RESUMO
In cereal grains, starch is synthesized by the concerted actions of multiple enzymes on the surface of starch granules within the amyloplast. However, little is known about how starch-synthesizing enzymes access starch granules, especially for amylopectin biosynthesis. Here, we show that the rice (Oryza sativa) floury endosperm9 (flo9) mutant is defective in amylopectin biosynthesis, leading to grains exhibiting a floury endosperm with a hollow core. Molecular cloning revealed that FLO9 encodes a plant-specific protein homologous to Arabidopsis (Arabidopsis thaliana) LIKE EARLY STARVATION1 (LESV). Unlike Arabidopsis LESV, which is involved in starch metabolism in leaves, OsLESV is required for starch granule initiation in the endosperm. OsLESV can directly bind to starch by its C-terminal tryptophan (Trp)-rich region. Cellular and biochemical evidence suggests that OsLESV interacts with the starch-binding protein FLO6, and loss-of-function mutations of either gene impair ISOAMYLASE1 (ISA1) targeting to starch granules. Genetically, OsLESV acts synergistically with FLO6 to regulate starch biosynthesis and endosperm development. Together, our results identify OsLESV-FLO6 as a non-enzymatic molecular module responsible for ISA1 localization on starch granules, and present a target gene for use in biotechnology to control starch content and composition in rice endosperm.
Assuntos
Endosperma , Regulação da Expressão Gênica de Plantas , Oryza , Proteínas de Plantas , Amido , Oryza/genética , Oryza/metabolismo , Oryza/crescimento & desenvolvimento , Endosperma/metabolismo , Endosperma/genética , Amido/metabolismo , Amido/biossíntese , Proteínas de Plantas/metabolismo , Proteínas de Plantas/genética , Amilopectina/metabolismo , Mutação , Plantas Geneticamente ModificadasRESUMO
Starch is the major energy storage compound in plants. Both transient starch and long-lasting storage starch accumulate in the form of insoluble, partly crystalline granules. The structure of these granules is related to the structure of the branched polymer amylopectin: linear chains of glucose units organized in double helices that align to form semicrystalline lamellae, with branching points located in amorphous regions between them. EARLY STARVATION 1 (ESV1) and LIKE EARLY STARVATION 1 (LESV) proteins are involved in the maintenance of starch granule structure and in the phase transition of amylopectin, respectively, in Arabidopsis (Arabidopsis thaliana). These proteins contain a conserved tryptophan-rich C-terminal domain folded into an antiparallel ß-sheet, likely responsible for binding of the proteins to starch, and different N-terminal domains whose structure and function are unknown. In this work, we combined biochemical and biophysical approaches to analyze the structures of LESV and ESV1 and their interactions with the different starch polyglucans. We determined that both proteins interact with amylopectin but not with amylose and that only LESV is capable of interacting with amylopectin during starch biosynthesis. While the C-terminal domain interacts with amylopectin in its semicrystalline form, the N-terminal domain of LESV undergoes induced conformational changes that are probably involved in its specific function of mediating glucan phase transition. These results clarify the specific mechanism of action of these 2 proteins in the biosynthesis of starch granules.
Assuntos
Amilopectina , Proteínas de Arabidopsis , Arabidopsis , Amido , Amilopectina/metabolismo , Arabidopsis/metabolismo , Arabidopsis/genética , Amido/metabolismo , Amido/biossíntese , Proteínas de Arabidopsis/metabolismo , Proteínas de Arabidopsis/genética , Ligação Proteica , Amilose/metabolismoRESUMO
Amylose biosynthesis is strictly associated with granule-bound starch synthase I (GBSSI) encoded by the Waxy gene. Mutagenesis of single bases in the Waxy gene, which induced by CRISPR/Cas9 genome editing, caused absence of intact GBSSI protein in grain of the edited line. The amylose and amylopectin contents of waxy mutants were zero and 31.73%, while those in the wild type were 33.50% and 39.00%, respectively. The absence of GBSSI protein led to increase in soluble sugar content to 37.30% compared with only 10.0% in the wild type. Sucrose and ß-glucan, were 39.16% and 35.40% higher in waxy mutants than in the wild type, respectively. Transcriptome analysis identified differences between the wild type and waxy mutants that could partly explain the reduction in amylose and amylopectin contents and the increase in soluble sugar, sucrose and ß-glucan contents. This waxy flour, which showed lower final viscosity and setback, and higher breakdown, could provide more option for food processing.
