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Artykuły w czasopismach na temat "Xylose as substrate"
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van Bastelaere, P., W. Vangrysperre i H. Kersters-Hilderson. "Kinetic studies of Mg2+-, Co2+- and Mn2+-activated d-xylose isomerases". Biochemical Journal 278, nr 1 (15.08.1991): 285–92. http://dx.doi.org/10.1042/bj2780285.
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The kinetic parameters for the interconverting substrates D-xylose in equilibrium D-xylulose and D-glucose in equilibrium D-fructose were determined for several D-xylose isomerases, with Mg2+, Co2+ and Mn2+ as metal ion activators. The Km, kcat. and kcat./Km values are tabulated for the anomeric mixtures (observed parameters) as well as for the respective reactive species, i.e. the alpha-pyranose anomers of D-xylose and D-glucose and the alpha-furanose forms of D-xylulose and D-fructose (real parameters). The real Km values and catalytic efficiencies are more favourable for the ketose sugars (reverse reaction) than for the aldose sugars (forward reaction). Comparisons of the kinetic parameters further support the existence of two distinct groups of D-xylose isomerases. Inhibition constants for the cyclic substrate analogues 5-thio-alpha-D-xylopyranose and alpha-D-xylopyranosyl fluoride and for the acyclic substrate analogue xylitol and its dehydrated form 1,5-anhydroxylitol were determined and are discussed.
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Wang, Zi-Han, Jing-Yan Tan, Yu-Tong Zhang, Nan-Qi Ren i Lei Zhao. "Evaluating Bio-Hydrogen Production Potential and Energy Conversion Efficiency from Glucose and Xylose under Diverse Concentrations". Fermentation 8, nr 12 (14.12.2022): 739. http://dx.doi.org/10.3390/fermentation8120739.
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Lignocellulose bioconversion to hydrogen has been proposed as a promising solution to augment the fossil fuel dominated energy market. However, little is known about the effects of the substrate concentration supplied on hydrogen production. Herein, the hydrogen producing bacteria Thermoanaerobacter thermosaccharolyticum W16 feeding with respective glucose, xylose, and glucose and xylose mixture (glucose–xylose) at different concentrations was evaluated, to study whether substrate concentration could impact the lignocellulose bioconversion to hydrogen and the associated kinetics. An average bio-hydrogen yield of 1.40 ± 0.23 mol H2·mol−1 substrate was obtained at an average substrate concentration of 60.89 mM. The maximum bio-hydrogen production rate of 0.25 and 0.24 mol H2·mol−1 substrate h−1 was achieved at a substrate concentration of 27.75 mM glucose and 30.82 mM glucose–xylose, respectively, while the value reached the high point of 0.08 mol H2·mol−1 xylose·h−1 at 66.61 mM xylose. Upon further energy conversion efficiency (ESE) analysis, a substrate of 10 g·L−1 (amounting to 55.51 mM glucose, 66.61 mM xylose or 60.55 mM glucose–xylose) provided the maximum ESE of 15.3 ± 0.3%, which was 15.3% higher than that obtained at a substrate concentration of 5 g·L−1 (amounting to 27.75 mM glucose, 33.30 mM xylose or 30.28 mM glucose–xylose). The findings could be helpful to provide effective support for the future development of efficient and sustainable lignocellulosic bio-hydrogen production.
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Hermansyah, Hermansyah, Fachrijal Fachrijal, Miksusanti Miksusanti, Fatma Fatma, Getari Kasmiarti i Almunadi T. Panagan. "Xylose and Arabinose Fermentation to Produce Ethanol by Isolated Yeasts from Durian (Durio zibethinus L.) Fruit". Molekul 14, nr 2 (30.11.2019): 133. http://dx.doi.org/10.20884/1.jm.2019.14.2.562.
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Xylose and arabinose are pentosesugars that present in hemicellulose, part of lignocellulose biomass.These pentose sugars can be fermented by yeast into ethanol.The aim of this research was to utilize yeast isolated from durian fruit (DuriozibethinusL.) in fermentation of xylose and arabinose to produce bioethanol.Phenotypic test of isolates was conducted by growingthe isolates in various agar media, i.e.YPD (Yeast Peptone Dextrose), YPA (Yeast Peptone Arabinose), and YPX (Yeast Peptone Xylose) containing dextrose, arabinose, xylose, respectively, assole carbon source to see cell growth. The yeast isolates were further identified using API AOC 20C kit method. Yeast isolates were applied for fermentation of glucose, arabinose, and xylosein incubated cultures. Ethanol production in the fermentation was analyzed bygaschromatography. Yeast isolates were identified as Kodamaea ohmeri, Candida famata, Candida guilliermondii, and Crytococcuc laurentii. Based on gas chromatography data, it was found that ethanol produced in the fermentation for three days, the highest ethanol content on xylose substrate was fermented by Candida famata-Awhich is0.021% (v/v) ethanol resulted from initial concentration of 5% xylose (w/v). While on arabinose substrate, the highest ethanol content was fermented by Crytococcus laurentii-Bwhich is 0.0034% (v/v) ethanol resulted from initial concentration of 5% arabinose (w/v).
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Zepeda, S., O. Monasterio i T. Ureta. "NADP+-dependent d-xylose dehydrogenase from pig liver. Purification and properties". Biochemical Journal 266, nr 3 (15.03.1990): 637–44. http://dx.doi.org/10.1042/bj2660637.
