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At least 1,693 records · Page 94Linked to original sources
PubMed2004

Immobilisation of catalase on the surface of biodegradable starch-based polymers as a way to change its surface characteristics.

In this study, a specific enzyme catalase was immobilised onto the surface of two different biodegradable materials, starch cellulose acetate (SCA) and starch polycrapolactone (SPCL) blends. This immobilisation was achieved by several different routes, mainly by covalent binding and an adsorption method using as activation agents epichlorohydrin, cyanogen bromide (CNBr), and aminopropyltriethoxysilane. The effect of the coupling pH of the enzyme-support reaction was determined in terms of activity recovery (%). The catalase immobilised on SCA showed higher activity recovery (%) for all the methods used as compared with results obtained with SPCL. The immobilisation process using epichlorohydrin as an activation agent and polyethylenimine as a spacer-arm enhanced the stability and the half-lives at pH 7.0, 30 degrees C, for immobilised catalase on both SCA and SPCL. The half-lives were respectively, 1162 and 870 h compared with other treatments and free enzyme (480 h). The free glycerol present in the immobilisation medium was also a factor that contributed toward the better performance regarding the long-term stability at 30 degrees C and neutral pH. The extension of the morphological modifications on the surface of the materials was observed by scanning electron microscopy. In general, the results indicated that the chemical modification with epichlorohydrin could provide a simple and rather efficient technique to modify the starch-based materials' surface that might be useful in several biomedical applications.

Absorbable Implants↗
PubMed2000

Starch grains reveal early root crop horticulture in the Panamanian tropical forest.

Native American populations are known to have cultivated a large number of plants and domesticated them for their starch-rich underground organs. Suggestions that the likely source of many of these crops, the tropical forest, was an early and influential centre of plant husbandry have long been controversial because the organic remains of roots and tubers are poorly preserved in archaeological sediments from the humid tropics. Here we report the occurrence of starch grains identifiable as manioc (Manihot esculenta Crantz), yams (Dioscorea sp.) and arrowroot (Maranta arundinacea L.) on assemblages of plant milling stones from preceramic horizons at the Aguadulce Shelter, Panama, dated between 7,000 and 5,000 years before present (BP). The artefacts also contain maize starch (Zea mays L.), indicating that early horticultural systems in this region were mixtures of root and seed crops. The data provide the earliest direct evidence for root crop cultivation in the Americas, and support an ancient and independent emergence of plant domestication in the lowland Neotropical forest.

Agriculture↗
PubMed1992

The combination of degradable starch microspheres and angiotensin II in the manipulation of drug delivery in an animal model of colorectal metastasis.

Both biodegradable emboli and pharmacological agents can enhance regional therapy for hepatic targeting. Using a rat model with similar haemodynamic characteristics to human colorectal liver tumour and a radio-labelled marker of similar molecular weight to Adriamycin, we have combined the two approaches to see if the effect was addictive. Following induction of liver tumour in male hooded rats by intrahepatic injection of HSN sarcoma cells, the relative distribution of marker, 99mTc methylene diphosphonate (MDP), was studied in three groups given the following by injection into the hepatic artery. (1) Saline (Control) + MDP; (2) Degradable Starch Microspheres (DSM) + MDP; and (3) Angiotensin II + DSM + MDP. Both Degradable Starch Microspheres alone (P less than 0.001) and Degradable Starch Microspheres + Angiotensin II (P = 0.003) significantly increased the retention of marker in liver and tumour at 1 min following injection, with a 12-fold improvement over controls, but the tumour:liver ratio was unaltered. By 90 min the MDP levels in normal hepatic parenchyma had returned to control values. There was relatively less washout with significant retention in tumour tissue in both DSM (P = 0.03) and combination treated animals (P = 0.001), with a significantly improved (P = 0.001) tumour to liver ratio (5.22:1) in combination treated animal relative to those treated with DSM alone.