Assuntos
Amilose , Edição de Genes , Hordeum , Proteínas de Plantas , Sintase do Amido , Amilose/metabolismo , Hordeum/genética , Hordeum/metabolismo , Edição de Genes/métodos , Sintase do Amido/genética , Sintase do Amido/metabolismo , Proteínas de Plantas/genética , Proteínas de Plantas/metabolismo , Sistemas CRISPR-Cas , Amilopectina/metabolismo , Sacarose/metabolismo , Açúcares/metabolismo , Regulação da Expressão Gênica de Plantas , Mutação , beta-Glucanas/metabolismo , Plantas Geneticamente Modificadas , SolubilidadeRESUMO
In the present study, taking red yeast rice (RYR) as the raw material, the optimum extraction process of RYR starch was investigated through a single-factor experiment and the Box-Behnken design: The liquid-to-solid ratio was 5 mL/g, the concentration of sodium hydroxide solution was 0.075 mol/L, and the extraction time was 3.1 h. Under these extraction conditions, the extraction rate of starch reached 90.077%. To explore the influence of solid-state fermentation on RYR starch, three different fermentation stages of RYR starch, raw rice starch, semi-gelatinized rice starch, and RYR starch were used as test materials to determine the changes in the physicochemical properties and glycemic index (GI) values of RYR starch during solid-state fermentation. The results showed that with the advancement of the RYR solid-state fermentation process, the starch particle size gradually increased, the light transmittance gradually decreased, and the solubility and swelling power significantly increased. In addition, the amylose content of starch gradually increased, whereas the amylopectin content gradually decreased; the content of fast digestible starch and slow digestible starch decreased, whereas the content of resistant starch increased. In parallel, during solid-state fermentation, the hydrolysis index significantly decreased, and the GI values also decreased. In summary, solid-state fermentation reduced the digestibility of RYR starch. These results provide a theoretical basis for the structural and physicochemical properties of RYR starch and lay a foundation for its subsequent application and expansion of RYR starch.
Assuntos
Produtos Biológicos , Oryza , Amido , Amido/química , Oryza/química , Amilopectina/química , HidróliseRESUMO
Powdery scab disease, caused by the soilborne protist Spongospora subterranea f. sp. subterranea, poses a major constraint to potato production worldwide. Disease symptoms include damage to the tuber skin and the formation of root galls. This study aimed to investigate the potential mechanism behind the formation of sporosori, which are aggregates of resting spores, within root galls. Scanning electron microscopy analysis revealed that the early stage of gall formation, characterized by a white color, involved the accumulation of starch grains, which later disappeared as the gall matured and turned brown. The mature brown galls were found to contain fully formed sporosori. Light microscopy examination of ultramicrotome sections of the root galls showed that the high-amylopectin starches were surrounded by a plasmodium, a precursor to sporosorus. These findings suggest that starch grains contribute to the formation of a sponge-like structure within the sporosori. A significant reduction in total starch levels in both the root galls and their associated roots was observed compared with healthy roots. These findings indicate starch consumption by sporosori during the maturation of root galls. Interestingly, analysis of the transcript levels of starch-related genes showed downregulation of genes encoding starch degrading enzymes and an amylopectin-debranching enzyme, whereas genes encoding a starch synthase and a protein facilitating starch synthesis were upregulated in the infected roots. Overall, our results demonstrate that starch is consumed during sporosorus formation, and the pathogen likely manipulates starch homeostasis to its advantage for sporosorus development within the root galls.