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An NADP(+)-dependent D-xylose dehydrogenase from pig liver cytosol was purified about 2000-fold to apparent homogeneity with a yield of 15% and specific activity of 6 units/mg of protein. An Mr value of 62,000 was obtained by gel filtration. PAGE in the presence of SDS gave an Mr value of 32,000, suggesting that the native enzyme is a dimer of similar or identical subunits. D-Xylose, D-ribose, L-arabinose, 2-deoxy-D-glucose, D-glucose and D-mannose were substrates in the presence of NADP+ but the specificity constant (ratio kcat./Km(app.)) is, by far, much higher for D-xylose than for the other sugars. The enzyme is specific for NADP+; NAD+ is not reduced in the presence of D-xylose or other sugars. Initial-velocity studies for the forward direction with xylose or NADP+ concentrations varied at fixed concentrations of the nucleotide or the sugar respectively revealed a pattern of parallel lines in double-reciprocal plots. Km values for D-xylose and NADP+ were 8.8 mM and 0.99 mM respectively. Dead-end inhibition studies to confirm a ping-pong mechanism showed that NAD+ acted as an uncompetitive inhibitor versus NADP+ (Ki 5.8 mM) and as a competitive inhibitor versus xylose. D-Lyxose was a competitive inhibitor versus xylose and uncompetitive versus NADP+. These results fit better to a sequential compulsory ordered mechanism with NADP+ as the first substrate, but a ping-pong mechanism with xylose as the first substrate has not been ruled out. The presence of D-xylose dehydrogenase suggests that in mammalian liver D-xylose is utilized by a pathway other than the pentose phosphate pathway.
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Muñoz-Páez, Karla María, i Germán Buitrón. "Role of xylose from acidic hydrolysates of agave bagasse during biohydrogen production". Water Science and Technology 84, nr 3 (24.06.2021): 656–66. http://dx.doi.org/10.2166/wst.2021.242.
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Abstract This study compares the H2 production from glucose, xylose, and acidic hydrolysates of Agave tequilana bagasse as substrates. The fermentation was performed in a granular sludge reactor operated in two phases: (1) model substrates (glucose and xylose) and (2) acidic hydrolysates at 35 °C, pH 4.5 and a hydraulic retention time of 5.5 h with glucose (10 g L−1) and xylose (12 g L−1). A sequencing batch reactor was used to acclimate the biomass between the glucose and xylose continuous fermentation (with a mixture of xylose-glucose) and acidic hydrolysates. During the discontinuous acclimating step, the xylose/glucose ratio increment negatively affected the H2 productivity. Although the continuous H2 production with xylose was negligible, the co-fermentation with glucose (88–12%) allowed H2 productivity of 2,889 ± 502 mL H2 L−1d−1. An acidic hydrolysate concentration of 3.3 gcarbohydrate L−1 showed a three-fold higher H2 productivity than with a concentration of 10 g L−1. The results indicated that xylose, as the only substrate, was challenging to metabolize by the inoculum, and its mixture with glucose improved the H2 productivity. Therefore, the low H2 productivity with hydrolysates could be related to the presence of xylose.
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Kratzer, Regina, Stefan Leitgeb, David K. Wilson i Bernd Nidetzky. "Probing the substrate binding site of Candida tenuis xylose reductase (AKR2B5) with site-directed mutagenesis". Biochemical Journal 393, nr 1 (12.12.2005): 51–58. http://dx.doi.org/10.1042/bj20050831.
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Little is known about how substrates bind to CtXR (Candida tenuis xylose reductase; AKR2B5) and other members of the AKR (aldo–keto reductase) protein superfamily. Modelling of xylose into the active site of CtXR suggested that Trp23, Asp50 and Asn309 are the main components of pentose-specific substrate-binding recognition. Kinetic consequences of site-directed substitutions of these residues are reported. The mutants W23F and W23Y catalysed NADH-dependent reduction of xylose with only 4 and 1% of the wild-type efficiency (kcat/Km) respectively, but improved the wild-type selectivity for utilization of ketones, relative to xylose, by factors of 156 and 471 respectively. Comparison of multiple sequence alignment with reported specificities of AKR members emphasizes a conserved role of Trp23 in determining aldehyde-versus-ketone substrate selectivity. D50A showed 31 and 18% of the wild-type catalytic-centre activities for xylose reduction and xylitol oxidation respectively, consistent with a decrease in the rates of the chemical steps caused by the mutation, but no change in the apparent substrate binding constants and the pattern of substrate specificities. The 30-fold preference of the wild-type for D-galactose compared with 2-deoxy-D-galactose was lost completely in N309A and N309D mutants. Comparison of the 2.4 Å (1 Å=0.1 nm) X-ray crystal structure of mutant N309D bound to NAD+ with the previous structure of the wild-type holoenzyme reveals no major structural perturbations. The results suggest that replacement of Asn309 with alanine or aspartic acid disrupts the function of the original side chain in donating a hydrogen atom for bonding with the substrate C-2(R) hydroxy group, thus causing a loss of transition-state stabilization energy of 8–9 kJ/mol.
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Brink, Daniel P., Celina Borgström, Viktor C. Persson, Karen Ofuji Osiro i Marie F. Gorwa-Grauslund. "D-Xylose Sensing in Saccharomyces cerevisiae: Insights from D-Glucose Signaling and Native D-Xylose Utilizers". International Journal of Molecular Sciences 22, nr 22 (17.11.2021): 12410. http://dx.doi.org/10.3390/ijms222212410.
