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PubMed2006

[Key enzymes in starch synthesis in plants].

Starch, the most common form of stored carbon in plants, is both the major food source for mankind and important raw material for many industries. It is composed of two types of alpha-1,4-linked glucan polymer: essentially unbranched amylose and regularly branched amylopectin, and synthesized in photosynthetic and non-photosynthetic organs. Starch is synthesized via four committed enzyme steps: ADP-Glc pyrophosphorylase, which synthesizes sugar nucleotide precursors; starch synthase, which extends the alpha-1,4-linked glucan chains using ADP-Glc; starch-branching enzymes, which introduce alpha-1,6 branch points to form amylopectin; and starch debranching enzymes, which hydrolyze alpha-1,6 branches in glucans. In this paper, recent advances in biochemical characterizations and gene engineering concerning these enzymes were reviewed, and the achievements in gene engineering involved in manipulation of starch amount and quality were also cited.

1,4-alpha-Glucan Branching Enzyme↗
PubMed1999

Fermentation of starch by Klebsiella oxytoca p2, containing plasmids with alpha-amylase and pullulanase genes.

Klebsiella oxytoca P2(pC46), an ethanol-producing recombinant, has been evaluated in fermentation of maltose and starch. The maximum ethanol produced by P2(pC46) was 0.34 g ethanol/g maltose and 0.38, 0.40, or 0.36 g ethanol/g starch in fermentation of 1, 2, or 4% starch, representing 68, 71, and 64% the theoretical yield. The pC46 plasmid transformed to cells of K. oxytoca P2 reduced the ethanol production from maltose and starch. In fermentation of starch after its digestion at 60 degrees C for 24 h, in two-step fermentation, the time for maximum ethanol production was reduced to 12-24 h and the theoretical yield was around 90%. The increase in starch concentration resulted in lower alpha-amylase activity but in higher pullulanase activity. The high activity and thermostability of the amylolytic enzymes from this transformant suggest that it has a potential for amylolytic enzymes source.

Enzyme Stability↗
PubMed2000

Effect of processing on potato starch: in vitro availability and glycaemic index.

The content of digestible starch (DS) and resistant starch (RS) in processed potatoes was assessed. In addition, the effect of domestic cooking on the in vitro digestibility of starch in this tuber, which may influence the glycaemic response, was studied. Resistant starch in raw potato is high, however different RS values were obtained when processed, ranging from 1.18% in boiled potatoes to 10.38% in retrograded flour. In general, cooked potatoes have high levels of DS. Starch digestibility is improved after processing and it is affected by the cooking methods. Boiled and mashed potatoes showed the highest rate of digestion, on the contrary raw potato was hardly digested. The estimated Glycaemic Index (GI) from the degree of starch hydrolysis within 90 min was in accordance with the reported GI values, for potatoes processed in the same way.

Algorithms↗
PubMed2001

The effect of water content on the ordered/disordered structures in starches.

(13)C cross-polarization magic angle spinning NMR has been used to study the ordered and disordered structures of starches with different water contents. The amorphous regions of starch have been shown to produce NMR patterns only if they are in a glassy state, the widths, positions, and areas of the peaks to some extent being dependent on the temperature and the water content of the starch. In the amorphous region, the peaks were all Gaussian in shape, while the peaks in the ordered regions had Lorentz profiles. Water contents in the range 10-50% did not influence the proportion of double helices in the starch. Decreasing the water content to 1-3%, however, resulted in a significant decrease in the proportion of double helices, the effect being greater in B- than in A-type starches. It is suggested that short-range order structures in starches (double helices) are stabilized by becoming part of long-range order structures (crystallites).

Carbohydrate Conformation↗
PubMed2002

Capacity of edible seaweeds to modify in vitro starch digestibility of wheat bread.

The capacity of two species of edible seaweeds (Wakame, Undaria pinnatifida and Chondrus, Chondrus crispus) to modify the rate of white bread starch digestibility by an in vitro digestion system, as well as glucose retardation index and apparent viscosity were studied. Both Algae showed different effect on glucose retardation index. While Wakame did not make difficult dialysis of glucose, it only retained 2.50 +/- 2.99% to respect a negative control. Chondrus impaired the diffusion of a 28.70 +/- 2.35% of glucose, which are very close to those of citrus pectin (31.50 +/- 4.12%). On the other hand, viscosity of Chondrus solution was higher than Wakame and slightly lower than citrus pectin solution. The analysis showed a very low content of total starch in Wakame (0.51%) and Chondrus (0.47%). Algae reduced the digestion of white bread starch. The profile of starch hydrolysis was characteristic for each alga. Glycaemic index estimated from the degree of starch hydrolysis within 90 min was low (79) with respect to white bread (value 100). Seaweeds showed a suitable capacity to modify in vitro starch digestibility of white bread. Chondrus produces a more pronounced response. This fact seem to be due to different composition of samples.

