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Eckhard Boles - One of the best experts on this subject based on the ideXlab platform.
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Improving L-Arabinose utilization of pentose fermenting Saccharomyces cerevisiae cells by heterologous expression of L-Arabinose transporting sugar transporters
Biotechnology for biofuels, 2011Co-Authors: Thorsten Subtil, Eckhard BolesAbstract:Hydrolysates of plant biomass used for the production of lignocellulosic biofuels typically contain sugar mixtures consisting mainly of D-glucose and D-xylose, and minor amounts of L-Arabinose. The yeast Saccharomyces cerevisiae is the preferred microorganism for the fermentative production of ethanol but is not able to ferment pentose sugars. Although D-xylose and L-Arabinose fermenting S. cerevisiae strains have been constructed recently, pentose uptake is still a limiting step in mixed sugar fermentations. Here we described the cloning and characterization of two sugar transporters, AraT from the yeast Scheffersomyces stipitis and Stp2 from the plant Arabidopsis thaliana, which mediate the uptake of L-Arabinose but not of D-glucose into S. cerevisiae cells. A yeast strain lacking all of its endogenous hexose transporter genes and expressing a bacterial L-Arabinose utilization pathway could no longer take up and grow with L-Arabinose as the only carbon source. Expression of the heterologous transporters supported uptake and utilization of L-Arabinose especially at low L-Arabinose concentrations but did not, or only very weakly, support D-glucose uptake and utilization. In contrast, the S. cerevisiae D-galactose transporter, Gal2, mediated uptake of both L-Arabinose and D-glucose, especially at high concentrations. Using a newly developed screening system we have identified two heterologous sugar transporters from a yeast and a plant which can support uptake and utilization of L-Arabinose in L-Arabinose fermenting S. cerevisiae cells, especially at low L-Arabinose concentrations.
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codon optimized bacterial genes improve l Arabinose fermentation in recombinant saccharomyces cerevisiae
Applied and Environmental Microbiology, 2008Co-Authors: Beate Wiedemann, Eckhard BolesAbstract:Bioethanol produced by microbial fermentations of plant biomass hydrolysates consisting of hexose and pentose mixtures is an excellent alternative to fossil transportation fuels. However, the yeast Saccharomyces cerevisiae, commonly used in bioethanol production, can utilize pentose sugars like l-Arabinose or d-xylose only after heterologous expression of corresponding metabolic pathways from other organisms. Here we report the improvement of a bacterial l-Arabinose utilization pathway consisting of l-Arabinose isomerase from Bacillus subtilis and l-ribulokinase and l-ribulose-5-P 4-epimerase from Escherichia coli after expression of the corresponding genes in S. cerevisiae. l-Arabinose isomerase from B. subtilis turned out to be the limiting step for growth on l-Arabinose as the sole carbon source. The corresponding enzyme could be effectively replaced by the enzyme from Bacillus licheniformis, leading to a considerably decreased lag phase. Subsequently, the codon usage of all the genes involved in the l-Arabinose pathway was adapted to that of the highly expressed genes encoding glycolytic enzymes in S. cerevisiae. Yeast transformants expressing the codon-optimized genes showed strongly improved l-Arabinose conversion rates. With this rational approach, the ethanol production rate from l-Arabinose could be increased more than 2.5-fold from 0.014 g ethanol h−1 (g dry weight)−1 to 0.036 g ethanol h−1 (g dry weight)−1 and the ethanol yield could be increased from 0.24 g ethanol (g consumed l-Arabinose)−1 to 0.39 g ethanol (g consumed l-Arabinose)−1. These improvements make up a new starting point for the construction of more-efficient industrial l-Arabinose-fermenting yeast strains by evolutionary engineering.
