Mg Of Starch Research Articles

Starch Extraction and Amylose Analysis from Half Seeds

To allow genetic analysis of starch quality in wheat and its relatives, it was necessary to develop techniques suitable for use on endosperm halves of seeds, leaving the embryo half to be grown for the next generation. Seeds were split and the endosperm end was crushed and soaked in 0.5 M NaCl overnight. The solids were ground three times in 0.5 M NaCl, the supernatant starch slurries were pooled and washed through a series of 4 M NaCl, 6 M NaCl/50 %, sucrose, 2 % sodium dodecyl sulphate solution, and acetone before being dried over silica gel. Subsamples of 1 mg of starch were dispersed in ethanol in preweighed microfuge tubes, gelatinised in NaOH solution, diluted to constant concentration, and aliquots were neutralised with citric acid, stained with iodine, diluted with water, and evaluated in an ELISA plate reader at 620 nm. The overall method provided cleaner starch than earlier methods, as shown by higher apparent amylose values, and was highly repeatable. The method was used to demonstrate the variation in amylose content within single heads of an inbred tetraploid wheat. No consistent patterns of variation due to seed location were detected but the overall breadth of variation around the median value of 27 % was ± 5 %.

Preparation and evaluation of a time-controlled release capsule made of ethylcellulose for colon delivery of drugs.

A novel ethylcellulose (EC) capsule which releases drug with a time-controlled fashion has been prepared. This capsule is composed of four parts, drug container, swellable substance, capsule body and cap. At the bottom of the body, micropores are made. As water penetrates through these micropores, the swellable substance such as low substituted hydroxypropyl cellulose (L-HPC) swells. When the cap made of water-insoluble macromolecular substance such as EC cannot persist the swelling pressure, the EC cap disintegrates and the drug in the container is released from the capsule. The lag-time is utilized for the delivery of drug to the colon. The release time of the drug from the capsule was measured both in vitro and in vivo experiments. In the case of an in vitro experiment, after 12mg of fluorescein as a model drug and 238mg of starch were filled into the container, caps having different thickness were attached to the capsule body and release study was performed. The release time of the drug was mainly dependent on the thickness of the cap. Using test capsules of which mean cap thickness were 39.1 +/- 2.3 (SE)microns, 63.1 +/- 5.0 microns and 75.6 +/- 4.1 microns, the in vivo release time was estimated after administration to beagle dogs. As a parameter, the peak time (tmax) when plasma fluorescein concentration reached to its maximum level was determined for the estimation of the release time of the drug from the capsule in the gastrointestinal tract. The in vivo tmax was well correlated with the cap thickness.(ABSTRACT TRUNCATED AT 250 WORDS)

Assessing genotypic softness in single wheat kernels using starch granule-associated friabilin as a biochemical marker

The end-use quality of wheat (Triticum aestivum L.) is determined in large part by the texture of the grain (soft or hard). Endosperm texture is currently determined by several empirical methods. These methods are limited because the use bulk grain lots, as opposed to individual kernels; assess phenotypic, as opposed to genotypic hardness; require a quantity of grain greater than that generally available in the early generations of wheat breeding programs, and are destructive. Recent approaches that use single kernels address the problems associated with bulk grain lots, but suffer the other limitations of providing only the phenotype and being destructive. An objective method for determining the texture genotype of single kernels of wheat was developed using starch granule-associated friabilin, a family of closely related 15 kDa proteins, as a biochemical marker. The occurrence of friabilin on water-washed wheat starch granules is apparently unaffected by the environment and is perfectly correlated (no exceptions) with grain softness. The technique presented here can detect friabilin on as little as 0.2 mg of starch and provides a 250-fold improvement in friabilin detection compared to previous methods. The method is capable of correctly assessing the genotype of F1 heterozygotes from hard x soft and soft x hard crosses. Further, the method uses only a portion of the endosperm from the kernel and therefore accommodates embryo propagation and high molecular weight glutenin subunit characterization. This single kernel method also facilitates the genetic characterization of mixed, bulk grain lots.

Amylase synthesis inAspergillus flavus andAspergillus niger grown on cassava peel

Aspergillus flavus andAspergillus niger produce extracellular amylase into the culture medium when grown on basal medium containing 2% (w/v) soluble starch or cassava peel as the sole carbon source. On soluble tarch the highest amylase activities were 1.6 and 5.2 mg of starch hydrolyzed/min per mg protein forA. flavus andA. niger, respectively. When grown on cassava peel, the highest amylase activity in the culture filtrate ofA. flavus was 170-times higher than that on soluble starch, while that ofA. niger was 16-times higher. The mycelial dry weight for both organisms was not significantly affected by the carbon sources. Maximum enzyme activity was obtained at the growth temperature of 29.0±1°C and pH 7 for both organisms. It is concluded that cassava peel might be a better substrate for the production of amylase byA. flavus andA. niger than commercial soluble starch.