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Extension of the substrate range is among one of the metabolic engineering goals for microorganisms used in biotechnological processes because it enables the use of a wide range of raw materials as substrates. One of the most prominent examples is the engineering of baker’s yeast Saccharomyces cerevisiae for the utilization of d-xylose, a five-carbon sugar found in high abundance in lignocellulosic biomass and a key substrate to achieve good process economy in chemical production from renewable and non-edible plant feedstocks. Despite many excellent engineering strategies that have allowed recombinant S. cerevisiae to ferment d-xylose to ethanol at high yields, the consumption rate of d-xylose is still significantly lower than that of its preferred sugar d-glucose. In mixed d-glucose/d-xylose cultivations, d-xylose is only utilized after d-glucose depletion, which leads to prolonged process times and added costs. Due to this limitation, the response on d-xylose in the native sugar signaling pathways has emerged as a promising next-level engineering target. Here we review the current status of the knowledge of the response of S. cerevisiae signaling pathways to d-xylose. To do this, we first summarize the response of the native sensing and signaling pathways in S. cerevisiae to d-glucose (the preferred sugar of the yeast). Using the d-glucose case as a point of reference, we then proceed to discuss the known signaling response to d-xylose in S. cerevisiae and current attempts of improving the response by signaling engineering using native targets and synthetic (non-native) regulatory circuits.
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Furlan, Sandra A., i Heizir F. de Castro. "Xylitol production by Candida parapsilosis under fed-batch culture". Brazilian Archives of Biology and Technology 44, nr 2 (czerwiec 2001): 125–28. http://dx.doi.org/10.1590/s1516-89132001000200003.
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Xylitol production by Candida parapsilosis was investigated under fed-batch cultivation, using single (xylose) or mixed (xylose and glucose) sugars as substrates. The presence of glucose in the medium induced the production of ethanol as secondary metabolite and improved specific rates of growth, xylitol formation and substrate consumption. Fractionated supply of the feed medium at constant sugar concentration did not promote any increase on the productivity compared to the single batch cultivation.
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Kuenz, Anja, Malee Jäger, Harri Niemi, Mari Kallioinen, Mika Mänttäri i Ulf Prüße. "Conversion of Xylose from Birch Hemicellulose Hydrolysate to 2,3-Butanediol with Bacillus vallismortis". Fermentation 6, nr 3 (2.09.2020): 86. http://dx.doi.org/10.3390/fermentation6030086.
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Biotechnologically produced 2,3-butanediol (2,3-BDO) is a potential starting material for industrial bulk chemicals, such as butadiene or methyl ethyl ketone, which are currently produced from fossil feedstocks. So far, the highest 2,3-BDO concentrations have been obtained with risk class 2 microorganisms and pure glucose as substrate. However, as glucose stays in competition to food and feed industries, a lot of effort has been done in the last years finding efficient alternative substrates. Thereby xylose from hydrolysed wood hemicelluloses is a promising substrate for the production of 2,3-BDO. The risk class 1 microorganism Bacillus vallismortis strain was identified as a very promising 2,3-BDO producer. The strain is able to utilize xylose almost in the same manner as glucose. B. vallismortis is less prone to common inhibiting compounds in lignocellulosic extracts/hydrolysates. When using a concentrated hemicellulose fraction from birch wood hydrolysate, which was produced with ultrafiltration and after which the acetate concentration was reduced, a yield of 0.43 g g−1 was achieved and the xylose consumption and the 2,3-BDO production is basically the same as using pure xylose.
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Milessi-Esteves, Thais, Felipe Corradini, Willian Kopp, Teresa Zangirolami, Paulo Tardioli, Roberto Giordano i Raquel Giordano. "An Innovative Biocatalyst for Continuous 2G Ethanol Production from Xylo-Oligomers by Saccharomyces cerevisiae through Simultaneous Hydrolysis, Isomerization, and Fermentation (SHIF)". Catalysts 9, nr 3 (1.03.2019): 225. http://dx.doi.org/10.3390/catal9030225.
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Many approaches have been considered aimed at ethanol production from the hemicellulosic fraction of biomass. However, the industrial implementation of this process has been hindered by some bottlenecks, one of the most important being the ease of contamination of the bioreactor by bacteria that metabolize xylose. This work focuses on overcoming this problem through the fermentation of xylulose (the xylose isomer) by native Saccharomyces cerevisiae using xylo-oligomers as substrate. A new concept of biocatalyst is proposed, containing xylanases and xylose isomerase (XI) covalently immobilized on chitosan, and co-encapsulated with industrial baker’s yeast in Ca-alginate gel spherical particles. Xylo-oligomers are hydrolyzed, xylose is isomerized, and finally xylulose is fermented to ethanol, all taking place simultaneously, in a process called simultaneous hydrolysis, isomerization, and fermentation (SHIF). Among several tested xylanases, Multifect CX XL A03139 was selected to compose the biocatalyst bead. Influences of pH, Ca2+, and Mg2+ concentrations on the isomerization step were assessed. Experiments of SHIF using birchwood xylan resulted in an ethanol yield of 0.39 g/g, (76% of the theoretical), selectivity of 3.12 gethanol/gxylitol, and ethanol productivity of 0.26 g/L/h.
