Structural and property characterization of corn starch modified by cyclodextrin glycosyltransferase and specific cyclodextrinase

Gem-like starch granules engineered with different crystalline starches

The retrogradation property endows starch molecules with the unique ability to self-assemble crystals after encountering damage, which can restore the internal double helix structure to a limited extent. We devise a simple set of steps to grow perfect crystals of uniform size with different crystal systems in a given growth environment by first customizing the crystal seeds through enzymatic modification, and then exploiting the spontaneous recrystallization of starch. Optical microscopy confirmed the formation of gem-like starch granules (GSGs) in starches with 24.3 %-28.1 % amylose content, while no GSGs appeared in any of the other contents. FITR and XRD pattern revealed a shift in the double helix arrangement within the crystals, and the resultant change in starch crystal type from A-type to B-type provided theoretical support for the production of tetragonal, tetragonal, and hexagonal crystal systems. This work may provide a promising approach to the development of novel starch-based food/drug carriers.

β-Cyclodextrin modified imidazole probe specific recognition of organic acids based on nuclear magnetic resonance

Supramolecular interactions play an important role in molecular recognition. Cyclodextrins (CDs) are excellent hosts that are frequently utilized in the identification of chemical compounds. Proper modifications to CD can give it the ability to accurately recognize specific molecules. In this research, CD was modified with the allylimidazole moiety to generate a synergistic effect. Remarkably, the newly formed cation probe exhibits selective recognition of 1-adamantanecarboxylic acid from six guest molecules, which cannot be achieved by CD or allylimidazole alone. The recognition is evidenced by the retention of hydrogen-deuterium exchange (HDX) properties in the formed complexes and a change in the chemical shift of protons (H-4, H-5) in the allylimidazol backbone. Wavefunction analysis was employed to demonstrate that the mechanism of molecular recognition is the electrostatic interaction between host and guest molecules as well as the hydrogen bond formed by the guest molecule with the imidazole moiety H-2. This work reports an intramolecular synergistic strategy to specifically identify 1-adamantanecarboxylic acid, which could inspire probe design for various analysts.

Synergistic action of novel maltohexaose-forming amylase and branching enzyme improves the enzymatic conversion of starch to specific maltooligosaccharide

As attractive functional ingredients, maltooligosaccharides (MOS) are typically prepared by controlled enzymatic hydrolysis of starch. However, the random attack mode of amylase often leads to discrete product distribution, thereby reducing yields and purities. In this study, a novel glycoside hydrolase family 13 amylase AmyEs from marine myxobacteria Enhygromyxa salina was identified efficient maltohexaose (G6)-forming ability (40 %, w/w). By deciphering external chain length, we found that the high density of α-1,6-branching points benefits the G6 formation of AmyEs with high purity (71-82 %), indicating the substrate selectivity of AmyEs toward high-branched starch. Based on this, asynchronous conversion strategy was designed to enhance specific MOS yield from corn starch by exploiting branching enzymes and AmyEs, and the purity and yield of G6 respectively increased by 9.5 % and 5 % compared to single AmyEs treatment. Our results demonstrate that combinatorial catalysis of MOS-forming amylases and branching enzymes provides a favorable industrial preparation of specific MOS.

Research of saccharides and related biocomplexes: A review with recent techniques and applications

Saccharides and biocompounds as saccharide (sugar) complexes have various roles and biological functions in living organisms due to modifications via nucleophilic substitution, polymerization, and complex formation reactions. Mostly, mono-, di-, oligo-, and polysaccharides are stabilized to inactive glycosides, which are formed in metabolic pathways. Natural saccharides are important in food and environmental monitoring. Glycosides with various functionalities are significant in clinical and medical research. Saccharides are often studied with the chromatographic methods of hydrophilic interaction liquid chromatography and anion exchange chromatograpy, but also with capillary electrophoresis and mass spectrometry with their on-line coupling systems. Sample preparation is important in the identification of saccharide compounds. The cases discussed here focus on bioscience, clinical, and food applications.

Effects of maltogenic α-amylase on physicochemical properties and edible quality of rice cake

Maltogenic α-amylase (MA) are commercially used in the baking industry to retard starch retrogradation. However, whether MA can be used to modify rice flour during the fermentation process to improve the quality of rice flour remains unclear. In this study, MA was introduced during rice cake (RC) processing, and the modification effect and underlying mechanism were explored. Mn showed a decreasing trend except for 4.0 × 10-3 U/g sample. Chain length distribution data showed that MA effectively hydrolyzed long chains in amylopectin and increased the concentration of amylopectin chain length with a degree of polymerization of ≤ 9. High-performance liquid chromatography results suggested that the maltose content increased to 3.14% at an MA concentration of 9.5 × 10-3 U/g, which affected the fermentation effect of MA-treated RC. MA effectively reduced the viscosity of RC, and the gelatinization enthalpy of RC changed to 0.835 mJ/mg. MA also reduced the hardness and chewiness of RC after storage for 7 d. Moreover, rapidly digestible starch and slowly digestible starch contents of MA-treated RC decreased and increased, respectively, and resistant starch contents were remained unchanged. These results indicate that MA exerts a significant and effective antiretrogradation effect on RC. Combining the above results with sensory evaluation findings, an MA concentration of 4.0 × 10-3 U/g was the best supplemental concentration for obtaining RC with better edible quality. These findings suggest that MA treatment to rice flour during the fermentation process not only preserved the edible quality of RC but also retarded its retrogradation, thus, providing a novel processing method for the industrial production of RC.

