A two-stage modification method using 1,4-α-glucan branching enzyme lowers the in vitro digestibility of corn starch

Two-step modification of pullulanase and transglucosidase: A novel way to improve the gel strength and reduce the digestibility of rice starch

The multiscale structure, gel strength and digestibility of rice starch modified by the two-step modification of pullulanase (PUL) pretreatment and transglucosidase (TG) treatment for 6, 12, 18 and 24 h were investigated. The debranching hydrolysis of PUL produced some linear chains, which rearranged to form stable crystalline structures, reducing the digestible starch content, but weakening the gel strength. TG treatment connected some short chains to longer linear chains via α-1,6-glycosidic bonds, generating the structures of linear chain with fewer branches. The short branches promoted the interaction between starch molecules to form a more compact three-dimensional gel network structure, showing higher hardness and springiness. Moreover, these chains could form more stable crystals, reducing the digestible starch content, and the increase of branching degree inhibited digestive enzyme hydrolysis, reducing the digestion rate. The multiscale structure of starch tended to stabilize after TG treatment for 18 h, which could form a gel with stronger strength and lower digestibility than native starch gel. Therefore, the two-step modification of PUL and TG was an effective way to change the structure of rice starch to improve the gel strength and reduce the digestibility.

Starch spectra of Ampelopteris prolifera (Retz.) Copel, a new addition to the existing lexicon and its comparison with a local potato cultivar (Solanum tuberosum L. cv. Kufri Jyoti)

Novel kinds of starch spectra were generated from a lesser-known plant, making this investigation unique. The recent trend of starch characterization shows the establishment of novel bioresources from nonconventional unexplored databases. The present endeavor was made to obtain the starch fingerprint of Ampelopteris prolifera (rhizome) belonging to seedless vascular plants. For comparison, a commercial local cultivar of potato (Kufri Jyoti) was taken. The starch particle of A. prolifera shows much uniqueness depicting its novelty viz., crystallinity index of 60.04 %, powder diffractogram at (2θ scale)17.57° to 39.78°; this diffractogram pattern is reported from this study as newer one i.e. R type(whereas potato starch is CB type); characteristic peak at 2θ = 20.07° suggests starch-lipid complex formation and V type crystallinity (i.e. RS 5 type); FTIR spectra showing the presence of more short chain branching; high gelatinization temperature(84.62 ± 0.10), particle size and zeta value of A. prolifera is 4.00 ± 0.81 μm and - 18.91 ± 3.58 mV respectively. Bragg's peak from the single crystal X-ray diffraction has been generated for the first time of A. prolifera. Extraction of the starch particle was performed in chilled water. Therefore, the present study suggests wide-spectrum commercial utility and cost-effective production.

Jicama (Pachyrhizus spp.) a nonconventional starch: A review on isolation, composition, structure, properties, modifications and its application

Starch attracts food industries due to their availability in nature, cheapness, biodegradability and possibilities of endless applications. The starch properties and their modification affect food quality. Compared to other cereals, tuber and root starches, more systematic information is needed on the jicama starches (JS). This review article summarizes the isolation, composition, morphology, rheological, thermal and digestibility properties of JS. The modifications and its current and potential applications are also discussed. The chemical composition and structure of JS are different from other starches, influencing its properties. JS has been modified by physical and chemical methods to improve the properties of starch. However, there are very few studies on the modification of JS as compared with other commercial starch although it has been used in food formulation as a stabilizer and to improve the texture of food products. It is also applied as an edible coating to preserve the quality of food products and use as a raw material for making edible and bioplastic packaging. However, large-scale utilization of JS is unexplored compared to commercial starches. Therefore, this review would provide useful information and suggestions for more research on Jicama starch and its industrial applications.