Carbohydrate Partitioning and Nodule Function in Common Bean after Heat Stress

Previous work has shown that daily temperature maxima of 38 °C eliminate N2‐fixing activity in common bean (Phaseolus vulgaris L.) in less than 3 d. The purpose of this work was to (i) determine if this response is related to diminished supply of C to nodules and (ii) investigate the recovery of nodule function following short‐term heat stress. ‘Jutiapa’ was grown in sand culture at 26/22 °C (day/night) until 16 d after planting, then transferred to 38/22 °C for 6 d. Acetylene reduction activity (ARA) was eliminated at 38 °C, but nodule concentrations of sucrose and glucose at that temperature were equal or higher than at 26 °C throughout the 6‐d period. Stressed nodules and controls had 127 ± 12 and 90 ± 10 mg of starch per g of dry weight, respectively, after 3 d of treatment, which was the largest difference observed. Treated plants tended to have higher levels of sucrose, glucose, and starch in shoots, particularly in stems, than did controls. In a similar experiment, cells of stressed nodules showed loss of cytoplasm and rupture of peribacteroid membranes after 6 d of heat. Recovery of ARA started 1 wk after the removal of the stress; at that point, treated plants and controls had shoot N contents of 30 and 118 mg plant−1, respectively. This N deficiency caused long‐lasting alterations of plant growth and development. The inhibition of nodule function by high temperature was not related to availability of carbohydrate, but to the breakdown of the bacteria‐infected cells.

Naltrexone blocks the enhancing effect of novel experiences on performance in memory tests in humans

Two experiments were carried out in healthy human volunteers in order to investigate the effect of novel experiences on retrieval, and the influence of naltrexone thereupon. Naltrexone (50 mg) and placebo (50 mg of starch) were given orally using a double blind design. In Experiment 1, the subjects were asked, on two consecutive days, to recall well-known facts or events, and to recall the year in which major events took place. On Day 2, some subjects were, and others were not, exposed to a nonsense text prior to testing, which was viewed as a novel experience by the subjects. Exposure to the text was followed by enhanced scores in both memory tests. The effect was blocked by naltrexone, but not by the placebo, given 1 hr prior to the novel experience; the treatments had no effect of their own in subjects unexposed to the nonsense text. In Experiment 2, the memory tests were the recognition of famous faces, and the dates test (see above); and the novel experience was being taken for 5 min to a room where they had never been before. Again, the novel experience was followed by increased scores in both memory tests in the untreated and placebo groups, but not in the naltrexone treated subjects. These results confirm previous findings on memory enhancement by pre-test exposure to novel experiences, and suggests that endogenous opioid, or at least naltrexone-sensitive, mechanisms are involved in the effect.

The Interaction of the Amylose‐Extender and Waxy Mutants of Maize (Zea Mays L.) Fine Structure of Amylose‐Extender Waxy Starch

AbstractInvestigations into the nature of the effect of the amylose‐extender (ae) mutant of maize (Zea mays L.) on amylopectin structure were conducted by studying the fine structure of amylose‐extender waxy (ae wx) starch. Approximately 59.6% of the starch from ae wx endosperms was converted to maltose by β‐amylase. This starch contained 21% apparent amylose and had a λmax of 580 for the iodine‐starch complex. Fractionation of ae wx starch on Sepharose 4B‐200 gave an elution profile with a single peak characteristic of amylopectin. From these observations we concluded that ae wx starch consisted of an altered amylopectin, with iodine binding properties such that an apparent amylose content of 21% was measured.The fine structures of ae wx and waxy (wx) starches were determined. Pullulanase‐debranched chains of whole starches and β‐limit dextrins were fractionated by gel permeation. The amylopectin of ae wx was shown to be a loosely branched amylopectin with an average internal chain length of 52 glucose units compared with a length of 30 glucose units for wx. The ae wx outer chains were longer than those of wx and fewer in number per mg of starch. These characterizations demonstrate that ae wx starch has a unique structure which is similar to the anomalous amylopectin reported in ae starch.

STARCH PERITONITIS — A HAZARD OF SURGICAL GLOVE POWDER

Starch peritonitis, a granulomatous reacton to surgical glove powder, is reported in four patients. The condition presents as a well defined clinical syndrome, and should perferably be diagnosed clinically to avoid reoperation and the risk of introduction of more starch. Studies show that a mean of 107 mg of starch per pair is present on the outside of Austrailn-made surgical gloves. It is suggested that gloves be rinsed and dried before operation and it is recommended that a warning to this effect be printed on glove packets.

Quantitative separation of starch components on a cellulose column

Ethanol-induced adsorption of amylose on a cellulose column equilibrated with ethanol-urea is used for the quantitative separation of amylose and amylopectin from starch. Under these conditions, amylose is completely retained on the column. The column is washed free of amylopectin and the adsorbed amylose is eluted by gradient elution with ethanol-urea. Samples containing 300–400 mg of starch can be successfully fractionated on a column packed with defatted cellulose (20 g) with a recovery of 95±2%. The elution profile reveals the heterogeneity of native amylose.

