Changes in morphological, thermal and pasting properties of yam (Dioscorea alata) starch during growth

This study was carried out in order to compare and establish the changes in physicochemical properties of starch from four different cultivars of yam at various stages of maturity during growth. The results showed that the starch content of the four yam tubers increased as growth progressed and were in the range of 70.5–85.3% on a dry basis. The shapes of the starch granules were round to oval or angular in the four yams and the size of starch granule increased with growth time ranging from 10 to 40 μm. The X-ray diffraction patterns could be classified as typical of B-type starch for the four cultivars of yam starch. The transition temperature of gelatinization of the four yam starches decreased during maturity. The RVA parameters suggested that yam starch paste showed a lower breakdown at an early harvest time. It appeared to be thermo-stable during heating but had a high setback after cooling, which might result in a tendency towards high retrogradation. The results for pasting behaviors showed that higher amylose content was associated with a lower pasting temperature and a higher peak viscosity in these starches.     

Single and multi-step carboxymethylation of water yam (Dioscorea alata) starch: synthesis and characterization

Water yam (Dioscorea alata) starch was carboxymethylated by single and multi-step processes for nine times successively. Optimal degree of substitution (DS) of 0.98 and reaction efficiency (RE) of 70.5% were obtained in the single-step carboxymethylation at 40 degrees C, 3 h in isopropanol-water reaction mixture ratio 1:0.16. The ratio of sodium hydroxide and sodium monochloroacetate moles to anhydroglucose unit moles for the optimal DS and RE were 1.62 and 1.39, respectively. The DS increased progressively as the steps of carboxymethylation increased from 2 to 9 and an optimal DS of 2.24 was obtained. Initial increases in carboxymethylation step increased the RE progressively up to 82.1% after the seventh carboxymethylation step but declined with further increases in the carboxymethylation step. The wide angle X-ray diffractometry and the DSC revealed remarkable changes after carboxymethylation because starch crystallinity reduced significantly. Thermogram of native starch showed a characteristic three-step decomposition with 13.16%, 61.54% and 24.79% weight losses progressively while carboxymethyl derivative showed four decomposition stages with 9.86%, 36.57%, 3.04% and 23.07% weight losses progressively. Studies revealed that carboxymethylation improved thermal stability of the native starch. IR spectrometry revealed that carboxymethyl starch showed new bands at nu=1600, 1426 and 1324 cm(-1). The broad band (13)C NMR spectra of the ultrasonically degraded carboxymethyl starch showed a peak at delta=180 ppm which was assigned to carbonyl carbon.     

Synthesis and evaluation of physicochemical properties of cross-linked sago starch

Highly substituted sago starch phosphate was synthesized using POCl₃ as cross-linking reagent. Titrimetric and Fourier transform infra red (FT-IR) spectral analysis were used to characterize the substitution. Studying the different factors affecting the reaction parameters showed that the optimal conditions for starch phosphorylation were: 4 h reaction time and reagent concentration 1.5% (w/w). The physicochemical properties of cross-linked sago starch (CLSS) were done using Scanning electron micrograph (SEM), X-ray powder diffractometer (XRD and Thermogravimetric analysis (TGA). The results revealed that crystalline nature of native sago starch was transformed after cross-linking. TGA report exhibited higher thermal stability, which makes it suitable for various industrial applications. Swelling behavior showed high swelling at low temperature (30 and 60 °C) as compared to high temperature (90 °C).     

RVA analysis of mixtures of wheat flour and potato, sweet potato, yam, and cassava starches

Rapid visco analysis (RVA) was performed to study the pasting properties of mixtures of wheat flour and tuber starches, i.e., potato starch (PS), sweet potato starch (SPS), yam starch (YS), and cassava starch (CS), at 10–50% starch in the mixtures. Lower phosphorus and higher amylose contents were observed in CS, followed by YS, SPS, and PS. The peak, breakdown, final, and setback viscosities of the control wheat flour were lower than those of the control PS, SPS, YS, and CS. The peak viscosity of wheat–PS mixtures was higher than those of the wheat–SPS, wheat–YS, and wheat–CS because of the higher phosphorus and lower amylose content of PS, which resulted in higher swelling of PS than that of SPS, YS, and CS. The breakdown viscosities increased as the starch content of the PS, SPS, and CS in the mixtures increased to up to the 50%, and the values tended to decrease in the wheat–YS mixture. The setback viscosities of wheat–SPS, wheat–YS, and wheat–CS increased significantly as the starch content increased from 10% to 50%, and that of wheat–PS dropped dramatically at 50%. The findings in this work provide evidence that tuber starches could be used as a partial substitute for wheat flour in some wheat-based products.     

