D-Xylose

14,000,000 Leading Edge Experts on the ideXlab platform

Scan Science and Technology

Contact Leading Edge Experts & Companies

Scan Science and Technology

Contact Leading Edge Experts & Companies

The Experts below are selected from a list of 258 Experts worldwide ranked by ideXlab platform

Barbel Hahnhagerdal - One of the best experts on this subject based on the ideXlab platform.

  • the glucose xylose facilitator gxf1 from candida intermedia expressed in a xylose fermenting industrial strain of saccharomyces cerevisiae increases xylose uptake in sscf of wheat straw
    Enzyme and Microbial Technology, 2011
    Co-Authors: Cesar Fonseca, David Runquist, Kim Olofsson, Luis L Fonseca, Carla Ferreira, Barbel Hahnhagerdal, Gunnar Liden
    Abstract:

    Ethanolic fermentation of lignocellulose raw materials requires industrial xylose-fermenting strains capable of complete and efficient D-Xylose consumption. A central question in xylose fermentation by Saccharomyces cerevisiae engineered for xylose fermentation is to improve the xylose uptake. In the current study, the glucose/xylose facilitator Gxf1 from Candida intermedia, was expressed in three different xylose-fermenting S. cerevisiae strains of industrial origin. The in vivo effect on aerobic xylose growth and the initial xylose uptake rate were assessed. The expression of Gxf1 resulted in enhanced aerobic xylose growth only for the TMB3400 based strain. It displayed more than a 2-fold higher affinity for D-Xylose than the parental strain and approximately 2-fold higher initial specific growth rate at 4 g/L D-Xylose. Enhanced xylose consumption was furthermore observed when the GXF1-strain was assessed in simultaneous saccharification and co-fermentation (SSCF) of pretreated wheat straw. However, the ethanol yield remained unchanged due to increased by-product formation. Metabolic flux analysis suggested that the expression of the Gxf1 transporter had shifted the control of xylose catabolism from transport to the NAD(+) dependent oxidation of xylitol to xylulose. (C) 2011 Elsevier Inc. All rights reserved. (Less)

  • increased expression of the oxidative pentose phosphate pathway and gluconeogenesis in anaerobically growing xylose utilizing saccharomyces cerevisiae
    Microbial Cell Factories, 2009
    Co-Authors: David Runquist, Barbel Hahnhagerdal, Maurizio Bettiga
    Abstract:

    Background Fermentation of xylose to ethanol has been achieved in S. cerevisiae by genetic engineering. Xylose utilization is however slow compared to glucose, and during anaerobic conditions addition of glucose has been necessary for cellular growth. In the current study, the xylose-utilizing strain TMB 3415 was employed to investigate differences between anaerobic utilization of glucose and xylose. This strain carried a xylose reductase (XYL1 K270R) engineered for increased NADH utilization and was capable of sustained anaerobic growth on xylose as sole carbon source. Metabolic and transcriptional characterization could thus for the first time be performed without addition of a co-substrate or oxygen.

  • high capacity xylose transport in candida intermedia pycc 4715
    Fems Yeast Research, 2003
    Co-Authors: Mark Gardonyi, Mans Osterberg, Carla Rodrigues, Isabel Spencermartins, Barbel Hahnhagerdal
    Abstract:

    Xylose-utilising yeasts were screened to identify strains with high xylose transport capacity. Among the fastest-growing strains in xylose medium, Candida intermedia PYCC 4715 showed the highest xylose transport capacity. Maximal specific growth rate was the same in glucose and xylose media (μmax=0.5 h−1, 30°C). Xylose transport showed biphasic kinetics when cells were grown in either xylose- or glucose-limited culture. The high-affinity xylose/proton symport system (Km=0.2 mM, Vmax=7.5 mmol h−1 g−1) was more repressed by glucose than by xylose. The less specific low-affinity transport system (K=50 mM, Vmax=11 mmol h−1 g−1) appeared to operate through a facilitated-diffusion mechanism and was expressed constitutively. Inhibition experiments showed that glucose is a substrate of both xylose transport systems.

  • molecular analysis of a saccharomyces cerevisiae mutant with improved ability to utilize xylose shows enhanced expression of proteins involved in transport initial xylose metabolism and the pentose phosphate pathway
    Applied and Environmental Microbiology, 2003
    Co-Authors: Fredrik C Wahlbom, Barbel Hahnhagerdal, Ricardo Cordero R Otero, L Jonsson
    Abstract:

    Differences between the recombinant xylose-utilizing Saccharomyces cerevisiae strain TMB 3399 and the mutant strain TMB 3400, derived from TMB 3399 and displaying improved ability to utilize xylose, were investigated by using genome-wide expression analysis, physiological characterization, and biochemical assays. Samples for analysis were withdrawn from chemostat cultures. The characteristics of S. cerevisiae TMB 3399 and TMB 3400 grown on glucose and on a mixture of glucose and xylose, as well as of S. cerevisiae TMB 3400 grown on only xylose, were investigated. The strains were cultivated under chemostat conditions at a dilution rate of 0.1 h 1 , with feeds consisting of a defined mineral medium supplemented with 10 g of glucose liter 1 , 10 g of glucose plus 10 g of xylose liter 1 or, for S. cerevisiae TMB 3400, 20 g of xylose liter 1 . S. cerevisiae TMB 3400 consumed 31% more xylose of a feed containing both glucose and xylose than S. cerevisiae TMB 3399. The biomass yields for S. cerevisiae TMB 3400 were 0.46 g of biomass g of consumed carbohydrate 1 on glucose and 0.43 g of biomass g of consumed carbohydrate 1 on xylose. A Ks value of 33 mM for xylose was obtained for S. cerevisiae TMB 3400. In general, the percentage error was <20% between duplicate microarray experiments originating from independent fermentation experiments. Microarray analysis showed higher expression in S. cerevisiae TMB 3400 than in S. cerevisiae TMB 3399 for (i) HXT5, encoding a hexose transporter; (ii) XKS1, encoding xylulokinase, an enzyme involved in one of the initial steps of xylose utilization; and (iii) SOL3, GND1, TAL1, and TKL1, encoding enzymes in the pentose phosphate pathway. In addition, the transcriptional regulators encoded by YCR020C, YBR083W, and YPR199C were expressed differently in the two strains. Xylose utilization was, however, not affected in strains in which YCR020C was overexpressed or deleted. The higher expression of XKS1 in S. cerevisiae TMB 3400 than in TMB 3399 correlated with higher specific xylulokinase activity in the cell extracts. The specific activity of xylose reductase and xylitol dehydrogenase was also higher for S. cerevisiae TMB 3400 than for TMB 3399, both on glucose and on the mixture of glucose and xylose.

  • the non oxidative pentose phosphate pathway controls the fermentation rate of xylulose but not of xylose in saccharomyces cerevisiae tmb3001
    Fems Yeast Research, 2002
    Co-Authors: Bjorn Johansson, Barbel Hahnhagerdal
    Abstract:

    Saccharomyces cerevisiae is able to ferment xylose, when engineered with the enzymes xylose reductase (XYL1) and xylitol dehydrogenase (XYL2). However, xylose fermentation is one to two orders of magnitude slower than glucose fermentation. S. cerevisiae has been proposed to have an insufficient capacity of the non-oxidative pentose phosphate pathway (PPP) for rapid xylose fermentation. Strains overproducing the non-oxidative PPP enzymes ribulose 5-phosphate epimerase (EC 5.1.3.1), ribose 5-phosphate ketol isomerase (EC 5.3.1.6), transaldolase (EC 2.2.1.2) and transketolase (EC 2.2.1.1), as well as all four enzymes simultaneously, were compared with respect to xylose and xylulose fermentation with their xylose-fermenting predecessor S. cerevisiae TMB3001, expressing XYL1, XYL2 and only overexpressing XKS1 (xylulokinase). The level of overproduction in S. cerevisiae TMB3026, overproducing all four non-oxidative PPP enzymes, ranged between 4 and 23 times the level in TMB001. Overproduction of the non-oxidative PPP enzymes did not influence the xylose fermentation rate in either batch cultures of 50 g l(-1) xylose or chemostat cultures of 20 g l(-1) glucose and 20 g l(-1) xylose. The low specific growth rate on xylose was also unaffected. The results suggest that neither of the non-oxidative PPP enzymes has any significant control of the xylose fermentation rate in S. cerevisiae TM133001. However, the specific growth rate on xylulose increased from 0.02-0.03 for TMB3001 to 0.12 for the strain overproducing only transaldolase (TAL1) and to 0.23 for TMB3026, suggesting that overproducing all four enzymes has a synergistic effect. TMB3026 consumed xylulose about two times faster than TMB30001 in batch culture of 50 g l(-1) xylulose. The results indicate that growth on xylulose and the xylulose fermentation rate are partly controlled by the non-oxidative PPP, whereas control of the xylose fermentation rate is situated upstream of xylulokinase, in xylose transport, in xylose reductase, and/or in the xylitol dehydrogenase. (C) 2002 Federation of European Microbiological Societies. Published by Elsevier Science B.V. All rights reserved.

Bärbel Hahn-hägerdal - One of the best experts on this subject based on the ideXlab platform.