Assuntos
Doenças das Plantas , Plasmodioforídeos , Amido , Amilopectina , Metabolismo dos Carboidratos , Plasmodioforídeos/genéticaRESUMO
Grain size in rice (Oryza sativa L.) shapes yield and quality, but the underlying molecular mechanism is not fully understood. We functionally characterized GRAIN NUMBER AND LARGE GRAIN SIZE 44 (GNL44), encoding a RING-type protein that localizes to the cytoplasm. The gnl44 mutant has fewer but enlarged grains compared to the wild type. GNL44 is mainly expressed in panicles and developing grains. Grain chalkiness was higher in the gnl44 mutant than in the wild type, short-chain amylopectin content was lower, middle-chain amylopectin content was higher, and appearance quality was worse. The amylose content and gel consistency of gnl44 were lower, and protein content was higher compared to the wild type. Rapid Visco Analyzer results showed that the texture of cooked gnl44 rice changed, and that the taste value of gnl44 was lower, making the eating and cooking quality of gnl44 worse than that of the wild type. We used gnl44, qgl3, and gs3 monogenic and two-gene near-isogenic lines to study the effects of different combinations of genes affecting grain size on rice quality-related traits. Our results revealed additive effects for these three genes on grain quality. These findings enrich the genetic resources available for rice breeders.
Assuntos
Oryza , Oryza/genética , Amilopectina , Amilose , Carbonato de Cálcio , Culinária , Grão Comestível/genéticaRESUMO
BACKGROUND: There has been significant interest in pre-cooked noodles that have a long shelf life and are convenient to cook. However, the thermal processes during preparation, and their high moisture content, can lead to significant quality deterioration during storage. Nevertheless, a comprehensive evaluation of these quality losses has not yet been conducted. RESULTS: The effects of different storage temperatures (25, 4, and -20 °C) on the retrogradation-related physicochemical changes in pre-cooked rice noodles were elucidated mainly from the water dynamics and structural viewpoints. Thermal analysis demonstrated that amylopectin recrystallization took place in the noodles stored at refrigerated temperature, followed by room temperature. The refrigerated storage accelerated the starch retrogradation that caused the water molecules to become entrapped within the crystalline structure by lowering the water hydration properties and weighted T2 relaxation times of the pre-cooked noodles. These water mobility patterns were correlated with the textural changes in the noodles (greater hardness and Rmax /extensibility). Furthermore, the higher structural density and thickness derived from starch retrogradation were observed in the tomographic and microscopic images of the refrigerated noodles. The principal component analysis demonstrated that various physicochemical changes of the pre-cooked noodles during storage showed high correlations with the degree of starch retrogradation (r > 0.83). CONCLUSION: The physicochemical features of the precooked noodles stored under refrigerated conditions were involved in the molecular dynamics of water, showing a notable water mobility reduction derived from the starch retrogradation, which contributed to their thermal, tomographical, and textural changes. © 2023 Society of Chemical Industry.
Assuntos
Oryza , Temperatura , Oryza/química , Água/química , Amido/química , Amilopectina/químicaRESUMO
BACKGROUND: Rice taste is closely associated with endosperm composition, which varies among different rice layers. Although clarifying the relationship between this difference and nutritional taste can guide rice breeding and cultivation practices, research on this topic is limited. RESULTS: Here, typical rice varieties having excellent and poor taste characteristics were selected to analyze the distribution characteristics and differences of their components. The varieties with excellent taste exhibited lower apparent amylose content (AAC) and protein content (PC), lesser short-chain (Fa) and long-chain (Fb3 ) amylopectin (AP) and more medium-chain (Fb1+2 ) AP, higher long-to-short chain ratio (Fa:Fb3 ), and higher nitrogen (N), magnesium (Mg) and calcium (Ca) content in layer 1 (L1) than the varieties with poor taste. Layer 2 (L2) played a key role in AAC and PC regulation in the varieties with excellent taste by reducing AAC and appropriately increasing PC, consequently improving rice taste. AP structure in layer 3 (L3) substantially affected the taste of the two types of varieties. The mineral content was the highest in L1, and increased potassium (K), Ca, and Mg content improved taste in all varieties. CONCLUSION: AAC in each layer contributes to rice taste. PC and minerals primarily act on L1 and L2, whereas AP acts on L2 and L3. Therefore, the endosperm formation process should be exploited for improving rice taste. Furthermore, key resources and cultivation should be identified and regulated, respectively, to improve rice taste. © 2023 Society of Chemical Industry.