Rozprawy doktorskie na temat "Xylose as substrate"
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Lebeau, Thierry. "Fermentation alcoolique de mélanges glucose-xylose par les levures Candida shehatae et Saccharomyces cerevisiae co-immobilisées dans un nouveau type de bioréacteur à membrane". Rouen, 1997. http://www.theses.fr/1997ROUES014.
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Ce travail étudie la fermentation alcoolique d'un mélange de glucose (35 g/l) et de xylose (15 g/l) par Candida shehatae et Saccharomyces cerevisiae co-immobilisées dans une structure membranaire composite constituée d'une couche plane d'agar enserree entre deux membranes microporeuses. L'utilisation d'un bioréacteur à double chambre a permis une alimentation dissymétrique en substrats et en dioxygène de la structure immobilisatrice et de répondre ainsi aux exigences de culture de chacune des deux espèces. Lors de fermentations discontinues, nous avons montré que les levures consommaient totalement le glucose mais seulement 25% a 40% du xylose. Afin de comprendre les raisons de la faible conversion du xylose par les levures immobilisées, nous avons évalué la résistance opposée par la structure biocatalytique à la diffusion des divers solutés (glucose, xylose, éthanol et xylitol). Cette résistance double au cours de l'incubation : une augmentation de cet ordre ne peut expliquer à elle seule le blocage du système. Une étude des capacités fermentaires des cellules extraites de la structure immobilisatrice a montré que les levures localisées près de la source de substrats carbonés subissaient un fort stress, probablement du à l'accumulation de co-métabolites toxiques dans le milieu de culture. Nous avons enfin effectué des fermentations en continu dans un prototype de bioréacteur à double chambre possédant une surface d'échange élargie. Un taux de conversion du xylose de 73% (et de 100% pour le glucose) a pu être atteint pour un taux de dilution D de 0,04 h(-1), bien que la charge microbienne initiale du gel d'agar fut relativement faible (2,5 g/l de Candida shehatae + 2,5 g/l de Saccharomyces cerevisiae).
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Murray, Leslie Justin. "Dioxygen activation and substrate hydroxylation by the hydroxylase component of toluene/O-xylene monooxygenase from pseudomonas sporium OX1". Thesis, Massachusetts Institute of Technology, 2007. http://hdl.handle.net/1721.1/41556.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Chemistry, 2007.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
MIT Institute Archives copy includes accompanying CDROM with copy of thesis in .pdf format.
"September 2007." Vita.
Includes bibliographical references.
Non-heme carboxylate-bridged diiron centers in the hydroxylase components of the bacterial multicomponent monooxygenases activate dioxygen at structurally homologous active sites. Catalysis requires the management of four substrates: electrons, protons, dioxygen, and hydrocarbons. Protein component complexes control the delivery of these substrates to the diiron center in the hydroxylase ensuring selective hydrocarbon oxidation. A detailed mechanistic understanding of structural and chemical consequences of such interactions is a significant challenge. This thesis begins with an overview of our current understanding of these processes. The discussion is primarily on the methane monooxygenase systems (MMO) because these have been the most extensively studied BMMs to date. Recent results for the toluene/o-xylene monooxygenase (ToMO) and phenol hydroxylase systems from Pseudomonas sporium OX1 are also briefly summarized, the former being the research focus of this dissertation. Restricting access to the diiron center in ToMOH and other non-heme carboxylate-bridged diiron proteins was proposed to facilitate observation of oxygenated intermediates. To examine this hypothesis, dioxygen activation in ToMOH mutants that were predicted to occlude this channel was investigated by rapid-freeze quench (RFQ) EPR, Mossbauer, and ENDOR spectroscopy and stoppedflow optical spectroscopy. For the I100W mutant, a transient species is observed with an absorption maximum at 500 nm. EPR and Mossbauer spectra of RFQ samples identified this species as a diiron(III,IV) cluster spin-coupled to a neutral W radical. ENDOR spectra of this intermediate confirmed the protonation state and type of the amino acid radical and also identified a labile terminal water or hydroxide on the diiron center.
(cont.) Decay of this intermediate results in hydroxylation of the W radical. A diamagnetic precursor to the mixed-valent diiron(III,IV) center was also observed at an earlier time-point, with Mossbauer parameters typical of high-spin FeIII. We have tentatively assigned this antiferromagnetically-coupled diiron(III) intermediate as a peroxo-bridged cluster. A similar diiron(III) species is observed in RFQ Mossbauer samples from the reaction of reduced wild type hydroxylase with dioxygen. Substrate accelerates the decay rate of this species, providing evidence for the diiron(III) transient as the active oxidant. Under steady state conditions, hydrogen peroxide was generated in the absence of substrate. The oxidized hydroxylase also decomposed hydrogen peroxide to liberate dioxygen if no reducing equivalents were present. This catalase activity suggests that dioxygen activation could be reversible. The linear free energy relationship determined from steady state hydroxylation of para substituted phenols has a negative slope. A value of ? < 0 is indicative of electrophilic attack on the aromatic substrate by the oxidizing diiron(III) intermediate. The results from these steady state and pre-steady experiments provide compelling evidence that the diiron(III) transient is the active oxidant in ToMO and is a peroxodiiron(III) transient, despite differences between the optical and Mossbauer spectroscopic parameters and those of other peroxodiiron(III) centers. Enzymatic oxidation of the radical clock substrate probe, norcarane, by ToMO gives rise to both desaturation and hydroxylation products, norcarenes and norcaranols respectively.
