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PubMed1983

Regulation of hepatic receptor-dependent degradation of LDL by mevinolin in rabbits with hypercholesterolemia induced by a wheat starch-casein diet.

Rabbits fed a wheat starch-casein diet develop a marked hypercholesterolemia and have a slower rate of removal of rabbit 125I-labeled low density lipoproteins (LDL) from plasma. Treating rabbits with mevinolin, a highly potent competitive inhibitor of 3-hydroxy-3-methylglutaryl-CoA reductase, at a daily dose of 20 mg per animal prevents the increase in plasma and LDL cholesterol. The mevinolin effect is mediated through an increased rate of removal of rabbit 125I-labeled LDL from plasma. To study the role of mevinolin on the regulation of the hepatic LDL receptor in rabbits, the binding of 125I-labeled LDL and 125I-labeled beta-VLDL (beta-migrating very-low-density lipoproteins) to liver membranes prepared from rabbits fed the wheat starch-casein diet with or without mevinolin was investigated. Liver membranes from wheat starch-casein-fed rabbits have no demonstrable EDTA-sensitive binding activity of 125I-labeled LDL and low (37 ng/mg protein) binding activity of 125I-labeled beta-VLDL. Treatment of the wheat starch-casein fed rabbits with mevinolin results in high levels of specific EDTA-sensitive binding of 125I-labeled LDL (28.7 ng/mg protein) and 125I-labeled beta-VLDL (120 ng/mg protein). To assess the functional role of the hepatic LDL receptor in response to mevinolin, the catabolism of 125I-labeled LDL by perfused rabbit livers was studied. Perfused livers from mevinolin-treated rabbits show a 3.3-fold increase in the rate of receptor-dependent catabolism of 125I-labeled LDL (4.6% X h-1) when compared with that of livers from rabbits not treated with mevinolin (1.4% X h-1). Thus, these studies demonstrate that mevinolin prevents the increase of plasma LDL cholesterol level in rabbits fed a wheat starch-casein diet by regulating the levels of hepatic LDL-binding sites and the rate of receptor-dependent catabolism of LDL by the liver.

Animals↗

PubMed1986

Effects of decreasing intraluminal amylase activity on starch digestion and postprandial gastrointestinal function in humans.

We used an amylase inhibitor preparation that markedly improves postprandial carbohydrate tolerance in humans to investigate the effects of decreased intraluminal amylase activity on digestion of starch and postprandial gastrointestinal and hormonal responses. Four fasting volunteers were intubated with an oroileal tube to obtain duodenal, jejunal, and terminal ileal samples. After intubation, subjects ingested 50 g of rice starch given with placebo; on the second day, starch was given with the amylase inhibitor. Compared with placebo, the amylase inhibitor significantly (p less than 0.05) reduced duodenal, jejunal, and ileal intraluminal amylase activity by more than 95% for 1-2 h; increased postprandial delivery of total carbohydrate (glucose polymers in particular) to the distal small bowel; increased breath hydrogen concentrations; decreased intestinal water absorption and increased distal intestinal volume delivery to the distal bowel; shortened duodenoileal transit time but doubled postprandial gastric emptying time; reduced the early postprandial plasma glucose rise by 85% and eliminated the late postprandial glucose fall to below fasting levels; and abolished postprandial plasma concentrations of insulin, C-peptide, and gastric inhibitory polypeptide. Postprandial trypsin output was not influenced. We conclude that more than 95% inhibition of amylase reduces dietary starch digestion within the small intestine and uptake of dietary starch from the small intestine, markedly decreases postprandial release of insulin and gastric inhibitory polypeptide, and may alter postprandial upper gastrointestinal motor function.

Adult↗

PubMed1981

Time- and dose-dependency of intestinal lactase activity in adult rat on starch intake.

