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PubMed2001

Composite starch-based coatings applied to strawberries (Fragaria ananassa).

Starch-based coatings were used to the extend storage life of strawberries (Fragaria ananassa) stored at 0 degree C and 84.8% relative humidity. Effects of coating formulation (including starch type, plasticizer, lipid and antimicrobial agent) were analysed with respect to fruit quality. Plasticizer addition was necessary for film and coating integrity to avoid pores and cracks. Plasticizer presence reduced weight losses and maintained surface colour of fruits. Amylomaize coatings showed lower water vapour and gas permeabilities and decreased weight losses for longer periods than corn starch ones. Coatings with sorbitol showed lower permeabilities than glycerol ones. Coatings with antimicrobial agents decreased microbial counts, extending storage life of coated fruits by 10 to 14 days in comparison to the control. The addition of 2 g/l sunflower oil to the formulations decreased the water vapour permeability of starch-based films, maintained the surface colour of coated fruits and controlled effectively fruit weight losses during storage. Lipid addition minimized the effects of starch and plasticizer types. Composite starch-based coatings showed selective gas permeability (CO2 higher than O2) which helps to delay senescence of fruits.

Biofilms↗
PubMed2006

The evolution of putative starch-binding domains.

The present bioinformatics analysis was focused on the starch-binding domains (SBDs) and SBD-like motifs sequentially related to carbohydrate-binding module (CBM) families CBM20 and CBM21. Originally, these SBDs were known from microbial amylases only. At present homologous starch- and glycogen-binding domains (or putative SBD sequences) have been recognised in various plant and animal proteins. The sequence comparison clearly showed that the SBD-like sequences in genethonin-1, starch synthase III and glucan branching enzyme should possess the real SBD function since the two tryptophans (or at least two aromatics) of the typical starch-binding site 1 are conserved in their sequences. The same should apply also for the sequences corresponding with the so-called KIS-domain of plant AKINbetagamma protein that is a homologue of the animal AMP-activated protein kinase (AMPK). The evolutionary tree classified the compared SBDs into three distinct groups: (i) the family CBM20 (the motifs from genethonins, laforins, starch excess 4 protein, beta-subunits of the animal AMPK and all plant and yeast homologues, and eventually from amylopullulanases); (ii) the family CBM21 (the motifs from regulatory subunits of protein phosphatase 1 together with those from starch synthase III); and (iii) the (CBM20+CBM21)-related group (the motifs from the pullulanase subfamily consisting of pullulanase, branching enzyme, isoamylase and maltooligosyl trehalohydrolase).

Animals↗
PubMed2001

Repression of starch degradation under anaerobic conditions by irregularly high levels of ATP in Chlamydomonas sp. MGA161.

It is generally known that in green algal species the acceleration of starch degradation upon transition from aerobic to anaerobic conditions is a result of the Pasteur effect in glycolysis. However, the acceleration of starch degradation did not occur in cells of Chlamydomonas sp. MGA161. In MGA161 cells, the anaerobic ATP level, which decreased to about half of the aerobic ATP level in cells of Chlamydomonas reinhardtii after fermentation for 2 h, was kept higher than its aerobic ATP level. Gramicidin D, a monovalent cation ionophore, markedly decreased the anaerobic and aerobic ATP levels due to the increase in ATP demand, accompanied by the acceleration of starch degradation in MGA161 cells. Although the anaerobic ATP level of C. reinhardtii cells was partially decreased by gramicidin D, starch degradation did not accelerate markedly when compared with the result in MGA161 cells. Therefore, starch was degraded at nearly the maximum rate in C. reinhardtii cells under anaerobic conditions; in contrast, the high level of ATP in MGA161 cells repressed starch degradation even under anaerobic conditions, resulting in the absence of the Pasteur effect.

Journal Article↗
PubMed2004

Effects of culture and medium conditions on hydrogen production from starch using anaerobic bacteria.