Catalytic activity enhancement of 1,4-α-glucan branching enzyme by N-terminal modification

The 1,4-α-glucan branching enzyme (GBE, EC 2.4.1.18) has garnered considerable attention for its ability to increase the degree of branching of starch and retard starch digestion, which has great industrial applications. Previous studies have reported that the N-terminal domain plays an important role in the expression and stability of GBEs. To further increase the catalytic ability of Gt-GBE, we constructed five mutants in the N-terminal domain: L19R, L19K, L25R, L25K, and L25A. Specific activities of L25R and L25A were increased by 28.46% and 23.46%, respectively, versus the wild-type Gt-GBE. In addition, the α-1,6-glycosidic linkage ratios of maltodextrin samples treated with L25R and L25A increased to 5.71%, which were significantly increased by 19.96% compared with that of the wild-type Gt-GBE. The results of this study suggest that the N-terminal domain selective modification can improve enzyme catalytic activity, thus further increasing the commercial application of enzymes in food and pharmaceutical industries.

Designing a Specific Pretreatment on Corn Starch to Facilitate Enzymatic Rearrangement of Glycosidic Bonds for Efficiently Reducing Starch Digestibility

Bacterial 1,4-α-glucan branching enzymes (GBEs) provide a viable strategy for glycosidic bond rearrangement in starch and regulation of its digestion rate. However, the exponential increase in paste viscosity during starch gelatinization has a detrimental effect on the catalytic action of GBEs, thereby limiting productivity and product performance. Here, we designed an enzymatic treatment on corn starch granules by the GBE from Rhodothermus obamensis STB05 (Ro-GBE) prior to the glycosidic bond rearrangement of gelatinized starch catalyzed using the GBE from Geobacillus thermoglucosidans STB02 (Gt-GBE). Specifically, a moderate amount of Ro-GBE was required for the pretreatment stage. The dual GBE modification process enabled the treatment of more concentrated starch slurry (up to 20%, w/w) and effectively reduced starch digestibility. The resulting product contained a rapidly digestible starch fraction of 66.0%, which was 11.4% lower than that observed in the single Gt-GBE-modified product. The mechanistic investigation showed that the Ro-GBE treatment promoted swelling and gelatinization of starch granules, reduced starch paste viscosity, and increased the mobility of water molecules in the starch paste. It also created a preferable substrate for Gt-GBE. These changes improved the transglycosylation efficiency of Gt-GBE. These findings provide useful guidance for designing an efficient process to regulate starch digestibility.

Preparation and characterization of cationic hyperbranched maltodextrins as potential carrier for siRNA encapsulation

The present study sought to investigate the physicochemical properties of cationic branched maltodextrins with similar degrees of substitution but different degrees of branching and their siRNA delivery capacity. The results showed that the ratio of α-1,6 glycosidic bonds was significantly increased in the sample treated with dual enzymes. The structural characterization results showed that abundant short chains reassembled by 1,4-α-glucan branching enzyme (GBEs) hydrolysis formed hyperbranched short clustered structure. The absorption peaks that appeared in the FT-IR spectrum confirmed the occurrence of quaternization. The complexes formed by self-assembly of cationic maltodextrins and siRNA were verified by the gel retardation assay and atomic force microscopy, demonstrating a uniform spherical structure with a size close to 300-350 nm. Meanwhile, cationic branched maltodextrins could effectively reduce the change of secondary structure of siRNA. Overall, the results suggested that branched maltodextrins with a cationic surface had significant potential as siRNA carriers.

Analysis of carbohydrates and glycoconjugates by matrix-assisted laser desorption/ionization mass spectrometry: An update for 2019-2020

This review is the tenth update of the original article published in 1999 on the application of matrix-assisted laser desorption/ionization (MALDI) mass spectrometry to the analysis of carbohydrates and glycoconjugates and brings coverage of the literature to the end of 2020. Also included are papers that describe methods appropriate to analysis by MALDI, such as sample preparation techniques, even though the ionization method is not MALDI. The review is basically divided into three sections: (1) general aspects such as theory of the MALDI process, matrices, derivatization, MALDI imaging, fragmentation, quantification and the use of arrays. (2) Applications to various structural types such as oligo- and polysaccharides, glycoproteins, glycolipids, glycosides and biopharmaceuticals, and (3) other areas such as medicine, industrial processes and glycan synthesis where MALDI is extensively used. Much of the material relating to applications is presented in tabular form. The reported work shows increasing use of incorporation of new techniques such as ion mobility and the enormous impact that MALDI imaging is having. MALDI, although invented nearly 40 years ago is still an ideal technique for carbohydrate analysis and advancements in the technique and range of applications show little sign of diminishing.