  • The glucose/xylose facilitator gxf1 from Candida intermedia expressed in a xylose-fermenting industrial strain of Saccharomyces cerevisiae increases xylose uptake in SSCF of wheat straw.
    Enzyme and Microbial Technology, 2011
    Co-Authors: Cesar Fonseca, David Runquist, Kim Olofsson, Luis L Fonseca, Carla Ferreira, Bärbel Hahn-hägerdal, Gunnar Liden
    Abstract:

    Ethanolic fermentation of lignocellulose raw materials requires industrial xylose-fermenting strains capable of complete and efficient D-Xylose consumption. A central question in xylose fermentation by Saccharomyces cerevisiae engineered for xylose fermentation is to improve the xylose uptake. In the current study, the glucose/xylose facilitator Gxf1 from Candida intermedia, was expressed in three different xylose-fermenting S. cerevisiae strains of industrial origin. The in vivo effect on aerobic xylose growth and the initial xylose uptake rate were assessed. The expression of Gxf1 resulted in enhanced aerobic xylose growth only for the TMB3400 based strain. It displayed more than a 2-fold higher affinity for D-Xylose than the parental strain and approximately 2-fold higher initial specific growth rate at 4 g/L D-Xylose. Enhanced xylose consumption was furthermore observed when the GXF1-strain was assessed in simultaneous saccharification and co-fermentation (SSCF) of pretreated wheat straw. However, the ethanol yield remained unchanged due to increased by-product formation. Metabolic flux analysis suggested that the expression of the Gxf1 transporter had shifted the control of xylose catabolism from transport to the NAD(+) dependent oxidation of xylitol to xylulose. (C) 2011 Elsevier Inc. All rights reserved. (Less)

  • A mutated xylose reductase increases bioethanol production more than a glucose/xylose facilitator in simultaneous fermentation and co-fermentation of wheat straw
    AMB Express, 2011
    Co-Authors: Kim Olofsson, David Runquist, Bärbel Hahn-hägerdal, Gunnar Liden
    Abstract:

    Genetically engineered Saccharomyces cerevisiae strains are able to ferment xylose present in lignocellulosic biomass. However, better xylose fermenting strains are required to reach complete xylose uptake in simultaneous saccharification and co-fermentation (SSCF) of lignocellulosic hydrolyzates. In the current study, haploid Saccharomyces cerevisiae strains expressing a heterologous xylose pathway including either the native xylose reductase (XR) from P. stipiti s, a mutated variant of XR (mXR) with altered co-factor preference, a glucose/xylose facilitator (Gxf1) from Candida intermedia or both mXR and Gxf1 were assessed in SSCF of acid-pretreated non-detoxified wheat straw. The xylose conversion in SSCF was doubled with the S. cerevisiae strain expressing mXR compared to the isogenic strain expressing the native XR, converting 76% and 38%, respectively. The xylitol yield was less than half using mXR in comparison with the native variant. As a result of this, the ethanol yield increased from 0.33 to 0.39 g g^-1 when the native XR was replaced by mXR. In contrast, the expression of Gxf1 only slightly increased the xylose uptake, and did not increase the ethanol production. The results suggest that ethanolic xylose fermentation under SSCF conditions is controlled primarily by the XR activity and to a much lesser extent by xylose transport.

  • The glucose/xylose facilitator Gxf1 from Candida intermedia expressed in a xylose-fermenting industrial strain of Saccharomyces cerevisiae increases xylose uptake in SSCF of wheat straw.
    Enzyme and microbial technology, 2011
    Co-Authors: Cesar Fonseca, David Runquist, Kim Olofsson, Luis L Fonseca, Carla Ferreira, Bärbel Hahn-hägerdal, Gunnar Liden
    Abstract:

    Ethanolic fermentation of lignocellulose raw materials requires industrial xylose-fermenting strains capable of complete and efficient D-Xylose consumption. A central question in xylose fermentation by Saccharomyces cerevisiae engineered for xylose fermentation is to improve the xylose uptake. In the current study, the glucose/xylose facilitator Gxf1 from Candida intermedia, was expressed in three different xylose-fermenting S. cerevisiae strains of industrial origin. The in vivo effect on aerobic xylose growth and the initial xylose uptake rate were assessed. The expression of Gxf1 resulted in enhanced aerobic xylose growth only for the TMB3400 based strain. It displayed more than a 2-fold higher affinity for D-Xylose than the parental strain and approximately 2-fold higher initial specific growth rate at 4 g/L D-Xylose. Enhanced xylose consumption was furthermore observed when the GXF1-strain was assessed in simultaneous saccharification and co-fermentation (SSCF) of pretreated wheat straw. However, the ethanol yield remained unchanged due to increased by-product formation. Metabolic flux analysis suggested that the expression of the Gxf1 transporter had shifted the control of xylose catabolism from transport to the NAD(+) dependent oxidation of xylitol to xylulose.

  • Comparison of heterologous xylose transporters in recombinant Saccharomyces cerevisiae
    Biotechnology for Biofuels, 2010
    Co-Authors: David Runquist, Bärbel Hahn-hägerdal, Peter Rådström
    Abstract:

    Background Baker's yeast ( Saccharomyces cerevisiae ) has been engineered for xylose utilization to enable production of fuel ethanol from lignocellulose raw material. One unresolved challenge is that S. cerevisiae lacks a dedicated transport system for pentose sugars, which means that xylose is transported by non-specific Hxt transporters with comparatively low transport rate and affinity for xylose. Results In this study, we compared three heterologous xylose transporters that have recently been shown to improve xylose uptake under different experimental conditions. The transporters Gxf1, Sut1 and At5g59250 from Candida intermedia, Pichia stipitis and Arabidopsis thaliana , respectively, were expressed in isogenic strains of S. cerevisiae and the transport kinetics and utilization of xylose was evaluated. Expression of the Gxf1 and Sut1 transporters led to significantly increased affinity and transport rates of xylose. In batch cultivation at 4 g/L xylose concentration, improved transport kinetics led to a corresponding increase in xylose utilization, whereas no correlation could be demonstrated at xylose concentrations greater than 15 g/L. The relative contribution of native sugar transporters to the overall xylose transport capacity was also estimated during growth on glucose and xylose. Conclusions Kinetic characterization and aerobic batch cultivation of strains expressing the Gxf1, Sut1 and At5g59250 transporters showed a direct relationship between transport kinetics and xylose growth. The Gxf1 transporter had the highest transport capacity and the highest xylose growth rate, followed by the Sut1 transporter. The range in which transport controlled the growth rate was determined to between 0 and 15 g/L xylose. The role of catabolite repression in regulation of native transporters was also confirmed by the observation that xylose transport by native S. cerevisiae transporters increased significantly during cultivation in xylose and at low glucose concentration.

  • Expression of the Gxf1 transporter from Candida intermedia improves fermentation performance in recombinant xylose-utilizing Saccharomyces cerevisiae
    Applied Microbiology and Biotechnology, 2009
    Co-Authors: David Runquist, Isabel Spencer-martins, C Fonseca, Peter Rådström, Bärbel Hahn-hägerdal
    Abstract:

    The glucose/xylose facilitator Gxf1 from Candida intermedia was expressed in the recombinant xylose-fermenting Saccharomyces cerevisiae strain TMB 3057. The new strain, TMB 3411, displayed approximately two times lower K _m for xylose transport compared to a control strain not expressing Gxf1. In aerobic batch cultivation, the specific growth rate was significantly higher at low xylose concentration, 4 g/L, when Gxf1 was expressed, whereas it remained unchanged at high xylose concentration, 40 g/L. Similarly, in aerobic-xylose-limited chemostat culture, the Gxf1-expressing strain consumed more xylose than the control strain at low dilution rates (low xylose concentration), whereas the situation was reversed at higher dilution rates (high xylose concentration). Also, under anaerobic conditions, the Gxf1-expressing strain showed faster xylose uptake and ethanol formation at low substrate concentrations. The results are discussed in relation to previous observations, which suggested that transport controlled xylose utilization in recombinant xylose-utilizing S. cerevisiae only at low xylose concentrations.

David Runquist - One of the best experts on this subject based on the ideXlab platform.

  • the glucose xylose facilitator gxf1 from candida intermedia expressed in a xylose fermenting industrial strain of saccharomyces cerevisiae increases xylose uptake in sscf of wheat straw
    Enzyme and Microbial Technology, 2011
    Co-Authors: Cesar Fonseca, David Runquist, Kim Olofsson, Luis L Fonseca, Carla Ferreira, Barbel Hahnhagerdal, Gunnar Liden
    Abstract:

    Ethanolic fermentation of lignocellulose raw materials requires industrial xylose-fermenting strains capable of complete and efficient D-Xylose consumption. A central question in xylose fermentation by Saccharomyces cerevisiae engineered for xylose fermentation is to improve the xylose uptake. In the current study, the glucose/xylose facilitator Gxf1 from Candida intermedia, was expressed in three different xylose-fermenting S. cerevisiae strains of industrial origin. The in vivo effect on aerobic xylose growth and the initial xylose uptake rate were assessed. The expression of Gxf1 resulted in enhanced aerobic xylose growth only for the TMB3400 based strain. It displayed more than a 2-fold higher affinity for D-Xylose than the parental strain and approximately 2-fold higher initial specific growth rate at 4 g/L D-Xylose. Enhanced xylose consumption was furthermore observed when the GXF1-strain was assessed in simultaneous saccharification and co-fermentation (SSCF) of pretreated wheat straw. However, the ethanol yield remained unchanged due to increased by-product formation. Metabolic flux analysis suggested that the expression of the Gxf1 transporter had shifted the control of xylose catabolism from transport to the NAD(+) dependent oxidation of xylitol to xylulose. (C) 2011 Elsevier Inc. All rights reserved. (Less)

  • The glucose/xylose facilitator gxf1 from Candida intermedia expressed in a xylose-fermenting industrial strain of Saccharomyces cerevisiae increases xylose uptake in SSCF of wheat straw.
    Enzyme and Microbial Technology, 2011
    Co-Authors: Cesar Fonseca, David Runquist, Kim Olofsson, Luis L Fonseca, Carla Ferreira, Bärbel Hahn-hägerdal, Gunnar Liden
    Abstract:

    Ethanolic fermentation of lignocellulose raw materials requires industrial xylose-fermenting strains capable of complete and efficient D-Xylose consumption. A central question in xylose fermentation by Saccharomyces cerevisiae engineered for xylose fermentation is to improve the xylose uptake. In the current study, the glucose/xylose facilitator Gxf1 from Candida intermedia, was expressed in three different xylose-fermenting S. cerevisiae strains of industrial origin. The in vivo effect on aerobic xylose growth and the initial xylose uptake rate were assessed. The expression of Gxf1 resulted in enhanced aerobic xylose growth only for the TMB3400 based strain. It displayed more than a 2-fold higher affinity for D-Xylose than the parental strain and approximately 2-fold higher initial specific growth rate at 4 g/L D-Xylose. Enhanced xylose consumption was furthermore observed when the GXF1-strain was assessed in simultaneous saccharification and co-fermentation (SSCF) of pretreated wheat straw. However, the ethanol yield remained unchanged due to increased by-product formation. Metabolic flux analysis suggested that the expression of the Gxf1 transporter had shifted the control of xylose catabolism from transport to the NAD(+) dependent oxidation of xylitol to xylulose. (C) 2011 Elsevier Inc. All rights reserved. (Less)

  • A mutated xylose reductase increases bioethanol production more than a glucose/xylose facilitator in simultaneous fermentation and co-fermentation of wheat straw
    AMB Express, 2011
    Co-Authors: Kim Olofsson, David Runquist, Bärbel Hahn-hägerdal, Gunnar Liden
    Abstract:

    Genetically engineered Saccharomyces cerevisiae strains are able to ferment xylose present in lignocellulosic biomass. However, better xylose fermenting strains are required to reach complete xylose uptake in simultaneous saccharification and co-fermentation (SSCF) of lignocellulosic hydrolyzates. In the current study, haploid Saccharomyces cerevisiae strains expressing a heterologous xylose pathway including either the native xylose reductase (XR) from P. stipiti s, a mutated variant of XR (mXR) with altered co-factor preference, a glucose/xylose facilitator (Gxf1) from Candida intermedia or both mXR and Gxf1 were assessed in SSCF of acid-pretreated non-detoxified wheat straw. The xylose conversion in SSCF was doubled with the S. cerevisiae strain expressing mXR compared to the isogenic strain expressing the native XR, converting 76% and 38%, respectively. The xylitol yield was less than half using mXR in comparison with the native variant. As a result of this, the ethanol yield increased from 0.33 to 0.39 g g^-1 when the native XR was replaced by mXR. In contrast, the expression of Gxf1 only slightly increased the xylose uptake, and did not increase the ethanol production. The results suggest that ethanolic xylose fermentation under SSCF conditions is controlled primarily by the XR activity and to a much lesser extent by xylose transport.

  • The glucose/xylose facilitator Gxf1 from Candida intermedia expressed in a xylose-fermenting industrial strain of Saccharomyces cerevisiae increases xylose uptake in SSCF of wheat straw.
    Enzyme and microbial technology, 2011
    Co-Authors: Cesar Fonseca, David Runquist, Kim Olofsson, Luis L Fonseca, Carla Ferreira, Bärbel Hahn-hägerdal, Gunnar Liden
    Abstract:

    Ethanolic fermentation of lignocellulose raw materials requires industrial xylose-fermenting strains capable of complete and efficient D-Xylose consumption. A central question in xylose fermentation by Saccharomyces cerevisiae engineered for xylose fermentation is to improve the xylose uptake. In the current study, the glucose/xylose facilitator Gxf1 from Candida intermedia, was expressed in three different xylose-fermenting S. cerevisiae strains of industrial origin. The in vivo effect on aerobic xylose growth and the initial xylose uptake rate were assessed. The expression of Gxf1 resulted in enhanced aerobic xylose growth only for the TMB3400 based strain. It displayed more than a 2-fold higher affinity for D-Xylose than the parental strain and approximately 2-fold higher initial specific growth rate at 4 g/L D-Xylose. Enhanced xylose consumption was furthermore observed when the GXF1-strain was assessed in simultaneous saccharification and co-fermentation (SSCF) of pretreated wheat straw. However, the ethanol yield remained unchanged due to increased by-product formation. Metabolic flux analysis suggested that the expression of the Gxf1 transporter had shifted the control of xylose catabolism from transport to the NAD(+) dependent oxidation of xylitol to xylulose.

  • Comparison of heterologous xylose transporters in recombinant Saccharomyces cerevisiae
    Biotechnology for Biofuels, 2010
    Co-Authors: David Runquist, Bärbel Hahn-hägerdal, Peter Rådström
    Abstract:

    Background Baker's yeast ( Saccharomyces cerevisiae ) has been engineered for xylose utilization to enable production of fuel ethanol from lignocellulose raw material. One unresolved challenge is that S. cerevisiae lacks a dedicated transport system for pentose sugars, which means that xylose is transported by non-specific Hxt transporters with comparatively low transport rate and affinity for xylose. Results In this study, we compared three heterologous xylose transporters that have recently been shown to improve xylose uptake under different experimental conditions. The transporters Gxf1, Sut1 and At5g59250 from Candida intermedia, Pichia stipitis and Arabidopsis thaliana , respectively, were expressed in isogenic strains of S. cerevisiae and the transport kinetics and utilization of xylose was evaluated. Expression of the Gxf1 and Sut1 transporters led to significantly increased affinity and transport rates of xylose. In batch cultivation at 4 g/L xylose concentration, improved transport kinetics led to a corresponding increase in xylose utilization, whereas no correlation could be demonstrated at xylose concentrations greater than 15 g/L. The relative contribution of native sugar transporters to the overall xylose transport capacity was also estimated during growth on glucose and xylose. Conclusions Kinetic characterization and aerobic batch cultivation of strains expressing the Gxf1, Sut1 and At5g59250 transporters showed a direct relationship between transport kinetics and xylose growth. The Gxf1 transporter had the highest transport capacity and the highest xylose growth rate, followed by the Sut1 transporter. The range in which transport controlled the growth rate was determined to between 0 and 15 g/L xylose. The role of catabolite repression in regulation of native transporters was also confirmed by the observation that xylose transport by native S. cerevisiae transporters increased significantly during cultivation in xylose and at low glucose concentration.

Gunnar Liden - One of the best experts on this subject based on the ideXlab platform.

  • Development of a D-Xylose fermenting and inhibitor tolerant industrial Saccharomyces cerevisiae strain with high performance in lignocellulose hydrolysates using metabolic and evolutionary engineering
    Biotechnology for Biofuels, 2013
    Co-Authors: Mekonnen M Demeke, Gunnar Liden, Heiko Dietz, Yingying Li, María R Foulquié-moreno, Sarma Mutturi, Sylvie Deprez, Beatriz M Bonini, Françoise Dumortier, Alex Verplaetse
    Abstract:

    Background The production of bioethanol from lignocellulose hydrolysates requires a robust, D-Xylose-fermenting and inhibitor-tolerant microorganism as catalyst. The purpose of the present work was to develop such a strain from a prime industrial yeast strain, Ethanol Red, used for bioethanol production. Results An expression cassette containing 13 genes including Clostridium phytofermentans XylA , encoding D-Xylose isomerase (XI), and enzymes of the pentose phosphate pathway was inserted in two copies in the genome of Ethanol Red. Subsequent EMS mutagenesis, genome shuffling and selection in D-Xylose-enriched lignocellulose hydrolysate, followed by multiple rounds of evolutionary engineering in complex medium with D-Xylose, gradually established efficient D-Xylose fermentation. The best-performing strain, GS1.11-26, showed a maximum specific D-Xylose consumption rate of 1.1 g/g DW/h in synthetic medium, with complete attenuation of 35 g/L D-Xylose in about 17 h. In separate hydrolysis and fermentation of lignocellulose hydrolysates of Arundo donax (giant reed), spruce and a wheat straw/hay mixture, the maximum specific D-Xylose consumption rate was 0.36, 0.23 and 1.1 g/g DW inoculum/h, and the final ethanol titer was 4.2, 3.9 and 5.8% (v/v), respectively. In simultaneous saccharification and fermentation of Arundo hydrolysate, GS1.11-26 produced 32% more ethanol than the parent strain Ethanol Red, due to efficient D-Xylose utilization. The high D-Xylose fermentation capacity was stable after extended growth in glucose. Cell extracts of strain GS1.11-26 displayed 17-fold higher XI activity compared to the parent strain, but overexpression of XI alone was not enough to establish D-Xylose fermentation. The high D-Xylose consumption rate was due to synergistic interaction between the high XI activity and one or more mutations in the genome. The GS1.11-26 had a partial respiratory defect causing a reduced aerobic growth rate. Conclusions An industrial yeast strain for bioethanol production with lignocellulose hydrolysates has been developed in the genetic background of a strain widely used for commercial bioethanol production. The strain uses glucose and D-Xylose with high consumption rates and partial cofermentation in various lignocellulose hydrolysates with very high ethanol yield. The GS1.11-26 strain shows highly promising potential for further development of an all-round robust yeast strain for efficient fermentation of various lignocellulose hydrolysates.

  • the glucose xylose facilitator gxf1 from candida intermedia expressed in a xylose fermenting industrial strain of saccharomyces cerevisiae increases xylose uptake in sscf of wheat straw
    Enzyme and Microbial Technology, 2011
    Co-Authors: Cesar Fonseca, David Runquist, Kim Olofsson, Luis L Fonseca, Carla Ferreira, Barbel Hahnhagerdal, Gunnar Liden
    Abstract:

    Ethanolic fermentation of lignocellulose raw materials requires industrial xylose-fermenting strains capable of complete and efficient D-Xylose consumption. A central question in xylose fermentation by Saccharomyces cerevisiae engineered for xylose fermentation is to improve the xylose uptake. In the current study, the glucose/xylose facilitator Gxf1 from Candida intermedia, was expressed in three different xylose-fermenting S. cerevisiae strains of industrial origin. The in vivo effect on aerobic xylose growth and the initial xylose uptake rate were assessed. The expression of Gxf1 resulted in enhanced aerobic xylose growth only for the TMB3400 based strain. It displayed more than a 2-fold higher affinity for D-Xylose than the parental strain and approximately 2-fold higher initial specific growth rate at 4 g/L D-Xylose. Enhanced xylose consumption was furthermore observed when the GXF1-strain was assessed in simultaneous saccharification and co-fermentation (SSCF) of pretreated wheat straw. However, the ethanol yield remained unchanged due to increased by-product formation. Metabolic flux analysis suggested that the expression of the Gxf1 transporter had shifted the control of xylose catabolism from transport to the NAD(+) dependent oxidation of xylitol to xylulose. (C) 2011 Elsevier Inc. All rights reserved. (Less)

  • The glucose/xylose facilitator gxf1 from Candida intermedia expressed in a xylose-fermenting industrial strain of Saccharomyces cerevisiae increases xylose uptake in SSCF of wheat straw.
    Enzyme and Microbial Technology, 2011
    Co-Authors: Cesar Fonseca, David Runquist, Kim Olofsson, Luis L Fonseca, Carla Ferreira, Bärbel Hahn-hägerdal, Gunnar Liden
    Abstract:

    Ethanolic fermentation of lignocellulose raw materials requires industrial xylose-fermenting strains capable of complete and efficient D-Xylose consumption. A central question in xylose fermentation by Saccharomyces cerevisiae engineered for xylose fermentation is to improve the xylose uptake. In the current study, the glucose/xylose facilitator Gxf1 from Candida intermedia, was expressed in three different xylose-fermenting S. cerevisiae strains of industrial origin. The in vivo effect on aerobic xylose growth and the initial xylose uptake rate were assessed. The expression of Gxf1 resulted in enhanced aerobic xylose growth only for the TMB3400 based strain. It displayed more than a 2-fold higher affinity for D-Xylose than the parental strain and approximately 2-fold higher initial specific growth rate at 4 g/L D-Xylose. Enhanced xylose consumption was furthermore observed when the GXF1-strain was assessed in simultaneous saccharification and co-fermentation (SSCF) of pretreated wheat straw. However, the ethanol yield remained unchanged due to increased by-product formation. Metabolic flux analysis suggested that the expression of the Gxf1 transporter had shifted the control of xylose catabolism from transport to the NAD(+) dependent oxidation of xylitol to xylulose. (C) 2011 Elsevier Inc. All rights reserved. (Less)

  • A mutated xylose reductase increases bioethanol production more than a glucose/xylose facilitator in simultaneous fermentation and co-fermentation of wheat straw
    AMB Express, 2011
    Co-Authors: Kim Olofsson, David Runquist, Bärbel Hahn-hägerdal, Gunnar Liden
    Abstract:

    Genetically engineered Saccharomyces cerevisiae strains are able to ferment xylose present in lignocellulosic biomass. However, better xylose fermenting strains are required to reach complete xylose uptake in simultaneous saccharification and co-fermentation (SSCF) of lignocellulosic hydrolyzates. In the current study, haploid Saccharomyces cerevisiae strains expressing a heterologous xylose pathway including either the native xylose reductase (XR) from P. stipiti s, a mutated variant of XR (mXR) with altered co-factor preference, a glucose/xylose facilitator (Gxf1) from Candida intermedia or both mXR and Gxf1 were assessed in SSCF of acid-pretreated non-detoxified wheat straw. The xylose conversion in SSCF was doubled with the S. cerevisiae strain expressing mXR compared to the isogenic strain expressing the native XR, converting 76% and 38%, respectively. The xylitol yield was less than half using mXR in comparison with the native variant. As a result of this, the ethanol yield increased from 0.33 to 0.39 g g^-1 when the native XR was replaced by mXR. In contrast, the expression of Gxf1 only slightly increased the xylose uptake, and did not increase the ethanol production. The results suggest that ethanolic xylose fermentation under SSCF conditions is controlled primarily by the XR activity and to a much lesser extent by xylose transport.

  • The glucose/xylose facilitator Gxf1 from Candida intermedia expressed in a xylose-fermenting industrial strain of Saccharomyces cerevisiae increases xylose uptake in SSCF of wheat straw.
    Enzyme and microbial technology, 2011
    Co-Authors: Cesar Fonseca, David Runquist, Kim Olofsson, Luis L Fonseca, Carla Ferreira, Bärbel Hahn-hägerdal, Gunnar Liden
    Abstract:

    Ethanolic fermentation of lignocellulose raw materials requires industrial xylose-fermenting strains capable of complete and efficient D-Xylose consumption. A central question in xylose fermentation by Saccharomyces cerevisiae engineered for xylose fermentation is to improve the xylose uptake. In the current study, the glucose/xylose facilitator Gxf1 from Candida intermedia, was expressed in three different xylose-fermenting S. cerevisiae strains of industrial origin. The in vivo effect on aerobic xylose growth and the initial xylose uptake rate were assessed. The expression of Gxf1 resulted in enhanced aerobic xylose growth only for the TMB3400 based strain. It displayed more than a 2-fold higher affinity for D-Xylose than the parental strain and approximately 2-fold higher initial specific growth rate at 4 g/L D-Xylose. Enhanced xylose consumption was furthermore observed when the GXF1-strain was assessed in simultaneous saccharification and co-fermentation (SSCF) of pretreated wheat straw. However, the ethanol yield remained unchanged due to increased by-product formation. Metabolic flux analysis suggested that the expression of the Gxf1 transporter had shifted the control of xylose catabolism from transport to the NAD(+) dependent oxidation of xylitol to xylulose.