Angiotensin II↗
PubMed2002

Starch content and yield increase as a result of altering adenylate pools in transgenic plants.

Starch represents the most important carbohydrate used for food and feed purposes. With the aim of increasing starch content, we decided to modulate the adenylate pool by changing the activity of the plastidial adenylate kinase in transgenic potato plants. As a result, we observed a substantial increase in the level of adenylates and, most importantly, an increase in the level of starch to 60% above that found in wild-type plants. In addition, concentrations of several amino acids were increased by a factor of 2-4. These results are particularly striking because this genetic manipulation also results in an increased tuber yield. The modulation of the plastidial adenylate kinase activity in transgenic plants therefore represents a potentially very useful strategy for increasing formation of major storage compounds in heterotrophic tissues of higher plants.

Adenylate Kinase↗
PubMed2002

Resistant starch content in a selection of starchy foods on the Swedish market.

OBJECTIVE: The objective was to determine the resistant starch (RS) content in a selection of typical starchy foods on the Swedish market. In addition, the daily RS intake was estimated from Swedish food consumption data. DESIGN: The major forms of RS, including physically encapsulated starch, were determined with an in vitro method using chewing as a pre-step before enzymatic incubation. SETTING: The study was performed at the Department of Applied Nutrition and Food Chemistry, Lund University, Sweden. SUBJECTS: Six healthy subjects were used to chew the food products before enzymatic incubation of the samples. RESULTS: Twenty-five cereal, potato and legume products were included in the study. The highest RS concentration was noted in the legume group (9.5-11.1% total starch basis). Commercially processed potato products were found to have a higher RS content (4.8-5.9%), compared with boiled potatoes (2.0%). Among the cereal products, bread with enclosure of intact rye grains, barley flakes and semolina porridge, respectively, were identified to have a RS level in the higher range (4.5-6.0%). The daily RS intake was estimated to be 3.2 g. CONCLUSIONS: The main RS sources in the Swedish diet are bread and potato products, which contribute approximately 1.3 and 1.2 g RS per day, respectively. Based on food habits the RS intake may vary considerably, thus when added to dietary fibre intake, the contribution of RS may be of nutritional importance for certain individuals.

Bread↗
PubMed2002

Production of butanol from starch-based waste packing peanuts and agricultural waste.

We examined the fermentation of starch-based packing peanuts and agricultural wastes as a source of fermentable carbohydrates using Clostridium beijerinckii BA101. Using semidefined P2 medium containing packing peanuts and agricultural wastes, instead of glucose as a carbohydrate source, we measured characteristics of the fermentation including solvent production, productivity, and yield. With starch as substrate (control), the culture produced 24.7 g l(-1) acetone-butanol-ethanol (ABE), while with packing peanuts it produced 21.7 g l(-1) total ABE with a productivity of 0.20 g l(-1) h(-1) and a solvent (ABE) yield of 0.37. Cell growth in starch, packing peanuts, and agricultural wastes medium was different, possibly due to the different nature of these substrates. Using model agricultural waste, 20.3g l(-1) ABE was produced; when using actual waste, 14.8 g l(-1) ABE was produced. The use of inexpensive substrates will increase the economic viability of the conversion of biomass to butanol, and can provide new markets for these waste streams.

Acetic Acid↗
PubMed1968

Methods for starch-gel electrophoresis of sarcoplasmic proteins. An investigation of the relative mobilities of the glycolytic enzymes from the muscles of a variety of species.

1. Details of an improved method for starch-gel electrophoresis of water-soluble muscle proteins are given. 2. Methods are described for detecting enzyme activities on the starch gel after electrophoresis, by using pieces of filter paper. 3. Compositions of incubation mixtures suitable for detecting any of the enzymes of glycolysis, and certain other enzymes, are given. 4. A comparison of the various enzymes in extracts of several muscles from one rabbit was made; most differences are quantitative only. 5. A detailed comparison of the mobilities of various enzymes in extracts of muscles from a wide variety of species was made. Each species was found to have a characteristic pattern of proteins on the starch gel, and the mobilities of individual enzymes varied considerably. 6. Potential uses and extensions of the methods are discussed.