Structural and Functional Properties of Porous Corn Starch Obtained by Treating Raw Starch with AmyM

Porous starch is attracting considerable attention for its high surface area and shielding ability, properties which are useful in many food applications. In this study, native corn starch with 15, 25, and 45% degrees of hydrolysis (DH-15, DH-25, and DH-45) were prepared using a special raw starch-digesting amylase, AmyM, and their structural and functional properties were evaluated. DH-15, DH-25, and DH-45 exhibited porous surface morphologies, diverse pore size distributions and pore areas, and their adsorptive capacities were significantly enhanced by improved molecular interactions. Structural measures showed that the relative crystallinity decreased as the DH increased, while the depolymerization of starch double helix chains promoted interactions involving disordered chains, followed by chain rearrangement and the formation of sub-microcrystalline structures. In addition, DH-15, DH-25, and DH-45 displayed lower hydrolysis rates, and DH-45 showed a decreased C∞ value of 18.9% with higher resistant starch (RS) content and lower glucose release. Our results indicate that AmyM-mediated hydrolysis is an efficient pathway for the preparation of porous starches with different functionalities which can be used for a range of applications.

Deciphering the structural and functional characteristics of an innovative small cluster branched α-glucan produced by sequential enzymatic synthesis

Highly branched α-glucan (HBAG) proved to be a promising material as an osmotic agent in peritoneal dialysis solutions. However, high resistance of HBAG to amylolytic enzymes might be a potential drawback for peritoneal dialysis due to its high degree of branching (20-30 %). To address this issue, we designed a small-clustered α-glucan (SCAG) with a relatively low molecular weight (Mw) and limited branching. Structural characteristics revealed that SCAG was successfully synthesized by modifying waxy rice starch (WRS) using sequential maltogenic α-amylase (MA) and starch branching enzyme (BE). The Mw of SCAG was 1.40 × 10⁵ Da, and its (α1 → 6) bonds ratio was 8.93 %, which was below that of HBAG. A relatively short branch distribution was observed in SCAG (CL = 6.27). Short-range orderliness of WRS was reduced from 0.749 to 0.322 with the MABE incubation. Additionally, SCAG had an extremely low viscosity (~12 cP) and nearly no retrogradation. Although the resistance of SCAG to amylolytic enzymes was enhanced by 15.22 % compared with native WRS, the extent was significantly lower than that of HBAG in previous studies. These new findings demonstrate the potential of SCAG as a novel functional α-glucan in food and pharmaceutical applications.

Malto-oligosaccharides as critical functional ingredient: a review of their properties, preparation, and versatile applications

Malto-oligosaccharides (MOS) are α-1,4 glycosidic linked linear oligosaccharides of glucose, which have a diverse range of functional applications in the food, pharmaceutical, and other industries. They can be used to modify the physicochemical properties of foods thereby improving their quality attributes, or they can be included as prebiotics to improve their nutritional attributes. The degree of polymerization of MOS can be controlled by using specific enzymes, which means their functionality can be tuned for specific applications. In this article, we review the chemical structure, physicochemical properties, preparation, and functional applications of MOS in the food, health care, and other industries. Besides, we offer an overview for this saccharide from the perspective of prospect functional ingredient, which we feel lacks in the current literature. MOS could be expected to provide a novel promising substitute for functional oligosaccharides.

Dual Modification of Starch by Physical Methods Based on Corona Electrical Discharge and Ionizing Radiation: Synergistic Impact on Rheological Behavior

The present paper focuses on evaluating the synergistic effects of dual modification with corona electric discharge (CED) and electron beam irradiation (EBI) on the rheological behavior of starch. Combined treatments were applied successively (CED/EBI and EBI/CED) and compared with single treatments. The outcomes showed that the rheological features of starch were altered by the dual modification in correlation with the irradiation dose mainly as a result of radiation-induced degradation. Decreases in apparent viscosity were described by exponential-like-models according to the order of application of the treatment sequences. The mathematical models allowed the estimation of the irradiation doses for which the viscosity decreased by e times for the dual modified starches (3.3 ± 1.3 kGy for CED/EBI and 5.6 ± 0.5 kGy for EBI/CED, respectively) and the fraction (f) of 0.47 ± 0.10 corresponding to starch granule considered to be affected by plasma. Both dual treatments yielded a synergistic effect, regardless of the order of application of the treatment sequences, being more effective in decreasing starch apparent viscosity than single EBI. However, synergism evaluation proved that the use of plasma as a pre-treatment to irradiation processing could provide benefits up to 20 kGy. These findings support the practical goals of technologists with valuable information that may facilitate or simplify the experimental design of starch dual modification with plasma and ionizing radiation.