Protection against Oxidative Stress and Metabolic Alterations by Synthetic Peptides Derived from Erythrina edulis Seed Protein

The ability of multifunctional food-derived peptides to act on different body targets make them promising alternatives in the prevention/management of chronic disorders. The potential of Erythrina edulis (pajuro) protein as a source of multifunctional peptides was proven. Fourteen selected synthetic peptides identified in an alcalase hydrolyzate from pajuro protein showed in vitro antioxidant, anti-hypertensive, anti-diabetic, and/or anti-obesity effects. The radical scavenging properties of the peptides could be responsible for the potent protective effects observed against the oxidative damage caused by FeSO4 in neuroblastoma cells. Moreover, their affinity towards the binding cavity of angiotensin-converting enzyme (ACE) and dipeptidyl peptidase IV (DPP-IV) were predicted by molecular modeling. The results demonstrated that some peptides such as YPSY exhibited promising binding at both enzymes, supporting the role of pajuro protein as a novel ingredient of functional foods or nutraceuticals for prevention/management of oxidative stress, hypertension, and metabolic-alteration-associated chronic diseases.

Antidiabetic bio-peptides of soft and hard wheat glutens

•

Effect of enzyme purification techniques on kiwifruit extract and gluten peptides were investigated.

•

Ammonium sulfate was the most efficient kiwifruit enzyme purification method.

•

Ammonium sulfate based purified enzyme produced bio-active peptides (<1 kDa).

•

The highest in vitro inhibitory activities was observed on gliadin based peptides.

•

High Pro, Ser, and Asp contents of sub-fraction (P3) explain the inhibitory effects.

The effects of various purification techniques on kiwifruit enzyme characteristics (protease activity, kinetic parameters, and protein patterns) and production of wheat gluten bio-active peptides were investigated. The enzyme extract purified by ammonium sulfate precipitation method exhibited the highest protease activity (26), K_m (0.04 ± 0.002 mM), K_cat/K_m (40), and yield (96%). Using actinidin, the hard and soft wheat gluten subunit proteins produced antidiabetic inhibitory (α-glucosidase and α-amylase) peptides. The smallest M_w fraction of soft wheat gliadin peptide (<1 kDa) showed the highest inhibitory capacity against α-glucosidase (18.4 ± 0.7%) and α-amylase (53.3 ± 1.9%). The presence of high levels of amino acids with hydroxyl groups and proline in P3 sub-fraction had a critical role on α-glucosidase (47.2%) and α-amylase (71.2%) inhibitory activities. In conclusion, wheat gluten subunit peptides showed significant metabolic effects relevant to glucose and insulin control in vitro.

Effect of Starch Primers on the Fine Structure of Enzymatically Synthesized Glycogen-like Glucan

Glycogen-like glucan (GnG) is a unique hyperbranched polysaccharide nanoparticle which is drawing increasing attention due to its biodegradability and abundant short branches that can be functionalized. Because starch and GnG are both composed of glucose residues and have similar glucosidic bonds, GnG could be fabricated by sucrose phosphorylase, α-glucan phosphorylase, and branching enzymes from starch primers and sucrose. In this study, high-amylose starch, normal starch, and waxy corn starch were used as primers to synthesize GnG, and their impact on the fine structure of GnG was investigated. Structural analysis indicated that with increasing content of amylopectin in the starch primer, the proportion of short chains in GnG decreased, and the degree of β-amylolysis and α-amylolysis was enhanced. Amylose in the primer contributed to a compact and homogeneous structure of GnG, while amylopectin triggered the formation of branch points with a more open distribution. These findings provide a new strategy for regulating the fine structure of GnG.