Animals↗
PubMed1972

Protein, nucleic acid and starch metabolism in the duckweed, Spirodela oligorrhiza, treated with cytokinins.

Bacteria-free cultures of Spirodela oligorrhiza continue to increase in frond number for 2 to 3 days after transfer to darkness. There is then no further increase in frond number for 3 to 4 weeks, although DNA, RNA and protein synthesis continue at decreased rates and starch accumulates in the plants. We refer to such ;non-growing' plants in darkness as dormant. Adding kinetin to dormant Spirodela initiated increased DNA, RNA and protein synthesis within 1h, although new fronds were not detected until 24h after the addition of kinetin. The frond number then continued to increase. Starch accumulated in dormant plants. Accumulation of starch appeared to be a consequence of inhibition of growth rather than the converse. No evidence was obtained for a block in [(14)C]glucose metabolism that might explain the lack of growth in darkness in the absence of kinetin. In darkness, more ribosomes were membrane-bound in dormant Spirodela than in Spirodela growing with kinetin. Similarities between the response of Spirodela to darkness, stringent control in bacteria and pleiotypic controls in animal cells are discussed. It is suggested that all three processes are ultimately controlled by specific protein kinases that are individually sensitive to different effectors.

Carbon Isotopes↗
PubMed2005

Catalytic mechanism of alpha-retaining glucosyl transfer by Corynebacterium callunae starch phosphorylase: the role of histidine-334 examined through kinetic characterization of site-directed mutants.

Purified site-directed mutants of Corynebacterium callunae starch phosphorylase in which His-334 was replaced by an alanine, glutamine or asparagine residue were characterized by steady-state kinetic analysis of enzymic glycosyl transfer to and from phosphate and studies of ligand binding to the active site. Compared with wild-type, the catalytic efficiencies for phosphorolysis of starch at 30 degrees C and pH 7.0 decreased approx. 150- and 50-fold in H334Q (His334-->Gln) and H334N mutants, and that of H334A was unchanged. In the direction of alpha-glucan synthesis, selectivity for the reaction with G1P (alpha-D-glucose 1-phosphate) compared with the selectivity for reaction with alpha-D-xylose 1-phosphate decreased from a wild-type value of approximately 20000 to 2600 and 100 in H334N and H334Q respectively. Binding of G1P to the free enzyme was weakened between 10-fold (H334N, H334Q) and 50-fold (H334A) in the mutants, whereas binding to the complex of enzyme and alpha-glucan was not affected. Quenching of fluorescence of the pyridoxal 5'-phosphate cofactor was used to examine interactions of the inhibitor GL (D-gluconic acid 1,5-lactone) with wild-type and mutant enzymes in transient and steady-state experiments. GL binding to the free enzyme and the enzyme-phosphate complex occurred in a single step. The 50-fold higher constant (K(d)) for GL dissociation from H334Q bound to phosphate resulted from an increased off-rate for the ligand in the mutant, compared with wild-type. A log-log correlation of catalytic-centre activity for phosphorolysis of starch with a reciprocal K(d) value established a linear free-energy relationship (slope=1.19+/-0.07; r2=0.991) across the series of wild-type and mutant enzymes. It reveals that GL in combination with phosphate has properties of a transition state analogue and that the His-334 side chain has a role in selectively stabilizing the transition state of the reaction.

Amino Acid Sequence↗
PubMed2006

Thermostability enhancement and change in starch hydrolysis profile of the maltohexaose-forming amylase of Bacillus stearothermophilus US100 strain.

