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At least 1,153 records · Page 64Linked to original sources
PubMed1999

Nutrient removal and starch production through cultivation of Wolffia arrhiza.

Wolffia arrhiza, a small weed found mostly in tropical and subtropical water environments, exhibits a high growth rate and consequently absorbs large amounts of nitrogen and phosphorus. Its vegetative frond contains 40% protein on a dry weight basis and its turion, which is the dormant form, has a similar starch content. The applicability of this weed to nutrient removal from secondary-treated waste water combined with starch resource production was evaluated. The nitrogen and phosphorus removal capabilities of the vegetative frond and the optimal conditions for inducing of the formation of turions from harvested biomass of vegetative fronds for the production of starch were investigated using artificial nutrient solutions. The vegetative frond showed high contents of nitrogen (6-7% of the total dry weight) and phosphorus (1-2% of the total dry weight). The nutrient removal rates of the vegetative frond were estimated to be 126 mg-N/m(2)/d and 38 mg-P/m(2)/d under a continuous flow condition. For turion formation from the vegetative fronds, a low nutrient concentration and a high plant density were most effective. Under the optimum conditions, the starch production rate was estimated to be 6 g-starch/m(2) (nutrient removal tank)/d.

Journal Article↗
PubMed2003

Enzyme-aided investigation of the substituent distribution in cationic potato amylopectin starch.

The distribution of substituents along the polymer chain in cationic potato amylopectin starch, modified in solution, granular slurry, or dry state, was investigated. The starch derivatives were successively hydrolyzed by different enzymes, followed by characterization of the hydrolysis products obtained by means of electrospray mass spectrometry (ESI-MS) and matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS). ESI-MS and MALDI-MS were proved to be appropriate techniques for identification of the substituted hydrolysis products, for which there are no standard compounds available. No highly substituted oligomers were found in the hydrolysates, which was taken as an indication of a more or less homogeneous distribution of cationic groups in the amylopectin molecules. Furthermore, from the results obtained it was suggested that the enzymes cleave glucosidic linkages only between unsubstituted glucose units and, preferentially, linkages in sequences containing more than two adjacent unsubstituted units. The determination of the amount of unsubstituted glucose produced from every successive hydrolysis step revealed slight differences between the different starch samples with respect to the homogeneity of the substitution pattern. Among the three samples under investigation, starch cationized in solution was found to have the most and dry-cationized starch the least homogeneous distribution of substituents.

Amylopectin↗
PubMed2003

Evaluation of the potential of starch-based biodegradable polymers in the activation of human inflammatory cells.

The inflammatory response resulting from the implantation of a medical device may compromise its performance and efficiency leading, in certain cases, to the failure of the implant. Thus, the assessment of the behavior of inflammatory cells in vitro, constitutes a key feature in the evaluation of the adverse potential, or not, of new promising biomaterials. The objectives of this study were to determine whether starch-based polymers and composites activated human neutrophils. Blends of starch with ethylene-vinyl alcohol, with cellulose acetate and polycaprolactone, as well as composites based on all these materials filled with hydroxyapatite have been studied. A lysozyme assay was adapted to examine enzyme secretion from human neutrophils incubated with different starch-based materials. Changes in the free radical and degranulation activity of the neutrophil were also determined by measuring the luminescent response of Pholasin, a photoprotein that emits light after excitation by reactive oxygen species. The amount of lysozyme secreted by neutrophils incubated with the polymers did not exhibit significant differences between the tested materials. Results were in all cases similar to those obtained for the control (polypropylene) except for one of the starch blends (corn starch with polycaprolactone reinforced with 30% (w/w) of HA). The chemiluminescence experiments showed that polymers reduce the signal produced by activated neutrophils. Furthermore, for some polymers it was demonstrated that the phenomenon was due to an effect of the surface of the materials in cell adhesion or a simultaneous competition for the photoprotein in solution, which results in the decrease of the intensity of light emitted and detected.

Journal Article↗
PubMed1991

Direct transport of ADPglucose by an adenylate translocator is linked to starch biosynthesis in amyloplasts.