The influences of initial pH (4.0-9.0), iron concentration (1.2-100 mg/l), nitrogen concentration (NH4HCO3, 0.56-11.28 g/l) and starch concentration (2-32 g/l) on hydrogen production and volatile fatty acid (VFA) production were studied. Batch experiments using starch as a substrate and mixed bacteria were conducted at 35 degrees C. The optimum pH, iron concentration and nitrogen concentration for hydrogen production at a starch concentration of 15 g/l were 7.0-8.0, Fe2+ 10 mg/l and NH4HCO3 5.64 g/l, respectively. The typical VFAs were acetate, propionate and butyrate, with acetate as the major component. The maximum specific hydrogen production rate of 146 ml/g-VSS.d (volatile suspended solids, VSS) and the hydrogen yield of 178 ml/g-starch were obtained at a starch concentration of 15 g/l under optimum environmental conditions. The maximum hydrogen yield of 194 ml/g-starch was obtained at a starch concentration of 2 g/l. The maximum specific hydrogen production rate of 237 ml/g-VSS.d was found at a starch concentration of 24 g/l.

Journal Article↗
PubMed1999

Photoproduction of hydrogen from raw starch using a halophilic bacterial community.

The bacterial community designated BC1, which originates from night soil treatment sludge, exhibited a strong ability to produce H2 from raw starch in the light in the presence of 3% NaC1. Three halophilic or halotolerant bacterial species, Vibrio fluvialis, Rhodobium marinum, and Proteus vulgaris, were isolated from BC1 and identified. The level of H2 production from starch by coculture of V. fluvialis and R. marinum was nearly equal to that by BC1, indicating that these two strains play roles in starch degradation and H2 production from the degraded products in BC1, respectively. Acetic acid and ethanol, which were detected as the major products of degradation of starch by V. fluvialis in pure culture, seemed to be mainly utilized for H2 production by R. marinum in BC1 and the coculture. However, R. marinum in pure culture could not produce H2 from a synthetic medium containing acetic acid and ethanol, suggesting that V. fluvialis supplied not only substrates but also some unknown factors capable of inducing H2 production from these substrates by R. marinum. A study using the starch-rich microalgae, Chlamydomonas reinhardtii and Dunaliella tertiolecta, demonstrated that the above coculture could be applied to the production of H2 at high yield from raw starch in an algal biomass.

Journal Article↗
PubMed2006

Adsorption of hydrophobically modified starch at oil/water interfaces during emulsification.

The adsorption of starch that had been hydrophobically modified with octenyl succinate anhydride (OSA) at the oil/water interface during emulsification was studied. The starch samples were of waxy barley origin and were varied in molar mass and degree of substitution (DS). The particle size of the emulsions was measured and the adsorbed amount of starch was determined through serum depletion. The results show that adsorption is governed by the relationship between interfacial area and OSA-starch concentration. The surface load of OSA-starch can in some cases become very high, reaching 16 mg/m(2). The emulsification occurs under nonequilibrium and turbulent flow conditions. Under these conditions kinetic factors are likely to play an important role in the adsorption process. Turbulent flow favors transport to the interface of larger molecules over small ones, which could lead to higher surface loads by causing jamming at the interface. A model that treats the adsorption as a collision between particles in turbulent flow has been used, and it shows that the adsorption time of a polymer decreases with increasing polymer radius. It also shows that the time scale of adsorption is shorter than the time scales for configurational changes of macromolecules at interfaces and that emulsion droplet-droplet collisions are of similar time scales as adsorption, which gives further indications that kinetic factors are important during adsorption. The simulation results give a reasonable explanation to why large molecules such as OSA-starch can be efficient as emulsifiers.

Journal Article↗
PubMed1996

The influence of starch structure on glycogen resynthesis and subsequent cycling performance.