(cont.) Norcarenes are better substrates for this enzyme system than norcarane, producing additional oxidation products. In all, more than twenty oxidation products were characterized in these reaction mixtures, half of which arose from norcarene oxidation. Accounting for these secondary oxidation products, we determined that no substrate radical intermediates with a significant lifetime (t < 25 ps) are formed during catalysis.
by Leslie Justin Murray.
Ph.D.
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Babau, Maud. "Croissance et accumulation lipidique de Rhodotorula glutinis (rhodosporidium toruloides) sur glucose, xylose et glycérol : vers la valorisation des coproduits agricoles et industriels pour la production de lipides à usages énergétiques". Thesis, Toulouse, INSA, 2015. http://www.theses.fr/2015ISAT0027/document.
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Rhodotorula glutinis (Rhodosporidium toruloides) est une levure oléagineuse dont les fortes capacités d’accumulation lipidique à partir de glucose comme source carbonée ont fait de la souche un modèle d’étude. La capacité de cette levure à utiliser le glycérol ou le xylose en simple ou co-substrat avec le glucose est toutefois encore peu explorée. De l’analyse des travaux antérieurs il a été possible de dégager les verrous scientifiques qui nécessitent une amélioration des connaissances du comportement physiologique de cette levure pour la conversion des substrats cités. Des stratégies expérimentales adaptées à la quantification rationnelle des dynamiques de Rhodotorula glutinis en conditions de croissance et accumulation lipidique à partir de xylose et de glycérol en simple ou co-substrats avec le glucose ont été développées. Des résultats originaux ont été obtenus dont :- la mise en évidence des potentialités de co-consommation des substrats xylose et glucose ou glycérol et glucose sans accumulation de substrat ni production de métabolites en conditions contrôlées des flux de substrats. Il a été possible de déterminer la vitesse spécifique maximale de consommation du carbone de la souche qui diminue lorsque la part de xylose ou glycérol augmente dans l’apport de carbone total.- la quantification de la dynamique de croissance sur xylose et glycérol pur en terme de taux de croissance et de rendement : sur xylose µmax= 0.034h-1 et RS/X= 0.28 Cmolx.Cmolxylose-1; sur glycérol µmax=0.04h-1 RS/X=0.31Cmolx.Cmolglycérol-1.- la quantification des vitesses spécifiques et rendements de production de lipides à partir de xylose ou de glycérol en simple ou co-substrat avec du glucose : 20%xylose-80%glucose : qp=0.065CmolTAG.Cmolbiomasse.h-1, RS/P=0.3CmoleTAG.Cmolesubstrat-1 100%xylose : qp=0.035065CmolTAG.Cmolbiomasse.h-1, RS/P=0.31CmoleTAG.Cmolesubstrat-1, 25% glycérol-75%glucose : qp=0.07065CmolTAG.Cmolbiomasse.h-1, RS/P=0.25CmoleTAG.Cmolesubstrat-1 , 100% glycérol : qp=0.03065CmolTAG.Cmolbiomasse.h-1, RS/P= 0.29CmoleTAG.Cmolesubstrat-1.- L’impact de la nature des substrats sur le profil lipidique de Rhodotorula glutinis demeure léger : il apparait que le xylose entraîne une surproduction de C16:0 et C18:3et le glycérol favorise l’accumulation de C18:0Rhodotorula glutinis (Rhodosporidium toruloides) is an oleaginous yeast. The micro-organism has demonstrated high lipid accumulation when utilizing glucose as a substrate, and has become a model for oil production. Glycerol and xylose are interesting as substrates for production of oil from renewable resources, but the capacity of R. glutinis to utilize glycerol and xylose as substrates has not been characterized well. Fermentation strategies were designed to quantify growth and lipid accumulation dynamics of R. glutinis when utilizing glycerol and xylose - either as pure substrates, or as co-substrates with glucose. Several original results have been found, including: - Co-consumption of xylose or glycerol along with glucose was observed, without carbon substrate accumulation or byproduct formation, when the carbon feed rate was carefully controlled. The specific carbon consumption rate decreases when the proportion of the second substrate (glycerol or xylose) increases in the feed, relative to glucose. - Growth capacities were characterized on pure xylose and pure glycerol in terms of growth rate and carbon yields: on xylose μmax= 0.034h-1 and RS/X= 0.28 Cmolx.Cmolxylose-1; on glycerol μmax=0.04h-1 RS/X=0.31Cmolx.Cmolglycerol-1. - specific production rate of lipid production and substrate to product carbon conversion yields from xylose or glycerol as single or cosubstrate with glucose were determinated: 20%xylose-80%glucose : qp=0.065CmolTAG.Cmolbiomasse.h-1, RS/P=0.3CmoleTAG.Cmolesubstrat-1 100%xylose : qp=0.035065CmolTAG.Cmolbiomasse.h-1, RS/P=0.31CmoleTAG.Cmolesubstrat-1, 25% glycerol-75%glucose : qp=0.07065CmolTAG.Cmolbiomasse.h-1, RS/P=0.25CmoleTAG.Cmolesubstrat-1 , 100% glycerol : qp=0.03065CmolTAG.Cmolbiomasse.h-1, RS/P= 0.29CmoleTAG.Cmolesubstrat-1. - Substrate diversification slightly impacts Rhodotorula glutinis´s lipid profile: xylose leads to an overproduction of C16:0 and C18:3 and glycerol increases C18:0 accumulation
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Ponaire, Sarah. "Synthèse d'analogues de substrats ou d'inhibiteurs d'enzymes de la voie du 2-C-méthyl-D-érythritol 4-phosphate (MEP) pour la synthèse des isoprénoïdes". Strasbourg, 2010. https://publication-theses.unistra.fr/public/theses_doctorat/2010/PONAIRE_Sarah_2010_ED222.pdf.