Starch biosynthesis has been studied by using amyloplasts isolated from cultured cells of sycamore trees (Acer pseudoplatanus L.). Highly purified intact amyloplasts, free from mitochondria and starch granules derived from broken amyloplasts, were isolated from a Percoll step gradient. Subsequently, the double silicone oil layer centrifugation technique was used to study adenylate transport in the amyloplasts. An adenylate-specific carrier was found to be active in the uptake of ATP, ADP, AMP, and most importantly, ADPglucose (ADP-Glc). Kinetic analyses showed that the uptake of these adenylates was mutually competitive with each other. In contrast to the mitochondrial adenylate carrier, in amyloplasts only ATP and ADP-Glc uptake were inhibited by carboxyatractyloside. Evidence is presented that the ADP-Glc transported into the amyloplast stroma can be used in starch synthesis catalyzed by starch synthase (ADP-Glc:1,4-alpha-D-glucan 4-alpha-D-glucosyltransferase, EC 2.4.1.21). We propose that starch biosynthesis in amyloplasts is tightly coupled with the direct transport of ADP-Glc synthesized in the cytosol by sucrose synthase (ADP-Glc:D-fructose 2-alpha-D-glucosyltransferase, EC 2.4.1.13)

Journal Article↗
PubMed2002

Effect of rice starch as a bath additive on the barrier function of healthy but SLS-damaged skin and skin of atopic patients.

Rice starch added to bath water was studied for its possible beneficial effects on impaired barrier function as evaluated by transepidermal water loss measurements. The forearm skin of healthy volunteers was irritated by sodium lauryl sulphate. Exposure to rice-starch-containing bath water--twice daily for 15 min--led to a 20% improvement on the healing capacity of damaged skin. The beneficial effect was also observed for a rice-starch-containing lipid-free bath formulation, and an oil-in-water bath lotion enriched with evening primrose oil. Skin barrier function in patients with atopic dermatitis also improved after the addition of starch powder to bath water. Rice starch in powder or formulated in a bath product can therefore be recommended as a skin repair bathing additive for barrier damaged skin, particularly in the case of atopic dermatitis patients.

Adult↗
PubMed1977

[The effect of physical shape of dried green feed and of various sources of starch on the site of digestion of carbohydrates and proteins and on the protein synthesis in the cow rumen].

The experiments were performed on cows with duodenal bridge fistulae to study the influence of the physical form of roughage (forage rye, chopped or pelleted) and of the starch source (barley or maize) on the place of carbohydrate digestion and on microbial protein synthesis. The organic matter digested in the stomachs contained more than 90% carbohydrates. Their digestibility was not found to be influenced by the physical form of the roughage and by the kind of starch source. Feeding pelleted roughage (30% crude fibre) as against chopped roughage increased the share of intestinal digestion of crude cellulose from 5 to 13%, whilst it remained relatively constant with starch (alpha-polymer bound glucose). Under high-starch feeding (some 2100 g/day) 710 g (maize) and 400 g (barley) of alpha-polmer bound glucose entered the duodenum. This corresponds to 29.6 and 17.6% of the starch consumed with maize and barley, respectively. When feeding the pelleted roughage (as compared to chopped roughage) a large amount of the non-bacterial N derived from feed protein and endogenous N (69.6 and 52.8 g/day) was available in the duodenum. Against this, the synthesis of bacterial N decreased (82.7 and 109.0 g/day). In the intestine, 107.1 and gN were absorbed daily from pelleted and chopped forage rye, respectively. In comparison with maize, barley was found to promote N availibility in the intestine (108.9 and 115.3 g N/day). Out of every 100 g of organic matter digested in the stomachs 28 and 21 g of bacterial protein were synthesized under chop and pellet feeding, respectively. Referred to the same amount, 6.6 g and 6.2 g N were found to enter the duodenum for chopped and pelleted roughage, respectively.

Animal Feed↗
PubMed1989

Diets containing high amylose vs amylopectin starch: effects on metabolic variables in human subjects.

Twelve men consumed a diet containing 34% of calories as 70% amylose or amylopectin starch to determine if the structure of starch could influence metabolic factors associated with abnormal states. Each starch was fed to subjects for 5 wk in a crossover design. No significant differences were observed in glucose or insulin levels when a glucose tolerance was given after 4 wk on each starch. However, glucose and insulin responses were significantly lower when a meal containing amylose compared with amylopectin was consumed after 5 wk on each starch. Summation of 0.5 through 2-h levels of insulin but not glucose were significantly lower after amylose compared with levels after amylopectin. Mean fasting triglyceride and cholesterol levels were significantly lower during the period when amylose was consumed. Long-term intake of dietary amylose may be valuable in decreasing insulin response while maintaining proper control of glucose tolerance and low levels of blood lipids.