Bread↗
PubMed2002

Fabrication of porous hydroxyapatite bodies by a new direct consolidation method: starch consolidation.

A new direct consolidation method known as "starch consolidation" was developed especially for the fabrication of porous ceramics, as adopted to prepare hydroxyapatite (OHAp) bodies with different pore sizes and pore volume fractions. The method is based on the swelling ability of starch when it is heated to 80 degrees C in the presence of water. An OHAp powder prepared by a precipitation method and heat treated at 900 degrees C to obtain an appropriate specific surface area for colloidal processing was used in the present work. Wet ball milling was required to deagglomerate the powder and improve its processing ability. Different starch volume fractions and starch particle sizes were added to the OHAp slurries, which were then heat treated to promote consolidation by starch gelification. A linear relationship between the planned and measured porosity values was observed. SEM pictures reveal the presence of interconnected pores with shape and sizes corresponding to starch granules used. Flexural strength varied from about 2 to 15 MPa, for pore volume fractions of approximately 70 and 45%, respectively. A degradation study in an acellular synthetic body fluid (SBF) has shown that the prepared bodies keep their integrity under physiological conditions during the studied time. The method offers possibilities of manufacturing materials that can be used as scaffolds engineering and/or systems for controlled delivery of drugs.

Adsorption↗
PubMed1995

Development of yeast strains for the efficient utilisation of starch: evaluation of constructs that express alpha-amylase and glucoamylase separately or as bifunctional fusion proteins.

Eight constructions involving the Bacillus subtilis alpha-amylase gene (amyE), a mouse pancreatic alpha-amylase cDNA (AMY2) and an Aspergillus awamori glucoamylase cDNA (glaA) were prepared: three fusion genes, involving one alpha-amylase and the glucoamylase, two double-cassette plasmids (expressing one or other alpha-amylase and the glucoamylase) and three single-cassette plasmids, expressing the individual coding sequences. Following transformation of each plasmid into Saccharomyces cerevisiae, a plate test revealed that the largest starch hydrolysis halo was produced by the strain bearing the B. subtilis alpha-amylase/glucoamylase fusion (BsAAase/GAase), and the smallest halo by the one expressing the mouse pancreatic alpha-amylase/glucoamylase fusion (MAAase/GAase). When assayed for enzymatic activity in liquid medium, the strains bearing the fusion and the double-cassette plasmids involving B. subtilis alpha-amylase and the glucoamylase exhibited both enzymic activities. Moreover, the BsAAase/GAase hybrid was able to adsorb and digest raw starch. The MAAse/GAase fusion protein was found to exhibit only alpha-amylase activity. Finally, the capacity to grow on soluble and corn starch was tested in liquid medium for the strains bearing plasmids coding for the fusion proteins and the separate enzymes. The strain carrying the double-cassette BsAAase + GAase, which produced one of the smallest hydrolysis haloes in the place test, showed the best performance, not only in digesting soluble and corn starch but also in using all of the hydrolysis products for growth. The transformant bearing the BsAAase/GAase fusion was able to grow on soluble starch, but not on corn starch.

Animals↗
PubMed1991

Inhibition of the expression of the gene for granule-bound starch synthase in potato by antisense constructs.

Granule-bound starch synthase [GBSS; EC 24.1.21] determines the presence of amylose in reserve starches. Potato plants were transformed to produce antisense RNA from a gene construct containing a full-length granule-bound starch synthase cDNA in reverse orientation, fused between the cauliflower mosaic virus 35S promoter and the nopaline synthase terminator. The construct was integrated into the potato genome by Agrobacterium rhizogenes-mediated transformation. Inhibition of GBSS activity in potato tuber starch was found to vary from 70% to 100%. In those cases where total suppression of GBSS activity was found both GBSS protein and amylose were absent, giving rise to tubers containing amylose-free starch. The variable response of the transformed plants indicates that position effects on the integrated sequences might be important. The results clearly demonstrate that in tubers of potato plants which constitutively synthesize antisense RNA the starch composition is altered.

Amylose↗
PubMed1995

Effects of soaking, cooking and fermentation on composition, in-vitro starch digestibility and nutritive value of common beans.

