New definition of resistant starch types from the gut microbiota perspectives - a review

Current definition of resistant starch (RS) types is largely based on their interactions with digestive enzymes from human upper gastrointestinal tract. However, this is frequently inadequate to reflect their effects on the gut microbiota, which is an important mechanism for RS to fulfill its function to improve human health. Distinct shifts of gut microbiota compositions and alterations of fermented metabolites could be resulted by the consumption of RS from the same type. This review summarized these defects from the current definitions of RS types, while more importantly proposed pioneering concepts for new definitions of RS types from the gut microbiota perspectives. New RS types considered the aspects of RS fermentation rate, fermentation end products, specificity toward gut microbiota and shifts of gut microbiota caused by the consumption of RS. These definitions were depending on the known outcomes from RS-gut microbiota interactions. The application of new RS types in understanding the complex RS-gut microbiota interactions and promoting human health should be focused in the future.

A randomized double-blind cross-over trial to study the effects of resistant starch prebiotic in chronic kidney disease (ReSPECKD)

Background

Chronic kidney disease (CKD) is associated with a reduced quality of life and an increased risk of kidney failure, cardiovascular events, and all-cause mortality. Accumulation of nitrogen-based uremic toxins leads to worsening of symptoms in individuals with CKD. Many uremic toxins, such as indoxyl and p-cresol sulphate, are produced exclusively by the gut microbiome through the proteolytic digestion of aromatic amino acids. Strategies to reduce the production of these toxins by the gut microbiome in individuals with CKD may lessen symptom burden and delay the onset of dialysis. One such strategy is to change the overall metabolism of the gut microbiome so that less uremic toxins are produced. This can be accomplished by manipulating the energy source available to the microbiome. Fermentable carbohydrates which reach the gut microbiome, like resistant starch (RS), have been shown to inhibit or reduce bacterial amino acid metabolism. This study aims to investigate the effects of resistant potato starch (RPS) as a prebiotic in individuals with CKD before the onset of dialysis.

Methods

This is a double-blind, randomized two-period crossover trial. Thirty-six eligible participants will consent to follow a 26-week study regimen. Participants will receive 2 sachets per day containing either 15 g of RPS (MSPrebiotic, resistant potato starch treatment) or 15 g cornstarch (Amioca TF, digestible starch control). Changes in blood uremic toxins will be investigated as the primary outcome. Secondary outcomes include the effect of RPS consumption on symptoms, quality of life and abundance, and diversity and functionality of the gut microbiome.

Discussion

This randomized trial will provide further insight into whether the consumption of RPS as a prebiotic will reduce uremic toxins and symptoms in individuals who have CKD.

Trial registration

ClinicalTrials.govNCT04961164. Registered on 14 July 2021

Does a high dietary intake of resistant starch affect glycaemic control and alter the gut microbiome in women with gestational diabetes? A randomised control trial protocol

BACKGROUND

Gestational Diabetes Mellitus (GDM) is prevalent with lasting health implications for the mother and offspring. Medical nutrition therapy is the foundation of GDM management yet achieving optimal glycaemic control often requires treatment with medications, like insulin. New dietary strategies to improve GDM management and outcomes are required. Gut dysbiosis is a feature of GDM pregnancies, therefore, dietary manipulation of the gut microbiota may offer a new avenue for management. Resistant starch is a fermentable dietary fibre known to alter the gut microbiota and enhance production of short-chain fatty acids. Evidence suggests that short-chain fatty acids improve glycaemia via multiple mechanisms, however, this has not been evaluated in GDM.

METHODS

An open-label, parallel-group design study will investigate whether a high dietary resistant starch intake or resistant starch supplement improves glycaemic control and changes the gut microbiome compared with standard dietary advice in women with newly diagnosed GDM. Ninety women will be randomised to one of three groups - standard dietary treatment for GDM (Control), a high resistant starch diet or a high resistant starch diet plus a 16 g resistant starch supplement. Measurements taken at Baseline (24 to 30-weeks' gestation), Day 10 and Day 56 (approximately 36 weeks' gestation) will include fasting plasma glucose levels, microbial composition and short-chain fatty acid concentrations in stool, 3-day dietary intake records and bowel symptoms questionnaires. One-week post-natal data collection will include microbial composition and short-chain fatty acid concentrations of maternal and neonatal stools, microbial composition of breastmilk, birthweight, maternal and neonatal outcomes. Mixed model analysis of variance will assess change in glycaemia and permutation-based multivariate analysis of variance will assess changes in microbial composition within and between intervention groups. Distance-based linear modelling will identify correlation between change in stool microbiota, short-chain fatty acids and measures of glycaemia.

