Assimilation Of Fructose Research Articles

Fermentative and Enological Features of Saccharomyces cerevisiae Populations Generated Through Adaptive Laboratory Evolution

Adaptive laboratory evolution (ALE) is a non-GMO technique utilized for the amelioration of wine yeast strains. Employing two-step ALE strategies, we recently acquired six evolved Saccharomyces cerevisiae populations with improved fermentative abilities compared to their parental strains in synthetic broths. Herein, we evaluated the qualities of the abovementioned evolved populations under real winemaking conditions, using the grape musts Assyrtiko and Roditis. The ethanol-tolerant populations evolved solely with glucose delayed to complete the fermentation due to slow fructose assimilation, albeit showing improved ethanol yields, compared to their parental strains. The volatile compounds of the evolved populations were significantly different from those of parental strains. Statistically significant differences were observed in the organoleptic profiles between the evolved populations’ and parental strains’ wines. Notably, wine from one evolved population (BLR200) was rated higher in overall aroma and quality. This study supports the magnitude of ALE strategies for the generation of novel wine yeasts.

Mosquito sex and mycobiota contribute to fructose metabolism in the Asian tiger mosquito Aedes albopictus

BackgroundPlant floral nectars contain natural sugars such as fructose, which are a primary energy resource for adult mosquitoes. Despite the importance of carbohydrates for mosquito metabolism, a limited knowledge is available about the pathways involved in sugar assimilation by mosquitoes and their associated microbiota. To this end, we used 13C-metabolomic and stable isotope probing approaches coupled to high-throughput sequencing to reveal fructose-related mosquito metabolic pathways and the dynamics of the active gut microbiota following fructose ingestion.ResultsOur results revealed significant differences in metabolic pathways between males and females, highlighting different modes of central carbon metabolism regulation. Competitive and synergistic interactions of diverse fungal taxa were identified within the active mycobiota following fructose ingestion. In addition, we identified potential cross-feeding interactions between this. Interestingly, there is a strong correlation between several active fungal taxa and the presence of fructose-derived metabolites.ConclusionsAltogether, our results provide novel insights into mosquito carbohydrate metabolism and demonstrate that dietary fructose as it relates to mosquito sex is an important determinant of mosquito metabolism; our results also further highlight the key role of active mycobiota interactions in regulating the process of fructose assimilation in mosquitoes. This study opens new avenues for future research on mosquito-microbiota trophic interactions related to plant nectar-derived sugars.Graphical 8ZSbNdwh9FSfnhR6eQHKUrVideo abstract

Identification of genes related to hydrolysis and assimilation of Agave fructans in Candida apicola NRRL Y-50540 and Torulaspora delbrueckii NRRL Y-50541 by denovo transcriptome analysis.

Fructans are the main sugar in agave pine used by yeasts during mezcal fermentation processes, from which Candida apicola NRRL Y-50540 and Torulaspora delbrueckii NRRL Y-50541 were isolated. De novo transcriptome analysis was carried out to identify genes involved in the hydrolysis and assimilation of Agave fructans (AF). We identified a transcript annotated as SUC2, which is related to β-fructofuranosidase activity, and several differential expressed genes involved in the transcriptional regulation of SUC2 such as: MIG1, MTH1, SNF1, SNF5, REG1, SSN6, SIP1, SIP2, SIP5, GPR1, RAS2, and PKA. Some of these genes were specifically expressed in some of the yeasts according to their fructans assimilation metabolism. Different hexose transporters that could be related to the assimilation of fructose and glucose were found in both the transcriptomes. Our findings provide a better understanding of AF assimilation in these yeasts and provide resources for further metabolic engineering and biotechnology applications.