Adult↗
PubMed1993

Seasonal variations in soluble sugars and starch within woody stems of Cornus sericea L.

Carbohydrate composition changed seasonally in red osier dogwood (Cornus sericea L.) stem tissues. Starch concentration was highest in fall and decreased to a minimum in midwinter. Coincident with the breakdown of starch in fall, there was an increase in the concentrations of soluble sugars. Soluble sugars were present in highest concentrations in midwinter. Glucose, fructose, sucrose, and raffinose were the predominant soluble sugars present in both bark and wood tissues. In early spring, the soluble sugar concentration decreased and the concentration of starch increased. The seasonal interchange between sugars and starch did not simply reflect a general quantitative shift in the balance between sugars and starch because qualitative changes in soluble sugars were also noted. The most striking changes involved the trisaccharide raffinose. Raffinose was barely detectable in summer and early fall, but increased to one fifth and one third of the total soluble sugars in January samples of bark and wood tissues, respectively. The potential physiological role of raffinose in overwintering red osier dogwood tissue is discussed.

Journal Article↗
PubMed1990

Late-season changes in allocation of starch and sugar to shoots, coarse roots, and fine roots in two hybrid poplar clones.

Two hybrid Populus clones, Tristis and Eugenei, which had been grown from cuttings in 114-liter pots sunk in the ground, were sequentially harvested during the latter part of the first growing season. Pots were supplied with water and nitrogen at two different rates. Starch and sugar concentrations were determined in samples taken from stems, branches, cuttings, and five diameter classes of roots. Concentrations of starch and sugar in all components of the trees were significantly affected by time of harvest and clone. Water and nitrogen treatments, however, did not significantly affect carbohydrate concentrations. From August to November, as plants developed cold hardiness, starch concentrations declined and sugar concentrations increased in stems and branches, especially in Tristis. In both clones, the large roots (> 1 mm diameter) were major repositories of starch and sugar late in the season. By the end of September, 80% of total-tree nonstructural carbohydrates in Eugenei were located in the roots. Even the fine-root fraction (< 0.5 mm diameter) showed substantial carbohydrate loading in late season, contradicting the hypothesis that starch deposition in fine roots occurs only when they are being formed.

Journal Article↗
PubMed2000

Resistant starches.

Initially, it was hoped that resistant starches (ie, starches that enter the colon) would have clear advantages in the reduction of colon cancer risk and possibly the treatment of ulcerative colitis. Recent studies have confirmed the ability of resistant starch to increase fecal bulk, to increase the molar ratio of butyrate in relation to other short-chain fatty acids, and to dilute fecal bile acids. However, reduction in fecal ammonia, phenols, and N-nitroso compounds have not been achieved. At this point the picture from the standpoint of colon cancer risk reduction is not clear. Nevertheless, there is a fraction of what has been termed resistant starch (RS1), which enters the colon and acts as slowly digested, or lente, carbohydrate. Foods in this class are low glycemic index and have been shown to reduce the risk of chronic disease. They have been associated with systemic physiologic effects such as reduced postprandial insulin levels and higher high-density lipoprotein cholesterol levels. Consumption of low glycemic index foods has been shown to be related to a reduced risk of type 2 diabetes. Type 2 diabetes has in turn been related to a higher risk of colon cancer, especially colon cancer deaths. If carbohydrate has a protective role in colon cancer prevention, it may lie in the systemic effects of low glycemic index foods. The colonic advantages of different carbohydrates, therefore, remain to be documented. However, there is reason for optimism about the possible health advantages of so-called resistant starches that are slowly digested in the small intestine.

Journal Article↗
PubMed1993

Sucrose Synthase, Starch Accumulation, and Tomato Fruit Sink Strength.

Contrasting evidence has accumulated regarding the role of acid invertase and sucrose synthase in tomato fruit sink establishment and maintenance. In this work the relationships among the activities of sucrose synthase and acid invertase, Lycopersicon esculentum Mill cv UC-82B fruit growth, and starch accumulation were analyzed in fruit at 0 to 39 d after anthesis. Sucrose synthase, but not acid invertase, was found to be positively correlated with tomato fruit relative growth rate and with starch content in the pericarp tissue. A similar association between sucrose synthase activity and starch accumulation was also evident in the basal portion of the stem. Heat-shock treatments, which inhibited the increase in sucrose synthase activity at the beginning of the light period and had no effect on acid invertase activity, were used to examine the importance of sucrose synthase in relation to sucrose metabolism and starch synthesis. After the heat-shock treatment, concomitantly with the suppressed sucrose synthase activity relative to the controls, there was a reduction in sucrose cleavage and starch accumulation. These data substantiate the conclusion that, during the early phases of tomato fruit development, sucrose synthase rather than acid invertase is the dominant enzyme in metabolizing imported sucrose, which in turn plays a part in regulating the import of sucrose into the fruit.