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La résistance de plus en plus importante des microorganismes aux antibiotiques et antiparasitaires actuels, nous incite à identifier de nouvelles cibles thérapeutiques pour lutter contre ces agents pathogènes. Les isoprénoïdes constituent une vaste famille de composés naturels présents chez tous les organismes vivants. Ils peuvent être biosynthétisés selon deux voies: la voie du mévalonate et la voie du 2-C-méthylérythritol 4-phosphate (MEP) ; Cette dernière voie est présente chez de nombreux microorganismes pathogènes ou parasites, mais absente chez l’homme. La voie de biosynthèse des isoprénoïdes selon la voie du MEP devient donc une cible parfaite pour identifier de nouveaux antimicrobiens. Dans cette optique, nous avons choisi de synthétiser dans une première partie six prodrogues de deux acides phosphoniques déjà synthétisés au laboratoire. Ces derniers, dérivés de la fosmidomycine, s’étant déjà distingués par leur pouvoir inhibiteur sur la DXR d’Escherichia coli. Ces prodrogues ont été testées sur des cultures de cellules de tabac, les BY-2 ainsi que sur une bactérie, Mycobacterium smegmatis. Les résultats obtenus sur BY-2 révèlent que ces prodrogues sont de meilleurs inhibiteurs que la fosmidomycine et qu’ils sont toujours actifs à des concentrations auxquelles la fosmidomycine n’a plus aucun effet. Parallèlement à ce travail une synthèse de MEP sous forme de prodrogue a été envisagée ; malgré les différents groupements utilisés pour masquer le phosphate ainsi que les nombreux jeux de protections et déprotections, le MEP prodrogue n’a pu être obtenu. Dans une troisième partie nous nous sommes intéressés à la synthèse de la DHAP (dihydroxyacétonephosphate) qui est une petite molécule hautement fonctionnalisée intervenant dans bon nombre de voies métaboliques. La synthèse mise au point dépasse par sa simplicité et son efficacité toutes les préparations de DHAP réalisées à ce jour. La dernière partie de ce travail est consacrée à l’étude de la sélectivité de la première enzyme de la voie du MEP, la désoxyxylulose phosphate synthase (DXS). Pour ce faire, nous avons tenté de synthétiser le L-GAP (L-glycéraldéhyde 3- phosphate) qui est l’énantiomère du substrat naturel de la DXS. Malgré les différents chemins réactionnels testés, cette synthèse n’a pu être menée à son termeIsoprenoïds are components of the vast family of « natural compounds » present in all living organisms. They are biosynthetically obtained by two distinct pathways: the mevalonate pathway and the 2-C-methylerithritol 4-phosphate pathway; the latter is present in numerous pathogenous microorganisms and parasites. Growing microorganism resistance to antibiotics and antiparasitics forces us to identify new therapeutic targets to fight against pathogens. The great advantage of the 2-C-methylerithritol 4-phosphate pathway is that it is absent in humans thus being the ideal target to discover new antibiotics. To that end, we decided to synthesize six prodrugs derived from two phosphonic acids previously obtained in our research group. The latter, directly related to fosmidomycin were proven to be potent inhibitors of E. Coli’s DXR enzyme. The new prodrugs were tested on tobacco cell cultures, on BY-2 as well on Mycobacterium smegmatis. Results obtained on BY-2 show that our prodrugs are stronger inhibitors than fosmidomycin. Moreover, they still have an inhibitory effect on very low concentrations were fosmidomycin does not. In addition, organic synthesis of 2-C-methylerithritol 4-phosphate was studied. Though various protecting groups of the phosphate moiety were used and numerous protection / deprotection steps were tested, 2-C-methylerithritol 4-phosphate was never obtained. We then pursued our efforts on synthesizing dihydroyacetone phosphate, a small organic compound found in various metabolic pathways. The organic synthesis we propose surpasses all others by its simplicity and efficiency. Finally, we tried to synthesize L-glyceraldehyde 3-phosphate; this compound is the enantiomericaly pure substrate of DXS (deoxyxylulose phosphate synthase). Though many different synthetic schemes were tested, none of them yielded the desired product
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Shu, Bing-Jui, i 許秉叡. "Using Glucose and Xylose as Sole Substrate for Fermentative Hydrogen Production in CSABRs". Thesis, 2006. http://ndltd.ncl.edu.tw/handle/80578896322180405004.
