Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “PENTOSES”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,243 records · Page 69Linked to original sources
PubMed1982

Sterol synthesis by the ocular lens of the rat during postnatal development.

Great amounts of plasma membranes are formed during early postnatal development of the ocular lens as lens epithelial cells differentiate into fiber cells. Little information is available on the source of the lipids, and particularly cholesterol, required for formation of these plasma membranes. The present study measured the capacity of the lens of the rat to synthesize cholesterol during this dynamic period of growth. Incorporation by lens of (3)H(2)O into total fatty acids was also examined. Absolute rates of cholesterol synthesis per whole lens were estimated in vitro from incorporation of (3)H from (3)H(2)O into digitonide precipitable sterols (DPS) by intact lenses of 6- to 30-day old rats. Rates of cholesterol synthesis were calculated which were adequate to furnish from either 50-100% or 20-40% of the cholesterol required by the lens for growth, depending upon the animal's age and upon whether one considered NADPH to be generated by the pentose phosphate pathway or by oxidative enzymatic processes (NADPH from the pentose pathway is not labeled from (3)H(2)O). Generation of the NADPH necessary for cholesterol synthesis principally by the pentose pathway would support the higher percent contribution of synthesis to the total growth requirement. The pentose pathway was clearly active in the young rat lens, since between 7.5 to 9.0 times more [1-(14)C]glucose than [6-(14)C]glucose was oxidized in vitro to (14)CO(2) by 6- and 22-day old lenses. Incorporation of (3)H(2)O into DPS decreases sharply after 2 weeks of age in spite of a constant rate of cholesterol accumulation by the lens. These results indicate that the ocular lens of the rat can furnish most if not all of its cholesterol requirements by synthesis de novo during the first 2 weeks of life, and imply a contribution from another source at older ages. Whether lipoproteins can supply cholesterol to the lens is still unclear, although neither HDL nor LDL altered the incorporation in vitro of [U-(14)C]glucose into DPS by lens.-Cenedella, R. J. Sterol synthesis by the ocular lens of the rat during postnatal development.

Animals↗
PubMed1981

[Interaction of the Embden-Meyerhof pathway and hexose monophosphate shunt in erythrocytes].

A mathematical model of glycolysis in human erythrocytes for the interaction between the Embden-Meyerhof and the pentose phosphate pathways has been developed. The characteristic surfaces, i. e. interdependencies between the rates of metabolite flows in both pathways and ATP and NADPH concentrations have been calculated. The model obtained is well correlated with the experimental data on glycolysis characteristic at low rates of the pentose phosphate pathway reactions. The model suggests that NADPH and GSH concentrations should be stabilized. At ATP and NADPH concentrations close to the physiological ones the Embden-Meyerhof and pentose phosphate pathways function practically independently. When the NADPH concentration is decreased below 80% of the physiological value, the system ceases to stabilize the ATP concentration. In its turn, a decrease of ATP concentration results in a corresponding decrease of the maximal rate of the pentose phosphate pathway.

Adenosine Triphosphate↗
PubMed2002

Sugar specificity of bacterial CMP kinases as revealed by crystal structures and mutagenesis of Escherichia coli enzyme.

Bacterial cytidine monophosphate (CMP) kinases are characterised by an insert enlarging their CMP binding domain, and by their particular substrate specificity. Thus, both CMP and 2'-deoxy-CMP (dCMP) are good phosphate acceptors for the CMP kinase from Escherichia coli (E. coli CMPK), whereas eukaryotic UMP/CMP kinases phosphorylate the deoxynucleotides with very low efficiency. Four crystal structures of E. coli CMPK complexed with nucleoside monophosphates differing in their sugar moiety were solved. Both structures with CMP or dCMP show interactions with the pentose that were not described so far. These interactions are lost with the poorer substrates AraCMP and 2',3'-dideoxy-CMP. Comparison of all four structures shows that the pentose hydroxyls are involved in ligand-induced movements of enzyme domains. It also gives a structural basis of the mechanism by which either ribose or deoxyribose can be accommodated. In parallel, for the four nucleotides the kinetic results of the wild-type enzyme and of three structure-based variants are presented. The phosphorylation rate is significantly decreased when either of the two pentose interacting residues is mutated. One of these is an arginine that is highly conserved in all known nucleoside monophosphate kinases. In contrast, the other residue, Asp185, is typical of bacterial CMP kinases. It interacts with Ser101, the only residue conserved in all CMP binding domain inserts. Mutating Ser101 reduces CMP phosphorylation only moderately, but dramatically reduces dCMP phosphorylation. This is the first experimental evidence of a catalytic role involving the characteristic insert of bacterial CMP kinases. Furthermore, this role concerns only dCMP phosphorylation, a feature of this family of enzymes.