DISCUSSION

To improve outcomes for GDM dyads, evaluation of a high dietary intake of resistant starch to improve glycaemia through the gut microbiome needs to be established. This will expand the dietary interventions available to manage GDM without medication.

TRIAL REGISTRATION

Australian New Zealand Clinical Trial Registry, ACTRN12620000968976p . Registered 28 September 2020.

Influence of corn resistant starches type III on the rheology, structure, and viable counts of set yogurt

The study intended to explore the influence of corn resistant starches type III (RS3s) prepared by autoclave, debranching, and microwave heat on the rheology, structure, and viable counts of set yogurt. The rheological analysis suggested that RS3s enhanced the elastic and viscous modulus of yogurt, and that microwave-heated RS was the most effective for improving viscoelasticity. Fitting the creep data using the Burger model showed that yogurt with microwave-heated RS increased the structural strength of yogurt, which displayed the highest instantaneous and viscoelastic deformations. The confocal laser scanning microscopy and scanning electron microscopy micrographs demonstrated that autoclaved and debranched RS3s formed large fragments and disrupted the continuity of the milk protein structure; however, microwave-heated RS evenly filled the gel network and formed an interpenetrating network with proteins. The bacterial count and acidity of yogurt indicated that microwave-heated and debranched RS3s promoted the growth of lactic acid bacteria and accelerated the fermentation process of yogurt. The results of this study demonstrated that microwave-heated RS is a favorable supplement to the microstructure and rheological properties of yogurt compared with autoclaved and debranched RS3s.

Human gut commensal bacterium Ruminococcus species FMB-CY1 completely degrades the granules of resistant starch

Resistant starch (RS) in the diet reaches the large intestine and is fermented by the gut microbiota, providing beneficial effects on human health. The human gut bacterium FMB-CY1 was isolated and identified as a new species closest to Ruminococcus bromii. Ruminococcus sp. FMB-CY1 completely degraded RS including commercial RS types 2, 3, and 4, and generated glucose and maltose; however, it did not assimilate glucose. Genome analysis revealed 15 amylolytic enzymes (Amy) present in FMB-CY1. The evolutionary trees revealed that the Amys were well divided each other. All Amys (4, 9, 10, 12, and 16) containing cohesin and/or dockerin and scaffolding proteins known to be involved in constituting the amylosome, were identified. A new species of Ruminococcus, strain FMB-CY1, was considered to have the ability to form amylosomes for the degradation of RS. This new RS-degrading Ruminococcus species provides insights into the mechanism(s) underlying RS degradation in the human gut.

SUPPLEMENTARY INFORMATION

The online version contains supplementary material available at 10.1007/s10068-021-01027-2.

The effect of high-amylose resistant starch on the glycogen structure of diabetic mice

Glycogen is a complex branched glucose polymer found in many tissues and acts as a blood-glucose buffer. In the liver, smaller β glycogen particles can bind into larger composite α particles. In mouse models of diabetes, these liver glycogen particles are molecularly fragile, breaking up into smaller particles in the presence of solvents such as dimethyl sulfoxide (DMSO). If this occurs in vivo, such a rapid enzymatic degradation of these smaller particles into glucose could exacerbate the poor blood-glucose control that is characteristic of the disease. High-amylose resistant starch (RS) can escape digestion in the small intestine and ferment in the large intestine, which elicits positive effects on glycemic response and type 2 diabetes. Here we postulate that RS would help attenuate diabetes-related liver glycogen fragility. Normal maize starch and two types of high-amylose starch were fed to diabetic and non-diabetic mice. Molecular size distributions and chain-length distributions of liver glycogen from both groups were characterized to test glycogen fragility before and after DMSO treatment. Consistent with the hypothesis that high blood glucose is associated with glycogen fragility, a high-amylose RS diet prevented the fragility of liver-glycogen α particles. The diets had no significant effect on the glycogen chain-length distributions.