Although it is generally accepted that lactase (beta-D-galactosidase, EC 3.2.1.23) activity is not influenced by intake of saccharides containing alpha-linkages, an effect of these carbohydrates on lactase activity was never thoroughly investigated. Activity of lactase and sucrose alpha-D-glucohydrolase, EC 3.2.1 48) was determined in proximal, middle and distal thirds of the jejunoileum of female, 12-week-old rats, fed for 2 weeks a low-starch (5 cal%), high-fat (73%) diet, and in rats, that after this introduction period were fed for 1, 2 and 3 days, an isocaloric middle-starch (40%), middle-fat (36%) diet or an isocaloric high-starch (70%), low-fat (7%) diet. During the entire experimental period, the body weight changes, food intake and the amount of protein per segment were practically the same in all three dietary groups. In all intestinal segments, increased intake of starch was followed by an increase of lactase and sucroase activity (both expressed as per tissue protein or per intestinal segment ) within the first day. The increase continued during the second day and leveled off during the third day. A highly significant linear correlation was found between the search content of the diets and the lactase activity in all three segments. A highly significant correlation was also established in all three segments between sucrase and lactase activities. These studies thus demonstrated a dose- and time-dependency between the intake of starch (a carbohydrate containing only alpha-linkages) and the activity of lactase, a neutral beta-galactosidase in adult rats.

Animals↗

PubMed2006

Anaerobic treatment of cassava starch extraction wastewater using a horizontal flow filter with bamboo as support.

Small-scale sour starch agroindustry in Colombia suffer from absence of water treatment. Although starch processing plants produce diluted wastewater, it is a source of pollution and cause environmental problems to the nearby rural population. A laboratory scale anaerobic horizontal flow filter packed with bamboo pieces was evaluated for the treatment of cassava starch extraction wastewater. The wastewater used in the experimentation was the draining water of the starch sedimentation basin. The reactor was operated for 6 months. It was inoculated with a semi-granular sludge from an anaerobic UASB reactor of a slaughterhouse. Maximum organic loading rate (OLR) applied was 11.8g COD/L d without dilution of the wastewater. At steady state and maximum OLR applied, 87% of the COD was removed and a gas productivity of 3.7L/L d was achieved. The average biogas yield was 0.36L/g COD removed. Methane content in the biogas was in the range of 69-81%. The total suspended solids (TSS) removed were 67%. The relative high lactic acid content did not negatively influence the performance of the reactor. No perturbation due to cyanide (3-5mg/L) was observed during the reactor operation. The results obtained indicated that the anaerobic horizontal flow filter could be used efficiently for the treatment of wastewater from Colombian starch processing small-scale agroindustry.

Bacteria, Anaerobic↗

PubMed2006

Controlled peeling of the surfaces of starch granules by gelatinization in aqueous dimethyl sulfoxide at selected temperatures.

Microscopic examination of starch granules in 90:10 (v/v) Me(2)SO-H(2)O indicated that the granules were slowly being gelatinized from their surfaces. The rate of gelatinization was dependent on two variables: (1) the amount of water in Me(2)SO and (2) the temperature. An increase of water in Me(2)SO and/or an increase in temperature increased the rate of gelatinization and vice versa. Specific ratios of Me(2)SO and H(2)O (85:15-95:5) and temperatures (0-15 degrees C) were found to give controlled sequential peeling/gelatinization of eight kinds of starch granules in 1-12h, with amounts of 10-25% gelatinization per hour. It was observed that the percent of starch granule remaining versus time gave curves that were linear and others that had linear parts separated by one or more abrupt changes. No two starches had a similar gelatinization curve for the same two conditions of the amount of water and the temperature. It is hypothesized that these curves reflect different structural characteristics for the individual kinds of starch granules.

Dimethyl Sulfoxide↗

PubMed2006

Sedimentation field flow fractionation monitoring of bimodal wheat starch amylolysis.

Enzymatic starch granule hydrolysis is one of the most important reactions in many industrial processes. In this study, we investigated the capacity of sedimentation field flow fractionation (SdFFF) to monitor the amylolysis of a bimodal starch population: native wheat starch. Results demonstrated a correlation between fractogram changes and enzymatic hydrolysis. Furthermore, SdFFF was used to sort sub-populations which enhanced the study of granule size distribution changes occurring during amylolysis. These results show the interest in coupling SdFFF with particle size measurement methods to study complex starch size/density modifications associated to hydrolysis. These results suggested different applications such as the association of SdFFF with structural investigations to better understand the specific mechanisms of amylolysis or starch granule structure.

Amylases↗

PubMed2005

Starch-dextrin mixtures as base excipients for extrusion-spheronization pellets.

