Effect of acidolysis and oxidation on structure and properties of konjac glucomannan

Use of ozone oxidation in combination with deacetylation for improving the structure and gelation properties of konjac glucomannan

In this study, oxidized deacetylated konjac glucomannans with different degrees of oxidation were prepared by a combination of deacetylation and ozone oxidation. Carboxyl groups were found to be introduced into the modified konjac glucomannan while acetyl groups were removed. The backbone, branched chains, and crystal structure of modified konjac glucomannan were not significantly affected. The whiteness was enhanced to 97-99 % and the thermal degradation temperature was up to 250 °C after modification. The solubility of the modified konjac glucomannan (oxidized for 60 min) was significantly increased to 84.56 % (p < 0.05), while its viscosity and swelling power were notably decreased owing to the changes in molecular weight (from 106 to 104) and functional groups. Rheological analysis showed that oxidized deacetylated konjac glucomannan has the ability to form soft-textured gels and the potential to develop dysphagia foods. Future studies should focus on the gelation mechanisms of oxidized deacetylated konjac glucomannan.

Konjac glucomannan: A comprehensive review of its extraction, health benefits, and pharmaceutical applications

Konjac glucomannan (KG) is a dietary fiber hydrocolloid derived from Amorphophallus konjac tubers and is widely utilized as a food additive and dietary supplement. As a health-conscious choice, purified KG, along with konjac flour and KG-infused diets, have gained widespread acceptance in Asian and European markets. An overview of the chemical composition and structure of KG is given in this review, along with thorough explanations of the processes used in its extraction, production, and purification. KG has been shown to promote health by reducing glucose, cholesterol, triglyceride levels, and blood pressure, thereby offering significant weight loss advantages. Furthermore, this review delves into the extensive health benefits and pharmaceutical applications of KG and its derivatives, emphasizing its prebiotic, anti-inflammatory, and antitumor activities. This study highlights how these natural polysaccharides can positively influence health, underscoring their potential in various biomedical applications.

Stability enhancement of proanthocyanidin-loaded liposomes via surface decoration with oxidized konjac glucomannan

The stability enhancement of proanthocyanidin-loaded liposomes (PC-Lip) via surface decoration with oxidized konjac glucomannan (OKGM) was investigated. The encapsulation efficiency and drug loading capacity of OKGM-coated PC-Lip (OKGM-PC-Lip) rose significantly. The average size and PDI of OKGM-PC-Lip increased, while the zeta potential decreased compared to those of PC-Lip. PC-Lip membrane fluidity reduced after coating with OKGM. The morphology of OKGM-PC-Lip showed that OKGM "halo layer" was formed on the liposome surface. Hydrogen bonding played an indispensable role in the combination between OKGM and PC-Lip, and the phase transition temperature of PC-Lip slightly increased after coating with OKGM. The retention rate of OKGM-PC-Lip was higher than that of PC-Lip at extreme pH. In vitro release, no significant difference in cumulative release was detected between OKGM-PC-Lip and PC-Lip at gastric stage, while the cumulative release rate of OKGM-PC-Lip was remarkably lower than that of PC-Lip at intestinal stage. The antioxidant activity of OKGM-PC-Lip was notably higher than that of PC-Lip. These results suggested that the resistance of PC-Lip to external influences was fruitfully enhanced after coating with OKGM. Compared with other polysaccharides, OKGM-coated liposomes may be more promising and advantageous in functional foods due to the polysaccharide's benefits to human health.

Effect of pretreatment with electron beam irradiation on the deacetylation efficiency of konjac glucomannan and its structural, physicochemical and gel properties

Due to its emulsifying and thickening properties, konjac glucomannan (KGM) is widely used in the food, medicine, and materials industries. Nevertheless, its high viscosity and significant water absorption limit its application range. Therefore, electron beam (e-beam) irradiation pretreatment was carried out to improve the deacetylation efficiency of KGM, and the physicochemical and gel properties of KGM were investigated. The results show that e-beam irradiation and deacetylation decrease the water absorption, solubility, transparency, molecular weight, and viscosity of KGM. Conversely, the moisture content, thermal stability, and water-binding capacity increase. FTIR and X-ray diffraction analysis revealed no significant changes in the chemical and crystalline structure of KGM before and after modification. However, modification weakens the intermolecular interaction of KGM hydrosols, which affects their rheology. Furthermore, deacetylation improves the mechanical properties and water retention capacity of KGM gels. Overall, the e-beam irradiation pretreatment provides a method to increase the efficiency of KGM deacetylation and improve the physical and chemical properties of KGM, thus expanding its potential applications in the food and chemical industries, among others.

The Effect of Acid Hydrolysis on the Pickering Emulsifying Capacity of Tartary Buckwheat Flour

The effect of sulfuric acid hydrolysis on the Pickering emulsifying capacity of Tartary buckwheat flour (TBF) rich in starch was evaluated for the first time. The results indicate that the sulfuric acid concentration and hydrolysis time had a significant impact on the Pickering emulsifying capacity of acid-hydrolyzed Tartary buckwheat flour (HTBF). A low sulfuric acid concentration (1-2 mol/L) could reduce the particle size of HTBF, but it also decreased the Pickering emulsifying ability. At a sulfuric acid concentration of 3 mol/L, appropriate treatment time (2 and 3 days) led to particle aggregation but significantly improved wettability, thereby resulting in a rapid enhancement in emulsifying capacity. Under these conditions, the obtained HTBF (HTBF-D2-C3 and HTBF-D3-C3) could stabilize medium-chain triglyceride (MCT)-based Pickering high-internal-phase emulsions (HIPEs) with an oil-phase volume fraction of 80% at the addition amounts (c) of ≥1.0% and ≥1.5%, respectively. Its performance was significantly superior to that of TBF (c ≥ 2.0%). Furthermore, at the same addition amount, the droplet size of HIPEs constructed by HTBF-D3-C3 was smaller than that of HTBF-D2-C3, and its gel strength and microrheological performance were also superior to those of HTBF-D2-C3, which was attributed to the higher wettability of HTBF-D3-C3. The findings of this study can facilitate the in-depth application of Tartary buckwheat and provide references for the development of novel Pickering emulsifiers.

