Understanding Starch Structure: Recent Progress

Identification of Single Nucleotide Polymorphism in TaSBEIII and Development of KASP Marker Associated With Grain Weight in Wheat

Manipulation of genes involved in starch synthesis could significantly affect wheat grain weight and yield. The starch-branching enzyme (SBE) catalyzes the formation of branch points by cleaving the α-1,4 linkage in polyglucans and reattaching the chain via an α-1,6 linkage. Three types of SBE isoforms (SBEI, SBEII, and SBEIII) exist in higher plants, with the number of SBE isoforms being species-specific. In this study, the coding sequence of the wheat TaSBEIII gene was amplified. After the multiple sequence alignment of TaSBEIII genome from 20 accessions in a wheat diversity panel, one SNP was observed in TaSBEIII-A, which formed the allelic marker allele-T. Based on this SNP at 294 bp (C/T), a KASP molecular marker was developed to distinguish allelic variation among the wheat genotypes for thousand grain weight (TGW). The results were validated using 262 accessions of mini core collection (MCC) from China, 153 from Pakistan, 53 from CIMMYT, and 17 diploid and 18 tetraploid genotypes. Association analysis between TaSBEIII-A allelic variation and agronomic traits found that TaSBEIII-A was associated with TGW in mini core collection of China (MCC). The accessions possessing Allele-T had higher TGW than those possessing Allele-C; thus, Allele-T was a favorable allelic variation. By analyzing the frequency of the favorable allelic variation Allele-T in MCC, it increased from pre-1950 (25%) to the 1960s (45%) and increased continuously from 1960 to 1990 (80%). The results suggested that the KASP markers can be utilized in grain weight improvement, which ultimately improves wheat yield by marker-assisted selection in wheat breeding. The favorable allelic variation allele-T should be valuable in enhancing grain yield by improving the source and sink simultaneously. Furthermore, the newly developed KASP marker validated in different genetic backgrounds could be integrated into a breeding kit for screening high TGW wheat.

Structure and substrate recognition by the Ruminococcus bromii amylosome pullulanases

Pullulanases are glycoside hydrolase family 13 (GH13) enzymes that target α1,6 glucosidic linkages within starch and aid in the degradation of the α1,4- and α1,6- linked glucans pullulan, glycogen and amylopectin. The human gut bacterium Ruminococcus bromii synthesizes two extracellular pullulanases, Amy10 and Amy12, that are incorporated into the multiprotein amylosome complex that enables the digestion of granular resistant starch from the diet. Here we provide a comparative biochemical analysis of these pullulanases and the x-ray crystal structures of the wild type and the nucleophile mutant D392A of Amy12 complexed with maltoheptaose and 6³-α-D glucosyl-maltotriose. While Amy10 displays higher catalytic efficiency on pullulan and cleaves only α1,6 linkages, Amy12 has some activity on α1,4 linkages suggesting that these enzymes are not redundant within the amylosome. Our structures of Amy12 include a mucin-binding protein (MucBP) domain that follows the C-domain of the GH13 fold, an atypical feature of these enzymes. The wild type Amy12 structure with maltoheptaose captured two oligosaccharides in the active site arranged as expected following catalysis of an α1,6 branch point in amylopectin. The nucleophile mutant D392A complexed with maltoheptaose or 6³-α-D glucosyl-maltotriose captured β-glucose at the reducing end in the -1 subsite, facilitated by the truncation of the active site aspartate and stabilized by stacking with Y279. The core interface between the co-crystallized ligands and Amy12 occurs within the -2 through + 1 subsites, which may allow for flexible recognition of α1,6 linkages within a variety of starch structures.