Assuntos
Oryza , Oryza/química , Paladar , Melhoramento Vegetal , Amilopectina/química , Endosperma/química , Amilose/análise , Minerais/análise , Magnésio/análise , Amido/químicaRESUMO
BACKGROUND: The continuous cultivation of rice-wheat in the same field is a key element of double-cropping systems in the Indo-Gangetic plains. Yields of such cropping systems are increasingly challenged as climate change drives increases in temperature, terminal stress and uneven rainfall, delaying rice harvesting and subsequently delaying sowing of wheat. In this paper, we evaluate the optimum sowing dates to achieve high grain yield and quality of wheat cultivars in northwest India. Three cultivars of wheat, HD-2967, HD-3086 and PBW-723, were sown on three different dates at the research farm of ICAR-IARI, New Delhi, to generate different weather conditions at different phenological stages. Different biophysical attributes, photosynthetic rate, stomatal conductance and transpiration rate, were measured at different phenological stages. Yield and grain quality parameters such as protein, starch, amylopectin, amylose and gluten were measured in different cultivars sown on different dates. RESULTS: Biophysical parameters were found to be higher in timely sown crops followed by late-sown and very late-sown crops. Further, the different sowing dates had a significant (P < 0.05) impact on the grain quality parameters such as protein, starch, amylopectin, amylose and gluten content. Percentage increases in the value of starch and amylose content under timely sown were ~7% and 11.6%, ~5% and 8.4%, compared to the very late-sown treatment. In contrast, protein and amylopectin contents were found to increase by ~9.7% and 7.5%, ~13.8% and 16.6% under very late-sown treatment. CONCLUSION: High-temperature stress during the grain-filling periods significantly decreased the grain yield. Reduction in the grain yield was associated with a reduction in starch and amylose content in the grains. The protein content in the grains is less affected by terminal heat stress. Cultivar HD-3086 had higher growth, yield as well as quality parameters, compared to HD-2967 and PBW-723 in all treatments, hence could be adopted by farmers in northwest India. © 2024 Society of Chemical Industry.
Assuntos
Produção Agrícola , Triticum , Triticum/metabolismo , Triticum/crescimento & desenvolvimento , Triticum/química , Triticum/classificação , Índia , Produção Agrícola/métodos , Grão Comestível/química , Grão Comestível/crescimento & desenvolvimento , Grão Comestível/metabolismo , Amido/metabolismo , Amido/análise , Amido/química , Amilose/metabolismo , Amilose/análise , Estações do Ano , Fotossíntese , Amilopectina/metabolismo , Amilopectina/química , Proteínas de Plantas/metabolismo , Sementes/química , Sementes/metabolismo , Sementes/crescimento & desenvolvimento , Agricultura/métodosRESUMO
Ruminococcus bromii is a keystone species in the human gut that has the rare ability to degrade dietary resistant starch (RS). This bacterium secretes a suite of starch-active proteins that work together within larger complexes called amylosomes that allow R. bromii to bind and degrade RS. Starch adherence system protein 20 (Sas20) is one of the more abundant proteins assembled within amylosomes, but little could be predicted about its molecular features based on amino acid sequence. Here, we performed a structure-function analysis of Sas20 and determined that it features two discrete starch-binding domains separated by a flexible linker. We show that Sas20 domain 1 contains an N-terminal ß-sandwich followed by a cluster of α-helices, and the nonreducing end of maltooligosaccharides can be captured between these structural features. Furthermore, the crystal structure of a close homolog of Sas20 domain 2 revealed a unique bilobed starch-binding groove that targets the helical α1,4-linked glycan chains found in amorphous regions of amylopectin and crystalline regions of amylose. Affinity PAGE and isothermal titration calorimetry demonstrated that both domains bind maltoheptaose and soluble starch with relatively high affinity (Kd ≤ 20 µM) but exhibit limited or no binding to cyclodextrins. Finally, small-angle X-ray scattering analysis of the individual and combined domains support that these structures are highly flexible, which may allow the protein to adopt conformations that enhance its starch-targeting efficiency. Taken together, we conclude that Sas20 binds distinct features within the starch granule, facilitating the ability of R. bromii to hydrolyze dietary RS.