The present study was designed to evaluate the influence of starch structure on muscle glycogen resynthesis and cycling performance. Eight male cyclists (22 +/- 1 yr) completed an exercise protocol (DP) to decrease vastus lateralis glycogen concentration. This exercise consisted of 60 min cycling at 75% VO2max, followed by six 1-min sprints at approximately 125% VO2max with 1 min rest intervals. In the 12 hr after the exercise each subject consumed approximately 3000 kcal (65:20:15% carbohydrate, fat and protein). All of the carbohydrate (CHO) consumed was derived from one of four solutions; 1) glucose, 2) maltodextrin (glucose polymer), 3) waxy starch (100% amylopectin), or 4) resistant starch (100% amylose). Muscle biopsies were taken from the vastus lateralis muscle after DP and 24 hr later to determine glycogen concentrations. A 30 min cycling time trial (TT) was performed following the 24 hr post-DP muscle biopsy to examine the influence of the feeding regimen on total work output. The post-DP glycogen concentrations were similar among the four trials, ranging from 220.3 +/- 29.2 to 264 +/- 48.3 mmol.kg-1 dry weight (d.w.) muscle. Twenty-four hours after DP, muscle glycogen concentration had increased less (p < 0.05) in the resistant starch trial (+90.8 +/- 12.8 mmol.kg-1 d.w.) than in the glucose (+197.7 +/- 31.6 mmol.kg-1 d.w.), maltodextrin (+136.7 +/- 24.5 mmol.kg-1 d.w.) and waxy starch (+171.8 +/- 37.1 mmol.kg-1 d.w.) trials. There were no differences in total work output during the TT, or blood lactate concentration immediately following the TT in any of the CHO trials. In summary, glycogen resynthesis was attenuated following ingestion of starch with a high amylose content, relative to amylopectin or glucose; however, short duration time trial performance was unaffected.

Amylopectin↗
PubMed2002

Screening and characterization of facultative psychrophilic denitrifiers for treatment of nitrate contaminated groundwater using starch-based biodegradable carriers.

Potential starch degrading denitrifying microorganisms that can grow at 4 degrees C were isolated from lake sediments to remove nitrate from groundwater. Initial screening using soluble starch as the sole carbon source confirmed that two out of twenty-five isolates (strain no. 2 and 47) significantly reduced nitrate in the medium and liberated nitrogen gas during culture. In a second screening, several commercially available starch based materials and different kinds of starch were tested. Strain 47 was found to have the best denitrification performance compared with strain 2. Using starch based carrier C (a commercial packing material) as carbon source, strain 47 could completely reduce the nitrate nitrogen in the medium after one week of batch culture even at 10 degrees C. Strain 47 could remove nitrate even without trace element supplementation, and it could perform optimally at 1X (10ml l(-1) of trace element solution) level of trace element supplement. The best temperature for denitrification for strain 47 was 15 degrees C and 20 degrees C, but it could also remove nitrate nitrogen at 10 degrees C and 30 degrees C, although at a slower rate. Reactor studies in a simulated treatment well (a cylindrical reciprocating basket reactor) in a repeated fed batch mode showed a good stable denitrification performance as long as substrate limitation is avoided by adequate supply of starch based carrier. Although the similarity score obtained was not enough for phylogenic identification, the results of 16SrRNA sequences analysis for the strain 47 showed a dose relation to Janthinobacterium lividum or Pseudomonas (Janth) mephitica (95.77%).

Bacteria↗
PubMed1986

Seasonal patterns of radial root growth and starch dynamics in plantation-grown Sitka spruce trees of different ages.

Seasonal patterns of radial root growth within 1 m of tree stems were examined in Scottish plantations of Sitka spruce trees aged 9, 15 and 20 years. Results were compared with parallel measurements of shoot extension, radial growth of stems and amounts of starch stored in tissues external to root wood. Youngest trees produced the largest annual increments in root cross-sectional area and numbers of new cells along radial files of tracheids. Irrespective of tree age, new cells were present in roots before bud burst and the onset of radial growth occurred progressively later with increasing distances from the stems. At ages 15 and 20, both stem cross-sectional area and radial root growth up to 0.5 m from the stem base had a minor peak of activity preceding and a major peak following shoot elongation. Further than 0.5 m from the stem, root growth was frequently restricted to the period following shoot extension. Starch storage in the roots reached a maximum in April and May, which was greatest for 9-year-old trees and least for 20-year-old trees. At all ages, radial root growth in early spring occurred concurrently with increased starch storage. Later in the season starch reserves declined rapidly during the period of shoot elongation and root growth occurred whilst reserves were low. At all ages for positions on the root at the base of the stem and 0.25 m from it, starch depletion, at its maximum rate during June, accounted for less than the measured increment of root wood growth at that point. This indicates a substantial translocation of substrates to these zones during growth. At the same time, the reduction in starch concentrations at more distal points from the stem far exceeded that required for local root thickening.