The implications of Asn315 and Val450 in the atypical starch hydrolysis profile of Bacillus stearothermophilus Amy (a-amylase) US100 have been suggested previously [Ben Ali, Mhiri, Mezghani and Bejar (2001) Enzyme Microb. Tech. 28, 537-542]. In order to confirm this hypothesis, three mutants were generated. Of these two have a single mutation, N315D or V450G, whereas the third contains both mutations. Analysis of the starch breakdown-profile of these three mutants, as well as of the wild-type, allowed us to conclude that each single mutation induces a small variation in the hydrolysis product. However, the major end product produced by the double mutant shifts from maltopentaose/maltohexaose to maltose/maltotriose, confirming the involvement of these two residues in starch hydrolysis. The superimposition of AmyUS100 model with that of Bacillus licheniformis shows in AmyUS100 an additional loop containing residues Ile214 and Gly215. Remarkably, the deletion of these two residues increases the half-life at 100 degrees C from 15 min to approx. 70 min. Moreover, this engineered amylase requires less calcium, 25 p.p.m. instead of 100 p.p.m., to reach maximal thermostability.

Amino Acid Substitution↗
PubMed1993

Purification of highly intact plastids from various heterotrophic plant tissues: analysis of enzymic equipment and precursor dependency for starch biosynthesis.

Starting with a protocol originally developed for the purification of intact plastids from cauliflower buds [Journet and Douce (1985) Plant Physiol. 79, 458-467] we have modified this method to obtain intact heterotrophic plastids from etiolated barley leaves (Hordeum vulgare) and pea (Pisum sativum) and maize (Zea mays) endosperm. Two subsequent centrifugation steps on Percoll gradients were performed, the first as an isopycnic, the second as zonal, centrifugation step in a swing-out rotor. Percoll density and centrifugation time were adjusted for the various tissues. The obtained plastid preparations are characterized by a low degree of contamination with other cellular components and an intactness of at least 90%. In isolated maize endosperm amyloplasts, starch synthesis is driven by exogenously applied hexose phosphates (glucose 6-phosphate and glucose 1-phosphate) rather than by dihydroxyacetone phosphate. The hexose-phosphate-dependent starch synthesis is strictly dependent upon the intactness of the plastids and is increased up to 9-fold when ATP and 3-phosphoglyceric acid are added to the incubation medium. The occurrence of fructose-1,6-bisphosphatase and malate dehydrogenases in some plastid types is discussed in relation to their possible role in starch synthesis.

Brassica↗
PubMed2004

Development of an ideal starch saccharification process using amylolytic enzymes from thermophiles.

The extensive efforts to screen thermophilic fungi and bacteria, isolated from various environmental samples, have resulted in the selection of Thermomucor indicae-seudaticae, Geobacillus thermoleovorans NP33 and G. thermoleovorans NP54 for the production of glucoamylase, amylopullulanase and alpha-amylase, respectively. Submerged and solid-state fermentation processes were optimized for maximizing the secretion of glucoamylase by T. indicae-seudaticae. The production of amylopullulanase and alpha-amylase by NP33 and NP54 in submerged fermentation was also optimized. Glucoamylase was optimally active at pH 7.0 and 60 degrees C and was shown to saccharify soluble as well as raw starches. Amylopullulanase and alpha-amylase exhibited optima at pH 7.0 and 100 degrees C and saccharified starch efficiently. Differential inhibition and action on mixed substrates clearly suggested that there are two separate active sites for alpha-amylase and pullulanase activities of amylopullulanase. Both alpha-amylase and amylopullulanase are high maltose-forming and Ca(2+)-independent. These amylolytic enzymes have been shown to be useful in starch saccharification alone and in combination.

Amyloid↗
PubMed2000

Sucrose transport into barley seeds: molecular characterization of two transporters and implications for seed development and starch accumulation.