Promoting apical-to-basolateral unidirectional transport of nanoformulations by manipulating the nutrient-absorption pathway

The epithelium is a formidable barrier to the absorption of orally delivered nano-vehicles. Here, by exploring a nutrient-absorption pathway, a self-amplified nanoplatform was developed to promote apical-to-basolateral transcytosis across the epithelium. The nanoplatform consisted of fructose-modified polyethylene glycol coated nanoparticles (Fru-PEG NPs) and a sweetener, acesulfame potassium (AceK) in combination. Compared with regular PEGylated nanoparticles, the combination exhibited a 3.9-fold increase of absorption following oral gavage in mice and an 8.8-fold increase of transepithelial transport in vitro. When encapsulated with insulin, the combination regimen elicited a stronger hypoglycemic effect, with a pharmacological bioavailability of 18.56%, which was 3.2-fold higher than that of PEG NPs. We demonstrated that a large proportion of Fru-PEG NPs underwent internalization and basolateral exocytosis via a glucose transporter type 2 (GLUT2)-dependent process, which is an important fructose assimilation pathway. Notably, co-administered AceK could prime the epithelial cells with increased apical distribution of GLUT2, thus amplifying this unidirectional transcytosis of nanoparticles. This work is the first proof-of-concept study of manipulating and amplifying a nutrient-absorption pathway to facilitate the unidirectional trans-epithelial transport of orally administered nano-delivery vehicles.

Влияние источника углерода на синтез биомассы и экзополисахаридов бактериями Paenibacillus mucilaginosus

Paenibacillus mucilaginosus bacteria are one of the most promising soil microorganisms for obtaining microbiological fertilisers. These bacteria produce indolyl-3-acetous acid and ammonia, as well as possessing the capability of nitrogen fixation and solubilisation of undissolved soil minerals yielding potassium and phosphorus accessible to plants and consequently stimulating plant growth. P. mucilaginosus biological preparations are also useful in the form of fertiliser additives leading to immune stimulation and increase in the productivity of agricultural animals. For the cultivation of P. mucilaginosus bacterial strains, sucrose is recommended. At the same time, little research has been carried out on the influence of glucose and fructose on the growth of these bacteria. The aim of the work was to study the effect of various carbon sources in the composition of the nutrient medium on the biomass synthesis of P. mucilaginosus strains. As a result, a double growth cycle was observed under the conditions of culture on a nutrient medium with a sucrose and a glucose-fructose mixture. The specific growth rate of the bacterial strains under consideration in the assimilation of glucose is higher than in the assimilation of fructose. Accordingly, the generation time for glucose assimilation turned out to be lower than that for fructose assimilation. The growth of the considered bacterial strains on a single fructose nutrient medium was not observed. Glucose demonstrated similar effectiveness of application in culture media to sucrose for the cultivation of all considered bacterial strains of P. mucilaginosus. During culturing of P. mucilaginosus bacteria on nutrient media from glucose and sucrose, the yield of biomass and exopolysaccharides was established to be higher than for the case of a nutrient medium presented by a glucose-fructose mixture. Promising strains for industrial application include 563, 567 and 574, providing a high yield of biomass and exopolysaccharides with culture on a glucose-admixed nutrient medium, and 560, 568 and 572 strains when cultivated on a nutrient medium containing sucrose.

Optimization of date syrup as a novel medium for lovastatin production by Aspergillus terreus ATCC 20542 and analyzing assimilation kinetic of carbohydrates

Lovastatin is a statin drug, which lowers cholesterol level in blood due to inhibition of (S)-3-hydroxy-3-methylglutaryl-CoA reductase. Date syrup is a rich medium for microbial growth and metabolite production. The main carbohydrates present in the date syrup are glucose and fructose. In this study, date syrup was used as a complex and bioresource medium for lovastatin production by Aspergillus terreus in the submerged cultivation. Optimization of the date syrup medium in order to achieve the highest titers of lovastatin and biomass was carried out. Four factors were studied by response surface methodology including concentration of date syrup carbohydrates, yeast extract concentration, pH, and rotation speed of the shaker. Optimal conditions for these factors found were as follows: concentration of date syrup carbohydrates, 64 g/l; yeast extract concentration, 15 g/l; pH, 6.5; and agitation speed, 150 rpm. It gave lovastatin concentration of 105.6 mg/l. Next, batch cultures in the optimal conditions were performed in a 2.5-l working volume bioreactor and led to the lovastatin titer of 241.1 mg/l during 12 days. Aspergillus terreus showed diauxic growth in the optimized medium with a shift from glucose to fructose assimilation during the run. Glucose and fructose assimilation kinetic parameters revealed that more lovastatin is produced during glucose assimilation, while more biomass was formed during fructose assimilation.