Eco-friendly synthesis of silver nanoparticles from the whole plant of Cleome viscosa and evaluation of their characterization,antibacterial, antioxidant and antidiabetic properties

The current research is to develop an easy and eco-friendly method for the synthesis of three different concentrations of silver nanoparticles (1mMCvAgNPs, 2mMCvAgNPs and 3mMCvAgNPs) using aqueous whole plant extract of Cleome viscosa and to evaluate their antibacterial, antioxidant and antidiabetic properties. CvAgNPs were characterized by Using UV–vis spectrophotometer, X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscope (SEM) and transmission electron microscope (TEM). The formation of CvAgNPs was confirmed by the observation of band between 250 nm to 600 nm UV–vis spectrum. The crystalline structure of CvAgNPs with a face-centered cubic (FCC) was confirmed by XRD. The responsible phytochemicals for the reduction and capping material of CvAgNPs were observed with FT-IR. The SEM analysis confirmed the size and shapes of CvAgNPs. The CvAgNPs have shown the rich content of total phenolic and total flavonoid components. The CvAgNPs have shown significant antibacterial activity on multi drug resistance Gram-negative and Gram-positive bacteria and also have shown significant strong antioxidant activities (DPPH, ABTS, H₂O₂ scavenging, Phosphomolybdenum assay and reducing power). The inhibitory action of CvAgNPs on α-glucosidase and α-amylase was stronger than the inhibitory action of acarbose. To best of our knowledge, this is the first attempt on the synthesis of AgNPs using C. viscosa whole plant aqueous extract. The synthesized CvAgNPs exhibited good antimicrobial, antioxidant and antidiabetic properties. Hence, to validate our results, the in vivo studies at the molecular level are needed to develop Cleome viscosa as an antibacterial, antioxidant and anti-diabetic agent.     

Corn porous starch: preparation, characterization and adsorption property

This study was carried out to develop a new type of modified starch based on α-amylase and glucoamylase. The structural and chemical characteristics of the porous starch were determined by Fourier-transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), X-ray diffraction (XRD) and differential scanning calorimetry (DSC). The potential application of the porous starch as an adsorbent was evaluated using methyl violet as an adsorbed model. The adsorption capacity was optimized by investigating the reaction factors, including the mass ratio of α-amylase to glucoamylase (m_α-amylase/m_glucoamylase), the mass ratio of total amount of enzymes to starch (m_enzyme/m_St), the ratio of liquid volume to starch mass (VH₂O/mSt), pH value of the reaction solution, enzymatic reaction temperature, and enzymatic reaction time. The hydrolysis ratio of each sample was also determined to investigate the effect of different reaction conditions on the hydrolysis degree. The results suggest that the porous starch has a more excellent adsorption capacity than the native starch, and may be expected to have wide potential applications in many fields.     

A facile and rapid method for green synthesis of Achyranthes aspera stem extract-mediated silver nano-composites with cidal potential against Aedes aegypti L.

