Effects of Ultrasonication on the Conformational, Microstructural, and Antioxidant Properties of Konjac Glucomannan

Chemical modification of bacterial exopolysaccharides: Antioxidant properties and health potentials

In recent years, there has been a burgeoning interest in the utilization of microbial exopolysaccharides (EPS) because of the added advantage of their renewable, biocompatible, and biodegradable nature in addition to intended applications. The endowed properties of bacterial EPS make them valuable candidates for a wide array of industrial applications. Modification of native EPS is known to enhance various physico-chemical and functional properties. Various modifications such as physical, chemical, biological, and enzymatic modifications were practiced improving the bioactivity of EPS. This paper comprehensively aims to review the most recent chemical modification techniques employed to modify the physico-chemical and functional changes of bacterial EPS in comparison with the unmodified forms. Chemical modification entails strategic alterations to the structure and properties of EPS through various synthetic and semi-synthetic methodologies. Emphasis is given to the antioxidant potential and functional role of these EPS derivatives in human health. Antioxidant properties reveal a significant augmentation in activity compared to their native counterparts. Such enhancement holds a strong promise for potential benefits and therapeutic applications. Chemical derivatives of EPS with overwhelming functional benefits could surely encourage EPS application, particularly as potential hydrocolloids in industrial and biomedical contexts.

Effects of KGM and Degradation Products on Appetite Regulation and Energy Expenditure in High-Fat-Diet Mice via the Adipocyte-Hypothalamus Axis

Konjac glucomannan (KGM), high-viscosity dietary fiber, is utilized in weight management. Previous investigations on the appetite-suppressing effects of KGM have centered on intestinal responses to nutrients and gastric emptying rates, with less focus on downstream hypothalamic neurons of satiety hormones. In our studies, the molecular mechanisms through which KGM and its degradation products influence energy homeostasis via the adipocyte-hypothalamic axis have been examined. It was found that high-viscosity KGM more effectively stimulates enteroendocrine cells to release glucagon-like peptide-1 (GLP-1) and reduces ghrelin production, thereby activating hypothalamic neurons and moderating short-term satiety. Conversely, low-viscosity DKGM has been shown to exhibit stronger anti-inflammatory properties in the hypothalamus, enhancing hormone sensitivity and lowering the satiety threshold. Notably, both KGM and DKGM significantly reduced leptin signaling and fatty acid signaling in adipose tissue and activated brown adipose tissue thermogenesis to suppress pro-opiomelanocortin (POMC) expression and activate agouti-related protein (AgRP) expression, thereby reducing food intake and increasing energy expenditure. Additionally, high-viscosity KGM has been found to activate the adipocyte-hypothalamus axis more effectively than DKGM, thereby promoting greater daily energy expenditure. These findings provide novel insights into the adipocyte-hypothalamic axis for KGM to suppress appetite and reduce weight.

Physicochemical and Rheological Properties of Degraded Konjac Gum by Abalone (Haliotis discus hannai) Viscera Enzyme

In the present study, a new degraded konjac glucomannan (DKGM) was prepared using a crude enzyme from abalone (Haliotis discus hannai) viscera, and its physicochemical properties were investigated. After enzymatic hydrolysis, the viscosity of KGM obviously decreased from 15,500 mPa·s to 398 mPa·s. The rheological properties analysis of KGM and DKGMs revealed that they were pseudoplastic fluids, and pseudoplasticity, viscoelasticity, melting temperature, and gelling temperature significantly decreased after enzymatic hydrolysis, especially for KGM-180 and KGM-240. In addition, the molecular weight of KGM decreased from 1.80 × 106 Da, to 0.45 × 106 Da and the polydispersity index increased from 1.17 to 1.83 after 240 min of degradation time. Compared with natural KGM, the smaller particle size distribution of DKGM further suggests enzyme hydrolysis reduces the aggregation of molecular chains with low molecular weight. FT-IR and FESEM analyses showed that the fragmented KMG chain did not affect the structural characteristics of molecular monomers; however, the dense three-dimensional network microstructure formed by intermolecular interaction changed to fragment microstructure after enzyme hydrolysis. These results revealed that the viscosity and rheological properties of KGM could be controlled and effectively changed using crude enzymes from abalone viscera. This work provides theoretical guidance for the promising application of DKGM in the food industry.