Effects of supplemental irrigation on winter wheat starch structure and properties under ridge-furrow tillage and flat tillage

Supplemental irrigation (SI) is an important strategy to improve the water-use efficiency (WUE) of crops without compromising the yield. However, such strategy can influence the starch and grain quality. Hence, the effects of SI on winter wheat starch structure and functionality were studied on ridge-furrow (RF) and flat tillage (FT) treated fields. Flat irrigation was set as control. RF + SI significantly increased the grain yield throughout the study period (2016-2018). SI decreased the amylose content and the content of amylopectin chains with DP 13-24 but increased the proportions of amylopectin chains with DP 6-12 and 25-36. The starch granule relative crystallinity decreased, and more B-type granules were produced by SI treatment. SI significantly increased the resistant starch content in both raw and cooked starch systems. Flat tillage enhanced the effect of SI on granule specific surface area (SSA) and viscosity, which increased starch paste viscosity, while SI + RF showed the opposite effects. Our study demonstrates important combined effects of SI and tillage on wheat starch quality.

Investigation of starch functionality and digestibility in white wheat bread produced from a recipe containing added maltogenic amylase or amylomaltase

In the crumb of fresh white wheat bread, starch is fully gelatinized. Its molecular and three-dimensional structure are major factors limiting the rate of its digestion. The aim of this study was to in situ modify starch during bread making with starch-modifying enzymes (maltogenic amylase and amylomaltase) and to investigate the impact thereof on bread characteristics, starch retrogradation and digestibility. Maltogenic amylase treatment increased the relative content of short amylopectin chains (degree of polymerization ≤ 8). This resulted in lower starch retrogradation and crumb firmness upon storage, and reduced extent (up to 18%) of in vitro starch digestion for fresh and stored breads. Amylomaltase only modestly shortened amylose chains and had no measurable impact on amylopectin structure. Modification with this enzyme led to slower bread crumb firming but did not influence starch digestibility.

Essential oils as additives in active starch-based food packaging films: A review

The production of sustainable food packaging from renewable sources represents a prominent alternative to the use of petrochemical-based plastics. For example, starch remains one of the more closely studied replacement options due to its broad availability, low cost and significant advances in improving properties. In this context, essential oils as additives fulfil a key role in the manufacture of renewable active packaging with superior performances. In this review, a comprehensive summary of the impact of adding essential oils to the starch-based films is provided. After a brief introduction to the fundamental concepts related to starch and essential oils, details on the most recent advances in obtaining active starch-based films are presented. Subsequently, the effects of essential oils addition on the structure-property relationships (from physicochemical to antimicrobial ones) are thoroughly addressed. Finally, applications and challenges to the widespread use of essential oils are critically discussed.

Mango seed starch: A sustainable and eco-friendly alternative to increasing industrial requirements

During processing of mango (Mangifera indica) into beverages, squashes and jellies, by-products such as peel and kernel are generated. The higher generation volume of mango-seed makes it cheaper and readily available material for extraction of starch. The current article addresses the mango-seed as potential source of starch over the conventional sources. The starch isolation, its composition structural morphology along with the various physicochemical properties are well discussed. Various modifications for improving the functionality of mango-seed starch (MSS) are comprehensively investigated based on the previous findings. Digestibility profile and glycaemic index of MSS reflected the presence of more resistant starch compared to other conventional starches; making it suitable ingredient for managing diabetes. The structure of mango seed starch can be easily manipulated using biological, chemical and physical methods for improving its application in the foods. Possible utilization of the MSS at large scale will improve the economic viability of the mango processing industries.

Long chains and crystallinity govern the enzymatic degradability of gelatinized starches from conventional and new sources

Slowly digestible starches have received interest due to their lower increase of postprandial blood glucose and insulin levels and, hence, modification of starches towards slower digestibility has commercial interest. However, chemical characteristics driving enzymatic (digestive) degradation are not fully unraveled. The digestion properties of starches have been linked to their crystalline type, chain length distribution, amylose content or degree of branching, but content and length of relatively long side-chains in amylopectin has not been paid attention to. Therefore, this research focusses on the unique content and length of amylopectin side-chains from conventional and new starch sources (potato, corn, pea, and tulip) correlated to the enzymatic digestion. The rate of hydrolysis was found to be correlated with the crystalline type of starch, as previously suggested, however, the complete hydrolysis of all starches, independent of the crystalline type and source, was shown to be governed by the content of longer amylopectin chains.