A common bean variety, grown in Burundi, was either fermented, soaked and/or cooked, and then assessed for nutrient composition, in-vitro starch digestibility and protein nutritive value. A decrease in ash, most minerals, vitamins, and some essential amino acids was noted for soaked, cooked and soaked-cooked beans. Compared to untreated beans, soaking decreased soluble sugar (9.8 percent) but increased starch (7.3 percent) and soluble fiber (16.9 percent). In cooked beans, an increase in soluble sugar (1.5 percent), and a decrease in thiamine (81.7 percent), starch (24.6 percent) and soluble fiber (16.6 percent) and nitrogen (2.9 percent) contents were observed. Crude fiber (6.9 percent) and starch (10.0 percent) increased while fat (17.6 percent), fatty acids (linoleic: 10.7 percent; linolenic: 14.3 percent) and soluble sugars (25.4 percent) and nitrogen (14.4 percent) decreased in soaked-cooked beans. Fermentation increased potassium (11.6 percent), soluble fiber (18.9 percent), and some amino acids but decreased fatty acids (linoleic: 13.5 percent; linolenic: 19.9 percent), soluble sugar (75.2 percent) and vitamin (riboflavin: 41.0 percent; niacin: 24.5 percent) contents in common beans. However, the in-vitro starch digestibility was greatly improved (12.3 percent) by cooking while it decreased in soaked beans (29.2 percent). Soaking-cooking and fermentation did not have any significant effect on the digestibility of common bean starch. Finally, among the five treatments applied to common beans, only fermentation showed a significant improvement (8.3 percent) on the protein nutritive value of this legume.

Amino Acids↗
PubMed1992

Commercial soybean starch blocker consumption: impact on weight gain and on copper, lead and zinc status of rats.

A commercial 'starch blocker' was used to study the digestion of starch (potato) in mature female rates for four weeks. Two levels of 'starch blocker' were used. The first level was calculated to inhibit starch digestion at 50%, the second was calculated to inhibit starch digestion at 100%. No significant effects on the body weights (271.10 +/- 29, 277.7 +/- 43, 259.1 +/- 25 g) were found among the groups of rats at 0%, 50% and 100% inhibition levels, respectively. Feed intakes were not affected. However, fecal copper and zinc excretions increased significantly (p less than 0.05) due to the inhibitors. Fecal copper excretions were 0.468 +/- 0.14, 0.578 +/- 0.09, 0.617 +/- 0.07 mg/rat/week, while fecal zinc values were 0.625 +/- 0.14, 0.859 +/- 0.32 and 0.778 +/- 0.26 mg/rat/week when no inhibitor was fed, at 50% inhibition and at 100% inhibition respectively. Thus, while use of 'starch blockers' did not promote weight loss in the mature female rats, utilization of copper and zinc were negatively affected.

Amylases↗
PubMed1994

The effect of hydroxyethyl starch and other plasma volume substitutes on endothelial cell activation; an in vitro study.

OBJECTIVE: To study the effect of medium molecular weight hydroxyethyl starches on endothelial cell and neutrophil activation in vitro. SETTING: Laboratory analysis. METHODS: The effects of albumin and hydroxyethyl starch on the neutrophil adhesion molecule (CD11bCD18), with and without lipopolysaccharide stimulation, were studied in whole blood. E-selectin expression on human umbilical vein endothelial cells was stimulated with lipopolysaccharide alone and in the presence of either albumin or hydroxyethyl starch. The effect of albumin and hydroxyethyl starches on rapid endothelial cell activation was studied using von Willebrand factor release as a marker. MEASUREMENTS AND RESULTS: Hydroxyethyl starches but not albumin inhibited stimulated vWF release in a dose dependent manner. No effect was seen on endothelial E-selectin or neutrophil CD11bCD18 expression. CONCLUSIONS: these results suggest a possible beneficial role of hydroxyethyl starches in the inhibition of endothelial activation thus preventing neutrophil adhesion during sepsis syndrome.

Cell Adhesion↗
PubMed2001

Anaerobic fermentation of gelatinized sago starch-derived sugars to acetone-1-butanol-ethanol solvent by Clostridium acetobutylicum.