Amino Acid Sequence↗
PubMed2002

Carbon flux distribution in antibiotic-producing chemostat cultures of Streptomyces lividans.

The carbon metabolism of derivatives of Streptomyces lividans growing under phosphate limitation in chemostat cultures and producing the antibiotics actinorhodin and undecylprodigiosin was investigated. By applying metabolic flux analysis to a stoichiometric model, the relationship between antibiotic production, biomass accumulation, and carbon flux through the major carbon metabolic pathways (the Embden Meyerhoff Parnas and pentose-phosphate pathways) was analyzed. Distribution of carbon flux through the catabolic pathways was shown to be dependent on growth rate, as well as on the carbon and energy source (glucose or gluconate) used. Increasing growth rates promoted an increase in the flux of carbon through glycolysis and the pentose-phosphate pathway. The synthesis of both actinorhodin and undecylprodigiosin was found to be inversely related to flux through the pentose-phosphate pathway.

Anthraquinones↗
PubMed1990

Integration of lipid metabolism in the mammary gland and adipose tissue by prolactin during lactation.

Prolactin deficiency, induced by bromocryptine treatment, brought about reciprocal changes in the ability of adipocytes and acini isolated from lactating rats to synthesize lipids. The capacity to synthesize fatty acids and phospholipids decreased in the mammary gland and increased in adipocytes by bromocryptine treatment. In the mammary gland, the maximum potential activity of the pentose shunt as well as the specific activities of the pathway dehydrogenases were significantly reduced by bromocryptine treatment. Simultaneously, adipose tissue increased its lipogenic capacity but neither the maximum potential of the shunt nor the specific activities of the pentose phosphate shunt dehydrogenases were significantly changed with respect to the control lactating rats. Thus, a differential regulatory mechanism(s) of the pentose phosphate shunt activity appears to operate in these two tissues. Adipocytes from lactating rats showed a poor responsiveness to insulin in terms of lipid synthesis from glucose. In contrast, in adipocytes from bromocryptine treated rats insulin was able to increase lipid synthesis (105%). Sheep prolactin administration 'in vivo' partially reversed the effects of bromocryptine. These data suggest that prolactin mediates adipocytes resistance to insulin during lactation. Phospholipid synthesis, as occurred in fatty acid synthesis, is increased in adipose tissue and decreased in mammary gland by bromocryptine treatment. However, alpha 1-adrenergic stimulation increases phosphatidylinositol turnover to about the same percentages in both mammary gland acini and adipocytes from lactating rats independently of bromocryptine treatment.

Adipose Tissue↗
PubMed2001

Increased islet DNA synthesis and glucose-derived lipid and amino acid production in association with beta-cell hyperproliferation in normoglycaemic 60 % pancreatectomy rats.

AIMS/HYPOTHESIS: Glycaemia does not change following a 60 % pancreatectomy in rats because of enhanced beta-cell function and proliferation (so-called beta-cell adaptation). We previously studied these rats 4 weeks after surgery and showed hypersensitization of glucose-induced insulin secretion because of increased glucokinase activity. In this study of 60 % pancreatectomy rats 5 days after surgery, when beta-cell proliferation increased threefold, we investigated whether increases in glucose metabolism enhance the production of glucose-derived lipid, amino acids and DNA. METHODS: Isolated islets from 60 % pancreatectomy and sham-operated control rats 5 days or 4 weeks after surgery were studied. RESULTS: Five days after 60 % pancreatectomy surgery, islet glucose phosphorylation increased threefold, but overall glucose usage increased only twofold. The glucose-6-phosphate (G6P) concentration thus doubled, resulting in a sixfold increase in G6P metabolism through the pentose phosphate shunt (PPS). The pentose phosphate shunt generates ribose-5-phosphate for nucleotide synthesis, and DNA synthesis doubled in the partial pancreatectomy islets. In contrast, partial pancreatectomy rats 4 weeks after surgery had a smaller increase in glucokinase activity and their islet glucose-6-phosphate concentration and pentose phosphate shunt activity were equal to that of the control rats. DNA synthesis and beta-cell proliferation, based on BrdU incorporation were close to normal. Another consequence of the heightened glucose metabolism in the 5-day partial pancreatectomy islets was twofold increase in production of glucose-derived lipid and the amino acids, alanine and glutamate. CONCLUSIONS/INTERPRETATION: The enhanced glucokinase activity in 60 % pancreatectomy rats supports the compensatory beta-cell hyperproliferation by increasing production of glucose-derived DNA, lipids and amino acids.