Deacetylated Konjac Glucomannan with a Slower Hydration Rate Delays Rice Digestion and Weakens Appetite Response

The physical characteristics of chyme during gastrointestinal digestion are considered to significantly affect nutrient digestion and absorption (such as glucose diffusion), which has an impact on postprandial satiety. The present study aims to analyze the hydration rate (HR) and rheological properties of deacetylated konjac glucomannan (DKGM) at different degrees and then explore their effects on rice texture, digestive properties, and the subjects' post-meal appetite. The present results show that, as the deacetylation degree (DD) of KGM increased, the intersection point of the viscoelastic modulus shifted to a high shear rate frequency, and as the swelling time of the DKGM was prolonged, its HR decreased significantly. The results of the in vitro gastrointestinal digestion tests show that the hardness and chewability of the rice in the fast-hydration group (MK1) were remarkably reduced. In contrast, the slow-hydration group (MK5) exhibited an outstanding ability to resist digestion. The kinetics of starch hydrolysis revealed that the HR of the rice in the fast-hydration group was 1.8 times faster than that of the slow-hydration group. Moreover, it was found that the subjects' appetite after the meal was highly related to the HR of the MK. Their hunger (p < 0.001), desire to eat (p < 0.001), and prospective food consumption (p < 0.001) were significantly inhibited in the slow-hydration group (MK5) compared to the control. This study explored the nutritional effects of the hydration properties derived from the DKGM, which may contribute to modifying the high glycemic index food and provide ideas for the fabrication of food with enhanced satiating capacity.

Fuc-S-A New Ultrasonic Degraded Sulfated α-l-Fucooligosaccharide-Alleviates DSS-Inflicted Colitis through Reshaping Gut Microbiota and Modulating Host-Microbe Tryptophan Metabolism

SCOPE

The dysbiosis of intestinal microecology plays an important pathogenic role in the development of inflammatory bowel disease.

METHODS AND RESULTS

A polysaccharide named Fuc-S, with a molecular weight of 156 kDa, was prepared by the ultrasonic degradation of fucoidan. Monosaccharide composition, FTIR, methylation, and NMR spectral analysis indicated that Fuc-S may have a backbone consisting of →3)-α-L-Fucp-(1→, →4)-α-L-Fucp-(1→ and →3, 4)-α-D-Glcp-(1→. Moreover, male C57BL/6 mice were fed three cycles of 1.8% dextran sulfate sodium (DSS) for 5 days and then water for 7 days to induce colitis. The longitudinal microbiome alterations were evaluated using 16S amplicon sequencing. In vivo assays showed that Fuc-S significantly improved clinical manifestations, colon shortening, colon injury, and colonic inflammatory cell infiltration associated with DSS-induced chronic colitis in mice. Further studies revealed that these beneficial effects were associated with the inhibition of Akt, p-38, ERK, and JNK phosphorylation in the colon tissues, regulating the structure and abundance of the gut microbiota, and modulating the host-microbe tryptophan metabolism of the mice with chronic colitis.

CONCLUSION

Our data confirmed the presence of glucose in the backbone of fucoidan and provided useful information that Fuc-S can be applied as an effective functional food and pharmaceutical candidate for IBD treatment.

Sulfated Galactans from Gracilaria fisheri with Supplementation of Octanoyl Promote Wound Healing Activity In Vitro and In Vivo

Sulfated galactans (SG) isolated from Gracilaria fisheri is partially degraded (DSG), and subsequentially supplemented with octanoyl (DSGO) and sulfate (DSGS) groups. The molecular weights of DSG, DSGO, and DSGS are 7.87, 152.79, and 97.07 kDa, respectively. The modification is confirmed using FTIR and NMR, while in vitro wound healing activity is assessed using scratched wound fibroblasts. The results reveal that DSGO exhibits highest percentage of wound closure in scratched fibroblast L929 cells. Furthermore, DSGO is able to promote proliferation and accelerate migration of scratched fibroblasts, which correspond to the regulation of proteins and mRNA (Ki67, p-FAK, vimentin, and E-cadherin) determined by Western blotting and qPCR analysis. The superior wound healing activity of DSGO is also confirmed in excision wound of rats. The results demonstrate that DSGO significantly enhances the percentage of wound closure, re-epithelialization, and collagen arrangement, increases α-smoth muscle actin (α-SMA) and vimentin expression, and decreases that of tumor necrosis factor-α (TNF-α) at the wound site. The results suggest that degraded SG supplemented with medium-chain fatty acids of octanoyl group may pass through the membrane, subsequently activating the mediators associated with proliferation and migration of fibroblasts, which can potentially lead to the promotion of wound healing activity.

Preparation and characterization of konjac glucomannan (KGM) and deacetylated KGM (Da-KGM) obtained by sonication

BACKGROUND

Konjac glucomannan (KGM) has been widely applied in the food industry as a thickening and gelation agent because of its unique colloidal properties of viscosity enhancement and gelling ability. The current study aimed to prepare and characterize KGM and deacetylated KGM (Da-KGM) samples obtained by sonication in neutral and alkali ethanol-water solutions.