Extrusion-spheronization pellets are generally produced with microcrystalline cellulose (MCC) as the principal excipient, giving rise to particles of very high quality. A number of alternative excipients have been proposed and evaluated, mostly other cellulose derivatives (e.g. different grades of Avicel), or mixtures of MCCs and other excipients. In the present study, we evaluated the possible use of starch+agglutinant mixtures as principal excipients for extrusion-spheronization pellets, with the aim of producing pellets with more suitable properties for certain types of release. We first characterized the different excipients in terms of morphometry and basic physical properties. Subsequently, torque-rheometry was used to characterize the rheology of wetted masses of the different excipients and excipient mixtures, with the aim of determining optimal amount of wetting agent (water). We also evaluated the water absorption and water retention capacities of each excipient. In view of the results obtained, we produced pellets with the different starch+agglutinant mixtures (but without drug), and used image analysis to characterize pellet morphology. Our results show that some of the mixtures-notably starch (corn starch or wheat starch)+20% white dextrin-gave high-quality pellets with good size and shape distributions. In addition, the properties of the different materials tested suggest that it may be possible to obtain pellets with very different properties.

Dextrins↗

PubMed2006

Phosphorylation of C6- and C3-positions of glucosyl residues in starch is catalysed by distinct dikinases.

Glucan, water dikinase (GWD) and phosphoglucan, water dikinase (PWD) are required for normal starch metabolism. We analysed starch phosphorylation in Arabidopsis wild-type plants and mutants lacking either GWD or PWD using (31)P NMR. Phosphorylation at both C6- and C3-positions of glucose moieties in starch was drastically decreased in GWD-deficient mutants. In starch from PWD-deficient plants C3-bound phosphate was reduced to levels close to the detection limit. The latter result contrasts with previous reports according to which GWD phosphorylates both C6- and C3-positions. In these studies, phosphorylation had been analysed by HPLC of acid-hydrolysed glucans. We now show that maltose-6-phosphate, a product of incomplete starch hydrolysis, co-eluted with glucose-3-phosphate under the chromatographic conditions applied. Re-examination of the specificity of the dikinases using an improved method demonstrates that C6- and C3-phosphorylation is selectively catalysed by GWD and PWD, respectively.

Arabidopsis Proteins↗

PubMed2006

Enzymatic esterification of starch using recovered coconut oil.

Modification of maize and cassava starches was done using recovered coconut oil and microbial lipase. Microwave esterification was advantageous as it gave a DS 1.55 and 1.1 for maize starch and cassava starch, respectively. Solution state esterification of cassava starch for 36 h at 60 degrees C gave a DS of 0.08 and semi-solid state esterification gave a DS of 0.43. TGA and DSC studies showed that the higher DS attributed to the thermostability, since onset of decomposition is at a higher temperature (492 degrees C) than the unmodified (330 degrees C) and was stable above 600 degrees C. alpha-Amylase digestibility and viscosity reduced for modified starch.

Calorimetry, Differential Scanning↗

PubMed2004

Partitioning and mobilization of starch and N reserves in grapevine (Vitis vinifera L.).

We followed C and N reserves of grapevines grown in trenches under semi-controlled conditions over a 3-year period after planting. Temporal mobilization of stored C and N and subsequent distribution of reserve materials within the vines were described in parallel with 15N uptake, particularly during the third growing season. Storage C in the perennial tissues (roots, trunk, canes) was mainly made of starch, which accumulated in the ray parenchyma of the wood. In the permanent tissues, starch and total nitrogen contents were found to decrease early in the development (bleeding sap, budbreak) whereas, on a concentration basis, they decreased only after stage 7 (first leaf fully expanded). Starch started to accumulate again in the perennial tissues during flowering. The same observation was made with total nitrogen, although N levels were much lower than those of starch. The 15N study showed that N uptake by the roots started at budbreak and increased with vine development, becoming predominant over reserve mobilization only after the onset of flowering. Taken together, these results indicate that the spring growth period can be divided into three main phases: In the first (dormancy to budbreak), significant losses of C and N proceed mainly via root necrosis. In the second period (first leaf to the onset of bloom), a strong mobilization of starch (and, to a lower extent, of N) occurred for supporting vegetative and reproductive growth. At that point, most of the C and N reserves used on the spring flush were those of the roots, rather than those of the old wood (trunk, canes). In the third period (bloom and early berry development), the mobilization process became low and was relieved by N uptake (and CO2 assimilation) supplying nutrients to the sink structures.

