Deficiency of maize starch-branching enzyme i results in altered starch fine structure, decreased digestibility and reduced coleoptile growth during germination.
Xia, H., Yandeau-Nelson, M., Thompson, D. B. & Guiltinan, M. J. (2011). BMC Plant Biology, 11(1), 95-107.
Background: Two distinct starch branching enzyme (SBE) isoforms predate the divergence of monocots and dicots and have been conserved in plants since then. This strongly suggests that both SBEI and SBEII provide unique selective advantages to plants. However, no phenotype for the SBEI mutation, sbe1a, had been previously observed. To explore this incongruity the objective of the present work was to characterize functional and molecular phenotypes of both sbe1a and wild-type (Wt) in the W64A maize inbred line. Results: Endosperm starch granules from the sbe1a mutant were more resistant to digestion by pancreatic α-amylase, and the sbe1a mutant starch had an altered branching pattern for amylopectin and amylose. When kernels were germinated, the sbe1a mutant was associated with shorter coleoptile length and higher residual starch content, suggesting that less efficient starch utilization may have impaired growth during germination. Conclusions: The present report documents for the first time a molecular phenotype due to the absence of SBEI, and suggests strongly that it is associated with altered physiological function of the starch in vivo. We believe that these results provide a plausible rationale for the conservation of SBEI in plants in both monocots and dicots, as greater seedling vigor would provide an important survival advantage when resources are limited.
Effect of a gibberellin-biosynthesis inhibitor treatment on the physicochemical properties of sorghum starch.
Li, E., Hasjim, J., Dhital, S., Godwin, I. D. & Gilbert, R. G. (2011). Journal of Cereal Science, 53(3), 328-334.
Inhibition of plant growth by Trinexapac-ethyl, TE, a gibberellin-biosynthesis inhibitor, can produce a shorter stemmed plant, requiring less nutrients and water to grow, while maintaining grain yield. Although TE and other plant growth regulators are commonly used in grain crops, their effects on starch biosynthesis in the grains have not been systematically examined. The changes in the structural and functional properties of starch in grains harvested from TE-treated sorghum (Sorghum bicolor (L.) Moench) were examined, and the results compared with those from the untreated controls. TE treatment had little or no effects on the molecular structures of starch, starch granule morphology, and starch and amylose contents, but increased the protein content of the grains significantly. Consistent with the lack of change in the molecular structure, there were no significant effects on the thermal properties of the starch. The pasting properties of TE-treated sorghum flours, however, showed lower peak viscosity, trough, and final viscosity, which were attributed to their higher protein contents. The TE treatment thus does not have an appreciable effect on the biosynthesis of starch during grain development in sorghum.
Characterization of starch granules in rice culms for application of rice straw as a feedstock for saccharification.
Matsuki, J., Park, J. Y., Shiroma, R., Arai-Sanoh, Y., Ida, M., Kondo, M., Motobayashi, K. & Tokuyasu, K. (2010). Bioscience, Biotechnology, and Biochemistry, 74(8), 1645-1651.
Rice plants are known to accumulate starch in leaf sheaths and culms, and in some cultivars significant amounts of starch are present at the mature stage. This can be considered as potential feedstock for the recovery of fermentable sugars. We isolated starches from the culms of cultivars Yumeaoba, Koshihikari, and Leafstar to investigate their structural and physical features. Yumeaoba culm starch contained 20.2% amylose, whereas Koshihikari and Leafstar contained 25.8% and 25.2%. Yumeaoba culm starch was found by chain-length distribution analysis to contain higher amounts of short chains, resulting in lower gelatinization temperature by 7°C, as compared to Koshihikari and Leafstar. Consequently, the rate of enzymatic hydrolysis of Yumeaoba culm starches reached maximum at a lower temperature than Leafstar. Rice culm starch, with a lower gelatinization temperature, can provide an advantageous material for feedstock for bioethanol production in terms of energy conservation.
Physico-chemical properties of potato starches.
Alvani, K., Qi, X., Tester, R. F. & Snape, C. E. (2011). Food Chemistry, 125(3), 958-965.
Starches were isolated and characterised from 10 potato cultivars grown under the same conditions (with a commercial starch for reference). The chemical composition revealed some differences amongst the starches with protein ranging from 0.30% to 0.34%, amylose 25.2% to 29.1% and phosphorus 52.6–66.2 mg 100 g-1. High performance size-exclusion chromatography (HPSEC) fractionation of isoamylase debranched amylopectin showed that the amylopectin molecules were less branched and consisted of more B1, but less A-chains, than cereal starches. Gelatinisation onset (T>o), peak (T>p) and conclusion (T>c) temperatures of the native potato starches ranged from 58.7 to 62.5°C, 62.5 to 66.1°C and 68.7 to 72.3°C, respectively, whilst the gelatinisation enthalpies ranged from 15.1 to 18.4 J g-1. The gelatinisation temperatures of the starches increased in common with the amounts of short and intermediate sized amylopectin chains. The 13 C magic angle spinning nuclear magnetic resonance (13C CP-MAS NMR) and wide angle X-ray diffraction (XRD) data (30.6% ± 0.22% crystallinity on average) showed little variance amongst the samples. Particle sizing results, however, revealed more variance (20.6–30.9 µm mean diameter). Overall, these data reveal the subtleties of cultivar specific variation against a background of constant environmental conditions.