Fermentation study of Cassava bagasse starch hydrolyzed's using INIAP 650 and INIAP 651 varieties and a strain of Lactobacillus leichmannii for the lactic acid production

Ecuador is an agricultural country, which has an actual production of starch obtained from cassava. Tuber processing residues do not have an economic impact; for example, the cassava bagasse, only used for plant fertilization and animal feeding. This project aimed to study the influence of the fermentation variables (pH and agitation), on the lactic acid production. Enzymatic hydrolysis of cassava bagasse starch for the varieties INIAP 650 and INIAP 651 was performed using α-amylase and glucoamylase. Then, glucose was fermented by Lactobacillus leichmannii ATCC 7830 strains, varying conditions such as agitation (150 rpm and absence) and pH (4.5, 5.0, and 5.5). Finally, the determination of lactic acid was performed by potentiometric and FTIR analysis. Conversions of cassava bagasse to reduced sugars were 71.66 and 85.05 % for INIAP 650 and INIAP 651 varieties. The best lactic acid concentrations were 27.62 and 33.48 g/L, obtained at pH 5.5 and agitation, for INIAP 650 and INIAP 651 varieties. Qualitative analysis conducted by FTIR spectrophotometry confirmed the presence of lactic acid in the reacted products. Lactic acid production from cassava bagasse starch could contribute to the Manabí and Esmeraldas provinces of Ecuador's economic development.

Trend of Modification by Autoclave at Low Pressure and by Natural Fermentation in Sweet Potato and Cassava Starches

Sweet potatoes (Ipomoea batatas L.) and cassava (Manihot esculenta C.) are part of the largest food crops in many countries. They have good nutritional value because, in addition to containing vitamins, minerals, carotenoids, and anthocyanins in varied contents, due to the existence of various colors of their pulps, they have starch as their major constituent. As such, they are considered valuable raw materials for the food factory. The starch granules have distinct morphologies and properties, related to the type of cultivar, planting conditions, storage, and processing, which in turn can affect the quality of the final products to which they have been added. The use of native starches in the food industry has limitations, which can be improved by modifications. Physical methods, as they are associated with green technology, and do not pollute the environment, have demonstrated great potential for this purpose. Both modifications—by autoclave at low pressure and natural fermentation—have shown potential in modifying these starches.

Structural breakdown of starch-based foods during gastric digestion and its link to glycemic response: In vivo and in vitro considerations

The digestion of starch-based foods in the small intestine as well as factors affecting their digestibility have been previously investigated and reviewed in detail. Starch digestibility has been studied both in vivo and in vitro, with increasing interest in the use of in vitro models. Although previous in vivo studies have indicated the effect of mastication and gastric digestion on the digestibility of solid starch-based foods, the physical breakdown of starch-based foods prior to small intestinal digestion is often less considered. Moreover, gastric digestion has received little attention in the attempt to understand the digestion of solid starch-based foods in the digestive tract. In this review, the physical breakdown of starch-based foods in the mouth and stomach, the quantification of these breakdown processes, and their links to physiological outcomes, such as gastric emptying and glycemic response, are discussed. In addition, the physical breakdown aspects related to gastric digestion that need to be considered when developing in vitro-in vivo correlation in starch digestion studies are discussed. The discussion demonstrates that physical breakdown prior to small intestinal digestion, especially during gastric digestion, should not be neglected in understanding the digestion of solid starch-based foods.

Biopolymer-derived (nano)catalysts for hydrogen evolution via hydrolysis of hydrides and electrochemical and photocatalytic techniques: A review

Over the course of a few decades, the concern of environmental damages of fossil fuels, an increase in CO₂ emission and a decrease of hydrogen have been growing more and more. Accordingly, hydrogen production is a crucial issue nowadays. Different polymers are applied to attain the purpose. Among all polymers, biodegradables polymers are the best choices to develop the main aim. Polysaccharides and proteins are biodegradable polymers with unique places and advantages with regards to their ecofriendly properties. There are different techniques to apply and achieve the foremost purpose. It is worthwhile to mention that green and facile methods are always attracting attention in different aspects and fields. The three non-polluting and economical techniques, that is, electrochemical hydrogen evolution reaction (HER), photocatalytic technique, and hydrolysis of hydrides, are reviewed in this paper. This review helps researchers, who are environment supporters, to evaluate and choose the most ecological biopolymers and processes in their work.