Nitrates↗

PubMed2005

Possible role played by R1 protein in starch accumulation in bean (Phaseolus vulgaris) seedlings under phosphate deficiency.

The effect of phosphate (Pi) deficiency on starch accumulation was studied in bean (Phaseolus vulgaris). After 3 weeks of Pi deprivation total Pi concentration in root and shoot was reduced by 68% and 42%, respectively; however, only shoot growth was affected. In leaves, Pi deprivation induced glucose, fructose and starch accumulation. Pi deficiency did not affect starch synthesis, but it reduced its mobilization during the dark period. At the same time, starch produced by Pi deficient plants have fewer Pi bound and was also less susceptible to beta-amylase hydrolysis. R1 protein is the protein responsible of phosphorylating C3 and C6 glucosyl residues of the polyglucan, increasing the hydration capacity and the interaction with amylolytic enzymes. Pi deprivation did not change the amount of R1 protein detected in total extracts but decreased its association with starch granules.

Phaseolus↗

PubMed2005

Microbial starch-binding domain.

Glucosidic bonds from different non-soluble polysaccharides such as starch, cellulose and xylan are hydrolyzed by amylases, cellulases and xylanases, respectively. These enzymes are produced by microorganisms. They have a modular structure that is composed of a catalytic domain and at least one non-catalytic domain that is involved in polysaccharide binding. Starch-binding modules are present in microbial enzymes that are involved in starch metabolism; these are classified into several different families on the basis of their amino acid sequence similarities. Such binding domains promote attachment to the substrate and increase its concentration at the active site of the enzyme, which allows microorganisms to degrade non-soluble starch. Fold similarities are better conserved than sequences; nevertheless, it is possible to notice two evolutionary clusters of microbial starch-binding domains. These domains have enormous potential as tags for protein immobilization, as well as for the tailoring of enzymes that play a part in polysaccharide metabolism.

Bacteria↗

PubMed2004

Current models for starch synthesis and the sugary enhancer1 (se1) mutation in Zea mays.

Among the desirable quality traits essential for commercial production of fresh or processed sweet corn, kernel sugar content is universally important. In sweet corn genotypes the primary kernel sugar is sucrose, which is elevated at the expense of starch, particularly amylopectin. Sweet corn mutations have been traditionally divided into two classes. Generally speaking, class one mutations affect cytosolic reactions early in the process of starch synthesis, before starch is synthesized, and class two mutations affect reactions within the amyloplast directly involving starch granule assembly. Two widely used but previously unclassified mutations are sugary1 (su1) and sugary enhancer1 (se1). The se1 gene is a recessive modifier of su1; therefore, both genes require mutual discussion. This review provides current information about the su1 and se1 maize endosperm mutations and describes evidence further supporting previous suggestions that they fit criteria for categorization as class two mutants [Science 151 (1966) 341]. Information on the genetics and phenotype of se1 will be summarized and the hypothesized role of the se1 gene product discussed within the context of current models for starch synthesis in Zea mays L.

Mutation↗

PubMed2005

Leaf starch degradation comes out of the shadows.

During the day, plants accumulate starch in their leaves as an energy source for the coming night. Based on recent findings, the prevailing view of how the transitory starch is remobilized needs considerable revision. Analyses of transgenic and mutant plants demonstrate that plastidic glucan phosphorylase is not required for normal starch breakdown and cast doubt on the presumed essential role of alpha-amylase but do show that beta-amylase is important. Repression of the activity of a plastidic beta-amylase, the export of its product (maltose) or further metabolism of maltose by a newly identified transglucosidase impairs starch degradation. Breakdown of particulate starch also depends on the activity of glucan-water dikinase, which phosphorylates glucosyl residues within the polymer.

Arabidopsis↗

PubMed2001

Synthesis, analysis and reduction of 2-nitropropyl starch.

Granular 2-nitropropyl potato starch was synthesized by reaction with 2-nitropropyl acetate in an aqueous suspension. Nitroalkylation occurs preferentially with the amylose fraction of potato starch, as was confirmed by leaching experiments and digestion of the modified starch with alpha-amylase. The 2-nitropropyl substituent is a mixture of the nitroalkane and nitronic acid tautomer. Some grafting occurs and to a lesser extent additional reactions (formation of carbonyls and oximes) of the nitro group take place. After catalytic hydrogenation of water soluble 2-nitropropyl starch only a small amount of the nitro functionality was reduced to the corresponding amine. Reduction of granular 2-nitropropyl starch with sodium dithionite did not go to completion and led to a complex mixture of starting material, several intermediates and side products (for example sulfamates).