In order to understand sucrose transport in developing seeds of cereals at the molecular level, we cloned from a caryopses library two cDNAs encoding sucrose transporters, designated HvSUT1 and HvSUT2. Sucrose uptake activity was confirmed by heterologous expression in yeast. Both transporter genes are expressed in maternal as well as filial tissues. In a series of in situ hybridizations we analysed the cell type-specific expression in developing seeds. HvSUT1 is preferentially expressed in caryopses in the cells of the nucellar projection and the endospermal transfer layer, which represent the sites of sucrose exchange between the maternal and the filial generation and are characterized by transfer cell formation. HvSUT2 is expressed in all sink and source tissues analysed and may have a general housekeeping role. The rapid induction of HvSUT1 gene expression in caryopses at approximately 5-6 days after fertilization coincides with increasing levels of sucrose as well as sucrose synthase mRNA and activity, and occurs immediately before the onset of rapid starch accumulation within the endosperm. Starch biosynthesis requires sucrose to be imported into the endosperm, as direct precursor for starch synthesis and to promote storage-associated processes. We discuss the possible role of HvSUT1 as a control element for the endospermal sucrose concentration.

Base Sequence↗
PubMed2000

Antisense-inhibition of ADP-glucose pyrophosphorylase in developing seeds of Vicia narbonensis moderately decreases starch but increases protein content and affects seed maturation.

The small subunit of a Vicia faba ADP-glucose pyrophosphorylase (AGP) cDNA was expressed in antisense orientation in Vicia narbonensis under the control of the seed-specific legumin B4 promoter. From several independent transgenic lines both ADP-glucose pyrophosphorylase AGP-mRNA and AGP enzyme activity were reduced by up to 95% in the cotyledons during the mid- to late-maturation phase. Starch was moderately decreased and sucrose was increased. In two of three lines, transcripts encoding the large subunit of AGP and the storage protein vicilin were increased, whereas legumin B-mRNA was decreased. Transcripts of other storage-associated genes were not altered. The cotyledons contained more protein and total nitrogen. Despite the reduction in starch, total carbon was not decreased and dry weight was unchanged. Compared to the wild type, transgenic seeds contained more water and accumulated dry weight during a longer period, and therefore had a prolonged seed-filling period. Transgenic cotyledon cells of comparable age to the wild type were more highly vacuolated and contained smaller starch grains, indicating a delay in cellular differentiation. We conclude that a specific alteration in carbon metabolism can have pleiotropic effects on water and nitrogen content and induces temporal changes in seed development.

Cotyledon↗
PubMed2000

An in vitro method for predicting the efficacy of WBC separation using different starch preparations and anticoagulant ratios.

BACKGROUND: Separation of blood components depends on a number of factors, including the viscosity of the plasma and the number and size of the various cellular elements. To enhance granulocyte collection, it is common practice to alter the plasma environment by the addition of sedimenting agents such as hydroxyethyl starch. Recently, because of its prolonged persistence in the circulation, the higher-molecular-weight form of hydroxyethyl starch, Hespan (HP), has been replaced by the lower-molecular-weight form, pentastarch (PS). However, the yield appears to be lower. A rapid in vitro approach was used to permit comparison of the efficiency of separation of WBCs by the use of PS and HP and different ratios of anticoagulants that also alter the sedimenting characteristics of blood. STUDY DESIGN AND METHOD: Blood from individual persons was collected into sodium citrate at ratios of 1:8, 1:12, and 1:16. Samples were evaluated either before or after the addition of PS or HP and after centrifugation. RESULTS: The addition of HP increased the sedimentation rate to at least four times that of plasma (10.9 vs. 47.9 mm); PS approximately doubled the rate. Viscosity was altered by the introduction of either starch. These changes (ranging from a rate of 4.2 in HP with a 1:16 anticoagulant to 3.6 in PS with a 1:8 ratio of anticoagulant) reflected the anticipated effects of anticoagulant dilution and carbohydrate addition. Granulocyte recovery was highest, with a 1:12 anticoagulant ratio in all tests with HP producing the greatest yield (HP, 101%; PS, 89%; control, 78%). CONCLUSION: HP is far more effective than its lower-molecular-weight substitute PS in the generation of granulocytes in the buffy coat of whole blood. This method provides a simple, rapid, in vitro approach to evaluating the separating efficiency of solutions.