Assuntos
Proteínas de Bactérias/metabolismo , Proteínas de Transporte , Ruminococcus , Amilopectina/metabolismo , Amilose/metabolismo , Proteínas de Transporte/metabolismo , Carboidratos da Dieta , Humanos , Amido/metabolismoRESUMO
Not all starches in the human diet are created equal: "resistant starches" are consolidated aggregates of the α-glucan polysaccharides amylose and amylopectin, which escape digestion by salivary and pancreatic amylases. Upon reaching the large intestine, resistant starches become fodder for members of the human gut microbiota, impacting the metabolism of both the symbionts and the host. In a recent study, Koropatkin et al. provided new molecular insight into how a keystone bacterium in the human gut microbiota adheres to resistant starches as a prelude to their breakdown and fermentation.
Assuntos
Microbioma Gastrointestinal , Amido , Amilopectina/metabolismo , Amilose/metabolismo , Glucanos , Humanos , Amido/metabolismo , alfa-Amilases/metabolismoRESUMO
Amylopectin is a highly branched glucan which accounts for approximately 65-85% of starch in most plant tissues. It is crucially important to understand the biosynthetic process of this glucan in regulating the structure and functional properties of starch granules. Currently, the most accepted ideas of structural feature and biosynthesis of amylopectin are that amylopectin is composed of a branched element called "cluster" and that the essential process of amylopectin biosynthesis is to reproduce a new cluster from the existing cluster. The present paper proposes a model explaining the whole process of amylopectin biosynthesis as to how the new cluster is reproduced by concerted actions of multiple isoforms of starch biosynthetic enzymes, particularly by combinations of distinct roles of starch branching enzyme (BE) isoforms. This model proposes for the first time the molecular mechanism as to how the formation of a new cluster is initiated, and the reason why BEI can play a major role in this step. This is because BEI has a rather broad chain-length preference compared to BEIIb, because a low preference of BEI for the substrate chain-length is advantageous for branching a couple of elongated chains that are not synchronously formed and thus these chains having varied lengths could be safely attacked by this isoform. On the contrary, it is unlikely that BEIIb is involved in this reaction because it can react to only short chains having degree of polymerization of 12-14. BEIIa is possibly able to complement the role of BEI to some extent, because BEIIa can attack basically short chains but its chain-length preference is lower compared with BEIIb. The model implies that the first branches mainly formed by BEI to construct the amorphous lamellae whereas the second branches predominantly formed by BEIIb are located mainly in the crystalline lamellae. This paper provides new insights into the roles of BEI, BEIIb, and BEIIa in amylopectin biosynthesis in cereal endosperm.
Assuntos
Enzima Ramificadora de 1,4-alfa-Glucana , Oryza , Amilopectina/química , Enzima Ramificadora de 1,4-alfa-Glucana/genética , Isoenzimas/genética , Amido , Glucanos , ReproduçãoRESUMO
Rice is the model C3 crop for investigating the starch biosynthesis mechanism in endosperm because of its importance in grain production. However, little is known about starch biosynthesis in the vegetative organs of rice. In this study, we used novel rice mutants by inserting Tos17 into the starch synthase (SS) IIIb gene, which is mainly expressed in the leaf sheath (LS) and leaf blade (LB), and an ss1 mutant to clarify the differences in roles among SS isozymes during starch biosynthesis. Native polyacrylamide gel electrophoresis (PAGE)/activity staining for SS, using LS and LB of ss mutants, revealed that the lowest migrating SS activity bands on the gel were derived from SSIIIb activity and those of two ss3b mutants were not detected. The apparent amylose content of LS starch of ss3b mutants increased. Moreover, the chain-length distribution and size-exclusion chromatography analysis using ss mutants showed that SSIIIb and SSI synthesize the B2-B3 chain and A-B1 chain of amylopectin in the LS and LB respectively. Interestingly, we also found that starch contents were decreased in the LS and LB of ss3b mutants, although SSI deficiency did not affect the starch levels. All these results indicated that SSIIIb synthesizes the long chain of amylopectin in the LS and LB similar to SSIIIa in the endosperm, while SSI synthesizes the short chain in the vegetative organ as the same in the endosperm.