Alanine↗
PubMed2002

Two different pathways for D-xylose metabolism and the effect of xylose concentration on the yield coefficient of L-lactate in mixed-acid fermentation by the lactic acid bacterium Lactococcus lactis IO-1.

In lactic acid bacteria, pentoses are metabolized via the phosphoketolase pathway, which catalyzes the cleavage of D-xylulose-5-phosphate to equimolar amounts of glyceraldehyde 3-phosphate and acetylphosphate. Hence the yield coefficient of lactate from pentose does not exceed 1.0 mol/mol, while that of Lactococcus lactis IO-1(JCM7638) at high D-xylose concentrations often exceeds the theoretical value. This suggests that, in addition to the phosphoketolase pathway, L. lactisIO-1 may possess another metabolic pathway that produces only lactic acid from xylose. In the present study, the metabolism of xylose in L. lactisIO-1 was deduced from the product formation and enzyme activities of L. lactisIO-1 in batch culture and continuous culture. During cultivation with xylose concentrations above ca. 50 g/l, the yield coefficient of L-lactate exceeded 1.0 mol/mol while those of acetate, formate and ethanol were very low. At xylose concentrations less than 5 g/l, acetate, formate and ethanol were produced with yield coefficients of about 1.0 mol/mol, while L-lactate was scarcely produced. In cells grown at high xylose concentrations, a marked decrease in the specific activities of phosphoketolase and pyruvate formate lyase (PFL), and an increase in those of transketolase and transaldolase were observed. These results indicate that in L. lactisIO-1 xylose may be catabolized by two different pathways, the phosphoketolase pathway yielding acetate, formate and ethanol, and the pentose phosphate (PP)/glycolytic pathway which converts xylose to L-lactate only. Furthermore, it was deduced that the change in the xylose concentration in the culture medium shifts xylulose 5-phosphate metabolism between the phosphoketolase pathway and the PP/glycolytic pathway in L. lactisIO-1, and pyruvate metabolism between cleavage to acetyl-CoA and formic acid by PFL and the reduction to L-lactate by lactate dehydrogenase.

Enzymes↗
PubMed1988

Furanose ring anomerization: a kinetic study of the 5-deoxypentoses and 5-O-methylpentoses.

The anomerization of 5-deoxy-L-pentoses (1-4) and 5-O-methyl-D-pentoses (5-8) in aqueous solution has been studied by 13C saturation-transfer n.m.r. (s.t.-n.m.r.) spectroscopy, using compounds substituted with 13C at the anomeric carbon atom. Unidirectional rate-constants of ring-opening (k open) and ring-closing (k close) have been obtained for these compounds under identical solution conditions (50mM acetate buffer, pH 4.0 at 60 degrees), and have been compared to those measured for the D-tetroses (9 and 10) and the four D-pentose 5-phosphates (11-14). Based on these comparisons, several correlations between furanose structure and reactivity have been revealed, and models have been proposed to explain the observed kinetic behavior of compounds (1-10). The effect of exocyclic structure on acid-catalyzed rate-constants was also examined by comparing the behavior of 5-deoxy-L-(1-13C)-lyxose and 5-O-methyl-D-(1-13C)lyxose. Some consideration has been given to identifying the factors (enthalpic and entropic) that may play roles in determining the effect of structure on anomerization reactivity.

Chemical Phenomena↗
PubMed1996

Gluconeogenesis from ascorbic acid: ascorbate recycling in isolated murine hepatocytes.

Ascorbic acid synthesis and breakdown were investigated in isolated hepatocytes prepared from fasted mice. Stimulation of gluconeogenesis by alanine or xylitol led to ascorbate synthesis. On the other hand, ascorbate or dehydroascorbate addition resulted in concentration-dependent glucose production and elevation of the pentose phosphate pathway intermediate xylulose 5-phosphate. Stimulation of ascorbate oxidation and/or the inhibition of dehydroascorbate reduction increased glucose formation. Inhibition of the pentose phosphate pathway decreased glucose production from dehydroascorbate with increased accumulation of xylulose 5-phosphate. These results suggest that ascorbate can be recycled by a novel way involving intermediates of the pentose phosphate pathway, gluconeogenesis and hexuronic acid pathway.