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Co-utilization of L-Arabinose and D-xylose by laboratory and industrial Saccharomyces cerevisiae strains
Microbial Cell Factories, 2006Co-Authors: Kaisa Karhumaa, Beate Wiedemann, Eckhard Boles, Bärbel Hahn-hägerdal, Marie-francoise Gorwa-grauslundAbstract:Background Fermentation of lignocellulosic biomass is an attractive alternative for the production of bioethanol. Traditionally, the yeast Saccharomyces cerevisiae is used in industrial ethanol fermentations. However, S. cerevisiae is naturally not able to ferment the pentose sugars D-xylose and L-Arabinose, which are present in high amounts in lignocellulosic raw materials. Results We describe the engineering of laboratory and industrial S. cerevisiae strains to co-ferment the pentose sugars D-xylose and L-Arabinose. Introduction of a fungal xylose and a bacterial Arabinose pathway resulted in strains able to grow on both pentose sugars. Introduction of a xylose pathway into an Arabinose-fermenting laboratory strain resulted in nearly complete conversion of Arabinose into arabitol due to the L-Arabinose reductase activity of the xylose reductase. The industrial strain displayed lower arabitol yield and increased ethanol yield from xylose and Arabinose. Conclusion Our work demonstrates simultaneous co-utilization of xylose and Arabinose in recombinant strains of S. cerevisiae . In addition, the co-utilization of Arabinose together with xylose significantly reduced formation of the by-product xylitol, which contributed to improved ethanol production.
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a modified saccharomyces cerevisiae strain that consumes l Arabinose and produces ethanol
Applied and Environmental Microbiology, 2003Co-Authors: Jessica Becker, Eckhard BolesAbstract:Metabolic engineering is a powerful method to improve, redirect, or generate new metabolic reactions or whole pathways in microorganisms. Here we describe the engineering of a Saccharomyces cerevisiae strain able to utilize the pentose sugar L-Arabinose for growth and to ferment it to ethanol. Expanding the substrate fermentation range of S. cerevisiae to include pentoses is important for the utilization of this yeast in economically feasible biomass-to-ethanol fermentation processes. After overexpression of a bacterial L-Arabinose utilization pathway consisting of Bacillus subtilis AraA and Escherichia coli AraB and AraD and simultaneous overexpression of the L-Arabinose-transporting yeast galactose permease, we were able to select an L-Arabinose-utilizing yeast strain by sequential transfer in L-Arabinose media. Molecular analysis of this strain, including DNA microarrays, revealed that the crucial prerequisite for efficient utilization of L-Arabinose is a lowered activity of L-ribulokinase. Moreover, high L-Arabinose uptake rates and enhanced transaldolase activities favor utilization of L-Arabinose. With a doubling time of about 7.9 h in a medium with L-Arabinose as the sole carbon source, an ethanol production rate of 0.06 to 0.08 g of ethanol per g (dry weight). h(-1) under oxygen-limiting conditions, and high ethanol yields, this yeast strain should be useful for efficient fermentation of hexoses and pentoses in cellulosic biomass hydrolysates.
Antonius J A Van Maris - One of the best experts on this subject based on the ideXlab platform.
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the penicillium chrysogenum transporter pcarat enables high affinity glucose insensitive l Arabinose transport in saccharomyces cerevisiae
Biotechnology for Biofuels, 2018Co-Authors: Jasmine M Bracher, Maarten D Verhoeven, Wouter H Wisselink, Barbara Crimi, Jeroen G Nijland, Arnold J M Driessen, Paul Klaassen, Antonius J A Van MarisAbstract:l-Arabinose occurs at economically relevant levels in lignocellulosic hydrolysates. Its low-affinity uptake via the Saccharomyces cerevisiae Gal2 galactose transporter is inhibited by d-glucose. Especially at low concentrations of l-Arabinose, uptake is an important rate-controlling step in the complete conversion of these feedstocks by engineered pentose-metabolizing S. cerevisiae strains. Chemostat-based transcriptome analysis yielded 16 putative sugar transporter genes in the filamentous fungus Penicillium chrysogenum whose transcript levels were at least threefold higher in l-Arabinose-limited cultures than in d-glucose-limited and ethanol-limited cultures. Of five genes, that encoded putative transport proteins and showed an over 30-fold higher transcript level in l-Arabinose-grown cultures compared to d-glucose-grown cultures, only one (Pc20g01790) restored growth on l-Arabinose upon expression in an engineered l-Arabinose-fermenting S. cerevisiae strain in which the endogenous l-Arabinose transporter, GAL2, had been deleted. Sugar transport assays indicated that this fungal transporter, designated as PcAraT, is a high-affinity (Km = 0.13 mM), high-specificity l-Arabinose-proton symporter that does not transport d-xylose or d-glucose. An l-Arabinose-metabolizing S. cerevisiae strain in which GAL2 was replaced by PcaraT showed 450-fold lower residual substrate concentrations in l-Arabinose-limited chemostat cultures than a congenic strain in which l-Arabinose import depended on Gal2 (4.2 × 10−3 and 1.8 g L−1, respectively). Inhibition of l-Arabinose transport by the most abundant sugars in hydrolysates, d-glucose and d-xylose was far less pronounced than observed with Gal2. Expression of PcAraT in a hexose-phosphorylation-deficient, l-Arabinose-metabolizing S. cerevisiae strain enabled growth in media supplemented with both 20 g L−1 l-Arabinose and 20 g L−1 d-glucose, which completely inhibited growth of a congenic strain in the same condition that depended on l-Arabinose transport via Gal2. Its high affinity and specificity for l-Arabinose, combined with limited sensitivity to inhibition by d-glucose and d-xylose, make PcAraT a valuable transporter for application in metabolic engineering strategies aimed at engineering S. cerevisiae strains for efficient conversion of lignocellulosic hydrolysates.