Assuntos
Oryza , Sintase do Amido , Amilopectina , Oryza/genética , Sintase do Amido/genética , Sementes/genética , Amido , AmiloseRESUMO
BACKGROUND: Induction of mutation through chemical mutagenesis is a novel approach for preparing diverse germplasm. Introduction of functional alleles in the starch biosynthetic genes help in the improvement of the quality and yield of cereals. RESULTS: In the present study, a set of 350 stable mutant lines were used to evaluate dynamic variation of the total starch contents. A megazyme kits were used for measuring the total starch content, resistant starch, amylose, and amylopectin content. Analysis of variance showed significant variation (p < 0.05) in starch content within the population. Furthermore, two high starch mutants (JE0173 and JE0218) and two low starch mutants (JE0089 and JE0418) were selected for studying different traits. A multiple comparison test showed that significant variation in all physiological and morphological traits, with respect to the parent variety (J411) in 2019-2020 and 2020-2021. The quantitative expression of starch metabolic genes revealed that eleven genes of JE0173 and twelve genes of JE0218 had consistent expression in high starch mutant lines. Similarly, in low starch mutant lines, eleven genes of JE0089 and thirteen genes of JE0418 had consistent expression in all stages of seed development. An additional two candidate genes showed over-expression (PHO1, PUL) in the high starch mutant lines, indicating that other starch metabolic genes may also contribute to the starch biosynthesis. The overexpression of SSII, SSIII and SBEI in JE0173 may be due to presence of missense mutations in these genes and SSI also showed overexpression which may be due to 3-primer_UTR variant. These mutations can affect the other starch related genes and help to increase the starch content in this mutant line (JE0173). CONCLUSIONS: This study screened a large scale of mutant population and identified mutants, could provide useful genetic resources for the study of starch biosynthesis and genetic improvement of wheat in the future. Further study will help to understand new genes which are responsible for the fluctuation of total starch.
Assuntos
Amido , Triticum , Amido/metabolismo , Triticum/genética , Triticum/metabolismo , Proteínas de Plantas/genética , Proteínas de Plantas/metabolismo , Amilose/metabolismo , Amilopectina/genética , Amilopectina/metabolismoRESUMO
Starch accounts for up to 90% of the dry weight of rice endosperm and is a key determinant of grain quality. Although starch biosynthesis enzymes have been comprehensively studied, transcriptional regulation of starch-synthesis enzyme-coding genes (SECGs) is largely unknown. In this study, we explored the role of a NAC transcription factor, OsNAC24, in regulating starch biosynthesis in rice. OsNAC24 is highly expressed in developing endosperm. The endosperm of osnac24 mutants is normal in appearance as is starch granule morphology, while total starch content, amylose content, chain length distribution of amylopectin and the physicochemical properties of the starch are changed. In addition, the expression of several SECGs was altered in osnac24 mutant plants. OsNAC24 is a transcriptional activator that targets the promoters of six SECGs; OsGBSSI, OsSBEI, OsAGPS2, OsSSI, OsSSIIIa and OsSSIVb. Since both the mRNA and protein abundances of OsGBSSI and OsSBEI were decreased in the mutants, OsNAC24 functions to regulate starch synthesis mainly through OsGBSSI and OsSBEI. Furthermore, OsNAC24 binds to the newly identified motifs TTGACAA, AGAAGA and ACAAGA as well as the core NAC-binding motif CACG. Another NAC family member, OsNAP, interacts with OsNAC24 and coactivates target gene expression. Loss-of-function of OsNAP led to altered expression in all tested SECGs and reduced the starch content. These results demonstrate that the OsNAC24-OsNAP complex plays key roles in fine-tuning starch synthesis in rice endosperm and further suggest that manipulating the OsNAC24-OsNAP complex regulatory network could be a potential strategy for breeding rice cultivars with improved cooking and eating quality.