Animals↗
PubMed1988

Interrelations between glycolysis and the hexose monophosphate shunt in erythrocytes as studied on the basis of a mathematical model.

A mathematical model is presented which comprises the reactions of glycolysis, the hexose monophosphate shunt (HMS) and the glutathione system in erythrocytes. The model is used to calculate stationary and time-dependent metabolic states of the cell in vitro and in vivo. The model properly accounts for the following metabolic features observed in vitro: (a) stimulation of the oxidative pentose pathway after addition of pyruvate due to a NADP-dependent lactate dehydrogenase as coupling enzyme between glycolysis and the oxidative pentose pathway, (b) relative share of the oxidative pentose pathway in the total consumption of glucose amounting to approximately 10% in the normal case and to approximately 90% under conditions of oxidative stress excreted by methylene blue. From the application of the model to in vivo conditions it is predicted that (c) under normal conditions glycolysis and the HMS are independently regulated by the energetic and oxidative load, respectively, (d) under conditions of enhanced energetic or oxidative load both glycolysis and the HMS are mainly controlled by the hexokinase; in this situation the highest possible values of the energetic and oxidative load which are compatible with cell integrity are strongly coupled and considerably restricted in comparison with the normal case, (e) the stationary states possess bifurcation points at high and low values of the energetic load.

Energy Metabolism↗
PubMed1990

Studies on the pigeon red blood cell metabolism.

1. Pigeon erythrocyte was found to depend on the glycolytic and pentose phosphate pathway for most of its energy production in the form of adenosine triphosphate and reducing potential, since there was no detectable activity of any of the citric acid cycle (TCA) cycle enzymes measured. 2. The absence of detectable amounts of 2,3-diphosphoglyceric acid (2-3-DPG) indicated that there is no direct relationship between the active glycolytic system and the function of these cells. 3. A comparison of the mass action ratios with the equilibrium constants of the glycolytic reactions showed that hexokinase, phosphofructokinase and pyruvate kinase reactions are displaced from equilibrium, implying that these are the key regulatory enzymes of glycolysis in pigeon erythrocytes. 4. The changes in the concentrations of the glycolytic metabolites under hypoxic conditions that stimulate the flux through the glycolytic pathway were found to be consistent with the above hypothesis. 5. Flux measurements of the pentose phosphate pathway showed that it metabolizes only 3.4% of the total glucose consumed by the resting erythrocyte. 6. Hypoxic conditions resulted in a stimulation of the pentose phosphate pathway by as much as four-fold, whilst the glycolytic pathway was not stimulated by more than about twice.

Adenine Nucleotides↗
PubMed2005

A novel gnd mutation leading to increased L-lysine production in Corynebacterium glutamicum.

Toward more efficient L-lysine production, we have been challenging genome-based strain breeding by the approach of assembling only relevant mutations in a single wild-type background. Following the creation of a new L-lysine producer Corynebacterium glutamicum AHP-3 that carried three useful mutations (lysC311, hom59, and pyc458) on the relevant downstream pathways, we shifted our target to the pentose phosphate pathway. Comparative genomic analysis for the pathway between a classically derived L-lysine producer and its parental wild-type identified several mutations. Among these mutations, a Ser-361-->Phe mutation in the 6-phosphogluconate dehydrogenase gene (gnd) was defined as a useful mutation for L-lysine production. Introduction of the gnd mutation into strain AHP-3 by allelic replacement led to approximately 15% increased L-lysine production. Enzymatic analysis revealed that the mutant enzyme was less sensitive than the wild-type enzyme to allosteric inhibition by intracellular metabolites, such as fructose 1,6-bisphosphate, D-glyceraldehyde 3-phosphate, phosphoribosyl pyrophosphate, ATP, and NADPH, which were known to inhibit this enzyme. Isotope-based metabolic flux analysis demonstrated that the gnd mutation resulted in 8% increased carbon flux through the pentose phosphate pathway during L-lysine production. These results indicate that the gnd mutation is responsible for diminished allosteric regulation and contributes to redirection of more carbon to the pentose phosphate pathway that was identified as the primary source for NADPH essential for L-lysine biosynthesis, thereby leading to improved product formation.