Journal Article↗
PubMed1993

Characterization of Glucose-6-Phosphate Incorporation into Starch by Isolated Intact Cauliflower-Bud Plastids.

Intact plastids from cauliflower (Brassica oleracea var Prince de Bretagne) buds were isolated according to the method described by Journet and Douce (E.P. Journet and R. Douce [1985] Plant Physiol 79: 458-467). Incubation of these plastids with various 14C-labeled compounds revealed that glucose-6-phosphate can act as a precursor for starch synthesis. However, significant rates (incorporation of 120 nmol glucose mg-1 protein h-1) could only be observed when both 3-phosphoglyceric acid and ATP were present as well. Starch synthesis in isolated plastids was strongly dependent upon the intactness of the organelle. The presence of a high-affinity ATP/ADP translocator with a Km for ATP of 12 [mu]M was demonstrated by uptake experiments with [14C]ATP. ADP inhibited both ATP uptake and effector-stimulated starch synthesis. Effector-stimulated glucose-6-phosphate-dependent starch synthesis was not significantly influenced by fructose-6-phosphate or 2-deoxyglucose-6-phosphate but was strongly inhibited by triose phosphate and inorganic phosphate. Starch synthesis was also inhibited by 4,4[prime]-diisothio-cyanostilbene-2,2[prime]-disulfonate, which is known to be a potent inhibitor of the chloroplast phosphate translocator. The data presented here support the view that starch biosynthesis in heterotrophic tissues is powered by increasing levels of cytosolic 3-phosphoglyceric acid and ATP when glucose-6-phosphate is available.

Journal Article↗
PubMed1993

Biochemical Evidence for the Role of the Waxy Protein from Pea (Pisum sativum L.) as a Granule-Bound Starch Synthase.

Proteins were solubilized from starch extracted from developing pea (Pisum sativum L.) embryos and chromatography of these proteins on a Mono-Q column separated two peaks of starch synthase activity. The major activity peak comprised more than 80% of the total activity. This fraction contained only the Waxy protein, as shown by polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate followed by staining for proteins or by immunoblot. A 77-kD polypeptide associated with the starch granules and presumed by others to be a starch synthase could not be detected in any of the active fractions. The native molecular weight of the solubilized starch synthase was 59,600 [plus or minus] 1700 as determined by sucrose density gradient. It is concluded that in pea seeds the Waxy protein and the starch synthase bound to the granule are the same protein.

Journal Article↗
PubMed1995

The Role of Pea Chloroplast [alpha]-Glucosidase in Transitory Starch Degradation.

Pea chloroplastic [alpha]-glucosidase (EC 3.2.1.20) involved in transitory starch degradation was purified to apparent homogeneity by ion exchange, reactive dye, hydroxylapatite, hydrophobic interaction, and gel filtration column chromatography. The native molecular mass and the subunit molecular mass were about 49.1 and 24.4 kD, respectively, suggesting that the enzyme is a homodimer. The enzyme had a Km of 7.18 mM for maltose. The enzyme's maximal activity at pH 7.0 and stability at pH 6.5 are compatible with the diurnal oscillations of the chloroplastic stromal pH and transitory starch accumulation. This pH modulation of the [alpha]-glucosidase's activity and stability is the only mechanism known to regulate starch degradative enzymes in leaves. Although the enzyme was specific for the [alpha]-D-glucose in the nonreducing end as the glycon, the aglycon moieties could be composed of a variety of groups. However, the hydrolysis rate was greatly influenced by the aglycon residues. Also, the enzyme could hydrolyze glucans in which carbon 1 of the glycon was linked to different carbon positions of the penultimate glucose residue. The ability of the [alpha]-glucosidase to hydrolyze [alpha]-1,2- and [alpha]-1,3-glucosidic bonds may be vital if these bonds exist in starch granules because they would be barriers to other starch degradative enzymes. This purified pea chloroplastic [alpha]-glucosidase was demonstrated to initiate attacks on native transitory chloroplastic starch granules.