Relationship between molecular structure and lamellar and crystalline structure of rice starch

The relationship between molecular structure and crystalline and lamellar structures of fifteen types of rice starches was studied. GPC and HPAEC were used for the molecular chain analysis and WAXS, SAXS, and CP/MAS ¹³C NMR were employed for aggregation structural analysis. The amylopectin content and the average lengths of fb₁-chains (the degree of polymerization (DP) 13-24) were positively correlated with the amount of double helices (r² = 0.92 and 0.57, respectively). In contrast, amylose content was positively correlated with the amounts of amorphous materials in starch (r² = 0.77). The amount of double helices, which constitute a major part of the crystalline matrix, was positively correlated with the lamellar ordering (r² = 0.81), and negatively correlated with the thickness of crystalline lamellae (r² = 0.90) and lamellar repeat distance (r² = 0.84). Conversely, the amount of the amorphous matrix was correlated with these parameters in the opposite way (r² = 0.50, 0.75, and 0.75, respectively).

Study of cassava starch degradation using sonication process in aqueous sodium chloride

BACKGROUND

Starch degradation is an important process that can increase starch utilization in some industrial applications. In many polysaccharide compounds, the addition of salt is an alternative method to enhance the structural degradation of starch by sonication. This study aimed to investigate the effect of sonication in aqueous NaCl solution on the structural degradation of cassava starch.

RESULTS

This method produces reducing sugar which its amount is relatively smaller than the amount of total dissolved solid product. The maximum total reducing sugar (TRS) was 0.365 ± 0.005 kg m^-3 (or about 7.3 mg g^-1 ) that resulted by S50 for 60 min reaction. The increase of sonication amplitude was in line with the increase of granule defect in SEM image. X-ray diffraction (XRD) showed that the degradation process was characterized by rupturing of the amorphous region.

CONCLUSION

The structural alteration and the increase in NaCl weight suggest that this process may become a useful method for starch modification. © 2020 Society of Chemical Industry.

Towards targeted starch modification in plants

Genetic approaches to modify starch in crops have been limited by our knowledge of starch biosynthesis. Recent advances in Arabidopsis have revealed key genetic components determining the size, shape and number of granules in a plastid. This has opened the doors to new discoveries on granule initiation in crop species. In parallel, advances in genomic resources and gene editing technologies allow targeted manipulation of starch biosynthesis genes in isogenic crop backgrounds. Such technologies have been successfully deployed to alter starch composition, and can now be used to modify other starch traits. This will allow the complex relationships between starch structure and physicochemical properties to be elucidated, which will facilitate the rational manipulation of starches in crops.

Structural features of five types of maize starch granule subgroups sorted by flow cytometry

Subgroups of starch granules from five maize phenotypes including waxy-, normal-, popcorn-, sweet corn- and high-amylose maize were sorted by flow cytometry (FC) utilizing the side scatter channel (SSC) and forward scatter channel (FSC). SSC and FSC mainly reflecting internal object complexity, and object size, respectively. Subgroups with higher FSC signal always showed higher SSC signal, indicating larger granules exhibited higher internal structural complexity. Wide-angle and small-angle X-ray scattering analysis showed that the subgroups showing high SSC signal intensity also had high lamellar scattering intensity, and low crystallinity. Vibrational transitions of bonds analyzed by Fourier Transform Infrared Spectroscopy (FT-IR) showed that the subgroups of maize starches, except sweet corn starch, with high SSC signal had high intensities at 1045 and 1022 cm^-1. Hence, our data demonstrate that the structural complexity detected by the SSC signal is mainly associated with lamellar and crystalline features of starch granules.