Corynebacterium↗
PubMed2004

Metabolic network analysis on Phaffia rhodozyma yeast using 13C-labeled glucose and gas chromatography-mass spectrometry.

Carotenoid production by microorganisms, as opposed to chemical synthesis, could fulfill an ever-increasing demand for 'all natural' products. The yeast Phaffia rhodozyma has received considerable attention because it produces the red pigment astaxanthin, commonly used as an animal feed supplement. In order to have a better understanding of its metabolism, labeling experiments with [1-(13)C]glucose were conducted with the wildtype strain (CBS5905T) and a hyper-producing carotenoid strain (J4-3) in order to determine their metabolic network structure and estimate intracellular fluxes. Amino acid labeling patterns, as determined by GC-MS, were in accordance with a metabolic network consisting of the Embden-Meyerhof-Parnas pathway, the pentose phosphate pathway, and the TCA cycle. Glucose was mainly consumed along the pentose phosphate pathway ( approximately 65% for wildtype strain), which reflected high NADPH requirements for lipid biosynthesis. Although common to other oleaginous yeast, there was no, or very little, malic enzyme activity for carbon-limited growth. In addition, there was no evidence of phosphoketolase activity. The central carbon metabolism of the mutant strain was similar to that of the wildtype strain, though the relative pentose phosphate flux was lower and the TCA cycle flux in accordance with the biomass yield being lower.

Basidiomycota↗
PubMed2004

Evaluation of pentitol metabolism in mammalian tissues provides new insight into disorders of human sugar metabolism.

To more completely elucidate the pathways of sugar metabolism in human, we have evaluated the formation and degradation of pentitols in human fibroblasts and erythrocytes. Cultured human fibroblasts were incubated with d-arabinose, d-ribose, d-ribulose, and d-xylulose. Formation of arabitol and ribitol was analyzed by gas chromatography of the incubation medium and cell homogenate. We found that the pentoses d-arabinose and d-ribose could cross cell membranes, which indicate possible pentitol formation from extracellular pentoses. Fibroblasts formed 17+/-4 nmol arabitol/4 days/mg protein from d-arabinose and ribitol production rates of 70+/-15 nmol/4 days/mg protein were found after d-ribose incubation. Following d-ribulose incubation 13 nmol ribitol/4 days/mg protein was found. Human cultured fibroblasts were also incubated with d-arabitol, ribitol, and xylitol. Analyzing the incubation medium and cell homogenate revealed an absence of pentose formation. However, export of the pentitols arabitol and ribitol across the cell membrane was demonstrated, indicating that pentitols can be cleared from the body without metabolic conversion. Finally, human erythrocytes were incubated with d-/l-arabitol, ribitol, sorbitol, and xylitol. Activities of potential pentitol dehydrogenases were evaluated by a fluorometric assay. No evidence for ribitol and arabitol degradation was observed in human erythrocytes, as compared to polyol dehydrogenase activities ranging from 1.3 to 6.1 pmol NADH/min/microl erythrocytes observed using sorbitol and xylitol. Our results indicate that ribitol and arabitol are metabolic end products in humans.

Cell Membrane↗
PubMed2000

Exclusive expression of transketolase in the vanadocytes of the vanadium-rich ascidian, Ascidia sydneiensis samea.

Ascidians, especially those belonging to the Ascidiidae, are known to accumulate extremely high levels of vanadium in vanadocytes, one type of blood (coelomic) cell. Vanadium, which exists in the +5 oxidation state in seawater, is accumulated in the vanadocytes and reduced to the +3 oxidation state. We have been trying to characterize all of the polypeptides specific to vanadocytes and to specify the proteins that participate in the accumulation and reduction of vanadium. To date, we have localized three enzymes in vanadocytes: 6-phosphogluconate dehydrogenase (6-PGDH: EC 1.1.1.44), glucose-6-phosphate dehydrogenase (G6PDH: EC 1.1.1.49), and glycogen phosphorylase (GP: EC 2.4.1.1), all of which are involved in the pentose phosphate pathway. In the current study, we cloned a cDNA for transketolase, an essential and rate-limiting enzyme in the non-oxidative part of the pentose phosphate pathway, from vanadocytes. The cDNA encoded a protein of 624 amino acids, which showed 61.8% identity to the human adult-type transketolase gene product. By immunocytochemistry and immunoblot analyses, the transketolase was revealed to be a protein that was expressed only in vanadocytes and not in any of the more than ten other types of blood cell. This finding, taken together with the localized expression of the other three enzymes, strongly supports the hypothesis that the pentose phosphate pathway functions exclusively in vanadocytes.