Aedes aegypti L. is the primary vector associated with transmission of globally concerned diseases; Zika, yellow fever, dengue and Chikungunya. Present study investigates an efficient, alternative and comparative approach for mosquito control which is safe to environment and non-target organisms. The silver nano-composites (AgNCs) were synthesized from the aqueous stem extract of Achyranthes aspera (AASE) using different concentration of aqueous silver nitrate (AgNO₃). The synthesis was tracked by UV-vis spectrophotometer and particle size analyser (DLS). The evaluation of their larvicidal potential against early fourth instars of Ae. aegypti showed significant potency, the toxicity increasing with the concentration of silver nitrate. The 24, 48 and 72 h bioassays resulted in respective LC₅₀ values of 26.693, 1.113 and 0.610 μg/mL (3 mM AASE-AgNO₃) 9.119, 0.420 and 0.407 μg/mL (4 mM AASE-AgNO₃) and that of 4.283, 0.3 and 0.248 μg/mL (5 mM AASE-AgNO₃). Keeping in view the significantly high larvicidal efficiency at lower concentration of silver nitrate, the 4 mM nano-composites were selected over 5 mM composites for further biophysical characterization carried out by X-ray Diffraction (XRD), Fourier transform infrared spectrometer (FTIR), Scanning electron microscopy (SEM), Energy dispersive X-ray (EDX) spectroscopy and Transmission electron microscopy (TEM). SEM and TEM confirmed the synthesis of spherical poly-dispersed AgNCs with average size ranging from 1–30 nm. Characterization through XRD showed the crystalline face-centered-cubic (fcc) structure of AgNCs with the highest intense peak obtained at 2θ value of 31.82°. FT-IR data suggests complex nature of AgNCs showing clearly defined peaks in different ranges. The present investigations recommend AgNCs of A. aspera stems as a low-cost and eco-friendly alternative to chemical insecticides for mosquito control.     

Safety evaluation of formulations containing carboxymethyl derivatives of starch and chitosan in albino rats

Two composite formulations, based on carboxymethyl derivatives of starch (formulation I) and chitosan (formulation II), used in the preparation of coating formulations to enhance post harvest shelf-life of fruits and vegetables, were evaluated for safety by single dose dietary (formulation I, coating on feed pellet-1.3% w/w and formulation II, coating on feed pellet-1% w/w) and oral (1 ml, 2% aqueous solution) administration to albino rats. Experiment was carried out for 4 weeks. No significant changes were observed in gain in weekly body weight, weight of vital organs and in parameters of haematology and histopathology among experimental groups, thus indicating safety (and non-toxicity) of the coating formulations.     

Mechanical,barrier and morphological properties of pea starch and peanut protein isolate blend films

Mechanical, barrier and morphological properties of edible films based on blends of Pea starch (PS) and Peanut protein isolate (PPI) plasticized with glycerol (30%, w/w) were investigated. As PPI ratio in PS/PPI blends increased, the thickness of films decreased, the opacity slightly elevated and color intensified. The addition of PPI to the PS film significantly reduced tensile strength from 5.44 MPa to 3.06 MPa, but increased elongation from 28.56% to 98.12% with the incorporation of PPI into PS at 50% level. Film solubility value fell from 22.31% to 9.78% upon the incorporation of PPI ranged from 0 to 50% level. When PPI was added into PS film at 40% level, the WVP and WVTR of the films markedly dropped from 11.18% to 4.19% and 6.16 to 1.95%, respectively. Scanning electron microscopy (SEM) of the surface of films showed that many swollen starch granules were presented in the 100% PS film, while 100% PPI film was observed to have rougher surfaces with presence of pores or cavities. The PS/PPI blend films upon the incorporation of PPI at 20% and 50% level were not homogeneous. However, the smoother film surface was observed in PS/PPI blend films with the addition of PPI at 40% level. SEM image of the cross-sections of the films revealed that the 100% PS film showed a uniform and compact matrix without disruption, and pore formation and 100% PPI film displayed a smooth structure. Rougher and flexible network was shown in blend film with the addition of PPI reaching 40% level.     

Morphological properties and thermoanalysis of micronized cassava starch

The granule morphology, microstructure, and thermal properties of micronized cassava starch prepared by a vacuum ball-grinding machine were investigated. Scanning electron microscopy (SEM) analysis indicated that the morphology of starch granule changes during the ball-grinding treatment. Differential scanning calorimetry (DSC) analysis indicated that the maximum peak temperature (T_p) of the gelatinization process, the glass transition (T_g), and peak height index (PHI) for the starch granules decreased when the size of micronized starch granules was reduced. When the size of starch granules was reduced beyond 9.11 μm, they have a tendency to agglomerate and their ΔH were increased. The granule size has a significant effect on the gelatinization properties of cassava starch. This study will provide useful information of the micronized starch for its potential industrial application.     