Monovalent Salt and pH-Induced Gelation of Oxidised Cellulose Nanofibrils and Starch Networks: Combining Rheology and Small-Angle X-ray Scattering

Water quality parameters such as salt content and various pH environments can alter the stability of gels as well as their rheological properties. Here, we investigated the effect of various concentrations of NaCl and different pH environments on the rheological properties of TEMPO-oxidised cellulose nanofibril (OCNF) and starch-based hydrogels. Addition of NaCl caused an increased stiffness of the OCNF:starch (1:1 wt%) blend gels, where salt played an important role in reducing the repulsive OCNF fibrillar interactions. The rheological properties of these hydrogels were unchanged at pH 5.0 to 9.0. However, at lower pH (4.0), the stiffness and viscosity of the OCNF and OCNF:starch gels appeared to increase due to proton-induced fibrillar interactions. In contrast, at higher pH (11.5), syneresis was observed due to the formation of denser and aggregated gel networks. Interactions as well as aggregation behaviour of these hydrogels were explored via ζ-potential measurements. Furthermore, the nanostructure of the OCNF gels was probed using small-angle X-ray scattering (SAXS), where the SAXS patterns showed an increase of slope in the low-q region with increasing salt concentration arising from aggregation due to the screening of the surface charge of the fibrils.

Expression Pattern of Starch Biosynthesis Genes in Relation to the Starch Molecular Structure in High-Amylose Maize

The molecular structure and the expression levels of starch biosynthesis-related genes of three types of high-amylose maize (HAM) genotypes and one normal maize (NM) genotype at 5-35 days after pollination (DAP) were studied. Size exclusion chromatography (SEC) analysis showed that the molecular size of amylopectin molecules in NM increased from 5 to 35 DAP and the amylose content in HAM genotypes increased from 15 to 35 DAP. Correlation analysis for both NM and HAMs combined showed that SBEIIb and ISAII were negatively correlated with the contents of amylose and long amylopectin chains (DP > 30) and positively correlated with the content of short amylopectin chains (DP ≤ 31) and the molecular size of amylopectin molecules. Correlation analysis for only the HAMs showed that amylose content was negatively correlated with SBEI and SSIIa. In both correlation analyses, SSIIa showed a negative correlation with the average chain lengths of amylose chains.

Review of the Most Important Methods of Improving the Processing Properties of Starch toward Non-Food Applications

Starch is the second most abundantly available natural polymer in the world, after cellulose. If we add its biodegradability and non-toxicity to the natural environment, it becomes a raw material very attractive for the food and non-food industries. However, in the latter case, mainly due to the high hydrophilicity of starch, it is necessary to carry out many more or less complex operations and processes. One of the fastest growing industries in the last decade is the processing of biodegradable materials for packaging purposes. This is mainly due to awareness of producers and consumers about the dangers of unlimited production and the use of non-degradable petroleum polymers. Therefore, in the present review, an attempt was made to show the possibilities and limitations of using starch as a packaging material. The most important physicochemical features of this biopolymer are discussed, and special attention is paid to more or less environmentally friendly methods of improving its processing properties.

Seagrass-based platform strategies for sustainable hydroxymethylfurfural (HMF) production: toward bio-based chemical products

Today, sustainable chemistry is a key trend in the chemical manufacturing industry due mainly to concerns over the global environment and resource security. In sustainable chemical manufacture, the choice of a bio-based feedstock plays a pivotal pillar. In terms of feedstock utilization for producing HMF, which is a multivalent platform intermediate easily convertible to valuable chemical products; biopolymers, biofuels, and other important chemicals, seagrass biomasses can be more favorable feedstocks compared with land plant resources due primarily to easy availability and no systematic farming. Moreover, seagrass feedstocks could contribute cost-effectively and sustainably producing HMF by exploiting the beach-cast seagrasses on seagrass-prairies with no feedstock cost, indicating that seagrass biomasses could be a most promising biofeedstock source for sustainable HMF production. We afford a platform bioprocessing technology that has not been attempted before for sustainable HMF production using raw seagrass biomass. This bioprocess can be operated by simple reaction conditions using inorganic Brønsted acids (mainly HCl) and ionic liquid solvents at relatively low temperatures (120-130 °C). In addition, some bioengineering strategies for improving the growth of seagrass biomass and the quantity/quality of nonstructural carbohydrates (starch, sucrose) that can be used as the feeding substrates for HMF production are also discussed. The main aim of this review is to provide some important information about breakthrough bio/technologies conducive to cost-effective and sustainable HMF production.