Journal Article↗
PubMed1998

High-temperature perturbation of starch synthesis is attributable to inhibition of ADP-glucose pyrophosphorylase by decreased levels of glycerate-3-phosphate in growing potato tubers

To investigate the short-term effect of elevated temperatures on carbon metabolism in growing potato (Solanum tuberosum L.) tubers, developing tubers were exposed to a range of temperatures between 19 degreesC and 37 degreesC. Incorporation of [14C]glucose (Glc) into starch showed a temperature optimum at 25 degreesC. Increasing the temperature from 23 degreesC or 25 degreesC up to 37 degreesC led to decreased labeling of starch, increased labeling of sucrose (Suc) and intermediates of the respiratory pathway, and increased respiration rates. At elevated temperatures, hexose-phosphate levels were increased, whereas the levels of glycerate-3-phosphate (3PGA) and phosphoenolpyruvate were decreased. There was an increase in pyruvate and malate, and a decrease in isocitrate. The amount of adenine diphosphoglucose (ADPGlc) decreased when tubers were exposed to elevated temperatures. There was a strong correlation between the in vivo levels of 3PGA and ADPGlc in tubers incubated at different temperatures, and the decrease in ADPGlc correlated very well with the decrease in the labeling of starch. In tubers incubated at temperatures above 30 degreesC, the overall activities of Suc synthase and ADPGlc pyrophosphorylase declined slightly, whereas soluble starch synthase and pyruvate kinase remained unchanged. Elevated temperatures led to an activation of Suc phosphate synthase involving a change in its kinetic properties. There was a strong correlation between Suc phosphate synthase activation and the in vivo level of Glc-6-phosphate. It is proposed that elevated temperatures lead to increased rates of respiration, and the resulting decline of 3PGA then inhibits ADPGlc pyrophosphorylase and starch synthesis.

Journal Article↗
PubMed1968

Rapid starch synthesis associated with increased respiration in germinating lily pollen.

In vitro studies of germinating Lilium longiflorum pollen showed that starch increased more rapidly during the first 30 minutes of incubation than during the next several hours. The period of rapid starch formation coincided with the first period of high respiration. An estimate was made of the extra ATP utilized to form extra starch during the first 30 minutes, and this estimate indicates that starch synthesis accounts for a significant portion of the initial high rate of respiration. This pattern of respiration and starch synthesis was not altered when pollen germinated in a pentaerythritol medium that could not be metabolized instead of the standard sucrose medium.Sucrose was the predominant sugar in mature lily pollen. This sugar decreased 50% during several hours incubation in pentaerythritol culture medium. Reducing sugars remained low during incubation which may indicate that sucrose breakdown is regulated by the rate of utilization of hexose units.

Journal Article↗
PubMed1968

Enzymic mechanism of starch breakdown in germinating rice seeds I. An analytical study.

Time-sequence analyses of carbohydrate breakdown in germinating rice seeds shows that a rapid breakdown of starch reserve in endosperm starts after about 4 days of germination. Although the major soluble carbohydrate in the dry seed is sucrose, a marked increase in the production of glucose and maltooligosaccharides accompanies the breakdown of starch. Maltotriose was found to constitute the greatest portion of the oligosaccharides throughout the germination stage. alpha-Amylase activities were found to parallel the pattern of starch breakdown. Assays for phosphorylase activity showed that this enzyme may account for much smaller amounts of starch breakdown per grain, as compared to the amounts hydrolyzed by alpha-amylase. There was a transient decline in the content of sucrose in the initial 4 days of seed germination, followed by the gradual increase in later germination stages. During the entire germination stage, sucrose synthetase activity was not detected in the endosperm, although appreciable enzyme activity was present in the growing shoot tissues as well as in the frozen rice seeds harvested at the mid-milky stage. We propose the predominant formation of glucose from starch reserves in the endosperm by the action of alpha-amylase and accompanying hydrolytic enzyme(s) and that this sugar is eventually mobilized to the growing tissues, shoots or roots.

Journal Article↗
PubMed1970

Adenosine Diphosphate-Glucose Pyrophosphorylase Control of Starch Accumulation in Rust-infected Wheat Leaves.