Identification of hexose kinase genes in Kluyveromyces marxianus and thermo-tolerant one step producing glucose-free fructose strain construction

In yeast, the hexose assimilation is started at hexose phosphorylation. However, in Kluyveromyces marxianus, the hexokinase (HXK) and glucokinase (GLK) genes were not identified by experiments. Meanwhile, the glucose-free fructose product requires more cost-efficient method. In this study, the KmHXK1 and KmGLK1 genes were functionally identified through gene disruption, over-expression and recombinant enzymes characterization. Both glucose and fructose assimilation ability decreased significantly in KmHXK1 disrupted strain YLM001, however, this ability was not changed obviously in KmGLK1 disrupted strain YLM002. When over-expressing KmGLK1 in YLM001, only the glucose assimilation ability was recovered in obtained strain (YLM005). The kinetic constant analysis of recombinant enzymes also proved that KmHXK1 could phosphorylate glucose (Vmax 553.01 U/mg, Km 0.83 mM) and fructose (Vmax 609.82 U/mg, Km 0.52 mM), and KmGLK1 only phosphorylate glucose with a Vmax of 0.73 U/mg and a Km 4.09 mM. A thermo-tolerant strain YGR003 which produced glucose-free fructose from Jerusalem artichoke tuber in one step was constructed based on the obtained information. The highest production and fastest productivity were 234.44 g/L and 10.26 g/L/h, respectively, which were several folds of the results in previous reports.

Mannitol production by lactic acid bacteria grown in supplemented carob syrup

Detailed kinetic and physiological characterisation of eight mannitol-producing lactic acid bacteria, Leuconostoc citreum ATCC 49370, L. mesenteroides subsp. cremoris ATCC19254, L. mesenteroides subsp. dextranicum ATCC 19255, L. ficulneum NRRL B-23447, L. fructosum NRRL B-2041, L. lactis ATCC 19256, Lactobacillus intermedius NRRL 3692 and Lb. reuteri DSM 20016, was performed using a carob-based culture medium, to evaluate their different metabolic capabilities. Cultures were thoroughly followed for 30 h to evaluate consumption of sugars, as well as production of biomass and metabolites. All strains produced mannitol at high yields (>0.70 g mannitol/g fructose) and volumetric productivities (>1.31 g/l h), and consumed fructose and glucose simultaneously, but fructose assimilation rate was always higher. The results obtained enable the studied strains to be divided mainly into two groups: one for which glucose assimilation rates were below 0.78 g/l h (strains ATCC 49370, ATCC 19256 and ATCC 19254) and the other for which they ranged between 1.41 and 1.89 g/l h (strains NRRL B-3692, NRRL B-2041, NRRL B-23447 and DSM 20016). These groups also exhibited different mannitol production rates and yields, being higher for the strains with faster glucose assimilation. Besides mannitol, all strains also produced lactic acid and acetic acid. The best performance was obtained for L. fructosum NRRL B-2041, with maximum volumetric productivity of 2.36 g/l h and the highest yield, stoichiometric conversion of fructose to mannitol.

Bifidobacterium longum requires a fructokinase (Frk; ATP:D-fructose 6-phosphotransferase, EC 2.7.1.4) for fructose catabolism.