Contribution of sucrose synthase, ADP-glucose pyrophosphorylase and starch synthase to starch synthesis in developing pea seeds

Using genetic variability existing amongst nine pea genotypes (Pisum sativum L.), the biochemical basis of sink strength in developing pea seeds was investigated. Sink strength was considered to be reflected by the rate of starch synthesis (RSS) in the embryo, and sink activity in the seed was reflected by the relative rate of starch synthesis (RRSS). These rates were compared to the activities of three enzymes of the starch biosynthetic pathway [sucrose synthase (Sus), ADP-glucose pyrophosphorylase and starch synthase] at three developmental stages during seed filling (25, 50 and 75% of the dry seed weight). Complete sets of data collected during seed filling for the nine genotypes showed that, for all enzyme activities (expressed on a protein basis), only Sus in the embryo and seed coat was linearly and significantly correlated to RRSS. The contribution of the three enzyme activities to the variability in RSS and RRSS was evaluated by multiple regression analysis for the first two developmental stages. Only Sus activity in the embryo could explain, at least in part, the significant variability observed for both the RSS and the RRSS at each developmental stage. We conclude that Sus activity is a reliable marker of sink activity in developing pea seeds.     

苦荞薄壳种质的光合特性、淀粉合成与产量形成研究

为探索薄壳苦荞的"源-库"关系,提高产量水平,进而指导薄壳苦荞杂交育种。该研究选用杂交薄壳苦荞种质米55为材料,以母本小米荞为对照,对灌浆期的叶片光合特性、籽粒淀粉合成关键酶活性与主要农艺和产量性状进行测定分析。结果表明:(1)灌浆期米55叶片净光合速率显著或极显著高于对照。(2)籽粒蔗糖浓度稍低于对照,葡萄糖浓度稍高于对照,均未达到显著差异水平。(3)籽粒腺苷二磷酸葡萄糖焦磷酸化酶活性高于对照,且前期达到极显著差异水平。(4)籽粒淀粉合成酶活性和淀粉浓度都稍高于对照。(5)米55的株高降低,单株粒数提高,千粒重增加,产量显著提高。上述结果说明增"源"、扩"库"在杂交薄壳苦荞米55上取得一定进展,叶片光合同化能力、单株粒数和千粒重改良是未来薄壳苦荞育种的重要研究方向。     

Poly(ethylene glycol)-carboxymethyl chitosan-based pH-responsive hydrogels: photo-induced synthesis, characterization, swelling, and in vitro evaluation as potential drug carriers

In this study, carboxymethyl chitosan was prepared, characterized, and then photo-induced graft copolymerized with poly(ethylene glycol) under a nitrogen atmosphere in aqueous solution using 2,2-dimethoxy-2-phenyl acetophenone (DMPA) as the photo-initiator. The grafting copolymerization process was confirmed and the resulting copolymers were characterized using differential scanning calorimetry (DSC), FTIR spectroscopy, 2D-X ray diffraction, and elemental analysis. The kinetics of the grafting reactions was also studied. Under the applied experimental conditions, the optimum grafting values were obtained at: CMCs = 0.2 g, PEGA = 249 mM, DMPA = 10.4 mM at a 2 h reaction time. Some of the resulting copolymers were selected and used in the presence of methylene bisacrylamide (MBA) as a crosslinking agent to develop pH-responsive hydrogel matrices. The swelling characteristics and the in vitro release profiles of 5-fluorouracil (5-FU), as a model drug, from the hydrogels were investigated. The results revealed that the hydrogel matrices developed in this study can be customized to act as good candidates in drug delivery systems.     

Green synthesis of silver nanoparticles using Ocimum canum and their anti-bacterial activity

Green synthesis of nanoparticles is an important area in the field of nanotechnology, which has cost effective and environment friendly benefit over physical and chemical methods. The present study aims at preparation of silver nanoparticles through green route using leaves of Ocimum canum Sims, a widely distributed medicinal herb. The synthesized silver nanoparticles were characterized by SEM and XRD. The spherical and rod like morphological shapes were proven by SEM techniques. Crystallographic structure was confirmed by XRD and average particle size of synthesized silver nanoparticles was calculated which was found to be of 15.72 nm. The antibacterial activity of these prepared silver nanoparticles against pathogenic bacterium Escherichia coli (E. coli) has shown the highest ZOI of 2.45 cm at 30 ppm.     