Anticoagulants↗
PubMed1992

Intestinal mucosal morphometry and ileal epithelial renewal in conventional and germ-free rats fed an amylomaize starch diet.

Intestinal mucosal morphometry and ileal epithelial renewal were studied in conventional (CV) and germ-free (GF) rats fed either poorly digestible amylomaize or normal maize starch diets. Intestinal morphometry and position of labelled enterocytes were studied at various times after tritiated thymidine injection. With amylomaize starch diet, no difference was observed in the size of crypts (C), villi (V) and C + V between duodenum and jejunum both in CV and GF rats. In the ileum, however, values were significantly lower than those in the duodenum and jejunum. Furthermore, the presence of the microbial flora led to higher values when compared with GF values. Despite the morphological modifications in the ileum, no significant difference was detected in the labelled cell positions and epithelial renewal time between CV and GF values. This suggests that the resistant part of amylomaize starch was responsible for the modification in mucosal morphometry and the longer ileal epithelium renewal time in CV rats which then becomes similar to that in GF rats.

Amylopectin↗
PubMed2004

Engineering plants for elevated CO(2): a relationship between starch degradation and sugar sensing.

In the future, plants will have additional CO(2) for photosynthesis. However, plants do not take maximal advantage of this additional CO(2) and it has been hypothesized that end product synthesis limitations and sugar sensing mechanisms are important in regulating plant responses to increasing CO(2). Attempts to increase end product synthesis capacity by engineering increased sucrose-phosphate synthase activity have been generally, but not universally, successful. It was found that plants benefited from a two- to three-fold increase in SPS activity but a 10-fold increase did not increase yield. Despite the success in increasing yield, increasing SPS did not increase photosynthesis. However, carbon export from chloroplasts was increased during the day and reduced at night (when starch provides carbon for sucrose synthesis. We develop here a hypothesis that starch degradation is closely sensed by hexokinase because a newly discovered pathway required for starch to sucrose conversion that involves maltose is one of few metabolic pathways that requires hexokinase activity.

Biological Transport↗
PubMed1996

The effects of pre-exercise starch ingestion on endurance performance.

This study compared the physiological responses and performance following the ingestion of a waxy starch (WS), resistant starch (RS), glucose (GL) and an artificially-sweetened placebo (PL) ingested prior to exercise. Ten college-age, male competitive cyclists completed four experimental protocols consisting of a 30 min isokinetic, self-paced performance ride preceded by 90 min of constant load cycling at 66% VO2max. Thirty min prior to exercise, they ingested 1 g.kg-1 body weight of GL, WS, RS, or PL At rest, GL elicited greater (p < 0.05) serum glucose and insulin responses than all other trials. During exercise, however, serum glucose, insulin, blood C-peptide and glucagon responses were similar among trials. The mean total carbohydrate oxidation rates (CHOox) were higher (p < 0.05) during the GL, WS, and RS trials (2.59 +/- 0.13, 2.49 +/- 0.10, and 2.71 +/- 0.15 g.min-1, respectively) compared to PL (2.35 +/- 0.12 g.min-1). Subjects were able to complete more work (p < 0.05) during the performance ride when they ingested GL (434 +/- 25.2 kj) or WS (428 +/- 22.5 kj) compared to PL (403 +/- 35.1 kj). They also tended to produce more work with RS ingestion (418 +/- 31.4 kj), although this did not reach statistical significance (p < 0.09). These results indicate that preexercise CHO ingestion in the form of starch or glucose maintained higher rates of total carbohydrate oxidation during exercise and provided an ergogenic benefit during self-paced cycling.

Adult↗