Although the ability of Bifidobacterium spp. to grow on fructose as a unique carbon source has been demonstrated, the enzyme(s) needed to incorporate fructose into a catabolic pathway has hitherto not been defined. This work demonstrates that intracellular fructose is metabolized via the fructose-6-P phosphoketolase pathway and suggests that a fructokinase (Frk; EC 2.7.1.4) is the enzyme that is necessary and sufficient for the assimilation of fructose into this catabolic route in Bifidobacterium longum. The B. longum A10C fructokinase-encoding gene (frk) was expressed in Escherichia coli from a pET28 vector with an attached N-terminal histidine tag. The expressed enzyme was purified by affinity chromatography on a Co(2+)-based column, and the pH and temperature optima were determined. A biochemical analysis revealed that Frk displays the same affinity for fructose and ATP (Km(fructose) = 0.739 +/- 0.18 mM and Km(ATP) = 0.756 +/- 0.08 mM), is highly specific for D-fructose, and is inhibited by an excess of ATP (>12 mM). It was also found that frk is inducible by fructose and is subject to glucose-mediated repression. Consequently, this work presents the first characterization at the molecular and biochemical level of a fructokinase from a gram-positive bacterium that is highly specific for D-fructose.

Modeling growth and biochemical activities of Azospirillum spp.

An unstructured mathematical model was developed and used in the evaluation of biochemical activities of four Azospirillum spp. strains grown in batch cultures in a high C/N-ratio medium. The strains were evaluated for their ability to grow on fructose and produce exo-polysaccharide, and to sustain nitrogenase activity by using fructose or polysaccharides. Quantitative expression of the regulation of polysaccharide synthesis and nitrogenase (acetylene reduction) activity from the mineral nitrogen and sugar concentration in the culture medium was achieved. It was found that, during growth, Azospirillum spp. produced significant quantities of exocellular and capsular polysaccharide, whereas after depletion of the carbon source from the culture medium polysaccharides were consumed, especially in A. lipoferum strains. Significant nitrogenase activity was detected during polysaccharide degradation. Oxygen uptake was high during assimilation of fructose and low during polysaccharide degradation.

Inhibition of insulin-dependent lipogenesis and anti-lipolysis by protein tyrosine kinase inhibitors.

Protein tyrosine kinase (PTK) blockers which competitively inhibit the kinase activity of insulin receptors were synthesized and their properties examined. The best insulin receptor kinase (IRK) inhibitors possess either one hydroxyphenyl ring and two carboxyl groups or two phenyl rings and one carboxyl group. All the inhibitors, except tBoc-tyrosine aminomalonate, effectively block the IRK-catalyzed phosphorylation of exogenous substrate, but only partially block receptor autophosphorylation. These PTK blockers inhibit the insulin induced [14C]glucose assimilation into lipids (lipogenesis), but fail to inhibit the anti-lipolytic effect of the hormone. Only tBocTyr-aminomalonate was found to inhibit all the effects of insulin measured: insulin-stimulated phosphorylation of exogenous substrate, IRK autophosphorylation, insulin-dependent lipogenesis and the insulin-dependent anti-lipolytic effect. This inhibitor is the first blocker which is reported to block insulin-dependent anti-lipolysis. The inhibitors examined are devoid of general adverse effects since they have no effect on insulin-independent lipolysis, on [U14C]fructose assimilation or on (-)isoproterenol-stimulated lipolysis. These studies suggest that insulin-dependent lipogenesis and anti-lipolysis may be mediated by two distinguishable signalling pathways. This study also suggests that PTK inhibitors may become useful tools in the investigation of the signalling pathways of PTKs.

Dark hexose metabolism by photoautotrophically and heterotrophically grown cells of the blue-green alga (Cyanobacterium) Nostoc sp. strain Mac.

Photoautotrophically grown cells of the blue-green alga (cyanobacterium) Nostoc sp. strain Mac assimilated and oxidized both glucose and fructose in the dark at different rates. The rate of fructose metabolism in these cells could be stimulated by casein hydrolysate, the effect being most pronounced at low sugar concentrations. This stimulation was not seen in cells grown heterotrophically in the dark, suggesting that it is a transitory phenomenon which disappears during the autotrophy-heterotrophy growth transition. The stimulation of fructose assimilation by casein hydrolysate was abolished by chloramphenicol or streptomycin, suggesting there are rate-limiting steps in protein biosynthesis in the dark that ultimately lead to inhibition of fructose uptake. Glucose metabolism did not show these phenomena, indicating there are differences in the metabolism of the two sugars.

