Influence of Precipitation Conditions on Crystallinity of Amylose Nanoparticles

Characterization of a unique pH-dependent amylosucrase from Deinococcus cellulosilyticus

The amylosucrase (ASase, EC 2.4.1.4) utilizes sucrose as the sole substrate to catalyze multifunctional reactions. It can naturally synthesize α-1,4-linked glucans such as amylose as well as sucrose isomers with more favorable properties than sucrose with a lower intestinal digestibility and non-cariogenic properties. The amino acid sequence of the asase gene from Deinococcus cellulosilyticus (DceAS) exhibits low homology with those of other ASases from other Deinococcus species. In this study, we cloned and expressed DceAS and demonstrated its high activity at pH 6 and pH 8 and maintained stability. It showed higher polymerization activity at pH 6 than at pH 8, but similar isomerization activity and produced more turanose and trehalulose at pH 6 than at pH 8 and produced more isomaltulose at pH 8. Furthermore, the molecular weight of DceAS was 226.6 kDa at pH 6 and 145.5 kDa at pH 8, indicating that it existed as a trimer and dimer, respectively under those conditions. Additionally, circular dichroism spectra showed that the DceAS secondary structure was different at pH 6 and pH 8. These differences in reaction products at different pHs can be harnessed to naturally produce sucrose alternatives that are more beneficial to human health.

Extraction, purification and characterization of amylose from sago and corn: Morphological, structural and molecular comparison

In the present work, a comprehensive study was carried out to better understand the molecular characteristics of amylose extracted from sago starch, using butanol as the extraction solvent. The sago derived amylose was compared with amylose extracted from corn starch and both characterized through different techniques, i.e. size exclusion chromatography, X-ray diffraction (XRD), Fourier transform infrared spectroscopy, Raman spectroscopy, Scanning electron microscopy, Atomic force microscopy and Zeta potential measurements. The purity of the amylose extracted from sago and corn was 99.20 % and 93.46 %, respectively. From XRD results, it was revealed that sago amylose had more crystallinity with high thermal stability compared to corn amylose. Based on Raman spectra, single and double helices formed in both extracted amyloses, but due to their intrinsic differences, the intensities associated with these helices varied for sago and corn amylose. Purified amyloses were shown to have two different forms of spherulite morphology: torus and spherical shapes with varying degrees of roughness. Our findings demonstrated that sago starch is a novel and low-cost source for supplying amylose, a promising polymer for different applications.

Fabrication and characterization of octenyl succinate anhydride modified amylose with pH-responsive Pickering emulsion behavior

To make stable Pickering emulsion in stomach acid condition which are suitable for small intestine targeted delivery, the emulsifying ability and pH responsiveness mechanisms of octenyl succinate anhydride modified amylose (OSA-AM) with the formless state and nanoparticles (NP) form in the Pickering emulsion were compared. OSA-AMs and OSA-AM NPs were obtained by successively modification of OSA esterification reaction with amylose and nanoprecipitation process, respectively. OSA-AM NPs showed higher contact angle and lower interfacial tension than OSA-AMs, which suggested OSA-AM NPs have the stronger ability to form stable Pickering emulsion. In addition, to compare the stability of Pickering emulsion in different environment, the emulsion index (EI), photographs and microscopy images during storage time of 180 days in pH 2.0, pH 4.0 and pH 7.0 were monitored. Pickering emulsion formed by OSA-AM NPs exhibited stronger stability in acid environment (pH 2.0) than pH 4.0 and pH 7.0. However, Pickering emulsion stabilized by OSA-AMs presented the opposite pH-responsive behaviors with OSA-AM NPs. To further study the pH responsiveness mechanisms of Pickering emulsion, the morphology, contact angle, particle size and surface charge of OSA-AMs and OSA-AM NPs with pH changing were measured. These results suggested that the protonation/deprotonation process of carboxyl groups in difference pH condition revealed the pH-responsible behaviors of Pickering emulsion.

Preparation and characterization of quinoa starch nanoparticles as quercetin carriers

Quinoa starch nanoparticles (QSNPs) prepared by nanoprecipitation method under the optimal condition was developed as a carrier for quercetin. The QSNPs prepared under the optimal condition (90 DMSO/H₂O ratio, 10 ethanol/solvent ratio, and ultrasonic oscillation dispersion mode) had the smallest particle size and polymer dispersity index through full factorial design. Compared with maize starch nanoparticles (MSNPs), QSNPs exhibited a smaller particle size of 166.25 nm and a higher loading capacity of 26.62%. Starch nanoparticles (SNPs) interacted with quercetin through hydrogen bonding. V-type crystal structures of SNPs were disappeared and their crystallinity increased after loading with quercetin. QSNPs was more effective in protecting and prolonging quercetin bioactivity because of their small particle sizes and high loading capacities. This study will be useful for preparing starch-based carrier used to load sensitive bioactive compounds.

Improving the cold water swelling properties of oat starch by subcritical ethanol-water treatment

The granular cold water swelling oat starch was prepared by subcritical ethanol-water, and the changes of properties and structure on oat starch were investigated. The oat starch was modified at the temperature of 95 °C and ethanol concentration of 48% and showed a higher cold water swelling ability of 22.58 g/g, whereas native oat starch was 6.73 g/g. Modified oat starch granule was kept intact, and it was swollen when dispersing in the water. The gelatinization enthalpy declined to 0 J/g. The surface of modified oat starch granules was honeycomb and porous observed by scanning electron microscope. The X-ray diffraction showed the A-type crystal decreased and the V-type crystal increased, and the result was quantitatively confirmed by solid-state ¹³C NMR spectroscopy. The ratio of 1047 cm^-1/1022 cm^-1 (determined by Fourier transform infrared spectroscopy) of modified oat starch was decreased. The molecular weight distribution of modified oat starch was slightly reduced, and the amylose content increased from 26.18% to 31.68%, and only a small amount of carbohydrates leached during the modification. Subcritical ethanol-water modification improved the cold water swelling ability of oat starch. The starch crystals changed from A-type to V-type provide a potential mechanism of subcritical ethanol-water modified oat starch.

Acid hydrolysis of amylose granules and effect of molecular weight on properties of ethanol precipitated amylose nanoparticles

Amylose granules hydrolyzed with 2 M hydrochloric acid for various periods of time were used to prepare amylose nanoparticles through ethanol precipitation. Value of dextrose equivalent, viscosity average molecular weight and molecular chain length distribution of the acid hydrolyzed amylose granules were determined. The precipitated amylose nanoparticles were characterized by using dynamic light scattering and X-ray diffraction. Results showed that, after 48 h acid hydrolysis, viscosity average molecular weight of amylose decreased from 3.35 × 10⁵ to 0.336 × 10⁵ and the amylose macromolecular chains with DP > 1000 were cut into short ones. The short chain sugar molecules derived from the acid hydrolysis were not involved in the ethanol precipitation or incorporated into the precipitated amylose nanoparticles. The length and quantity of the residual amylose macromolecular chains after the acid hydrolysis were the main factors to influence size and crystallinity of the precipitated amylose nanoparticles.