Determination of polydextrose as dietary fiber in foods.
Craig, S. A. S., Holden, J. F. & Khaled, M. Y. (2000). Journal of AOAC International, 83(4), 1006-1012.
Polydextrose (Litesse®) provides physiological effects consistent with dietary fiber. However, AOAC methods for measuring total dietary fiber (TDF) in foods include an ethanol precipitation step in which polydextrose and similar carbohydrates are discarded and therefore not quantitated. This study describes a method developed to quantitate polydextrose in foods. The new method includes water extraction, centrifugal ultrafiltration, multienzyme hydrolysis, and anion exchange chromatography with electrochemical detection. Six foods were prepared with 4 levels of polydextrose to test the ruggedness of the method. Internal validation demonstrated the ruggedness of the method with recoveries ranging from 83 to 104% with an average of 95% (n = 24) and relative standard deviation of recoveries ranging from 0.7 to 13% with an average of 3.3% (n = 24). The value is added to that obtained for dietary fiber content of foods using the AOAC methods, to determine the TDF content of the food.
Amylolysis of wheat starches. II. Degradation patterns of native starch granules with varying functional properties.
Blazek, J. & Copeland, L. (2010). Journal of Cereal Science, 52(2), 295-302.
Scanning electron microscopy (SEM) and X-ray diffraction (XRD) were employed to investigate degradation patterns of native starch granules from wheat (Triticum aestivum L.) by different starch-degrading enzymes. The starches examined were from a waxy wheat and four varieties with slightly elevated amylose content, but with different functional properties. Differences in the digestion patterns after partial α-amylolysis of starch granules were noted between the starches. The waxy starch seemed to be degraded by endocorrosion, whereas the amylose-rich starches followed a slower mode of hydrolysis starting from the granular surface. X-ray diffractograms of the amylose-rich starches were not significantly altered by 2 h of α-amylolysis, whereas partial hydrolysis of the waxy starch decreased scattering intensity at higher 2θ°angles, consistent with a different mode of attack by α-amylase in the initial digestion stages of granules of waxy and amylose-rich starches. We propose these differences are due to the combined effects of the change in packing density and partial preference for hydrolysis of amorphous material. The native starch granules were also attacked by beta-amylase, isoamylase and amyloglucosidase, which indicates that α-amylase is not the only starch-degrading enzyme that is able to initiate starch hydrolysis of native granules.
Differences in structures of starch hydrolysates using saliva from different individuals.
Nantanga, K. K. M., Chan, E., Suleman, S., Bertoft, E. & Seetharaman, K. (2013). Starch‐Stärke, 65(7‐8), 709-713.
High salivary amylase activity is associated with improved glycemic homeostasis in humans. Therefore, high salivary amylase activity is associated with greater digestion of starch. However, it is unclear if the structures of the hydrolysates from different individuals with different salivary amylase activity are the same. To test this, cooked starch (1:2 starch/water ratio) was treated with saliva from six participants at equal activity and conditions mimicking oral digestion. Salivary amylase activities ranged from 470 × 103 to 118 × 103 U/mL among the participants. The composition of the hydrolysates was characterised by gel-permeation chromatography. All samples gave rise to different and complex mixtures of hydrolysates with different breakdown structures. While saliva from participant 2 (high amylase activity) greatly reduced the high MW fraction, the saliva from participant 6 (low amylase activity) more extensively hydrolysed the starch to small MW fractions of oligosaccharides. These results show that different starch hydrolysates are produced during oral digestion by saliva from different individuals. Further research is therefore needed to understand if hydrolysate structure, rather than level of amylase activity, impacts glucose homeostasis.
Determination of polydextrose in foods by ion chromatography: collaborative study.
Craig, S. A. S., Holden, J. F. & Khaled, M. Y. (2001). Journal of AOAC International, 84(2), 472-478.
Eight collaborating laboratories assayed 7 blind duplicate pairs of foods for polydextrose content. The 7 test sample pairs ranged from low (2%) to high (95%) levels. The following foods were prepared with polydextrose mixed into the other ingredients and then baked, cooked, or otherwise prepared: milk chocolate candy, iced tea, sugar cookie, grape jelly, soft jellied candy, and powdered drink mix. Collaborators received a polydextrose standard to develop a calibration curve. The method determined polydextrose by ion chromatography, after removal of interfering food components (high molecular weight solubles). Repeatability standard deviations (RSDr) ranged from 3.93 to 9.04%; reproducibility standard deviations (RSDR) ranged from 4.48 to 14.06%. The average recovery was 94%.