Amylose↗

PubMed2001

Physicochemical properties and structure of large, medium and small granule starches in fractions of normal barley endosperm.

Normal barley grain was milled to flour with a machine used to polish brewers' rice from the surface layer to the center. Large (18.4 microm, median size), medium (12.3 microm) and small (2.2 microm) granule starches were isolated from classified flours. Their physicochemical properties and fine structure were investigated. The percentage (w%) of large granules decreased from the surface layer to the center, while the amounts of medium and small granules increased. Although all the starch granules were an A-type crystal, the relative crystallinity varied from 22.0 to 27.4%. The DPn of the amyloses was around 1600 and similar for all the samples. But the amylose content of the starches varied from 21.9 to 26.4%. Also, the amylopectins showed differences in DPn (around 5700-7900) and chain-length distribution between granule size or fractions. The transition temperature ranges and the enthalpy values of the starch granules differed with granule size. The gelatinization properties showed no correlation with any of the parameters, except the enthalpy value and relative crystallinity (gamma = +0.73). The findings suggested that the structural characteristics of the starches in classified flours of normal barley differed essentially from those of waxy barley.

Amylopectin↗

PubMed1998

Cross-linking of starch with bifunctional precursors of nitroalkenes.

Granular starch was cross-linked with 1,3-di-O-acetyl-2-nitro-1,3-propanediol (1), 1,3-di-O-pivaloyl-2-nitro-1,3-propanediol (2), 2-nitro-3-O-pivaloyl-1-propene-3-ol (3), 1,3-di-O-acetyl-aci-2-nitro-1, 3-propanediol (4), 1,3-di-O-pivaloyl-aci-2-nitro-1,3-propanediol (5) and 1,6-di-O-acetyl-2,5-dinitro-1,6-hexanediol (6). The bifunctional precursors for the nitro-alkenes 1, 2, 3, and 4 were readily synthesized in high yields from nitromethane, paraformaldehyde and acetic anhydride (1, 3) or pivaloyl chloride (2, 4), respectively. The reaction rate for the cross-linking was very high, and for 1 and 3, the reaction reached completion within 1 h (at room temperature). The swelling capacities of the products obtained when starch was cross-linked with precursors for the nitroalkenes 1-4 and 6 were lower in comparison to epichlorohydrin cross-linked starch. These results indicate a high reaction efficiency at low degrees of substitution. Cross-linked 2-nitroalkyl starch ethers were synthesized in a one-pot synthesis by addition of 1 or 3 and 2-nitroalkyl acetates to granular suspensions of starch.

Alkylation↗

PubMed1994

Small intestinal glucoamylase deficiency and starch malabsorption: a newly recognized alpha-glucosidase deficiency in children.

To determine the prevalence of short polymers of glucose and starch malabsorption caused by small intestinal glucoamylase deficiency in children with chronic diarrhea, we studied small bowel biopsy specimens from 511 children (aged 1 month to 9 years) with chronic diarrhea evaluated at 54 medical centers. Glucoamylase and disaccharidase (lactase, sucrase, maltase, and palatinase) enzyme assays were performed. Of the 511 children, 15 had glucoamylase deficiency. Six who had significant small intestinal mucosal injury and disaccharidase deficiencies were defined as having secondary glucoamylase deficiency; the other nine patients with normal mucosal morphologic features were defined as having primary glucoamylase deficiency. Secretin tests showed normal pancreatic amylase values for age in all seven children tested. Four of them had abnormal findings on tolerance tests for starch and short polymers of glucose (rise in blood glucose concentration: < 20 mg/dl) and reducing substances in stools, and three of these four had symptoms of intolerance (abdominal distention, flatulence, and diarrhea). All seven patients responded to a starch elimination diet. After reintroduction of a starch diet, diarrhea recurred in four patients; this was alleviated 48 hours after reelimination of starch. We conclude that intestinal glucoamylase deficiency is present in some patients with chronic diarrhea.

Carbohydrate Metabolism, Inborn Errors↗