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novel evolutionary engineering approach for accelerated utilization of glucose xylose and Arabinose mixtures by engineered saccharomyces cerevisiae strains
Applied and Environmental Microbiology, 2009Co-Authors: Wouter H Wisselink, Maurice J Toirkens, Jack T Pronk, Antonius J A Van MarisAbstract:Lignocellulosic feedstocks are thought to have great economic and environmental significance for future biotechnological production processes. For cost-effective and efficient industrial processes, complete and fast conversion of all sugars derived from these feedstocks is required. Hence, simultaneous or fast sequential fermentation of sugars would greatly contribute to the efficiency of production processes. One of the main challenges emerging from the use of lignocellulosics for the production of ethanol by the yeast Saccharomyces cerevisiae is efficient fermentation of D-xylose and L-Arabinose, as these sugars cannot be used by natural S. cerevisiae strains. In this study, we describe the first engineered S. cerevisiae strain (strain IMS0003) capable of fermenting mixtures of glucose, xylose, and Arabinose with a high ethanol yield (0.43 g g–1 of total sugar) without formation of the side products xylitol and arabinitol. The kinetics of anaerobic fermentation of glucose-xylose-Arabinose mixtures were greatly improved by using a novel evolutionary engineering strategy. This strategy included a regimen consisting of repeated batch cultivation with repeated cycles of consecutive growth in three media with different compositions (glucose, xylose, and Arabinose; xylose and Arabinose; and only Arabinose) and allowed rapid selection of an evolved strain (IMS0010) exhibiting improved specific rates of consumption of xylose and Arabinose. This evolution strategy resulted in a 40% reduction in the time required to completely ferment a mixture containing 30 g liter–1 glucose, 15 g liter–1 xylose, and 15 g liter–1 Arabinose.
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engineering of saccharomyces cerevisiae for efficient anaerobic alcoholic fermentation of l Arabinose
Applied and Environmental Microbiology, 2007Co-Authors: Wouter H Wisselink, Maurice J Toirkens, M Del Rosario Franco Berriel, Aaron Adriaan Winkler, Johannes P Van Dijken, Jack T Pronk, Antonius J A Van MarisAbstract:For cost-effective and efficient ethanol production from lignocellulosic fractions of plant biomass, the conversion of not only major constituents, such as glucose and xylose, but also less predominant sugars, such as L-Arabinose, is required. Wild-type strains of Saccharomyces cerevisiae, the organism used in industrial ethanol production, cannot ferment xylose and Arabinose. Although metabolic and evolutionary engineering has enabled the efficient alcoholic fermentation of xylose under anaerobic conditions, the conversion of L-Arabinose into ethanol by engineered S. cerevisiae strains has previously been demonstrated only under oxygen-limited conditions. This study reports the first case of fast and efficient anaerobic alcoholic fermentation of L-Arabinose by an engineered S. cerevisiae strain. This fermentation was achieved by combining the expression of the structural genes for the L-Arabinose utilization pathway of Lactobacillus plantarum, the overexpression of the S. cerevisiae genes encoding the enzymes of the nonoxidative pentose phosphate pathway, and extensive evolutionary engineering. The resulting S. cerevisiae strain exhibited high rates of Arabinose consumption (0.70 g h–1 g [dry weight]–1) and ethanol production (0.29 g h–1 g [dry weight]–1) and a high ethanol yield (0.43 g g–1) during anaerobic growth on L-Arabinose as the sole carbon source. In addition, efficient ethanol production from sugar mixtures containing glucose and Arabinose, which is crucial for application in industrial ethanol production, was achieved.