Assuntos
Endosperma , Oryza , Endosperma/genética , Endosperma/metabolismo , Oryza/metabolismo , Melhoramento Vegetal , Amido/metabolismo , Amilopectina/metabolismo , Amilose/metabolismo , Fatores de Transcrição/genética , Fatores de Transcrição/metabolismoRESUMO
Extrusion-based 3D printing has emerged as the most versatile additive manufacturing technique for the printing of practically any material. However, 3D printing of functional materials often activates thermo-mechanical degradation, which affects the 3D shape quality. Herein, we describe the structural changes of eight different starch sources (normal or waxy) as a consequence of the temperature of an extrusion-based 3D printing system through in-depth characterization of their molecular and structural changes. The combination of size-exclusion chromatography, small-angle X-ray scattering, X-ray diffraction, dynamic viscoelasticity measurements, and in vitro digestion has offered an extensive picture of the structural and biological transformations of starch varieties. Depending on the 3D printing conditions, either gelatinization was attained ("moderate" condition) or single-amylose helix formation was induced ("extreme" condition). The stiff amylopectin crystallites in starch granules were more susceptible to thermo-mechanical degradation compared to flexible amorphous amylose. The crystalline morphology of the starch varieties varied from B-type crystallinity for the starch 3D printing at the "moderate" condition to a mixture of C- and V-type crystallinity regarding the "extreme" condition. The "extreme" condition reduced the viscoelasticity of 3D-printed starches but increased the starch digestibility rate/extent. In contrast, the "moderate" condition increased the viscoelastic moduli, decreasing the starch digestion rate/extent. This was more considerable mainly regarding the waxy starch varieties. Finally, normal starch varieties presented a well-defined shape fidelity, being able to form a stable structure, whereas waxy starches exhibited a non-well-defined structure and were not able to maintain their integrity after printing. The results of this research allow us to monitor the degradability of a variety of starch cultivars to create starch-based 3D structures, in which the local structure can be controlled based on the 3D printing parameters.
Assuntos
Amilose , Amido , Amido/química , Amilose/química , Amilopectina/análise , Amilopectina/química , Amilopectina/metabolismo , Difração de Raios X , TemperaturaRESUMO
In this study, as-is (ca. 12% moisture by mass) and hydrated (50% water by mass) granules of waxy potato (WP), waxy wheat (WW), waxy maize, normal maize, and high-amylose maize (HAM) starches were investigated by using small-angle neutron and X-ray scattering (SANS and SAXS), wide-angle X-ray scattering, and ultra-small-angle neutron scattering. The SANS and SAXS data were fitted using the two-phase stacking model of alternating crystalline and amorphous layers. The partial crystalline lamellar structures inside the growth rings of granules were analyzed based on the inter-lamellar distances, thicknesses of the crystalline lamellae and amorphous layers, thickness polydispersities, and water content in each type of layer. Despite having a longer average chain length of amylopectin, the WP and HAM starches, which had B-type allomorph, had a shorter inter-lamellar distance than the other three starches with A-type allomorph. The WP starch had the most uniform crystalline lamellar thickness. After hydration, the amorphous layers were expanded, resulting in an increase of inter-layer distance. The low-angle intensity upturn in SANS and SAXS was attributed to scattering from interfaces/surfaces of larger structures, such as growth rings and macroscopic granule surfaces. Data analysis methods based on model fitting and 1D correlation function were compared. The study emphasizedâowing to inherent packing disorder inside granulesâthat a comprehensive analysis of different parameters was essential in correlating the microstructures with starch properties.
Assuntos
Amilose , Amido , Amilose/química , Espalhamento a Baixo Ângulo , Difração de Raios X , Amido/química , Amilopectina/química , Água/químicaRESUMO
Nature has developed starch granules varying in size from less than 1 µm to more than 100 µm. The granule size is an important factor affecting the functional properties and the applicability of starch for food and non-food applications. Within the same botanical species, the range of starch granule size can be up to sevenfold. This review critically evaluated the biological and environmental factors affecting the size of starch granules, the methods for the separation of starch granules and the measurement of size distribution. Further, the structure at different length scales and properties of starch-based on the granule size is elucidated by specifying the typical applications of granules with varying sizes. An amylopectin cluster model showing the arrangement of amylopectin from inside toward the granule surface is proposed with the hypothesis that the steric hindrance for the growth of lamellar structure may limit the size of starch granules.