RESULTS

The results showed that the deacetylation degree (DD) of Da-KGM increased exponentially with alkali concentration. Fourier transform infrared spectrometry further confirmed the deacetylation reaction through the dramatic decrease in the acetyl group band at 1740 cm^-1 . Besides, the high similarity among the tested groups in terms of X-ray diffraction (XRD) spectra implied a similar crystalline structure, while differential scanning calorimetry (DSC) curves revealed that the water binding capacity and decomposition temperature of KGM changed slightly with alkali and sonication treatment. The rheological profiles indicated that apparent viscosity (η₀ ) of sonicated KGM samples was unchanged except for the T60 group (60 min sonication treatment). Particularly, ultrasonic treatment under high alkaline conditions (0.10 mol L^-1 NaOH) was noted to promote the deacetylation reaction, and the obtained samples showed decreased apparent viscosity and weakened the gelation process in aqueous solution. Partial correction analysis indicated that alkali rather than ultrasonic treatment resulted in the change of DD and η₀ in Da-KGM. Moreover, sonication contributed to off-white color by reducing the browning caused by alkali in Da-KGM products.

CONCLUSION

Ultrasound-mediated heterogeneous deacetylation reaction is a feasible way to prepare Da-KGM samples with lightened browning and controllable DD. © 2022 Society of Chemical Industry.

Konjac Glucomannan (KGM), Deacetylated KGM (Da-KGM), and Degraded KGM Derivatives: A Special Focus on Colloidal Nutrition

Konjac flour, mainly obtained and purified from the tubers ofAmorphophallus konjac C. Koch, yields a high molecular weight (M_w) and viscous hydrocolloidal polysaccharide: konjac glucomannan (KGM). KGM has been widely applied in the food industry as a thickening and gelation agent as a result of its unique colloidal properties of effective viscosity enhancement and thermal-irreversible gelling. This review first narrates the typical commercial KGM source species, the industrial production, and the purification process of KGM flour. The structural information on native KGM, gelation mechanisms of alkali-induced deacetylated KGM (Da-KGM) hydrogel, progress on degraded KGM derivatives, cryoprotection effect, and colloidal nutrition are highlighted. Finally, the regulatory requirements of konjac flour and KGM among different countries are briefly introduced. The fine structure and physicochemical properties of KGM can be regulated in a great range via the deacetylation or degradation reaction. Here, the relationship between the physicochemical properties, such as viscosity, solubility, gelation, and nutritional effects, of native KGM, Da-KGM, and degraded KGM derivatives was preliminary established, which would provide theoretical guidance for designing KGM-based products with certain nutritional needs.

Preparation of konjac oligoglucomannans with different molecular weights and their in vitro and in vivo antioxidant activities

In this paper, konjac oligoglucomannan (KOGM) was obtained with a hydrolysis rate of 56.24% by controlling the hydrolysis conditions. KOGM was passed through a 0.2 kDa dialysis bag, a 3 kDa ultrafiltration tube, and a 5 kDa ultrafiltration tube, creating samples with molecular weights of 0.2–3 kDa (IV), 3–5 kDa (III), and >5 kDa (II), respectively. The in vitro antioxidant activities of the KOGM samples were tested by measuring their removal effects on ˙OH, O2−\documentclass[10pt]{article}\usepackage{wasysym} \usepackage[substack]{amsmath} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage[mathscr]{eucal} \usepackage{mathrsfs} \usepackage{pmc} \usepackage[Euler]{upgreek} \pagestyle{empty} \oddsidemargin -1.0in \begin{document} {\text{O}}_{2}^{-} \end{document}, and DPPH˙. The in vivo antioxidant activities of the samples were analyzed by measuring their impacts on the malondialdehyde (MDA) content, superoxide dismutase (SOD) activity, and glutathione peroxidase (GSH-PX) activity in mice. The results show that the KOGM samples in groups III and IV could effectively remove ˙OH, O2−\documentclass[10pt]{article}\usepackage{wasysym} \usepackage[substack]{amsmath} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage[mathscr]{eucal} \usepackage{mathrsfs} \usepackage{pmc} \usepackage[Euler]{upgreek} \pagestyle{empty} \oddsidemargin -1.0in \begin{document} {\text{O}}_{2}^{-} \end{document}, and DPPH˙; the KOGM samples in all three groups could enhance the SOD and GSH-PX activities and reduce the MDA content in the liver tissues of mice; finally, the antioxidant activity of KOGM is negatively correlated with the molecular weight.