Robert Schleif - One of the best experts on this subject based on the ideXlab platform.
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Arabinose Alters Both Local and Distal H–D Exchange Rates in the Escherichia coli AraC Transcriptional Regulator
Biochemistry, 2019Co-Authors: Alexander Tischer, Robert Schleif, Matthew Brown, Matthew AutonAbstract:In the absence of Arabinose, the dimeric Escherichia coli regulatory protein of the l-Arabinose operon, AraC, represses expression by looping the DNA between distant half-sites. Binding of Arabinose to the dimerization domains forces AraC to preferentially bind two adjacent DNA half-sites, which stimulates RNA polymerase transcription of the araBAD catabolism genes. Prior genetic and biochemical studies hypothesized that Arabinose allosterically induces a helix-coil transition of a linker between the dimerization and DNA binding domains that switches the AraC conformation to an inducing state [Brown, M. J., and Schleif, R. F. (2019) Biochemistry, preceding paper in this issue (DOI: 10.1021/acs.biochem.9b00234)]. To test this hypothesis, hydrogen-deuterium exchange mass spectrometry was utilized to identify structural regions involved in the conformational activation of AraC by Arabinose. Comparison of the hydrogen-deuterium exchange kinetics of individual dimeric dimerization domains and the full-length dimeric AraC protein in the presence and absence of Arabinose reveals a prominent Arabinose-induced destabilization of the amide hydrogen-bonded structure of linker residues (I167 and N168). This destabilization is demonstrated to result from an increased probability to form a helix capping motif at the C-terminal end of the dimerizing α-helix of the dimerization domain that preceeds the interdomain linker. These conformational changes could allow for quaternary repositioning of the DNA binding domains required for induction of the araBAD promoter through rotation of peptide backbone dihedral angles of just a couple of residues. Subtle changes in exchange rates are also visible around the Arabinose binding pocket and in the DNA binding domain.
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Arabinose alters both local and distal h d exchange rates in the escherichia coli arac transcriptional regulator
Biochemistry, 2019Co-Authors: Alexander Tischer, Robert Schleif, Matthew Brown, Matthew AutonAbstract:In the absence of Arabinose, the dimeric Escherichia coli regulatory protein of the l-Arabinose operon, AraC, represses expression by looping the DNA between distant half-sites. Binding of Arabinose to the dimerization domains forces AraC to preferentially bind two adjacent DNA half-sites, which stimulates RNA polymerase transcription of the araBAD catabolism genes. Prior genetic and biochemical studies hypothesized that Arabinose allosterically induces a helix-coil transition of a linker between the dimerization and DNA binding domains that switches the AraC conformation to an inducing state [Brown, M. J., and Schleif, R. F. (2019) Biochemistry, preceding paper in this issue (DOI: 10.1021/acs.biochem.9b00234)]. To test this hypothesis, hydrogen-deuterium exchange mass spectrometry was utilized to identify structural regions involved in the conformational activation of AraC by Arabinose. Comparison of the hydrogen-deuterium exchange kinetics of individual dimeric dimerization domains and the full-length dimeric AraC protein in the presence and absence of Arabinose reveals a prominent Arabinose-induced destabilization of the amide hydrogen-bonded structure of linker residues (I167 and N168). This destabilization is demonstrated to result from an increased probability to form a helix capping motif at the C-terminal end of the dimerizing α-helix of the dimerization domain that preceeds the interdomain linker. These conformational changes could allow for quaternary repositioning of the DNA binding domains required for induction of the araBAD promoter through rotation of peptide backbone dihedral angles of just a couple of residues. Subtle changes in exchange rates are also visible around the Arabinose binding pocket and in the DNA binding domain.
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A genetic and physical study of the interdomain linker of E. Coli AraC protein--a trans-subunit communication pathway.