A study of the kinetics and performance of solvent-yielding batch fermentation of individual sugars and their mixture derived from enzymic hydrolysis of sago starch by Clostridium acetobutylicum showed that the use of 30 g/L gelatinized sago starch as the sole carbon source produced 11.2 g/L total solvent, i.e. 1.5-2 times more than with pure maltose or glucose used as carbon sources. Enzymic pretreatment of gelatinized sago starch yielding maltose and glucose hydrolyzates prior to the fermentation did not improve solvent production as compared to direct fermentation of gelatinized sago starch. The solvent yield of direct gelatinized sago starch fermentation depended on the activity and stability of amylolytic enzymes produced during the fermentation. The pH optima for alpha-amylase and glucoamylase were found to be at 5.3 and 4.0-4.4, respectively. alpha-Amylase showed a broad pH stability profile, retaining more than 80% of its maximum activity at pH 3.0-8.0 after a 1-d incubation at 37 degrees C. Since C. acetobutylicum alpha-amylase has a high activity and stability at low pH, this strain can potentially be employed in a one-step direct solvent-yielding fermentation of sago starch. However, the C. acetobutylicum glucoamylase was only stable at pH 4-5, maintaining more than 90% of its maximum activity after a 1-d incubation at 37 degrees C.

1-Butanol↗
PubMed2004

Why does the establishment of the starch preferring Entodinium caudatum in the rumen decrease the numbers of the fibrolytic ciliate Eudiplodinium maggii?

The effect of the establishment of Entodinium caudatum on the population of Eudiplodinium maggii was examined in the rumen of three sheep fed a hay/ground barley diet. The cell concentration of E. maggii were 15.9-38.5 and 11.7-12.4 x 10(3) cells per g of the rumen contents in the absence and presence of E. caudatum, respectively. Microscopic analysis showed that starch was the only material engulfed by eudiplodinia irrespective of the time after feeding and the presence or absence of E. caudatum. Up to 82-93% of individuals contained starch grains when E. maggii was the only ciliate species in the rumen; the proportion was 70-77% after entodinia had been established. The largest quantity of starch engulfed by E. maggii ciliates was 12.4-19.0 and 6.7-7.6 mg per 100 mg protozoal dry mass in the absence and presence of entodinia, respectively. No visible engulfment of hay was observed in vivo in spite of the fact that hay particles up to 42 microns in length were dominating in rumen fluid. Ingestion of fresh particles of hay separated from the rumen digesta was found when they were added in the proportion of 1 g per 40 mL suspension of ciliates. No preferential intake of starch was observed when E. maggii ciliates were incubated in vitro with a mixture of hay and barley starch. It is suggested that competition for starch between the two ciliate species was responsible for the drop in the numbers of E. maggii. This could result from a too low concentration of small particles of hay in the rumen fluid.

Animals↗
PubMed1997

Starch utilization by Bacteroides ovatus isolated from the human large intestine.

Starch supported growth of continuous cultures of Bacteroides ovatus when this carbohydrate provided the sole source of carbon and energy. Inducible amylase and alpha-glucosidase activities were inversely related to dilution rate in starch-limited and starch-excess chemostats over the dilution rate (D) range D = 0.03/h to D =0.20/h, and were partly repressed during growth under conditions of starch-excess. Preparative isoelectric focusing of B. ovatus cytoplasmic extracts indicated the existence of three distinct starch-hydrolyzing enzymes. Incubation of active fractions from the isoelectric focusing cell with maltose and a variety of low-molecular-weight oligosaccharides (maltotriose, maltotetraose, maltopentaose, maltohexaose, maltoheptaose) identified a single amylase activity, an enzyme with combined beta-amylase and glucoamylase/alpha-glucosidase properties, and also a possible pullulanase. The ability of B. ovatus to synthesize several starch-hydrolyzing enzymes with different specificities and activities may confer a significant competitive advantage to this organism in the colonic ecosystem.

Bacteroides↗
PubMed1998

[Energy utilization of retrograded starch by sows].

A total metabolism trial was conducted in eight adult sows to compare the energetic utilization, nitrogen balance, and passage rate of retrograded starch (RGS) with that of pregelatinized wheat starch (PWS). The starch was added at levels of 12 and 24 g/kg W0.75 to a basal ration that covered the maintenance requirement. Each animal received all four treatment combinations in a change-over design. At the start and end of the trial all sows were fed the basal ration alone. Feeding took place twice daily. During each 3-week metabolism period a complete balance measurement was performed for all animals, with 6 daily collections of feces and urine and a 48-h gas exchange measurement in a respiration chamber. The sows' heat production and energy retention were calculated by the carbon-nitrogen balance method and the RQ method. Digestibility and metabolizability of energy and energy retention were lower in the basal ration with RGS supplement than in the PWS supplemented ration. With regard to N exchange, sows supplemented with RGS excreted more N in the feces and less N in the urine, whereas N retention was equal with both rations. The production of CH4 was higher with RGS than after feeding pregelatinized wheat starch. When compared with the nonsupplemented basal ration, the fecal volume was unchanged with PWS but significantly increased with RGS. The feed passage, measured as the mean retention time of a marker in the digestive tract, was 86 h on the basal diet, falling to 75 h with PWS supplementation and 65 h with RGS. The utilization of the supplemented energy was 12% lower for RGS compared with PWS. This difference was due to a reduction in the digestibility and intermediate utilization of the energy. The amount of metabolizable energy was calculated as 16 kJ/g and the net energy as 12.5 kJ/g RGS. The results of the trial underline the importance of retrograded starch as a fiber type nutrient and the associated advantages for the bowel function. The energetic utilization on the other hand is only slightly lower than that of non-resistant starch; unlike pure fibrous feed materials, RGS can therefore not be regarded as a "low energy" substance.