Exploring differences in the physicochemical, functional, structural, and pasting properties of banana starches from dessert, cooking, and plantain cultivars (Musa spp.)

Banana starch, with its nutritional and functional properties, opens up new opportunities for the food industry, which is seeking new starch sources to fulfil rising demand. Herein, physico-chemical, and functional properties of banana starches isolated from dessert, plantain, and cooking cultivars were investigated. Starch yield was higher in Popoulu (30.58%) and Monthan (27.82%). Starch granules registered irregular forms with granule sizes ranging from 8.9 to 55.09 μm. Among the cultivars, the amylose content was ranged between 25.05 and 31.86%. Total starch (95.86 and 95.60%,) and resistant starch (65.56 and 59.20%) were higher in Saba and Monthan respectively. Flour colour index (86.2-90.6) was higher in banana starches. Differential scanning calorimetry and rapid viscosity studies confirmed that starches from Saba (87.67 and 85.71 °C) Monthan (85.36 and 81.65 °C) have a higher gelatinization property. Banana starches were B and C-type with varying crystallinity levels (21.19-52.01%). The in-vitro starch digestibility revealed that Saba starch has a lower hydrolysis rate with lesser glycemic index. PCA showed the greater impact of amylose and resistant starch content on the grouping of varieties. These findings would be useful for food and non-food industries in terms of using banana starch in various food compositions and other industrial applications.

Resistant starch: Implications of dietary inclusion on gut health and growth in pigs: a review

Starch from cereal grains, pulse grains, and tubers is a major energy substrate in swine rations constituting up to 55% of the diet. In pigs, starch digestion is initiated by salivary and then pancreatic α-amylase, and has as final step the digestion of disaccharides by the brush-border enzymes in the small intestine that produce monosaccharides (glucose) for absorption. Resistant starch (RS) is the proportion of starch that escapes the enzymatic digestion and absorption in the small intestine. The undigested starch reaches the distal small intestine and hindgut for microbial fermentation, which produces short-chain fatty acids (SCFA) for absorption. SCFA in turn, influence microbial ecology and gut health of pigs. These fermentative metabolites exert their benefits on gut health through promoting growth and proliferation of enterocytes, maintenance of intestinal integrity and thus immunity, and modulation of the microbial community in part by suppressing the growth of pathogenic bacteria while selectively enhancing beneficial microbes. Thus, RS has the potential to confer prebiotic effects and may contribute to the improvement of intestinal health in pigs during the post-weaning period. Despite these benefits to the well-being of pigs, RS has a contradictory effect due to lower energetic efficiency of fermented vs. digested starch absorption products. The varying amount and type of RS interact differently with the digestion process along the gastrointestinal tract affecting its energy efficiency and host physiological responses including feed intake, energy metabolism, and feed efficiency. Results of research indicate that the use of RS as prebiotic may improve gut health and thereby, reduce the incidence of post-weaning diarrhea (PWD) and associated mortality. This review summarizes our current knowledge on the effects of RS on microbial ecology, gut health and growth performance in pigs.

Resistant starch wheat increases PYY and decreases GIP but has no effect on self-reported perceptions of satiety

Dietary fiber has numerous health benefits, such as increasing satiety, and is regularly included in healthy dietary recommendations. However, different types and sources of fiber vary in their chemical properties and biological effects. This double-blind, randomized, placebo-controlled, crossover study investigated the effects of resistant starch type 2 (RS2) from wheat on self-reported perceptions of satiety and associated gut hormones in 30 healthy adults ages 40-65 years of age. Participants consumed rolls made using either RS2-enriched wheat flour or a wild-type flour for one week before a test day during which they ate a mixed meal containing the same roll type. Both self-reported perceptions of satiety and plasma concentrations of gut hormones were measured following the meal to assess whether the RS2-enriched wheat enhanced satiety and suppressed hunger for a longer period than the control wheat. Exploratory analysis indicated that fasting and peak concentration of peptide YY_3-36 (PYY_3-36; q_fast = 0.02, q_peak = 0.02) increased, while peak concentration and iAUC of glucose-dependent insulinotropic peptide (GIP; q_peak < 0.001, q_iAUC < 0.001) decreased after ingesting RS2-enriched wheat. However, self-reported perceptions of hunger or fullness using visual analog scales (VAS) did not differ following the test meal.