Amylose starch with no detectable branching developed through DNA-free CRISPR-Cas9 mediated mutagenesis of two starch branching enzymes in potato

DNA-free genome editing was used to induce mutations in one or two branching enzyme genes (Sbe) in tetraploid potato to develop starch with an increased amylose ratio and elongated amylopectin chains. By using ribonucleoprotein (RNP) transfection of potato protoplasts, a mutation frequency up to 72% was achieved. The large variation of mutations was grouped as follows: Group 1 lines with all alleles of Sbe1 mutated, Group 2 lines with all alleles of Sbe1 as well as two to three alleles of Sbe2 mutated and Group 3 lines having all alleles of both genes mutated. Starch from lines in Group 3 was found to be essentially free of amylopectin with no detectable branching and a chain length (CL) distribution where not only the major amylopectin fraction but also the shortest amylose chains were lost. Surprisingly, the starch still formed granules in a low-ordered crystalline structure. Starch from lines of Group 2 had an increased CL with a higher proportion of intermediate-sized chains, an altered granule phenotype but a crystalline structure in the granules similar to wild-type starch. Minor changes in CL could also be detected for the Group 1 starches when studied at a higher resolution.

Biotechnology and bioengineering of pullulanase: state of the art and perspectives

Pullulanase (EC 3.2.1.41) is a starch-debranching enzyme in the α-amylase family and specifically cleaves α-1,6-glycosidic linkages in starch-type polysaccharides, such as pullulan, β-limited dextrin, glycogen, and amylopectin. It plays a key role in debranching and hydrolyzing starch completely, thus bring improved product quality, increased productivity, and reduced production cost in producing resistant starch, sugar syrup, and beer. Plenty of researches have been made with respects to the discovery of either thermophilic or mesophilic pullulanases, however, few examples meet the demand of industrial application. This review presents the progress made in the recent years from the first aspect of characteristics of pullulanases. The heterologous expression of pullulanases in different microbial hosts and the methods used to improve the expression effectiveness and the regulation of enzyme production are also described. Then, the function evolution of pullulanases from a protein engineering view is discussed. In addition, the immobilization strategy using novel materials is introduced to improve the recyclability of pullulanases. At the same time, we indicate the trends in the future research to facilitate the industrial application of pullulanases.

Hydrophobic interactions control the self-assembly of DNA and cellulose

Desoxyribosenucleic acid, DNA, and cellulose molecules self-assemble in aqueous systems. This aggregation is the basis of the important functions of these biological macromolecules. Both DNA and cellulose have significant polar and nonpolar parts and there is a delicate balance between hydrophilic and hydrophobic interactions. The hydrophilic interactions related to net charges have been thoroughly studied and are well understood. On the other hand, the detailed roles of hydrogen bonding and hydrophobic interactions have remained controversial. It is found that the contributions of hydrophobic interactions in driving important processes, like the double-helix formation of DNA and the aqueous dissolution of cellulose, are dominating whereas the net contribution from hydrogen bonding is small. In reviewing the roles of different interactions for DNA and cellulose it is useful to compare with the self-assembly features of surfactants, the simplest case of amphiphilic molecules. Pertinent information on the amphiphilic character of cellulose and DNA can be obtained from the association with surfactants, as well as on modifying the hydrophobic interactions by additives.

Physicochemical properties of a new starch from ramie (Boehmeria nivea) root

A new starch was isolated from ramie root, and its physicochemical properties were investigated. Ramie dry root contained 45.9% starch. Starch had truncated, ellipsoidal, and spherical granule shapes with size from 7 to 30 μm and D[4,3] about 14.1 μm. Starch contained 38.9% apparent amylose content and 22.4% true amylose content, exhibited B-type crystallinity, and had 26.6% relative crystallinity, 0.82 ordered degree, and 9.2 nm lamellar thickness. Starch had 71.8 °C gelatinization peak temperature and 15.6 J/g gelatinization enthalpy, and exhibited 31.4 g/g swelling power and 17.1% water solubility at 95 °C. Starch had peak, hot, breakdown, final, and setback viscosities at 3048, 2768, 279, 4165, and 1397 mPa s, respectively, and showed peak time at 4.36 min and pasting temperature at 75.0 °C. The native, gelatinized, and retrograded starches contained 15.1%, 94.0%, and 86.5% rapidly digestible starch and 83.3%, 4.0%, and 10.7% resistant starch, respectively. Compared with potato and rice starches, ramie starch was somewhat similar to potato starch but significantly different from rice starch in starch component, crystalline structure, and functional properties. Therefore, ramie starch exhibited the potential to be used as a thickening agent, resistant-digesting food additive, and alternative to potato starch in food and nonfood industries.