Animals↗
PubMed2005

Construction and one-step purification of Bacillus kaustophilus leucine aminopeptidase fused to the starch-binding domain of Bacillus sp. strain TS-23 alpha-amylase.

The starch-binding domain of Bacillus sp. strain TS-23 alpha-amylase was introduced into the C-terminal end of Bacillus kaustophilus leucine aminopeptidase (BkLAP) to generate a chimeric enzyme (BkLAPsbd) with raw-starch-binding activity. BkLAPsbd, with an apparent molecular mass of approximately 65 kDa, was overexpressed in Escherichia coli M15 cells and purified to homogeneity by nickel-chelate chromatography. Native PAGE and chromatographic analyses revealed that the purified fusion protein has a hexameric structure. The half-life for BkLAPsbd was 12 min at 70 degrees C, while less than 20% of wild-type enzyme activity retained at the same heating condition. Compared with the wild-type enzyme, the 60% decrease in the catalytic efficiency of BkLAPsbd was due to a 91% increase in K (m) value. Starch-binding assays showed that the K (d) and B (max) values for the fusion enzyme were 2.3 microM and 0.35 micromol/g, respectively. The adsorption of the crude BkLAPsbd onto raw starch was affected by starch concentration, pH, and temperature. The adsorbed enzyme could be eluted from the adsorbent by 2% soluble starch in 20 mM Tris-HCl buffer (pH 8.0). About 49% of BkLAPsbd in the crude extract was recovered through one adsorption-elution cycle with a purification of 11.4-fold.

Bacillus↗
PubMed2005

Direct fermentation of potato starch wastewater to lactic acid by Rhizopus oryzae and Rhizopus arrhizus.

The biochemical kinetic of direct fermentation for lactic acid production by fungal species of Rhizopus arrhizus 3,6017 and Rhizopus oryzae 2,062 was studied with respect to growth pH, temperature and substrate. The direct fermentation was characterized by starch hydrolysis, accumulation of reducing sugar, and production of lactic acid and fungal biomass. Starch hydrolysis, reducing sugar accumulation, biomass formation and lactic acid production were affected with the variations in pH, temperature, and starch source and concentration. A growth condition with starch concentration approximately 20 g/l at pH 6.0 and 30 degrees C was favourable for both starch saccharification and lactic acid fermentation, resulting in lactic acid yield of 0.87-0.97 g/g starch associated with 1.5-2.0 g/l fungal biomass produced in 36 h fermentation. R. arrhizus 3,6017 had a higher capacity to produce lactic acid, while R. oryzae 2,062 produced more fungal biomass under similar conditions.

Industrial Microbiology↗
PubMed2006

Determination of the mineral fraction and rheological properties of microwave modified starch from Canna edulis.

The goal of this study was to evaluate the effect of the physical modification by microwave irradiation on the mineral fraction and rheological properties of starch isolated from Canna edulis rhizomes. Phosphorus, sodium, potassium, magnesium, iron, calcium and zinc were evaluated using atomic absorption spectrophotometry. Rheological properties were determined using both the Brabender amylograph and Brookfield viscosimeter. Except for the calcium concentration, mineral contents decreased significantly (p < 0.05) after microwave treatment. The amylographic profile was also modified, showing increased pasting temperature range and breakdown index, whereas the viscosity peak, viscosity at holding (95 degrees C) and cooling periods (50 degrees C), setback and consistency decreased as compared to the native starch counterpart. Although viscosity decreased in the microwaved sample, presumably due to starch changes at molecular level, it retained the general pseudo plastic behavior of native starch. It is concluded that canna starch may be modified by microwave irradiation in order to change its functional properties. This information should be considered when using microwave irradiation for food processing. Furthermore, the altered functional attributes of canna modified starch could be advantageous in new product development.

Food Irradiation↗