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碩士逢甲大學
化學工程學所
94
Hydrogen Economy is the trend of the world energy policy. Hydrogen from biomass is promising for renewable hydrogen production, especially for biological methods. To develop the clean, low cost and low energy consumed processes for hydrogen production is the goal of our research team, Research Center for Energy and Resources in Feng Chia University. The traditional CSTR, bacteria wash-out occurred obviously when low hydraulic retention times, HRT, say HRT ≦ 4 h. In this study, biohydrogen production was investigated with two different aspect ratios (H/D = 3:1 & 8:1) in continuously stirred anaerobic bioreactors (CSABR) with immobilized anaerobic sludge. First the dark fermentation of hydrogen production was carried out by the immobilized cells, Endo nutrition formulation, the operating temperature of 40 ℃, and an aspect ratio of H/D = 3:1. The xylose substrates (20000 mg COD/L) were fed into the system with different HRT, which are 12, 6, 4, 2, 1 and 0.5 hours respectively. Second the experimental conditions were the same as the first case, but the xylose substrates ranges changed from 5000, 10000, 20000 up to 30000 mgCOD/L. For the aspect ratio of H/D = 8:1, the glucose substrates various form 10000, 20000, 30000 to 40000 mgCOD/L with Endo nutrition formulation were fed into the system with different HRT, which were 4, 2, 1 and 0.5 hours respectively. The results show that the porosity materials, granules formation had the maximum hydrogen production rate of 1.53 ± 0.06 H2 L/h/L when CXo = 20000 mg COD/L, and the hydrogen yield of 0.60 ± 0.02 mol H2/mol xylose. In the same circumstance, for H/D = 3:1 the granules formation facilitated hydrogen production, there had the maximum hydrogen production rate of 2.33 ± 0.21 H2 L/h/L when CXo = 30000 mg COD/L, and the hydrogen yield of 0.58 ± 0.05 mol H2/mol xylose individually. The hydrogen concentrations of the biogas were above 27.3%. Under different influent xylose concentrations (CXo= 5000, 10000, 20000, and 30000 mg COD/L), the results show that the maximum H2 production rate was 2.33 ± 0.21 H2 L/h/L when CXo = 30000 mg COD/L, and HRT = 1 h. For different influent glucose concentrations (CGo= 10000, 20000, 30000, and 40000 mg COD/L), the results show that the maximum H2 production rate was 7.52 ± 0.27 H2 L/h/L when CGo = 20000 mg COD/L, and the hydrogen yield was 1.54 ± 0.05 mol H2/mol glucose at HRT = 0.5 h. From this investigation, we found that the hexose (glucose) and pentose (xylose) from cellulose and/or hemi-cellulose hydrolysis will be the good sources of biohydrogen production.
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Rung, Yang Jia, i 楊佳蓉. "Production of Xylo-oligosaccharides Using Corncob Substrate by Trametes versicolor LH1 Static Culture". Thesis, 2012. http://ndltd.ncl.edu.tw/handle/88428603069240814573.
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碩士大葉大學
生物產業科技學系碩士在職專班
100
The white-rot fungi Trametes versicolor LH1 belongs to the basidomycetes class of fungi and is used to degrade celluloses and hemicelluloses. Trametes versicolor LH1 can produce bioactive ingredients and secrete hemicelluloses enzymes such as: xylanase, laccase and manganese peroxidase. Xylooligsaccharides contain two to seven molecules of xylose have been widely used in the food industry. We monitored the effect on the production of xylooligosaccharides in different inoculua and initial pH using corncob substrates by employing Trametes versicolor LH1 static cultures. The results were optimal in 10% of the inocula where the production biomass, extracellular polysaccharides (EPS) and xylanase were 10.57mg/ml, 1.04mg/ml and 58.25U/100ml, respectively. The optimal pH level was found to be pH5 in different initial pH levels (pH3-7) where the the production biomass, extracellular polysaccharides (EPS) and xylanase were 13.94mg/ml, 1.46mg/ml, 82.81U/100ml and 52.97 mg/ml, respectively. A nitrogen source of 0.3% was employed in a peanut powder extract with different initial pH levels (pH3-7) and the optimal pH level was found to be pH5 where the production biomass, extracellular polysaccharides (EPS), xylanase and xylooligosaccharide were 19.36mg/ml, 1.64mg/ml, 104.98U/100ml and 109.01mg/ml, respectively. The different initial pH levels were pH5>pH6>pH7>pH4>pH3 in the production of xylooligosaccharides. The different initial pH levels in the production of xylooligosaccharides in a 0.3% peanut powder extract were identical.
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Fang, Kai-Ching, i 方凱慶. "Xylo-oligosaccharides Production of Submerged Fermentation by the Different Medicinal Fungi Using Corn Cob Substrate". Thesis, 2012. http://ndltd.ncl.edu.tw/handle/56409215413951183393.