A -D-fructofuranosidase from Claviceps purpurea.

Evidence suggests that sucrose is the main carbon source for growth of Claviceps spp. in the parasitic condition. The sucrose acts as substrate for an active beta-fructofuranosidase, produced by the fungus, which in the first instance converts the disaccharide into glucose and an oligofructoside. In this way, 50% of the glucose, supplied as sucrose, is made available to the parasite for assimilation. Subsequent action of the enzyme on both sucrose and the oligofructoside leads to the release of more glucose and the formation of additional oligosaccharides. The structures of the main oligosaccharides formed have been elucidated and the interactions of each compound studied. In experiments with purified enzyme in vitro the interaction of the oligosaccharides is rapid but in culture they are assimilated only slowly; in each case some free fructose is liberated. Free fructose is not assimilated in the presence of glucose and, further, inhibits growth at concentrations which might be expected to occur in the parasitic condition. A dual role has been suggested for the enzyme, with sucrose as substrate, in which glucose is made available to the growing parasite, while at the same time transfer of the fructose to form oligosaccharides prevents it from accumulating at inhibitory concentrations. Ultimately, when glucose becomes limiting, the fungus will adapt to fructose assimilation.

Fructose in medicine. A review with particular reference to diabetes mellitus.

Summary A review is given of the metabolism of fructose in the mammalian organism, and its significance in medicine. Emphasis is laid upon the absorption and assimilation of fructose through pathways not identical with those of glucose. The metabolism of fructose is largely insulin-independent, although the ultimate fate of fructose carbons is determined by the presence or the absence of insulin. Clinical and experimental work has suggested that fructose may exert beneficial effects as a component of the diet for patients with mild and well-balanced diabetes. Fructose is absorbed slowly from the gut, and does not induce drastic changes in blood sugar levels. Secondly, fructose is metabolized by insulin-independent pathways in the liver, intestinal wall, kidney and adipose tissue. As a consequence of the rapid and efficient utilization of fructose, it has been used widely for intravenous feeding in medicine and surgery. However, it has been shown that the rapid infusion of large amounts of fruetose may cause accumulation of lactic acid in the extracellular fluid. The possibility of lactate acidosis, with concomitant impairment of the acid-base balance, already disturbed, constitutes a relative contraindication to the use of intravenous fructose in the treatment of diabetic ketoacidosis. Fructose is known to accelerate ethanol metabolism in the liver. No well-documented reports on the use of fructose in the treatment of ethanol intoxication have been published, although it has recently been suggested that fructose might be of value in the treatment of delirium tremens. Fructose may be less cariogenic than sucrose, at least in short-term experiments. Long-term trials are lacking, and thus the potential advantages of fructose in preventive odontology have not been determined. Fructose does not seem to have any side-effects when used in reasonable amounts. However, it has been reported that the administration of fructose in large amounts induces hyperlipidemia both in man and in experimental animals. Earlier suggestions concerned with the atherogenic properties of fructose have recently been challenged. The apparent increase in the incidence of coronary disease among sucrose users seems to be a statistical artefact, caused by the increased ingestion of coffee and soft drinks by cigarette smokers.

The assimilation of fructose and galactose in the different tissues ofClarias lazera

1. The effect of administration of excess fructose as well as galactose (4 g/kg body weight) on the carbohydrates, lipides and water content of the different tissues ofClarias lazera was undertaken. 2. After the administration of similar doses of glucose, fructose and galactose, it was found that the blood glucose concentration and deposition of glycogen reach higher levels after the administration of glucose, and lower level after galactose. The rise in blood glucose as well as in tissue glycogen after the administration of similar doses of fructose was moderate. 3. The tissues which show maximum deposition of glycogen after fructose and galactose are the liver, kidney and spleen. While the brain and respiratory organs are the only tissues which showed no more glycogen than control values after excess sugar. 4. Also after excess fructose or galactose (4 g/kg body weight) all the tissues of the body except the blood, skin and ovary keep their water content more or less constant. 5. A pronounced rise in lipid content of most of the tissues was found after excess glucose, fructose and galactose. However higher deposition of fat occurs after the administration of fructose, while lower deposition of fat occurs after the introduction of excess glucose. The storage of fat in the tissues after galactose was intermediate between other two sugars. 6. A direct relation between carbohydrate and fat content of the different tissues of Clarias after excess fructose and galactose was found. Thus excess fructose which leads to a high deposition of glycogen on the one hand, shows also a higher rate of storage of fat in the different tissues on the other hand. While excess galactose which leads to minimum deposition of glycogen on the one hand shows also a decreased rate of storage of fat on the other hand.