Characterizing moisture uptake and plasticization effects of water on amorphous amylose starch models using molecular dynamics methods

Dynamics and thermophysical properties of amorphous starch were explored using molecular dynamics (MD) simulations. Using the OPLS3e force field, simulations of short amylose chains in water were performed to determine force field accuracy. Using well-tempered metadynamics, a free energy map of the two glycosidic angles of an amylose molecule was constructed and compared with other modern force fields. Good agreement of torsional sampling for both solvated and amorphous amylose starch models was observed. Using combined grand canonical Monte Carlo (GCMC)/MD simulations, a moisture sorption isotherm curve is predicted along with temperature dependence. Concentration-dependent activation energies for water transport agree quantitatively with previous experiments. Finally, the plasticization effect of moisture content on amorphous starch was investigated. Predicted glass transition temperature (T_g) depression as a function of moisture content is in line with experimental trends. Further, our calculations provide a value for the dry T_g for amorphous starch, a value which no experimental value is available.

Resistant starch, microbiome, and precision modulation

Resistant starch, microbiome, and precision modulation. Mounting evidence has positioned the gut microbiome as a nexus of health. Modulating its phylogenetic composition and function has become an attractive therapeutic prospect. Resistant starches (granular amylase-resistant α-glycans) are available as physicochemically and morphologically distinguishable products. Attempts to leverage resistant starch as microbiome-modifying interventions in clinical studies have yielded remarkable inter-individual variation. Consequently, their utility as a potential therapy likely depends predominantly on the selected resistant starch and the subject's baseline microbiome. The purpose of this review is to detail i) the heterogeneity of resistant starches, ii) how resistant starch is sequentially degraded and fermented by specialized gut microbes, and iii) how resistant starch interventions yield variable effects on the gut microbiome.

Analysis of the complexation process between starch molecules and trilinolenin

Starch is a basic biomacromolecule, and an in-depth understanding of the process and mechanism of starch-lipid complexation has great significance for starch based food and pharmaceutical. In this study, molecular dynamics simulation was used to explore the complexation details between starch molecules and trilinolenin, such as complexation process, interaction forces, conformation changes and stability changes, which are difficult to be verified by using other characterization methods. The results show that, firstly, starch residues of one turn helix (8 residues) are enough to bind a trilinolenin molecule firmly. Secondly, the complex is maintained by Van der Waals and electrostatic interaction. Thirdly, the residues complexed with trilinolenin become more stable than the former or the free residues. In brief, the complexation process, interaction forces, conformation changes and stability changes of the starch-trilinolenin complex were clarified in this study. The results may create new insights for the research about the interaction of starch and lipid, then provide theoretical guidance for the research on starch based food and pharmaceutical.

Sandwich panel biocomposite of thermoplastic corn starch and bacterial cellulose

Inadequate disposition and long period for degradation of Petroleum-derived polymers promote damages in the environment, which could be minimized by the use of biodegradable polymers such as starch and cellulose. Films of thermoplastic corn starch (TPS) and bacterial cellulose (BC) were used to produce sandwich panel biocomposite. RXD, SEM and FTIR were used to verify the transformation of TPS from native corn starch. TPS/BC is flexible and transparent, but it is less transparent that TPS and BC due to its multilayer format. TPS/BC presented similar thermal events to TPS and BC samples and thermal stability similar to TPS. The FTIR spectrum of the TPS/BC showed bands observed in the BC and TPS spectra. BC, TPS and TPS/BC showed faster water absorption in the initial stage reaching a stability at about 50 h and presenting Fickian behavior. TPS/BC showed lower water absorption and a good adhesion between the phases observed by SEM images, which can be associated to hydrogen interactions in the interface improving mechanical properties. TPS/BC showed an increase of about 3.6 times in the tensile strength compared to TPS, indicating that BC is a good reinforcement for TPS.