Amino Acid Sequence↗
PubMed2001

Mechanisms of ascorbic acid recycling in human erythrocytes.

Vitamin C, or ascorbic acid, is efficiently recycled from its oxidized forms by human erythrocytes. In this work the dependence of this recycling on reduced glutathione (GSH) was evaluated with regard to activation of the pentose cycle and to changes in pyridine nucleotide concentrations. The two-electron-oxidized form of ascorbic acid, dehydroascorbic acid (DHA) was rapidly taken up by erythrocytes and reduced to ascorbate, which reached intracellular concentrations as high as 2 mM. In the absence of D-glucose, DHA caused dose-dependent decreases in erythrocyte GSH, NADPH, and NADH concentrations. In the presence of 5 mM D-glucose, GSH and NADH concentrations were maintained, but those of NADPH decreased. Reduction of extracellular ferricyanide by erythrocytes, which reflects intracellular ascorbate recycling, was also enhanced by D-glucose, and ferricyanide activated the pentose cycle. Diethylmaleate at concentrations up to 1 mM was found to specifically deplete erythrocyte GSH by 75-90% without causing oxidant stress in the cells. Such GSH-depleted erythrocytes showed parallel decreases in their ability to take up and reduce DHA to ascorbate, and to reduce extracellular ferricyanide. These results show that DHA reduction involves GSH-dependent activation of D-glucose metabolism in the pentose cycle, but that in the absence of D-glucose DHA reduction can also utilize NADH.

Ascorbic Acid↗
PubMed2003

Genome-wide expression analyses: Metabolic adaptation of Saccharomyces cerevisiae to high sugar stress.

The transcriptional response of laboratory strains of Saccharomyces cerevisiae to salt or sorbitol stress has been well studied. These studies have yielded valuable data on how the yeast adapts to these stress conditions. However, S. cerevisiae is a saccharophilic fungus and in its natural environment this yeast encounters high concentrations of sugars. For the production of dessert wines, the sugar concentration may be as high as 50% (w/v). The metabolic pathways in S. cerevisiae under these fermentation conditions have not been studied and the transcriptional response of this yeast to sugar stress has not been investigated. High-density DNA microarrays showed that the transcription of 589 genes in an industrial strain of S. cerevisiae were affected more than two-fold in grape juice containing 40% (w/v) sugars (equimolar amounts of glucose and fructose). High sugar stress up-regulated the glycolytic and pentose phosphate pathway genes. The PDC6 gene, previously thought to encode a minor isozyme of pyruvate decarboxylase, was highly induced under these conditions. Gene expression profiles indicate that the oxidative and non-oxidative branches of the pentose phosphate pathway were up-regulated and might be used to shunt more glucose-6-phosphate and fructose-6-phosphate, respectively, from the glycolytic pathway into the pentose phosphate pathway. Structural genes involved in the formation of acetic acid from acetaldehyde, and succinic acid from glutamate, were also up-regulated. Genes involved in de novo biosynthesis of purines, pyrimidines, histidine and lysine were down-regulated by sugar stress.

Acetaldehyde↗
PubMedDate not supplied

Cost analysis of ethanol production from willow using recombinant Escherichia coli.

This study comprises a technical and economic analysis of the production of fuel ethanol by fermentation of a pentose-rich hydrolysate with recombinant Escherichia coli, strain KO11. Hydrolysate from steam-pretreated willow was used as raw material in calculations regarding the fermentation. The calculations were based on a feed capacity of 10 metric tons of dry willow per hour to the pretreatment stage, providing 35 metric tons of hydrolysate per hour, consisting of 45 g of sugars/L, to the pentose fermentation plant. A detoxification step was included, since the hydrolysate has been shown to have an inhibitory effect on the E. coli KO11. The technical data used in the calculations were based on a kinetic fermentation model, which was developed from laboratory-scale experiments in a previous study. The economic analysis predicted an ethanol production cost of 48/L in the pentose fermentation plant, indicating potentially good economy. The detoxification cost constitutes 22% of this cost. Sensitivity analyses revealed that if the concentration of sugars in the feed to the fermentation was decreased by 40% to 27 g/L, the ethanol production cost was increased to 54/L. The production cost was increased to 50/L ethanol if the cell mass was recirculated to the fermentation stage 5 times instead of 20.

Biotechnology↗