Effects of microwave treatments and retrogradation on molecular crystalline structure and in vitro digestibility of debranched mung-bean starches

The objective of this study was to investigate morphology, molecular crystalline structure, and digestibility of debranched mung bean starches with or without microwave treatment and retrogradation at different temperature. The mung bean starch was firstly debranched with pullulanase, and then the debranched starch containing 20% moisture content was treated by microwave irradiation for 3 min with or without further retrograded at +25, +4, or -18 °C for 24 h. All treated starches exhibited the B + V-type crystalline polymorph as determined by the XRD and the ¹³CNMR. The FT-IR results showed that the debranched starches had lower degree of order but higher degree of double helix than those of the native starch. The microwave treatment or further recrystallization of the debranched starch for more 24 h significantly improved crystalline structure of starch granules with higher degree of relative crystallinity, degree of order, and degree of double helices. The resistant starch content of the treated starch was in a range of 39.7-52.8%, significantly higher than that of the native starch (15.6%). As a result, the microwave-assisted debranched starch with further crystallization for 24 h was found to have highly ordered structure of granules, which highly resisted to the enzyme digestion.

Align resistant starch structures from plant-based foods with human gut microbiome for personalized health promotion

Resistant starch (RS) is beneficial for human health through its interactions with gut microbiota. However, the alignment between RS structures with gut microbiota profile and consequentially health benefits remain elusive. This review summarizes current understanding of RS complex structures and their interactions with the gut microbiota, aiming to highlight the possibility of manipulating RS structures for a targeted and predictable gut microbiota shift for human health in a personalized way. Current definition of RS types is strongly associated with starch digestion behaviors in small intestine, which does not precisely reflect their interactions with human gut microbiota. Distinct alterations of gut microbiota could be associated with the same RS type. The principles to describe the specificity of different RS structural characteristics in terms of aligning with human gut microbiota shift was proposed in this review, which could result in new definitions of RS types from the microbial perspectives. To consider the highly variable personal features, a machine-learning algorithm to integrate different personalized factors and better understand the complex interaction between RS and gut microbiota and its effects on individual health was explained. This review contains important information to bring interactions between RS and gut microbiota to translational practice.

Elucidation of the low resistant starch phenotype in Phaseolus vulgaris exhibited in the yellow bean Cebo Cela

Dry beans(Phaseolus vulgaris) are rich in complex carbohydrates including resistant starch (RS). RS, the starch fraction that escapes digestion, typically ranges from 35% in raw beans to 4% in cooked beans. A low RS bean genotype, Cebo Cela, was identified with 96% less RS (1.5% RS) than normal raw beans. The goal of this research was to elucidate the factors responsible for this low RS phenotype. The low RS phenotype was evaluated in whole bean flour and starch in Cebo Cela (yellow), Canario (yellow), Alpena (navy) and Samurai (otebo). α-Amylase activation was found to be a major contributor of the low RS content phenotype of the whole bean flour for Cebo Cela (-21.9% inhibition). Total starch (43.6%-40.2%), amylose (31.0%-31.5%), molecular weight and chain length distributions of amylose and amylopectin did not contribute to the low RS phenotype. Yellow bean starches were digested nearly 1.5 times (95%-94%) faster than starch granules from otebo and navy beans (65%-73%) due to lower proportions of amylopectin chains. PRACTICAL APPLICATION: This study is of value to the food industry because the yellow bean, Cebo Cela, is easily hydrolyzed by α-amylase and also has α-amylase promotion properties. Therefore, Cebo Cela can be used as an alternate starch source for ethanol fermentation and for the production of maltodextrins and fructose/glucose syrups which are used as food thickeners and sweeteners.

Isothermal and temperature-cycling retrogradation of high-amylose corn starch: Impact of sonication on its structural and retrogradation properties

In this study, the effects of sonication and temperature-cycled storage on the structural properties and resistant starch content of high-amylose corn starch were investigated. Sonication induced a partial depolymerization of the molecular structures of amylopectin and amylose. Sonication treatment induced the appropriate structural changes for retrogradation. Although the relative crystallinity of sonicated starch was lower than that of non-sonicated starch, sonicated starch after retrogradation showed much higher relative crystallinity than non-sonicated starch. Regardless of sonication treatment, temperature-cycled storage resulted in a higher degree of retrogradation than isothermal storage, but the rate of retrogradation was greater in sonicated starch than in non-sonicated starch, as supported by retrogradation enthalpy, the Avrami constant, and relative crystallinity. The highly developed crystalline structure in sonicated starches due to retrogradation was reflected by the large amount of resistant starch.