Structure and function of starch and resistant starch from corn with different doses of mutant amylose-extender and floury-1 alleles.
Yao, N., Paez, A. V. & White, P. J. (2009). Journal of Agricultural and Food Chemistry, 57(5), 2040-2048.
Four corn types with different doses of mutant amylose-extender (ae) and floury-1 (fl1) alleles, in the endosperm, including no. 1, aeaeae; no. 2, fl1fl1fl1; no. 3, aeaefl1; and no. 4, fl1fl1ae, were developed for use in making Hispanic food products with high resistant starch (RS) content. The RS percentages in the native starch (NS) of 1−4 were 55.2, 1.1, 5.7, and 1.1%, respectively. All NS were evaluated for pasting properties with a rapid viscoanalyzer (RVA) and for thermal properties with a differential scanning calorimeter (DSC). NS 1 had a low peak viscosity (PV) caused by incomplete gelatinization, whereas NS 3 had the greatest PV and breakdown of all four starch types. On the DSC, NS 2 had the lowest onset temperature and greatest enthalpy. NS 1 and 3 had similar onset and peak temperatures, both higher than those of NS 2 and 4. The gel strength of NS heated with a RVA was evaluated by using a texture analyzer immediately after RVA heating (fresh, RVA-F) and after the gel had been stored at 4°C for 10 days (retrograded, RVA-R). NS 1 gel was watery and had the lowest strength (30 g) among starch gel types. NS 3 gel, although exhibiting syneresis, had greater gel strength than NS 2 and 4. The structures of the NS, the RS isolated from the NS (RS-NS), the RS isolated from RVA-F (RS-RVA-F), and the RS isolated from RVA-R (RS-RVA-R) were evaluated by using size exclusion chromatography. NS 1 had a greater percentage of amylose (AM) (58.3%) than the other NS (20.4−26.8%). The RS from all NS types (RS-NS) had a lower percentage of amylopectin (AP) and a greater percentage of low molecular weight (MW) AM than was present in the original NS materials. The RS-RVA-R from all starches had no AP or high MW AM. The percentages of longer chain lengths (DP 35−60) of NS were greater in 1 and 3 than in 2 and 4, and the percentages of smaller chain lengths (DP 10−20) were greater in 2 and 4 than in 1 and 3. In general, NS 3 seemed to have inherited some pasting, thermal, and structural characteristics from both NS 1 and 2, but was distinctly different from 4.
Molecular structure and granule morphology of native and heat‐moisture‐treated pinhão starch.
Pinto, V. Z., Moomand, K., Vanier, N. L., Colussi, R., Villanova, F. A., Zavareze, E. R., Lim, L. T. & Dias, A. R. G. (2015). International Journal of Food Science & Technology, 50(2), 282-289.
Pinhão seed is an unconventional source of starch and the pines grow up in native forests of southern Latin America. In this study, pinhão starch was adjusted at 15, 20 and 25% moisture content and heated to 100, 110 and 120°C for 1 h. A decrease in λ max (starch/iodine complex) was observed as a result of increase in temperature and moisture content of HMT. The ratio of crystalline to amorphous phase in pinhão starch was determined via Fourier transform infra red by taking 1045/1022 band ratio. A decrease in crystallinity occurred as a result of HMT. Polarised light microscopy indicated a loss of birefringence of starch granules under 120°C at 25% moisture content. Granule size distribution was further confirmed via scanning electron microscopy which showed the HMT effects. These results increased the understanding on molecular and structural properties of HMT pinhão starch and broadened its food and nonfood industrial applications.
An exceptionally cold-adapted alpha-amylase from a metagenomic library of a cold and alkaline environment.
Vester, J. K., Glaring, M. A. & Stougaard, P. (2015). Applied Microbiology and Biotechnology, 99(2), 717-727.
A cold-active α-amylase, Amy13C6, identified by a functional metagenomics approach was expressed in Escherichia coli and purified to homogeneity. Sequence analysis showed that the Amy13C6 amylase was similar to α-amylases from the class Clostridia and revealed classical characteristics of cold-adapted enzymes, as did comparison of the kinetic parameters K m and K cat to a mesophilic α-amylase. Amy13C6 was shown to be heat-labile. Temperature optimum was at 10–15°C, and more than 70 % of the relative activity was retained at 1°C. The pH optimum of Amy13C6 was at pH 8–9, and the enzyme displayed activity in two commercial detergents tested, suggesting that the Amy13C6 α-amylase may be useful as a detergent enzyme in environmentally friendly, low-temperature laundry processes.