The variation in starch content in healthy and Puccinia striiformsi-infected wheat leaves was measured from 5 to 15 days after inoculation. The starch content of diseased leaves relative to healthy leaves decreased from 5 to 9 days, increased from 9 to 12 days to twice that of healthy leaves, and decreased from 12 to 15 days after inoculation. Electron micrographs of plant tissues indicated that the starch accumulated in the chloroplasts of host cells adjacent to fungal hyphae. Variations in sugar phosphates, ATP, and inorganic phosphate were measured during the infection process. ADP-glucose pyrophosphorylase was extracted and partially purified from healthy and diseased leaves. When proportionate concentrations of sugar phosphates and inorganic phosphate found in healthy and diseased leaves during the infection process were placed in the assay mixture, ADP-glucose pyrophosphorylase activity was similar to the pattern of starch accumulation and was almost the inverse of the variation observed in inorganic phosphate in diseased leaves during the infection process. A mechanism to explain the accumulation of starch is presented and discussed. This mechanism is based on the regulation of ADP-glucose pyrophosphorylase by changes in effector molecule concentrations during the infection process. Reasons for these changes are presented.

Journal Article↗
PubMed1971

Biogenesis and Degradation of Starch: I. The Fate of the Amyloplast Membranes during Maturation and Storage of Potato Tubers.

Storage of mature or developing potato tubers (Solanum tuberosum "Up-to-Date" variety) at 4 C causes a reduction in the starch content and the elevation in the level of free sugars. This phenomenon is not observed when the tubers are stored at 25 C. Changes in the morphology of cells from developing or mature tubers after storage at 4 or 25 C have been followed by electron microscopy. During all stages of the tuber development the starch granules are surrounded by a membrane derived from the plastid envelope. Storage in the cold induces disintegration of this membrane. A membrane fraction isolated from starch granules of tubers stored at 4 C has a lower buoyant density, and the electrophoretic pattern of its proteins is different from that of a similar membrane fraction obtained from tubers stored at 25 C. It is suggested that the cold-induced changes in the starch and sugar content during storage of potato tubers might be correlated with damage to the membranes surrounding the starch granules and changes in their permeability to degradative enzymes and substrates.

Journal Article↗
PubMed1976

Pyrophosphorylases in Solanum tuberosum: I. Changes in ADP-Glucose and UDP-Glucose Pyrophosphorylase Activities Associated with Starch Biosynthesis during Tuberization, Maturation, and Storage of Potatoes.

Changes in ADP-glucose and UDP-glucose pyrophosphorylase activities were followed during tuber development of Solanum tuberosum and prolonged storage at 4 and 11 C. Potato tuberization was accompanied by a sharp increase in starch synthesis simultaneous with a marked rise in ADP-glucose pyrophosphorylase activity. When tubers reached an average diameter of 1 centimeter (0.5 gram average tuber weight) and had already established 58% starch on a dry weight basis, ADP-glucose pyrophosphorylase increased 16- to 24-fold over its activity seen in low starch containing stolon tissue. During this same period UDP-glucose pyrophosphorylase increased approximately 2- to 3-fold. Although participation of UDP-glucose in starch formation can not be neglected, it is suggested that the onset of rapid non-photosynthetic potato tuber starch biosynthesis may be closely related to the simultaneous increase in ADP-glucose pyrophosphorylase activity.Evidence that UDP-glucose and ADP-glucose pyrophosphorylases are separate protein entities was indicated by their (a) activity ratio variations during tuber development and storage, (b) extraction stabilities, (c) morphological localization, (d) separation with ammonium sulfate, (e) pH optima, and (f) differential activation with 3-P-glycerate.

Journal Article↗
PubMed1980

Starch depletion and sugars in developing cotton leaves.

Cotton plants (cv. Coker 100) were exposed to a 14-hour dark period. Starch degradation occurred with no accumulation of sugars due mainly to translocation. Considerable amounts of starch degradation products however were detected from leaves after phloem transport was blocked. A minor component (10 to 25% of total starch) with a linear structure, amylose, was preferentially degraded, whereas the major multiple-branched component (about 80%), amylopectin, showed an increasing resistance to degradation with leaf age. This relationship was also shown by the decreasing iodine-binding capacity of unit starch with increasing leaf age. The structural resistance of amylopectin to enzymic dark degradation was one of the barriers to starch dissolution in cotton.

Journal Article↗