment. Our study also suggests redox imbalance caused by stressful conditions may trigger a metabolic reaction leading to the accumulation of toxic intermediates such as xylitol, but Z. mobilis manages its carbon and energy metabolism through the control of individual reactions to mitigate the stressful conditions. We have thus provided extensive transcriptomic datasets and gained insights into the molecular responses of Z. mobilis to the inhibitor acetate when grown in different sugar sources, which will facilitate future metabolic modeling studies and strain improvement efforts for better xylose utilization and acetate tolerance.
2014-09-08 | GSE57553 | GEO
Project description:Background: Lignocellulosic biomass is a promising renewable feedstock for the microbial production of fuels. To release the major fermentable sugars such as glucose and xylose, pretreatment, hydrolysis, and subsequent conditioning of biomass feedstock are needed. During this process, many toxic compounds are produced or introduced which subsequently inhibit microbial growth and in many cases the production titer and rate. An understanding of the toxic effects of compounds found in hydrolysate on the fermentation microorganism is critical to improving biofuel yields in the process. One of the inhibitory compounds is furfural, liberated from hemicelluloses, which strongly inhibits the cell growth and ethanol production especially from xylose. Zymomonas mobilis is a capable ethanologenic bacterium with high ethanol productivity and high levels of ethanol tolerance. The development of robust biocatalyst to tolerate the lignocellulosic pretreatment inhibitors is one of the key elements for economic biofuel production. Results: In this study, the molecular responses of Z. mobilis to furfural, one major pretreatment inhibitor, were investigated using transcriptomic approaches of chip-based microarray. Furfural shock time course experiment with 3 g/L furfural supplemented when cells reach exponential phase and stress response experiment in the presence of 2 g/L furfural from the beginning of fermentation were carried out to study the short and long-term effect of furfural on 8b physiological and transcriptional profiles. The presence and supplementation of furfural negatively affect 8b growth in terms of final biomass and the fermentation time. Transcriptomic studies indicated that the response of 8b to furfural is dynamic, complex and differences exist between short-term shock response and long-term stress response. However, the gene function categories are similar with most downregulated genes related to translation and biosynthesis, while the furfural-upregulated genes were mostly related to cellular processes of general stress response and energy metabolism. Conclusions: Similar to previous report that acetate inhibited the growth of Z. mobilis 8b in RM using glucose or xylose as carbon source, the existence or supplementation of another major hydrolysate inhibitor furfural also inhibited 8b growth with slowing the substrate utilization and ethanol production. The difference between carbon sources is more dramatic than that of the major hydrolysate inhibitors of both NH4OAc (GSE57553) and furfural (this study). Several gene targets have been selected for genetic studies with promising preliminary results.
2016-11-18 | GSE63540 | GEO
Project description:Purpose: The ability to rationally manipulate the transcriptional states of cells would be of great use in medicine and bioengineering. We have developed a novel algorithm, NetSurgeon, which utilizes genome-wide gene regulatory networks to identify interventions that force a cell toward a desired expression state. Results: We used NetSurgeon to select transcription factor deletions aimed at improving ethanol production in S. cerevisiae cultures that are catabolizing xylose. We reasoned that interventions that move the transcriptional states of cells utilizing xylose toward the fermentative state typical of cells that are producing ethanol rapidly (while utilizing glucose) might improve xylose fermentation. Some of the interventions selected by NetSurgeon successfully promoted a fermentative transcriptional state in the absence of glucose, resulting in strains with a 2.7-fold increase in xylose import rates, a 4-fold improvement in xylose integration into central carbon metabolism, or a 1.3-fold increase in ethanol production rate. Conclusions: We conclude by presenting an integrated model of transcriptional regulation and metabolic flux that will enable future metabolic engineering efforts aimed at improving xylose fermentation to prioritize functional regulators of central carbon metabolism.
2016-06-03 | GSE69682 | GEO
Project description:Liu2012 - Genome-scale metabolic network of Scheffersomyces stipitis (iTL885)
This model is described in the article:
A constraint-based model of
Scheffersomyces stipitis for improved ethanol production.
Liu T, Zou W, Liu L, Chen J.