Resistant starch type 2 from lotus stem: Ultrasonic effect on physical and nutraceutical properties

Resistant starch type 2 (RS) was isolated from lotus stem using enzymatic digestion method. The isolated RS was subjected to ultrasonication (US) at different sonication power (100-400 W). The US treated and untreated RS samples were characterized using dynamic light scattering (DLS), scanning electron microscopy (SEM), light microscopy and Fourier transform infrared spectroscopy (FT-IR). DLS revealed that particle size of RS decreased from 12.80 µm to 413.19 nm and zeta potential increased from -12.34 mV to -26.09 mV with the increase in sonication power. SEM revealed smaller, disintegrated and irregular shaped RS particles after ultrasonication. FT-IR showed the decreased the band intensity at 995 cm^-1 and 1047 cm^-1 signifying that US treatment decreased the crystallinity of RS and increased its amorphous character. The bile acid binding, anti-oxidant and pancreatic lipase inhibition activity of samples also increased significantly (p < 0.05) with the increase in sonication power. Increase in US power however increased the values of hydrolysis from 23.11 ± 1.09 to 36.06 ± 0.13% and gylcemic index from 52.39 ± 0.38 to 59.50 ± 0.11. Overall, the non-thermal process of ultrasonic treatment can be used to change the structural, morphological and nutraceutical profile of lotus stem resistant starch which can have great food and pharamaceutical applications.

Resistant starch levels and in vitro starch digestibility of selected cooked Philippine brown and milled rices varying in apparent amylose content and glycemic index

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Resistant starch content of rice correlates well with apparent amylose content.

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Cooked brown rices generally have more resistant starch than cooked milled rices.

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Resistant starch, hydrolysis index, and glycemic index of rice are all correlated.

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In vitro starch digestibility of cooked milled rice is greater than brown rice.

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Starch digestibility properties of cooked rice are vital in human nutrition and health.

Resistant starch (RS) content, starch digestibility, and hydrolysis index (HI) were analyzed in vitro for four selected Philippine rice varieties varying in apparent amylose content (AC) and glycemic index (GI), in cooked brown and milled rice forms. Starch digestibility curves were studied in relation to AC and reported GI values. Brown and milled rices of Improved Malagkit Sungsong 2 (IMS2), NSIC Rc160, IR64, and PSB Rc10 were cooked on separate beakers placed in automatic electric rice cookers and based on pre-determined water:rice ratios. RS levels of cooked milled rices ranged from 0.15 to 0.99% (mean = 0.45%). Their corresponding cooked brown rices had RS contents ranging from 0.24 to 1.61% (mean = 1.05%), with PSB Rc10 having the highest levels in both forms. HI ranged from 59.3 to 102.2%, with the highest noted for the waxy rice, IMS2, while corresponding brown rices had significantly lower HI spanning 49.2–66.9%. Previously reported GI values of these varieties were positively correlated with HI and estimated GI in this study. RS and non-resistant starch levels, and HI were highly correlated with AC. In vitro starch digestibility studies, as related to AC and GI, may be useful in screening for rice grain and nutritional properties aimed at developing new varieties with desirable quality and enhanced nutritional and functional properties.

Effects of treatment methods on the formation of resistant starch in purple sweet potato

In order to determine the mechanisms underlying resistant starch formation, three treatments were used to prepare resistant starch from purple sweet potato. The resistant starch yield, amylose content, chain length distribution, thermal properties, and crystal structure were determined, and the results were compared with those of unmodified starch. Autoclaving, pullulanase, and pullulanase-autoclaving treatments significantly increased the resistant starch yield, amylose content, shorter amylopectin branch content, and gelatinisation temperatures of native purple sweet potato starch. Resistant starch prepared via pullulanase-autoclaving combination treatment exhibited the highest gelatinisation enthalpy value and the greatest degree of overall thermal stability. X-ray diffraction patterns and Fourier-transform infrared spectra analysis demonstrated that all three treatments transformed the starch crystalline structure from C-type to B-type, and no new groups were generated during the modification process; all the processes were only physical modifications.