Proteins: Structure Function and Bioinformatics, 2016Co-Authors: Fabiana Malaga, Michael E. Rodgers, Ory Mayberry, David J. Park, Dmitri Toptygin, Robert SchleifAbstract:Genetic experiments with full length AraC and biophysical experiments with its dimerization domain plus linker suggest that Arabinose binding to the dimerization domain changes the properties of the inter-domain linker which connects the dimerization domain to the DNA binding domain via interactions that do not depend on the DNA binding domain. Normal AraC function was found to tolerate considerable linker sequence alteration excepting proline substitutions. The proline substitutions partially activate transcription even in the absence of Arabinose and hint that a structural shift between helix and coil may be involved. To permit fluorescence anisotropy measurements that could detect Arabinose-dependent dynamic differences in the linkers, IAEDANS was conjugated to a cysteine residue substituted at the end of the linker of dimerization domain. Arabinose, but not other sugars, decreased the steady-state anisotropy, indicating either an increase in mobility and/or an increase in the fluorescence lifetime of the IAEDANS. Time-resolved fluorescence measurements showed that the Arabinose-induced anisotropy decrease did not result from an increase in the excited-state lifetime. Hence Arabinose-induced decreases in anisotropy appear to result from increased tumbling of the fluorophore. Arabinose did not decrease the anisotropy in mutants incapable of binding Arabinose nor did it alter the anisotropy when IAEDANS was conjugated elsewhere in the dimerization domain. Experiments with heterodimers of the dimerization domain showed that the binding of Arabinose to one subunit of the dimer decreases the fluorescence anisotropy of only a fluorophore on the linker of the other subunit.
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Heterodimers Reveal That Two Arabinose Molecules Are Required for the Normal Arabinose Response of AraC
Biochemistry, 2012Co-Authors: Michael E. Rodgers, Robert SchleifAbstract:AraC protein, which regulates expression of the L- Arabinose operon in Escherichia coli, is a dimer whose DNA binding affinity for pairs of DNA half-sites is controlled by Arabinose. Here we have addressed the question of whether the Arabinose response of AraC requires the binding of one or two molecules of Arabinose. This was accomplished by measuring the DNA dissociation rates of wild-type AraC and heterodimeric AraC constructs in which one subunit is capable of binding Arabinose and the other subunit does not bind Arabinose. Solutions consisting entirely of heterodimers were formed by spontaneous subunit exchange between two different homodimers, with heterodimers being trapped by the formation of an intersubunit disulfide bond between cysteine residues strategically positioned within the dimerization interface. We found that the normal Arabinose response of AraC requires the binding of two Arabinose molecules. These results provide additional constraints on mechanistic models for the action of AraC.
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A new and unexpected domain-domain interaction in the AraC protein.
Proteins: Structure Function and Bioinformatics, 2012Co-Authors: Stephanie Dirla Cole, Robert SchleifAbstract:An interaction between the dimerization domains and DNA binding domains of the dimeric AraC protein has previously been shown to facilitate repression of the Escherichia coli araBAD operon by AraC in the absence of Arabinose. A new interaction between the domains of AraC in the presence of Arabinose is reported here, the regulatory consequences of which are unknown. Evidence for the interaction is the following: the dissociation rate of Arabinose-bound AraC from half-site DNA is considerably faster than that of free DNA binding domain, and the affinity of the dimerization domains for Arabinose is increased when half-site DNA is bound. In addition, an increase in the fluorescence intensity of tryptophan residues located in the Arabinose-bound dimerization domain is observed upon binding of half-site DNA to the DNA binding domains. Direct physical evidence of the new domain-domain interaction is demonstrated by chemical crosslinking and NMR experiments.
César Fonseca - One of the best experts on this subject based on the ideXlab platform.
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L-Arabinose transport and catabolism in yeast.
The FEBS journal, 2007Co-Authors: César Fonseca, Bärbel Hahn-hägerdal, Rute I. S. Romão, Helena Rodrigues De Sousa, Isabel Spencer-martinsAbstract:Two yeasts, Candida arabinofermentans PYCC 5603(T) and Pichia guilliermondii PYCC 3012, which show rapid growth on L-Arabinose and very high rates of L-Arabinose uptake on screening, were selected for characterization of L-Arabinose transport and the first steps of intracellular L-Arabinose metabolism. The kinetics of L-Arabinose uptake revealed at least two transport systems with distinct substrate affinities, specificities, functional mechanisms and regulatory properties. The L-Arabinose catabolic pathway proposed for filamentous fungi also seems to operate in the yeasts studied. The kinetic parameters of the initial L-Arabinose-metabolizing enzymes were determined. Reductases were found to be mostly NADPH-dependent, whereas NAD was the preferred cofactor of dehydrogenases. The differences found between the two yeasts agree with the higher efficiency of L-Arabinose metabolism in C. arabinofermentans. This is the first full account of the initial steps of L-Arabinose catabolism in yeast including the biochemical characterization of a specific L-Arabinose transporter.