Citrate Metabolism During Surgery

All postoperative patients are temporarily diabetic, at least with respect to the assimilation of exogenous glucose.1Generally, the severity of the change in glucose tolerance is proportional to the magnitude and extent of the operative procedure.2Unless the postoperative period is complicated by an infection or by conditions that preclude optimal alimentation, a normal tolerance for glucose is reestablished usually within a week. In marked contrast, there is no impairment in the rate of assimilation of fructose either during or after surgery in comparison with the preoperative rate.1 One interpretation of these findings is that surgical stress has some effect on factors responsible for the cellular transport of glucose, but it has no effect on the permeability of the cell wall to fructose. Another interpretation is that stimulation of the pituitary-adrenal axis results in a humoral inhibition of glucokinase with a consequent delay in the entrance of

Peripheral assimilation of fructose in man.

Summary1. Serial peripheral arteriovenous fructose differences were measured in 10 human subjects receiving a constant intravenous infusion of 10% fructose in water, following an initial priming injection. Maintenance of consistent and appreciable arteriovenous differences under these circumstances occurred in every case? and this finding is interpreted as evidence for direct assimilation of fructose by the peripheral tissues. 2. The problem of distinguishing between diffusion, assimilation and utilization is discussed.

Insulin and the Assimilation of Fructose.

Summary.In experiments with artificially perfused hind‐leg preparations it is shown that insulin has no effect on the assimilation of fructose in the muscular tissue, whereas the assimilation of glucose is promoted to a considerable extent.Even in experiments in which the glucose concentration in the blood is artificially reduced to the lowest possible values, insulin has no effect on the fructose assimilation.The assimilations of glucose and fructose seem to proceed quite independently of each other.

The Phosphate Esters Formed in the Liver Tissue of Rats and Rabbits during Assimilation of Hexoses and Glycerol.1

Summary.Phosphate esters are accumulated in the intact livers of rats and rabbits during assimilation of hexoses and glycerol, which latter was examined on rats only.During absorption of fructose the fructose ester accumulated showed qualities similar to those of fructose‐1‐phosphoric acid; no fructose‐6‐phosphoric acid was accumulated. The amounts of fructosephosphoric acid accumulated in the liver and in the intestinal mucosa of the same rabbit seem to be equal with regard to quantity and synthetising intensity. The amounts of ester may be calculated at about 100 mgs of the ester per 100 g of liver tissue; this amount was rebuilt almost completely within 4 minutes as shown in an experiment with radioactive phosphorus.The phosphate esters accumulated in livers of rats during absorption of glucose and galactose are probably to some extent aldose‐esters i. e. glucose‐6‐phosphoric acid (and galactose‐6‐phosphoric acid?). Some of the esters accumulated during absorption of glucose and galactose in the livers of rats and rabbits were very sensitive to acid hydrolysis and relatively resistant to hydrolysis with alkali; the possibility exists that these esters are glucose‐1‐ and galactose‐1‐esters respectively.During absorption of glycerol an amount of glycerol representing about 100 mgs glycerol per 100 g liver tissue of rats was esterified; as phosphoglyceric acid and triosephosphoric acid could be excluded, the ester in believed to be (α‐ ?)‐glycerophosphoric acid.No accumulation of fructose‐1‐phosphoric acid was observed in the kidneys or muscular tissue of rabbits during assimilation of fructose, but the contents of fructose‐6‐ester of the preexisting Embden‐ester was somewhat increased.