The amino acid on the top of the active groove allosterically modulates product specificity of the 1,4-α-glucan branching enzyme

The 1,4-α-glucan branching enzymes (GBEs, EC 2.4.1.18) catalyse the formation of α-1,6 branching points in starch, presenting several potential applications in modifying starch. Previous study proved that W285 is considered to act as a "switch" to stop extension of substrates in the structure of GBE from Cyanothece sp. (cceBE). In the structure of GBE from Rhodothermus obamensis STB05 (RoGBE), the amino acid 160 site is structurally similar to the W285 in cceBE. In order to explore the role of this site in RoGBE, several engineered mutants individually substituted with Arg, Phe and Ala at G160 were studied in our research. The results show that substitution with Arg and Phe increased branching activity significantly, and the ratio of short glucan chains among all oligosaccharides increased. Finally, we proposed that the G160 is a 'door model' to elucidate introduced mutagenesis that triggers and controls the length of binding glucan chains of starch.

New insights into the alleviating role of starch derivatives on dough quality deterioration caused by freeze

The alleviating role of starch derivatives on the quality deterioration of frozen steamed bread dough was investigated in terms of derivative structure, the bread characteristics and dough properties including freezable water contents, yeast activity as well as dough viscoelasticity. The addition of starch derivatives including short-clustered maltodextrin (SCMD), DE2 maltodextrin (MD) and pregelatinized starch (PGS) significantly increased the specific volume and decreased the hardness of steamed bread compared with Control bread after 8-week frozen storage. Lower freezable water content was found in PGS dough than SCMD dough, which was consistent with the results of water absorption index of starch derivatives. The analysis of dough gassing rate and yeast survival ratio demonstrated SCMD could provide more cryoprotection for yeast cells. Meanwhile, a higher elastic module and a more continuous gluten-network structure of SCMD dough were found after 8-week frozen storage. These results indicated starch derivatives especially SCMD were promising to be used as the alternative improvers in frozen dough production.

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.

An Innovative Short-Clustered Maltodextrin as Starch Substitute for Ameliorating Postprandial Glucose Homeostasis

Dietary starch is usually associated with elevated postprandial glycemic response. This is a potential risk factor of type 2 diabetes. Here, a 1,4-α-glucan branching enzyme (GBE) was employed to reassemble α-1,4 and α-1,6 glycosidic bonds in starch molecules. Structural characterization showed that GBE-catalyzed molecular reassembly created an innovative short-clustered maltodextrin (SCMD), which showed a dense internal framework along with shortened external chains. Such short-clustered molecules obstructed digestive enzymes attack and displayed dramatically reduced digestibility. Therefore, SCMD was served as a dietary starch substitute to improve postprandial glucose homeostasis. A 22.3% decrease in glycemic peak was therefore detected in ICR mice following SCMD intake (10.7 mmol/L), compared with that in the control (13.8 mmol/L). Moreover, an attenuated insulin response (40.5% lower than that in control) to SCMD intake was regarded suitable for diabetes management. These novel discoveries demonstrate that enzymatically rebuilding starch molecules may be a meaningful strategy for diabetes management.

Novel Short-Clustered Maltodextrin as a Dietary Starch Substitute Attenuates Metabolic Dysregulation and Restructures Gut Microbiota in db/db Mice

Molecular structure of starch in daily diet is closely associated with diabetes management. By enzymatically reassembling α-1,4 and α-1,6 glycosidic bonds in starch molecules, we have synthesized an innovative short-clustered maltodextrin (SCMD) which slowly releases glucose during digestion. Here, we investigated the potential benefits of the SCMD-containing diet using diabetic db/db mice. As compared to a diet with normal starch, this dietary style greatly attenuated hyperglycemia and repaired symptoms associated with diabetes. Additionally, in comparison with acarbose (an α-glucosidase inhibitor) administration, the SCMD-containing diet more effectively accelerated brown adipose activation and improved energy metabolism of db/db mice. Furthermore, the SCMD-containing diet was a more suitable approach to improving the intestinal microflora than acarbose administration, especially the proliferation of Mucispirillum, Akkermansia, and Bifidobacterium. These results reveal a novel strategy for diabetes management based on enzymatically rebuilding starch molecules in the daily diet.