High-Performance Colorimetric Humidity Sensors Based on Konjac Glucomannan

High-humidity conditions (85-100% relative humidity (RH)) have very diverse effects on many aspects of people's daily lives. Despite remarkable progress in the development of structural coloration-based humidity sensors, how to significantly improve the sensitivity and visual humidity resolution of these humidity sensors under a high-humidity environment remains a great challenge. In this study, high-performance colorimetric humidity sensors based on environment-friendly konjac glucomannan (KGM) via thin-film interference are developed using a simple, affordable, and scalable preparation method. An effective strategy is demonstrated for substantially improving the sensor sensitivity and visual humidity resolution under a high-humidity environment via synergistic integration of multiorder interference peaks, sensor array technology, and superior water-absorbing polymer. The KGM full-range humidity sensors exhibit fast and dynamic response toward the humidity change without power consumption, and they also show high sensitivity and selectivity, little hysteresis, and excellent stability against high-humidity conditions. The KGM humidity sensors display extraordinary red shift of the reflection peak (e.g., 385 nm) and the visual humidity resolution as high as 1.5% RH in the visible range from 85 to 100% RH, which represent the largest spectra shift and highest visual humidity resolution, respectively, for structural coloration-based humidity sensors in high-humidity conditions.

Amylose in starch: towards an understanding of biosynthesis, structure and function

Starch granules are composed of two distinct glucose polymers - amylose and amylopectin. Amylose constitutes 5-35% of most natural starches and has a major influence over starch properties in foods. Its synthesis and storage occurs within the semicrystalline amylopectin matrix of starch granules, this poses a great challenge for biochemical and structural analyses. However, the last two decades have seen vast progress in understanding amylose synthesis, including new insights into the action of GRANULE BOUND STARCH SYNTHASE (GBSS), the major glucosyltransferase that synthesises amylose, and the discovery of PROTEIN TARGETING TO STARCH1 (PTST1) that targets GBSS to starch granules. Advances in analytical techniques have resolved the fine structure of amylose, raising new questions on how structure is determined during biosynthesis. Furthermore, the discovery of wild plants that do not produce amylose revives a long-standing question of why starch granules contain amylose, rather than amylopectin alone. Overall, these findings contribute towards a full understanding of amylose biosynthesis, structure and function that will be essential for future approaches to improve starch quality in crops.

The architecture of starch blocklets follows phyllotaxic rules

The starch granule is Nature’s way to store energy in green plants over long periods. Irrespective of their origins, starches display distinct structural features that are the fingerprints of levels of organization over six orders of magnitude. We hypothesized that Nature retains hierarchical material structures at all levels and that some general rules control the morphogenesis of these structures. We considered the occurrence of a «phyllotaxis» like features that would develop at scales ranging from nano to micrometres, and developed a novel geometric model capable of building complex structures from simple components. We applied it, according to the Fibonacci Golden Angle, to form several Golden Spirals, and derived theoretical models to simulate scattering patterns. A GSE, constructed with elements made up of parallel stranded double-helices, displayed shapes, sizes and high compactness reminiscent of the most intriguing structural element: the ‘blocklet’. From the convergence between the experimental findings and the theoretical construction, we suggest that the «phyllotactic» model represents an amylopectin macromolecule, with a high molecular weight. Our results offer a new vision to some previous models of starch. They complete a consistent description of the levels of organization over four orders of magnitude of the starch granule.

Testing spore amyloidity in Agaricales under light microscope: the case study of Tricholoma

Although species of the genus Tricholoma are currently considered to produce inamyloid spores, a novel standardized method to test sporal amyloidity (which involves heating the sample in Melzer's reagent) showed evidence that in the tested species of this genus, which belong in all 10 sections currently recognized from Europe, the spores are amyloid. In two species, T. josserandii and T. terreum, the spores are also partly dextrinoid. This result provides strong indication that a positive reaction of the spores in Melzer's reagent could be a character shared by all genera in Tricholomataceae s. str.