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l Arabinose metabolism in candida arabinofermentans pycc 5603t and pichia guilliermondii pycc 3012 influence of sugar and oxygen on product formation
Applied Microbiology and Biotechnology, 2007Co-Authors: César Fonseca, I Spencermartins, Barbel HahnhagerdalAbstract:l-Arabinose utilization by the yeasts Candida arabinofermentans PYCC 5603T and Pichia guilliermondii PYCC 3012 was investigated in aerobic batch cultures and compared, under similar conditions, to d-glucose and d-xylose metabolism. At high aeration levels, only biomass was formed from all the three sugars. When oxygen became limited, ethanol was produced from d-glucose, demonstrating a fermentative pathway in these yeasts. However, pentoses were essentially respired and, under oxygen limitation, the respective polyols accumulated—arabitol from l-Arabinose and xylitol from d-xylose. Different l-Arabinose concentrations and oxygen conditions were tested to better understand l-Arabinose metabolism. P. guilliermondii PYCC 3012 excreted considerably more arabitol from l-Arabinose (and also xylitol from d-xylose) than C. arabinofermentans PYCC 5603T. In contrast to the latter, P. guilliermondii PYCC 3012 did not produce any traces of ethanol in complex l-Arabinose (80 g/l) medium under oxygen-limited conditions. Neither sustained growth nor active metabolism was observed under anaerobiosis. This study demonstrates, for the first time, the oxygen dependence of metabolite and product formation in l-Arabinose-assimilating yeasts.
Barbel Hahnhagerdal - One of the best experts on this subject based on the ideXlab platform.
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comparing the xylose reductase xylitol dehydrogenase and xylose isomerase pathways in Arabinose and xylose fermenting saccharomyces cerevisiae strains
Biotechnology for Biofuels, 2008Co-Authors: Maurizio Bettiga, Barbel Hahnhagerdal, Mariefrancoise GorwagrauslundAbstract:Background Ethanolic fermentation of lignocellulosic biomass is a sustainable option for the production of bioethanol. This process would greatly benefit from recombinant Saccharomyces cerevisiae strains also able to ferment, besides the hexose sugar fraction, the pentose sugars, Arabinose and xylose. Different pathways can be introduced in S. cerevisiae to provide Arabinose and xylose utilisation. In this study, the bacterial Arabinose isomerase pathway was combined with two different xylose utilisation pathways: the xylose reductase/xylitol dehydrogenase and xylose isomerase pathways, respectively, in genetically identical strains. The strains were compared with respect to aerobic growth in Arabinose and xylose batch culture and in anaerobic batch fermentation of a mixture of glucose, Arabinose and xylose.
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l Arabinose metabolism in candida arabinofermentans pycc 5603t and pichia guilliermondii pycc 3012 influence of sugar and oxygen on product formation
Applied Microbiology and Biotechnology, 2007Co-Authors: César Fonseca, I Spencermartins, Barbel HahnhagerdalAbstract:l-Arabinose utilization by the yeasts Candida arabinofermentans PYCC 5603T and Pichia guilliermondii PYCC 3012 was investigated in aerobic batch cultures and compared, under similar conditions, to d-glucose and d-xylose metabolism. At high aeration levels, only biomass was formed from all the three sugars. When oxygen became limited, ethanol was produced from d-glucose, demonstrating a fermentative pathway in these yeasts. However, pentoses were essentially respired and, under oxygen limitation, the respective polyols accumulated—arabitol from l-Arabinose and xylitol from d-xylose. Different l-Arabinose concentrations and oxygen conditions were tested to better understand l-Arabinose metabolism. P. guilliermondii PYCC 3012 excreted considerably more arabitol from l-Arabinose (and also xylitol from d-xylose) than C. arabinofermentans PYCC 5603T. In contrast to the latter, P. guilliermondii PYCC 3012 did not produce any traces of ethanol in complex l-Arabinose (80 g/l) medium under oxygen-limited conditions. Neither sustained growth nor active metabolism was observed under anaerobiosis. This study demonstrates, for the first time, the oxygen dependence of metabolite and product formation in l-Arabinose-assimilating yeasts.