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.

Structural and digestion properties of potato starch modified using an efficient starch branching enzyme AqGBE

Modified potato starch with slower digestion may aid the development of new starch derivatives with improved nutritional values, and strategies to increase nutritional fractions such as resistant starch (RS) are desired. In this study, a correspondence between starch structure and enzymatic resistance was provided based on the efficient branching enzyme AqGBE, and modified starches with different amylose content (Control, 100%; PS1, 90%; PS2, 72%; PS3, 32%; PS4, 18%) were prepared. Through SEM observation, NMR and X-ray diffraction analyses, we identified that an increased proportion of α-1,6-linked branches in potato starch changes its state of granule into large pieces with crystallinity. Molecular weight and chain-length distribution analysis showed a decrease of molecular weight (from 1.1 × 10⁶ to 1.1 × 10⁵ g/mol) without an obvious change of chain-length distribution in PS1, while PS2-4 exhibited an increased proportion of DP 6-12 with a stable molecular weight distribution, indicating a distinct model of structural modification by AqGBE. The enhancement of peak viscosity was related to increased hydrophobic interactions and pieces state of PS1, while the contents of SDS and RS in PS1 increased by 37.7 and 49.4%, respectively. Our result provides an alternative way to increase the RS content of potato starch by branching modification.

Formation of type 3 resistant starch from mechanical activation-damaged high-amylose maize starch by a high-solid method

This study focused on constructing a high-solid reaction system to prepare type 3 resistant starch (RS₃) with high-amylose maize starch as raw material by mechanical activation (MA) pretreatment combined with thermal and freeze-thaw treatments. MA pretreatment effectively destroyed the crystal structure and molecular structure of native starch. MA damaged starch with a certain viscosity could form dough with a small amount of water to construct a starch continuous phase system. RS content increased with the damage levels of starch as the formation of double helix structure, attributed to that the molecules of MA damaged starch could be easy to move and form recrystallization structure. Thermal and freeze-thaw treatments contributed to strong interaction of starch-water and the re-formation of internal crystal structure of MA damaged starch to form RS₃. This study provides insight into the development of a highly effective approach for large scale production of resistant starch.

Molecular-structure evolution during in vitro fermentation of granular high-amylose wheat starch is different to in vitro digestion

This study investigates the evolution of the distributions of whole molecular size and of chain length of granular wheat starches (37 ~ 93% amylose content), subjected to in vitro fermentation with a porcine faecal inoculum or digestion with pancreatic enzymes. The results showed that the molecular structures of high-amylose starch (HAS) unfermented residues largely remained unchanged during the fermentation process, while wild-type starch (37% amylose content) showed a preferential degradation of the amylopectin fraction. In contrast, under simulated digestion conditions, the undigested residues of HAS showed structural changes, including a decrease in amylose content, a shift of amylose peak position towards lower degrees of polymerisation, and an enzyme-resistant fraction. These changes of starch structure are likely to be dependent on the different starch-degrading enzyme activities present in pancreatic vs. microbial systems. Molecular changes in response to fermentation metabolism revealed by size-exclusion chromatography can help understand the microbial utilization of resistant starch.

Physicochemical characterizations of starches isolated from Tetrastigma hemsleyanum Diels et Gilg

Physicochemical characteristics of starch isolated from Tetrastigma hemsleyanum Diels et Gilg (T. hemsleyanum) tuber root of 4 different origins were firstly analyzed in this study. The starch granules of T. hemsleyanum tuber root were oval or globular, showed unimodal distribution with average size of 21.66-28.79 μm. T. hemsleyanum starch had typical B-type diffraction pattern. T. hemsleyanum root was rich in starch, and apparent amylose content ranged from 39.82% to 47.67%. The amylopectin chain profiles showed that over 50% of the total detectable chains had degree of polymerization (DP) with 13-24. T. hemsleyanum tuber root had high RS content, which reached up to 61.44% in flour and 68.81% in isolated starch. After cooking, the RS content decreased, but was still high up to 7.52% in flour and 9.93% in isolated starch. The peak gelatinization temperature of T. hemsleyanum starch ranged from 68.12 to 74.42 °C. The peak viscosity of T. hemsleyanum flour and starch ranged from 778 to 1258 cP and 1577 to 2009 cP respectively. The results indicate that T. hemsleyanum is a potential source for novel starch with high resistant starch and provide some guides for comprehensive utilization of T. hemsleyanum starch in food and pharmaceuticals industry.