Degradation of Exopolysaccharides from Lactic Acid Bacteria by Thermal, Chemical, Enzymatic and Ultrasound Stresses

During isolation, exopolysaccharides (EPS) from lactic acid bacteria are subject of thermal, chemical, enzymatic or ultrasound stress of different intensity that may affect macromolecular properties, for instance molecular mass or (intrinsic) viscosity. These parameters are, however, crucial, as they are associated with the technofunctional potential of EPS replacing commercial thickeners in nonfermented products. The aim of this study was to systematically examine treatments EPS are usually exposed to during isolation and to investigate the underlying degradation mechanisms. Solutions (1.0 g/L) of EPS from Streptococcus thermophilus, isolated as gently as possible, and commercial dextran were analyzed for molecular mass distributions as representative measure of molecule alterations. Generally, acid, excessive heat and ultrasonication, intensified by simultaneous application, showed EPS degradation effects. Thus, recommendations are given for isolation protocols. Ultrasonic degradation at 114 W/cm² fitted into the random chain scission model and followed third- (S. thermophilus EPS) or second-order kinetics (dextran). The degradation rate constant reflects the sensitivity to external stresses and was DGCC7710 EPS > DGCC7919 EPS > dextran > ST143 EPS. Due to their exceptional structural heterogeneity, the differences could not be linked to individual features. The resulting molecular mass showed good correlation (r² = 0.99) with dynamic viscosity.

Hypoglycemic effects and mechanism of different molecular weights of konjac glucomannans in type 2 diabetic rats

Konjac glucomannan (KGM) is a hypoglycemic polysaccharide with a wide range of molecular weights. But study on hypoglycemic effects of KGMs relate to molecular weight is limited. In this study, KGMs with high and medium molecular weights, and the degraded KGMs were analyzed with physicochemical properties, hypoglycemic effects and mechanisms. Results showed that as the molecular weight KGMs decreased, the viscosity decreased, molecular flexibility increased, while chemical groups, crystal structures and main chains showed little change. KGMs with medium molecular weights (KGM-M1, KGM-M2) showed better effects on increasing body weight, decreasing levels of fasting blood glucose, insulin resistance, total cholesterol and low density lipoprotein cholesterol, and enhancing integrity of pancreas and colon, than KGMs with high or low molecular weights (KGM-H, KGM-L) in type 2 diabetic rats. Mechanism analysis suggested that KGM-M1 and KGM-M2 had higher antioxidant and anti-inflammatory activities on elevating superoxide dismutase, decreasing malondialdehyde and tumor necrosis factor-α levels. Moreover, KGM-M1 and KGM-M2 increased gut microbiota diversity, Bacteroidetes/Firmicutes ratio and Muribaculaceae, decreased Romboutsia and Klebsiella, and improved 6 diabetic related metabolites. Combined, KGM-M1 and KGM-M2 showed higher hypoglycemic effects, due to regulatory activities of antioxidant, anti-inflammatory, intestinal microbiota, and relieved metabolic disorders.

Ultrasonic degradation effects on the physicochemical, rheological and antioxidant properties of polysaccharide from Sargassum pallidum

The aim of this study was to investigate the effects of ultrasound degradation on the physicochemical, rheological and antioxidant properties of Sargassum pallidum polysaccharides (SpPS). The results indicated that the ultrasound irradiation could significantly decrease the average molecule weight (MW), and particle size (Zavg) of native SpPS. The degradation pattern of SpPS was closely fitted to the first-order polymer degradation (random chain scission). The primary structure of SpPS before and after ultrasound degradation was not changed, and scanning electron microscopy (SEM) analysis showed that the morphology of SpPS was different from those of the degraded SpPS fractions. Rheological analysis indicated that the degraded SpPS solutions exhibited lower apparent viscosities than native SpPS solution at the same concentration, while the elasticity of the degraded fractions at a certain extent was enhanced. Furthermore, appropriately degraded SpPS fractions exhibited stronger DPPH and ABTS scavenging activity.

A high-molecular weight exopolysaccharide from the Cs-HK1 fungus: Ultrasonic degradation, characterization and in vitro fecal fermentation

This work was to examine the impact of power ultrasound (US) on the molecular properties of a high-molecular weight (MW) exopolysaccharide (EPS) from the Cs-HK1 medicinal fungus and the utilization, and prebiotic function of the US-treated EPS fractions in human fecal microflora in vitro. The US treatment caused notable reduction of intrinsic viscosity, average MW and aggregate size of EPS in water but no significant changes in the molecular structure. The US-treated EPS fractions were consumed more rapidly by the fecal microflora, resulting in a higher total level of short chain fatty acids. They also affected the relative abundance in the microflora more beneficially than the original EPS. The results suggest that power US is effective for modifying and improving the prebiotic properties of high-MW polysaccharides.