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碩士大葉大學
生物產業科技學系
100
Most medicinal fungi are rich in polysaccharides, which have been shown to have anti-tumor functions and inhibit cancer cell growth, strengthen the immune system or adjust the balance of the body, and exhibit other medicinally relevant properties such as anti-inflammatory or cholesterol regulatory properties. In addition, scholars have pointed out that medicinal fungi has a variety of enzymes, of which some like xylanase hemicellulose material produce xylooligosaccharides used in the pharmaceutical, cosmetics and food industries. Corn cob contains a lot of cellulose; a good source of raw materials for the production of xylooligosaccharides. In this experiment, cultures of Trametes versicolor, Antrodia camphorata, Grifola frondosa, Phellinus igniarius were placed in different media (corn cob as a carbon source, adding RO water; red sugar as the carbon source, adding peanut powder extract as a nitrogen source to explore xylooligosaccharide generation; corn cob and red sugar as a carbon source, adding add peanut powder extract as nitrogen source) employing temperatures (22℃, 25℃, 28℃) and oscillation rates (50rpm, 100rpm, 150rpm). The results show that at a temperature of 25℃ and an oscillation rate of 150rpm, Trametes versicolor can achieve a biomass and high extracellular polysaccharide and xylanase production, 2.59mg/mL, 0.99mg/mL and 32.57U/100mL respectively. Under the different temperatures condition, it was found that for Trametes versicolor the optimal temperature was 25℃, the biomass and extracellular polysaccharide and xylanase production were 3.63mg/mL, 2.96mg/mL and 43.08U/100mL respectively. Different oscillation rates proved to be optimal for Grifola frondosa, however, as the biomass and production of extracellular polysaccharides were higher at 150rpm, but the xylanase enzyme activity was higher at 100 rpm (2.53mg/mL 0.89mg/mL and 31.30 U/100mL, respectively). In different culture conditions in different media, the corn cob and red sugar as a carbon source with the addition of peanut powder extract as a nitrogen source, Antrodia camphorata was found to achieve a higher biomass and extracellular polysaccharide and xylanase activity (3.46mg/mL, 1.17mg/mL and 41.65U/100mL, respectively). With corn cob as the carbon source, Trametes versicolor achieved the highest biomass and xylooligosaccharides production (4.82mg/mL 54.32mg/mL, respectively), while Phellinus igniarius had the best extracellular polysaccharide production (1.48mg/mL). The highest xylanase activity was found in Antrodia camphorata in the corn cob as a nitrogen source (35.83U/100mL).
Streszczenia konferencji na temat "Xylose as substrate"
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Li, C. J., J. L. Li i W. B. Wang. "The Effect of Substrate Preheating and Surface Organic Covering on Splat Formation". W ITSC 1998, redaktor Christian Coddet. ASM International, 1998. http://dx.doi.org/10.31399/asm.cp.itsc1998p0473.
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Abstract The splashing usually occurs when a droplet impact on a substrate surface during thermal spraying, which results in the formation of splat with irregularly complicated morphology. In present study splats are formed on polished stainless steel substrate surface covered with different organic substances with different boiling points by plasma spraying under different preheating temperature of substrate in order to clarify the factors which control the splashing during droplet flattening in thermal spray process. The droplet materials used are aluminum, nickel, copper, Al2O3 and molybdenum. Three kinds of organic substances used are xylene, glycol and glycerol which are brushed on the surface of substrate before spraying. It is found that when the preheating temperature exceeds 50°C over the boiling point of organic substance brushed on substrate surface the regular disk type splats are formed in the case that no substrate melting occurs by molten droplet. When the flattening of droplet causes the melting of substrate such as the combination of Mo droplet with stainless steel substrate, the preheating of substrate has no influence on splat morphology. The evaporated gas induced splashing and substrate surface melting induced splashing models are proposed to interpret the formation of the annulus-ringed splat.
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Davis, Benjamin, Nitin Muralidharan, Cary Pint i Matthew R. Maschmann. "Electrically Addressable Hierarchical Carbon Nanotube Forests". W ASME 2016 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2016. http://dx.doi.org/10.1115/imece2016-67226.
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Hierarchical, branched carbon nanotube (CNT) forest assemblies were created by synthesizing a second generation of CNTs directly from the alumina-coated surface of a parent CNT forest. First, a parent CNT forest generation was synthesized using floating catalyst chemical vapor deposition (CVD) in which gaseous argon and hydrogen are flowed into a tube furnace, along with a controlled flow rate of ferrocene nanoparticles suspended in xylene solvent. Next, a thin alumina coating was applied to the parent CNT forest using atomic layer deposition (ALD). The ALD process pulses alternating gases of water vapor and trimethylaluminum (TMA) and is repeated for 100 cycles, yielding a 10nm coating. This coating adheres to the outer walls of the larger CNTs and serves as a supportive surface to enable the growth of a second CNT generation. Finally, a second CNT generation was synthesized from the parent CNT forest using a floating-catalyst CVD method similar to that used for the parent generation. The relatively low areal density of the parent CNT generation allows for gas-phase additive processing (i.e. ALD and floating catalyst CVD) to occur deep within the volume of the original parent CNT forest. Transmission electron microscopy analysis of the hierarchical CNT forests shows that second-generation CNTs nucleate and grow from the alumina-coated walls of the parent generation rather than nucleating from the original growth substrate, as has been previously reported. Further, physical confinement of the second-generation catalyst particle on the external surface of the parent generation CNTs (28 nm average diameter) leads to small-diameter CNTs (8 nm average) for the second generation. Further, radial breathing modes are detected by Raman spectroscopy, indicating single-walled or few-walled CNTs are synthesized in the second generation. The hierarchical forests exhibit many desirable properties compared to single generation forests. Because the second generation CNTs within the interstitial regions of the parent CNT forest, they increase the structural rigidity of the cellular CNT forest morphology, increasing in mechanical stiffness by ten-fold, relative to the parent CNT forest. Further, we demonstrate that electrical continuity between the CNT generations is retained. Because a thin alumina buffer layer exists between CNT generations, electrical continuity is not guaranteed. Cyclic voltammetry and electrochemical impedance spectroscopy are used to characterize the electrical resistance elements within the hierarchical forest. This hierarchical structure offers a new avenue to tailor the performance of CNT forests and offers performance enhancements for applications in thermal interfaces, electrical interconnects, dry adhesives and energy generation and storage.