Preparation and characterization of native and autoclaving-cooling treated Pinellia ternate starch and its impact on gut microbiota

The aim of this study was to investigate and compare the structural and physicochemical properties of native Banxia starch (BXS) and autoclaving-cooling treated Banxia starch (CTBXS) and its related impacts on production of short chain fatty acids (SCFAs) and human gut microbiota by in vitro fecal fermentation. BXS had semicircle to spherical granules, whereas CTBXS exhibited block-shape. According to XRD and TGA, BXS had a C-type crystalline pattern, while CTBXS had a B-type crystalline pattern. CTBXS had better thermal stability than BXS. In addition, BXS exhibited significantly higher solubility and swelling power than CTBXS, and CTBXS had higher content of SDS than BXS. Moreover, BXS and CTBXS could change the composition and abundance of gut microbiota, could also promote the production of SCFAs. This study is beneficial to well understand the in vitro digestion and fecal fermentation behaviors of BXS and CTBXS, and can be developed as a potential functional food with the aim of improving colonic health.

In vitro digestion and fecal fermentation of highly resistant starch rice and its effect on the gut microbiota

Highly resistant starch rice (HRSR) is of particular interest in terms of its capacity to deliver short-chain fatty acids (SCFAs) to the colon in the prevention of diabetes mellitus and obesity. In this study, HRSR was processed into cooked rice, rice milk, rice cake, and rice popcorn, and the in vitro digestion and fermentation processes were monitored. The results showed that the starch digestibility of the four samples conformed to a first-order two-phase equation, and the resistant starch content of rice cake was the highest (11.98%). Compared with inulin, rice cake had a slower fermentation rate, and the butyrate concentration increased by 67.85%. The abundances of Prevotellaceae, which promotes the synthesis of SCFAs, and anti-inflammatory Faecalibacterium increased. The abundances of Proteobacteria and Megamonas, markers of gut microbiota imbalance, decreased. The results might facilitate the design and production of functional food products for type 2 diabetic and obese patients and improving colonic health.

α-Amylase action on starch in chickpea flour following hydrothermal processing and different drying, cooling and storage conditions

Starch is present in many prepared 'ready-meals' that have undergone processing and/or storage in frozen or chilled state. Hydrothermal processing greatly increases starch digestibility and postprandial glycaemia. Effects of different heating/drying and cooling regimes on amylolysis have received little attention. Hence, we examined the effects of different processing treatments on in vitro digestibility of starch in chickpea flour. Solid-state 13C NMR was used to estimate ordered double-helical structure in the starch. Native starch with 25 % double-helical content was the most resistant to digestion but hydrothermal processing (gelatinisation) resulted in >95 % loss of order and a large increase in starch digestibility. Air-drying of pre-treated flour produced slowly-digestible starch (C∞, 55.9 %). Refrigeration of gelatinised samples decreased ease of amylolysis coincident with increase in double-helical content. Freezing maintained the same degree of digestibility as freshly gelatinised material and produced negligible retrogradation. Chilling may be exploited to produce ready-meals with a lower glycaemic response.

Manipulations of glucose/lipid metabolism and gut microbiota of resistant starch encapsulated Ganoderma lucidum spores in T2DM rats

Our team previously demonstrated that Ganoderma lucidum spores (GLS) and resistant starch (RS) had hypoglycemic effects separately on type 2 diabetic mellitus (T2DM) rats. This work was to explore the effects of administering encapsulated GLS within RS (referred to as EGLS) in the T2DM rats, which were induced by streptozotocin (STZ). The EGLS was orally administered to rats for 28 days. The parameters of glycometabolism and lipometabolism were evaluated, and fecal microbiota composition was investigated. The results showed that EGLS significantly enhanced glycometabolism and lipometabolism parameters in T2DM rats, which might be associate with the enhancement of the glucose and lipid metabolism, insulin secretion, and glycogen synthesis and reduced lipogenesis. Furthermore, the intervention of EGLS also reduced the Proteobacteria community and improved dysfunctional gut microbiota. This study indicated EGLS may be a potential candidate for dietary intervention to modulate diabetes.