Journal Article↗
PubMed1995

Influence of Elevated Fructose-2,6-Bisphosphate Levels on Starch Mobilization in Transgenic Tobacco Leaves in the Dark.

The aim of this work was to study the effect of elevated fructose-2,6-bisphosphate (Fru-2,6-bisP) levels on carbohydrate metabolism in leaves in the dark. In transgenic tobacco (Nicotiana tabacum L.) lines containing mammalian 6-phosphofructo-2-kinase activity there is an inverse relationship between the level of Fru-2,6-bisP in leaves and the rate of starch breakdown in the dark. Estimates of the flux response coefficient for the rate of net starch degradation with respect to changes in Fru-2,6-bisP level are -0.57 for whole leaves and -0.69 to -0.89 for excised leaf discs. We suggest that this decrease in the net rate of starch breakdown is caused, at least in part, by stimulation of unidirectional starch synthesis. Measurements of the levels of metabolic intermediates and the metabolism of [U-14C]glucose indicate that the stimulation of starch synthesis in the dark is a result of high Fru-2,6-bisP levels, increasing the 3-phosphoglycerate:inorganic phosphate ratio in leaves. We argue that the observed response to changes in the level of Fru-2,6-bisP are effected through activation of pyrophosphate:fructose-6-phosphate 1-phosphotransferase. However, the extent to which changes in Fru-2,6-bisP influence starch metabolism in wild-type plants is not known.

Journal Article↗
PubMed1997

Influence of Gene Dosage on Carbohydrate Synthesis and Enzymatic Activities in Endosperm of Starch-Deficient Mutants of Maize.

In cereals, starch is synthesized in endosperm cells, which have a ploidy level of three. By studying the allelic dosage of mutants affecting starch formation in maize (Zea mays L.) kernels, we determined the effect of down-regulated enzyme activity on starch accumulation and the activity of associated enzymes of carbohydrate metabolism. We found a direct relationship between the amount of starch produced in the endosperm and the gene dosage of amylose extender-1, brittle-2, shrunken1, and sugary-1 mutant alleles. Changes in starch content were found to be caused by changes in the duration as well as the rate of starch synthesis, depending on the mutant. Branching enzyme, ADP-glucose pyrophosphorylase, and sucrose synthase activities were linearly reduced in endosperm containing increasing dosages of amylose extender-1, brittle-2, and shrunken-1 alleles, respectively. De-branching enzyme activity declined only in the presence of two or three copies of sugary-1. No enzyme-dosage relationship occurred with the dull1 mutant allele. All mutants except sugary-1 displayed large increases (approximately 2- to 5-fold) in activity among various enzymes unrelated to the structural gene. This occurred in homozygous recessive genotypes, as did elevated concentrations of soluble sugars, and differed in magnitude and distribution among enzymes according to the particular mutation.

Journal Article↗
PubMed1997

Starches from A to C. Chlamydomonas reinhardtii as a model microbial system to investigate the biosynthesis of the plant amylopectin crystal.