Ronald E. Hector - One of the best experts on this subject based on the ideXlab platform.

  • A Synthetic Hybrid Promoter for Xylose-Regulated Control of Gene Expression in Saccharomyces Yeasts
    Molecular Biotechnology, 2017
    Co-Authors: Ronald E. Hector, Jeffrey A. Mertens
    Abstract:

    Metabolism of non-glucose carbon sources is often highly regulated at the transcriptional and post-translational levels. This level of regulation is lacking in Saccharomyces cerevisiae strains engineered to metabolize xylose. To better control transcription in S. cerevisiae , the xylose-dependent, DNA-binding repressor (XylR) from Caulobacter crescentus was used to block transcription from synthetic promoters based on the constitutive Ashbya gossypii TEF promoter. The new hybrid promoters were repressed in the absence of xylose and showed up to a 25-fold increase in the presence of xylose. Activation of the promoter was highly sensitive to xylose with activity seen at concentrations below 2 μM xylose. These new xylose-inducible promoters allow improved control of gene expression for engineered strains of Saccharomyces yeasts.

  • growth and fermentation of d xylose by saccharomyces cerevisiae expressing a novel d xylose isomerase originating from the bacterium prevotella ruminicola tc2 24
    Biotechnology for Biofuels, 2013
    Co-Authors: Ronald E. Hector, Michael A. Cotta, Bruce S Dien, Jeffrey A. Mertens
    Abstract:

    Background Saccharomyces cerevisiae strains expressing D-Xylose isomerase (XI) produce some of the highest reported ethanol yields from D-Xylose. Unfortunately, most bacterial XIs that have been expressed in S. cerevisiae are either not functional, require additional strain modification, or have low affinity for D-Xylose. This study analyzed several XIs from rumen and intestinal microorganisms to identify enzymes with improved properties for engineering S. cerevisiae for D-Xylose fermentation.

  • engineering industrial saccharomyces cerevisiae strains for xylose fermentation and comparison for switchgrass conversion
    Journal of Industrial Microbiology & Biotechnology, 2011
    Co-Authors: Ronald E. Hector, Michael A. Cotta, Bruce S Dien, Nasib Qureshi
    Abstract:

    Saccharomyces’ physiology and fermentation-related properties vary broadly among industrial strains used to ferment glucose. How genetic background affects xylose metabolism in recombinant Saccharomyces strains has not been adequately explored. In this study, six industrial strains of varied genetic background were engineered to ferment xylose by stable integration of the xylose reductase, xylitol dehydrogenase, and xylulokinase genes. Aerobic growth rates on xylose were 0.04–0.17 h−1. Fermentation of xylose and glucose/xylose mixtures also showed a wide range of performance between strains. During xylose fermentation, xylose consumption rates were 0.17–0.31 g/l/h, with ethanol yields 0.18–0.27 g/g. Yields of ethanol and the metabolite xylitol were positively correlated, indicating that all of the strains had downstream limitations to xylose metabolism. The better-performing engineered and parental strains were compared for conversion of alkaline pretreated switchgrass to ethanol. The engineered strains produced 13–17% more ethanol than the parental control strains because of their ability to ferment xylose.

  • Expression of a heterologous xylose transporter in a Saccharomyces cerevisiae strain engineered to utilize xylose improves aerobic xylose consumption
    Applied Microbiology and Biotechnology, 2008
    Co-Authors: Ronald E. Hector, Nasib Qureshi, Stephen R. Hughes, Michael A. Cotta
    Abstract:

    The goal of this investigation was to determine the effect of a xylose transport system on glucose and xylose co-consumption as well as total xylose consumption in Saccharomyces cerevisiae . We expressed two heterologous transporters from Arabidopsis thaliana in recombinant xylose-utilizing S. cerevisiae cells. Strains expressing the heterologous transporters were grown on glucose and xylose mixtures. Sugar consumption rates and ethanol concentrations were determined and compared to an isogenic control strain lacking the A. thaliana transporters. Expression of the transporters increased xylose uptake and xylose consumption up to 46% and 40%, respectively. Xylose co-consumption rates (prior to glucose depletion) were also increased by up to 2.5-fold compared to the control strain. Increased xylose consumption correlated with increased ethanol concentration and productivity. During the xylose/glucose co-consumption phase, strains expressing the transporters had up to a 70% increase in ethanol production rate. It was concluded that in these strains, xylose transport was a limiting factor for xylose utilization and that increasing xylose/glucose co-consumption is a viable strategy for improving xylose fermentation.