木薯蔗糖合成、转运与块根淀粉积累关系研究

该研究以淀粉含量不同的两个木薯品种(辐选01和华南124)为材料,通过测定各品种不同生育期叶、茎和根的蔗糖含量及块根淀粉含量,分析了蔗糖合成、转运和块根淀粉积累过程的相关性.结果表明:与华南124相比,在整个生育期内辐选01叶、茎的蔗糖含量均较高,块根蔗糖含量在块根膨大初期以前高于华南124,块根膨大初期以后则相反.在木薯的整个生育期,与辐选01相比,华南124的淀粉合成量和淀粉合成速率均较低.叶和茎蔗糖含量的变化规律与淀粉合成速率的变化规律相反,即块根淀粉积累明显加快时叶和茎的蔗糖含量略呈下降趋势,而块根淀粉合成减慢时叶、茎的蔗糖含量又开始上升.随着生育期的延后,块根蔗糖含量越来越低.在块根形成初期,蔗糖含量最高的组织部位为块根,其次为茎秆,最低的是叶片;而在块根成熟期时则相反,即蔗糖含量最高的部位是叶片,其次为茎杆,块根的蔗糖含量最小.相关性分析结果表明,木薯叶片蔗糖含量与块根淀粉含量呈显著的正相关;茎秆蔗糖含量与块根淀粉积累量呈不显著的正相关;块根蔗糖含量与淀粉积累量呈显著的负相关.由此可见,木薯叶、茎和根蔗糖与块根淀粉积累过程密切相关,其中叶片合成蔗糖的能力与块根利用蔗糖的能力在淀粉的积累过程中发挥关键作用.该研究结果为木薯的生产选育与高效栽培提供了理论依据.     

Functional and structural characterization of the catalytic domain of the starch synthase III from Arabidopsis thaliana

Glycogen and starch are the major energy storage compounds in most living organisms. The metabolic pathways leading to their synthesis involve the action of several enzymes, among which glycogen synthase (GS) or starch synthase (SS) catalyze the elongation of the alpha-1,4-glucan backbone. At least five SS isoforms were described in Arabidopsis thaliana; it has been reported that the isoform III (SSIII) has a regulatory function on the synthesis of transient plant starch. The catalytic C-terminal domain of A. thaliana SSIII (SSIII-CD) was cloned and expressed. SSIII-CD fully complements the production of glycogen by an Agrobacterium tumefaciens glycogen synthase null mutant, suggesting that this truncated isoform restores in vivo the novo synthesis of bacterial glycogen. In vitro studies revealed that recombinant SSIII-CD uses with more efficiency rabbit muscle glycogen than amylopectin as primer and display a high apparent affinity for ADP-Glc. Fold class assignment methods followed by homology modeling predict a high global similarity to A. tumefaciens GS showing a fully conservation of the ADP-binding residues. On the other hand, this comparison revealed important divergences of the polysaccharide binding domain between AtGS and SSIII-CD.     

Spectral characterization of hydroxyapatite extracted from Black Sumatra and Fighting cock bone samples: A comparative analysis

At present, chicken business is occupying a major portion in the market and huge amount of bone wastes are dumped into the open places lead in environmental pollution. In this analysis, natural hydroxyapatite was extracted by thermal calcination process at different temperature ranges from 700 °C, 900 °C and 1100 °C and compared its spectral characteristics. The crystalline nature, functional groups and morphological characteristics of hydroxyapatite obtained from both bone samples were studied using XRD, FTIR and SEM analysis. The crystallite size, lattice parameters, specific surface area, volume and degree of crystallinity were measured using XRD data. The mean grain size of Black Sumatra and Fighting Cock bone hydroxyapatite was 62.67 nm and 31.34 nm respectively. The FTIR spectrum showed major peaks at 634.58 cm⁻¹ and 470.63 cm⁻¹, 1413.82 cm⁻¹ and 1460 cm⁻¹ indicates the presence of carbonate group and phosphate groups in both samples. The SEM micrograph confirmed the existence of maximum pores in matrix of fighting cock bone than Black Sumatra bone sample. Thus, the comparative analysis concluded that nano-sized hydroxyapetite obtained from bone wastes of fighting cock can be utilized as a low-cost biomaterial for the production of various implant coating materials and substitute for ceramics in bones and dentistry applications.