Assuntos
Amilopectina , Amilose , Amilopectina/química , Amilose/química , Amido/química , AlimentosRESUMO
BACKGROUND: A preclinical study reported that the combination of an amylopectin/chromium complex (ACr) of branched-chain amino acids (BCAA) significantly enhanced muscle protein synthesis (MPS). This study was conducted to determine the effects of the addition of ACr complex to a pea/rice (PR) protein on MPS, insulin, muslin levels, and the mTOR pathway in exercised rats. METHODS: Twenty-four rats were divided into three groups: (i) exercise (Ex); (ii) Ex + PR 1:1 blend (0.465 g/kg BW); (iii) Ex + PR + ACr (0.155 g/kg BW). On the day of single-dose administration, after the animals were exercised at 26/m/min for 2 h, the supplement was given by oral gavage. The rats were injected with a bolus dose (250 mg/kg BW, 25 g/L) of deuterium-labeled phenylalanine to determine the protein fractional synthesis rate (FSR) one h after consuming the study product. RESULTS: The combination of PR and ACr enhanced MPS by 42.55% compared to the Ex group, while Ex + PR alone increased MPS by 30.2% over the Ex group (p < 0.0001) in exercised rats. Ex + PR plus ACr significantly enhanced phosphorylation of mTOR and S6K1 (p < 0.0001), and 4E-BP1 (p < 0.001) compared to the Ex (p < 0.0001). PR to ACr also significantly increased insulin and musclin levels (p < 0.0001) in exercised rats. Additionally, compared to Ex + PR alone, Ex + PR + ACr enhanced mTOR (p < 0.0001) and S6K1 (p < 0.0001) levels. CONCLUSION: These data suggested that PR + ACr may provide an alternative to animal proteins for remodeling and repairing muscle by stimulating MPS and mTOR signaling pathways in post-exercised rats. More preclinical and clinical human studies on combining pea/rice and amylopectin/chromium complex are required.
Assuntos
Insulinas , Oryza , Humanos , Ratos , Animais , Proteínas Musculares , Amilopectina/metabolismo , Amilopectina/farmacologia , Pisum sativum , Cromo , Músculo Esquelético/metabolismo , Serina-Treonina Quinases TOR/metabolismo , Fosforilação , Insulinas/metabolismo , Insulinas/farmacologiaRESUMO
Starch properties can be modified by mutating genes responsible for the synthesis of amylose and amylopectin in the endosperm. However, little is known about the effects of such targeted modifications on the overall starch biosynthesis pathway and broader metabolism. Here we investigated the effects of mutating the OsSBEIIb gene encoding starch branching enzyme IIb, which is required for amylopectin synthesis in the endosperm. As anticipated, homozygous mutant plants, in which OsSBEIIb was completely inactivated by abolishing the catalytic center and C-terminal regulatory domain, produced opaque seeds with depleted starch reserves. Amylose content in the mutant increased from 19.6 to 27.4% and resistant starch (RS) content increased from 0.2 to 17.2%. Many genes encoding isoforms of AGPase, soluble starch synthase, and other starch branching enzymes were up-regulated, either in their native tissues or in an ectopic manner, whereas genes encoding granule-bound starch synthase, debranching enzymes, pullulanase, and starch phosphorylases were largely down-regulated. There was a general increase in the accumulation of sugars, fatty acids, amino acids, and phytosterols in the mutant endosperm, suggesting that intermediates in the starch biosynthesis pathway increased flux through spillover pathways causing a profound impact on the accumulation of multiple primary and secondary metabolites. Our results provide insights into the broader implications of perturbing starch metabolism in rice endosperm and its impact on the whole plant, which will make it easier to predict the effect of metabolic engineering in cereals for nutritional improvement or the production of valuable metabolites.