Enzymes of starch metabolism in leaves and berries of Vitis vinifera

Leaves of Vitis vinifera L., cv. Cabernet Sauvignon contained 2.0 mg of starch per g fresh weight, whereas young green berries and maturing grape berries contained less than 0.03 mg of starch, despite the presence of abundant substrates (reducing sugars and sucrose) in berries for starch synthesis. the activities of several enzymes likely to be involved in starch synthesis were determined in extracts of berries and leaves. Fractionation procedures resulted in final recoverable ADPglucose-starch glucosyltransferase activity which was 2–3 times the activity measured in crude extracts of leaves. Compared to leaves, berries contained low activities of ADPglucose-starch glucosyltransferase and ADPglucose pyrophosphorylase. These enzymes increased only 2- to 3-fold from young to maturing berries. ADPglucose-starch glucosyltransferase activity in the absence of added primer was found in leaf extracts but not in berry extracts. The activities of UDP-glucose pyrophosphorylase, phosphorylase and amylase were comparable in both leaves and berries and increased 6- to 7-fold during berry development. The low activities of ADPglucose-starch glucosyltransferase and ADPglucose pyrophosphorylase probably account for the paucity of starch in grape berries.

Determination of the Tryptophan Content of Proteins by Ion Exchange Chromatography of Alkaline Hydrolysates

Abstract A study of the variables in techniques for alkaline hydrolysis of proteins and for chromatographic analysis of the products has led to a method for the accurate determination of tryptophan. Quantitative recoveries of tryptophan are obtained when proteins (1 to 5 mg) are hydrolyzed at 110° or 135° in 0.6 ml of 4.2 n NaOH containing 25 mg of starch. The hydrolysis is performed in polypropylene liners sealed inside glass tubes evacuated to below 50 µm of mercury. Ion exchange chromatography of tryptophan on Beckman PA-35 resin (column height 8 or 12 cm) has been accomplished in 30 to 50 min with pH 5.4 buffer, 0.21 n in Na+. The details in the procedure which make possible complete recovery of tryptophan include: (a) addition of the sample at pH 4.25 instead of at pH 2.2 in order to avoid loss of tryptophan in citrate buffer at acid pH; (b) the use of NaOH instead of Ba(OH)2 to avoid loss of tryptophan by adsorption on BaSO4 or BaCO3; (c) the inclusion of starch as the most effective antioxidant tested; and (d) chromatography with a buffer which separates tryptophan from Ne-(dl-2-amino-2-carboxyethyl)-l-lysine, which can be formed in significant quantities during alkaline hydrolysis. Molar calculations of protein concentrations are based on the results from analysis of an acid hydrolysate run parallel with the alkaline hydrolyses. Integral values (100 ± 3%) have been obtained for the expected number of tryptophan residues in tryptophyl-leucine, human serum albumin, porcine pepsin, sperm whale apomyoglobin, and in bovine α-chymotrypsin, trypsin, deoxyribonuclease, and serum albumin. Since carbohydrate does not interfere, the procedure is applicable to foods and has been tested on normal and opaque-2 maize meals and on wheat flours.

Studies on amylase of Fusarium vasinfectum

A method for the extraction and partial purification (about 20-fold) of amylase from the cotton wilt pathogen Fusarium vasinfectum is described. The enzyme exhibits maximum activity between 45 ° and 50 °C, with three pH optima between 4.4 to 8.0 and a Km value of 0.31 mg of starch. Inhibition studies with thiol group inhibitors and EDTA, as well as activation studies with metal ions, revealed no significant influence of these agents on enzyme activity. However, the enzyme is inhibited to some extent by Mn ++, Cu ++ and Zn ++ and is irreversibly denatured both at elevated temperatures (70 °C) and at high hydrogen ion concentration (pH 2.0). The results are discussed in relation to pathogenicity of this fungus towards the cotton plant.

Studies in bacterial amylase: III. Influence of the concentration of the cultural nutrients on the formation of bacterial amylase

1. 1. The ratio between ammonium nitrate and carbohydrate in the culture medium has been found to exert a definite influence on the amylase secretion of B. subtilis, N.C.T.C.; 2027 N, and on its growth. 2. 2. Among the various ratios 1:50 is the optimum, giving the maximum amylase yield. 3. 3. Higher concentrations of ammonium nitrate and starch, while maintaining the ration 1:50, are also found to influence the secretion of amylase. Amounts of 8 mag ammonium ntirate and 400 mg of starch per 10 ml of culture medium give the highest yield of the enzyme. 4. 4. Mineral salts are indespensable for the formation of bacterial amylase. The absence of any of the salt studied results in a decrease in amylase yield. 5. 5. Potassium hydrogen phosphate seems to be very essential, as its absence prevents the bacterial growth. 6. 6. The beneficial influence of salts on the formation of amylase is in the following order: K 2HPO 4 > CaCl 2 > NaCl > FeSo 4 > MgSO 4 > MnSO 4 7. 7. The optimum concenration of different salts for the production of amylase has been determined.