Highlight on mutations affecting the US132 cyclodextrin glucanotransferase binding specificity, thermal stability, and anti-staling activity

We have already reported that the triple mutant (K47E-S382P-N655S of Paenibacillus pabuli US132 cyclodextrin glucanotransferase US132 (CGTase)) altered the CGTase specificity. In the current study, the single (K47E, S382P and N655S) and double (K47E+S382P, K47E+N655S, and S382P+N655S) mutants were constructed to elucidate the synergic or antagonist substitutions effect on the enzyme behavior. For the six generated mutants, an improvement of the dextrinization/cyclization ratio from 4.4 to 6-fold was observed when compared to the wild-type enzyme. The mutations effect on enzyme specificity was not attributed to synergy modulation since the single mutant N655S had the highest ratio enhancement. Moreover, the mutant N655S revealed the highest β-cyclodextrin binding affinity with a high amount of hydrophobic bonds which might be contributed to the apparent decrease in the cyclization activity. On the other hand, mutations N655S, K47E, and (K47E-N655S) showed the same positive effect on thermal activity. The highest stability was attained at 70 °C by N655S to be 3.6-fold higher than the wild-type. The addition of N655S to wheat flour induced a decrease of dough and bread hardness and led to an increase in dough and bread cohesiveness and a rise in bread masticability values compared to the control. This mutant addition also corrected the dough elasticity decrease engendered by the wild-type CGTase indicating that N655S-CGTase could be an alternative anti-staling agent.

Effect of high-temperatures and aqueous ethanol treatment on the formation process and properties of V-type Granular Starch (VGS)

Starch-water-ethanol mixtures were heated between 80 and 160 °C. The formation process of V-type granular starch (VGS) was investigated. DSC analysis showed that starch gelatinization was completely inhibited in 70 % ethanol. Microscopic analysis showed that starch remained granular morphology after modification, but when temperature exceeded 110 °C, Maltese cross and A-type crystalline structure disappeared, a V-type crystalline structure developed with increasing temperature, and short-range order of modified starch was reduced. It was indicated that VGS was formed at temperatures exceeding 110 °C in 70 % ethanol. When temperature was increased from 80 to 140 °C, starch cold-water viscosity increased from 17.00 cP to 1932.00 cP. Further temperature increase resulted in decreased cold-water viscosity because of starch degradation. It was found that cold-water viscosity was positively correlated with the crystallinity of V-type starch structure. Ethanol washing before drying made VGS dispersed better, and strengthened V-type crystalline structure, so that ethanol washed VGS had better paste properties.

Efficient secretory expression of Bacillus stearothermophilus α/β-cyclodextrin glycosyltransferase in Bacillus subtilis

Bacillus stearothermophilus α/β-cyclodextrin glycosyltransferase (α/β-CGTase) is an excellent transglycosylase with broad potential for food application, but its expression level is low in Bacillus subtilis. In this study, the optimal signal peptide for α/β-CGTase expression was screened from 173 signal peptides in B. subtilis WS11. The α/β-CGTase activity in a 3-L fermentor reached 151.93 U⋅ mL^-1, but substantial amounts of inclusion bodies were produced. The N-terminal 12 amino acids of α/β-CGTase were then replaced with the N-terminal 15 amino acids of a β-CGTase from the same family that has a high percentage of disorder-promoting amino acids. As a result, the inclusion bodies were significantly reduced, and the enzyme activity increased to 249.35 U mL^-1, 2.3 times that of the strain constructed previously. Finally, the ppsE and sfp genes of B. subtilis WS11, which are related to lipopeptide biosurfactant synthesis, were knocked out to produce B. subtilis WS13. When B. subtilis WS13 was used to produce α/β-CGTase in a 3-L fermentor, 70 % less defoaming agent was required than with B. subtilis WS11. Furthermore, enzyme production and growth of WS13 were equivalent to those of WS11. This study is of great significance for future research to efficiently scale-up production of α/β-CGTase.

Synergetic modification of waxy maize starch by dual-enzyme to lower the in vitro digestibility through modulating molecular structure and malto-oligosaccharide content

Cyclodextrinase (CDase) and cyclodextrin glucosyltransferase (CGTase) were synergistically used to provide a novel enzymatic method in lowing in vitro digestibility of waxy maize starch. The molecular structure, malto-oligosaccharide composition, and digestibility properties of the generated products were investigated. The molecular weight was reduced to 0.3 × 10⁵ g/mol and 0.2 × 10⁵ g/mol by simultaneous and sequential treatment with CDase and CGTase, while the highest proportion of chains with degree of polymerization (DP) < 13 was obtained by simultaneous treatment. The resistant starch contents were increased to 27.5% and 36.9% by simultaneous and sequential treatments respectively. Dual-enzyme treatment significantly promoted the content of malto-oligosaccharides (MOSs) by hydrolyzing cyclodextrins from CGTase with CDase. However, the replacement of cyclodextrins by MOSs did not obviously influence the digestibility of the products. The starch digestion kinetics further revealed the hydrolysis pattern of these two enzymes on the starch hydrolysate. It was proved that the starch digestibility could be lowered by modulating the molecular structure and beneficial MOSs content by this dual-enzyme treatment.