Wide-angle powder x-ray diffraction analysis was carried out on starch extracted from wild-type and mutant Chlamydomonas reinhardtii cells. Strains containing no defective starch synthases as well as mutants carrying a disrupted granule-bound starch synthase structural gene displayed the A type of diffraction pattern with a high degree of crystallinity. Mutants carrying a defect for the major soluble starch synthase (SSS), SSS II, were characterized by a switch to the B type of diffraction pattern with very low crystallinity. Mutant strains carrying SSS I as the only glucan elongation enzyme regained some of their crystallinity but switched to the C type of diffraction pattern. Differential scanning calorimetry analysis correlated tightly with the x-ray diffraction results. Together with the electron microscopy analyses, these results establish C. reinhardtii as a microbial model system displaying all aspects of cereal starch synthesis and structure. We further show that SSS II is the major enzyme involved in the synthesis of crystalline structures in starch and demonstrate that SSS I alone builds a new type of amylopectin structure.

Amylopectin↗
PubMed2001

Identification of Mutator insertional mutants of starch-branching enzyme 2a in corn.

Starch-branching enzymes (SBE) break the alpha-1,4 linkage of starch, re-attaching the chain to a glucan chain by an alpha-1,6 bond, altering starch structure. SBEs also facilitate starch accumulation by increasing the number of non-reducing ends on the growing chain. In maize (Zea mays), three isoforms of SBE have been identified. To examine the function of the SBEIIa isoform, a reverse genetics polymerase chain reaction-based screen was used to identify a mutant line segregating for a Mutator transposon within Sbe2a. To locate the insertion within the second exon of Sbe2a, the genomic sequence of Sbe2a containing the promoter and 5' end was isolated and sequenced. Plants homozygous for sbe2a::Mu have undetectable levels of Sbe2a transcripts and SBEIIa in their leaves. Characterization of leaf starch from sbe2a::Mu mutants shows reduced branching similar to yet more extreme than that seen in kernels lacking SBEIIb activity. Characterization of endosperm starch from sbe2a::Mu mutants shows branching that is indistinguishable from wild-type controls. These mutant plants have a visible phenotype resembling accelerated senescence, which was correlated with the Mutator insertion within Sbe2a. This correlation suggests a specific role for SBEIIa in leaves, which may be necessary for normal plant development.

1,4-alpha-Glucan Branching Enzyme↗
PubMed1966

Auxin and gibberellin effects on cell growth and starch during abscission in cotton.

An increase in starch content of cells in the abscission zone of the cotton explant appeared correlated with an increase in number of cells. A large increase in the number of cells in the abscission zone, concomitant with an increase in starch content, followed treatment with gibberellin as compared to auxin. In the final stages of abscission starch was hydrolyzed in the cells of the separation layer. Some starch remained after the petiole abscised.A positive phloroglucinol-hydrochloric acid reaction in the cells of the petiole distal to the line of separation indicated the presence, not of lignin, but of soluble sugars and uronic acids. This reaction was especially intense following gibberellic acid treatment.It was concluded that gibberellin in accelerating abscission leads to (1) an increase in cell number and starch content in the abscission zone, (2) the hydrolysis of starch in the separation layer just before abscission, and (3) the breakdown of polysaccharides and the release of soluble sugars and uronic acids. Auxin, an abscission retardant, either delays or prevents these events.

Journal Article↗
PubMed1975

Zinc Nutrition and Starch Metabolism in Phaseolus vulgaris L.

The effect of Zn nutrition on leaf starch metabolism was studied in two navy bean (Phaseolus vulgaris L.) varieties, Sanilac and Saginaw. Sanilac is much more susceptible to Zn deficiency than is Saginaw. The variables examined in these two strains were starch content, the activity of soluble starch synthetase (ADP-glucose: starch alpha-4-glucosyltransferase, EC 2.4.1.b), and the size and number of starch grains. All of these variables decreased during Zn deficiency. The reductions were much greater in Sanilac than in Saginaw. Thus, positive correlations exist between the relative changes in these variables in Sanilac and Saginaw under low Zn and their genotypic difference in growth response to low Zn. These results are taken to purport that the above observations most likely represent characteristic responses to Zn deficiency. We therefore suggest that, as a possible role in plant metabolism, Zn is involved in starch formation.

Journal Article↗