Biotechnol Biofuels 2012; 5(1):
72
Abstract:
UNLABELLED: BACKGROUND: As one of the best xylose
utilization microorganisms, Scheffersomyces stipitis exhibits
great potential for the efficient lignocellulosic biomass
fermentation. Therefore, a comprehensive understanding of its
unique physiological and metabolic characteristics is required
to further improve its performance on cellulosic ethanol
production. RESULTS: A constraint-based genome-scale metabolic
model for S. stipitis CBS 6054 was developed on the basis of
its genomic, transcriptomic and literature information. The
model iTL885 consists of 885 genes, 870 metabolites, and 1240
reactions. During the reconstruction process, 36 putative sugar
transporters were reannotated and the metabolisms of 7 sugars
were illuminated. Essentiality study was conducted to predict
essential genes on different growth media. Key factors
affecting cell growth and ethanol formation were investigated
by the use of constraint-based analysis. Furthermore, the
uptake systems and metabolic routes of xylose were elucidated,
and the optimization strategies for the overproduction of
ethanol were proposed from both genetic and environmental
perspectives. CONCLUSIONS: Systems biology modelling has proven
to be a powerful tool for targeting metabolic changes. Thus,
this systematic investigation of the metabolism of S. stipitis
could be used as a starting point for future experiment designs
aimed at identifying the metabolic bottlenecks of this
important yeast.
This model is hosted on
BioModels Database
and identified by:
MODEL1507180026.
To cite BioModels Database, please use:
BioModels Database:
An enhanced, curated and annotated resource for published
quantitative kinetic models.
To the extent possible under law, all copyright and related or
neighbouring rights to this encoded model have been dedicated to
the public domain worldwide. Please refer to
CC0
Public Domain Dedication for more information.
2015-07-30 | MODEL1507180026 | BioModels
Project description:Caspeta2012 - Genome-scale metabolic network
of Pichia pastoris (iLC915)
This model is described in the article:
Genome-scale metabolic
reconstructions of Pichia stipitis and Pichia pastoris and in
silico evaluation of their potentials.
Caspeta L, Shoaie S, Agren R,
Nookaew I, Nielsen J.
BMC Syst Biol 2012; 6: 24
Abstract:
BACKGROUND: Pichia stipitis and Pichia pastoris have long
been investigated due to their native abilities to metabolize
every sugar from lignocellulose and to modulate methanol
consumption, respectively. The latter has been driving the
production of several recombinant proteins. As a result,
significant advances in their biochemical knowledge, as well as
in genetic engineering and fermentation methods have been
generated. The release of their genome sequences has allowed
systems level research. RESULTS: In this work, genome-scale
metabolic models (GEMs) of P. stipitis (iSS884) and P. pastoris
(iLC915) were reconstructed. iSS884 includes 1332 reactions,
922 metabolites, and 4 compartments. iLC915 contains 1423
reactions, 899 metabolites, and 7 compartments. Compared with
the previous GEMs of P. pastoris, PpaMBEL1254 and iPP668,
iLC915 contains more genes and metabolic functions, as well as
improved predictive capabilities. Simulations of physiological
responses for the growth of both yeasts on selected carbon
sources using iSS884 and iLC915 closely reproduced the
experimental data. Additionally, the iSS884 model was used to
predict ethanol production from xylose at different oxygen
uptake rates. Simulations with iLC915 closely reproduced the
effect of oxygen uptake rate on physiological states of P.
pastoris expressing a recombinant protein. The potential of P.
stipitis for the conversion of xylose and glucose into ethanol
using reactors in series, and of P. pastoris to produce
recombinant proteins using mixtures of methanol and glycerol or
sorbitol are also discussed. CONCLUSIONS: In conclusion the
first GEM of P. stipitis (iSS884) was reconstructed and
validated. The expanded version of the P. pastoris GEM, iLC915,
is more complete and has improved capabilities over the
existing models. Both GEMs are useful frameworks to explore the
versatility of these yeasts and to capitalize on their
biotechnological potentials.
This model is hosted on
BioModels Database
and identified by:
MODEL1507180065.
To cite BioModels Database, please use:
BioModels Database:
An enhanced, curated and annotated resource for published
quantitative kinetic models.
To the extent possible under law, all copyright and related or
neighbouring rights to this encoded model have been dedicated to
the public domain worldwide. Please refer to
CC0
Public Domain Dedication for more information.
2015-07-30 | MODEL1507180065 | BioModels