Regulation of glycose and lipid metabolism and application based on the colloidal nutrition science properties of konjac glucomannan: A comprehensive review

The physicochemical properties of dietary fiber in the gastrointestinal tract, such as hydration properties, adsorption properties, rheological properties, have an important influence on the physiological process of host digestion and absorption, leading to the differences in satiety and glucose and lipid metabolisms. Based on the diversified physicochemical properties of konjac glucomannan (KGM), it is meaningful to review the relationship of structural characteristics, physicochemical properties and glycose and lipid metabolism. Firstly, this paper bypassed the category of intestinal microbes, and explained the potential of dietary fiber in regulating glucose and lipid metabolism during nutrient digestion and absorption from the perspective of colloidal nutrition. Secondly, the modification methods of KGM to regulate its physicochemical properties were discussed and the relationship between KGM's molecular structure types and glycose and lipid metabolism were summarized. Finally, based on the characteristics of KGM, the application of KGM in the main material and ingredients of fat reduction food was reviewed. We hope this work could provide theoretical basis for the study of dietary fiber colloid nutrition science.

Enhanced hypoglycemic effects of konjac glucomannan combined with Polygonatum cyrtonema Hua polysaccharide in complete nutritional liquid diet fed type 2 diabetes mice

In our aging society, dysphagia and malnutrition are growing concerns, necessitating intervention. Liquid nutrition support offers a practical solution for traditional dietary issues, but it raises a key issue: the potential for post-meal glucose spikes impacting efficacy. This study examined the effects of supplementation of Polygonatum cyrtonema Hua polysaccharide (PCP), konjac glucomannan (KGM) and their combination on acute phase postprandial glycemic response and long-term glucose metabolism in T2DM mice on a complete nutritional liquid diet. KGM was more effective in reducing postprandial glucose response, while PCP was more prominent in ameliorating long-term glucose metabolism. The KGM-PCP combination demonstrated superior outcomes in fasting blood glucose, insulin, and glucose homeostasis. PCP and KGM also influenced the composition and abundance of the gut microbiome, with the H-PCP group showing optimal performance. Moreover, the KGM-PCP combination improved body weight, lipid homeostasis, and liver health the most. PCP potentially regulates glycemia through metabolic pathways, while KGM improves glycemic metabolism by reducing postprandial glucose levels in response to viscous intestinal contents. This research identifies the structure, viscosity properties, and hypoglycemic effects of KGM and PCP in complete nutritional liquid diet fed T2DM mice, enabling their strategic utilization as hypoglycemic components in nutritional administration and glycemic regulation.

Comparative study on the effect of inhibitory methods on the color and gelation properties of alkali induced heat-set konjac gel from Amorphophallus bulbifer

As a newly superior konjac variety, the Amorphophallus bulbifer (A. bulbifer) was easily browning during the alkali-induced process. In this study, five different inhibitory methods, such as citric-acid heat pretreatment (CAT), mixed with citric acid (CA), mixed with ascorbic acid (AA), mixed with L-cysteine (CYS), and mixed with potato starch (PS, containing TiO2), were separately used to inhibit the browning of alkali-induced heat-set A. bulbifer gel (ABG). The color and gelation properties were then investigated and compared. Results showed that the inhibitory methods had significant influences on the appearance, color, physicochemical properties, rheological properties, and microstructures of ABG. Among them, the CAT method not only significantly inhibited the browning of ABG (ΔE value dropped from 25.74 to 14.68) but also improved the water-holding capacity, moisture distribution, and thermal stability without damaging the textural properties of ABG. Moreover, SEM revealed that both CAT and adding PS methods could exhibit the more dense gel network structures of ABG than other methods. It was reasonable to conclude that ABG-CAT offered a superior method to prevent browning compared to the other methods based on the texture, microstructure, color, appearance, and thermal stability of the product.

Oral konjac glucomannan for prevention of ionizing radiation-induced injury by regulating gut microbiota and increasing short chain fatty acids

Ionizing radiation-induced injury commonly happens in radiotherapy, leading to damages of the hematopoietic and gastrointestinal systems. Radioprotective medications are mainly applied in hospitals, although only injections are available and their gut protection is limited. Here, oral konjac glucomannan (KGM), a natural macromolecule and soluble dietary fiber, was used against ionizing radiation-induced injury. The mice were fed with KGM (0.4 g/kg) for 3 days or injected with a clinical medication amifostine before 6.5 Gy γ-ray whole body irradiation (WBI) or 13 Gy whole abdominal irradiation (WAI). In the WBI experiments, KGM improved blood cell recovery and bone marrow cell proliferation in the femur and spleen, though its effect was weaker than or similar to that of amifostine. In the WBI experiments, the gut protection of KGM was similar to or a little better than that of amifostine, involving regenerated crypts numbers, villus length, and gut permeability. Moreover, KGM remarkably enhanced the survival rates of WBI and WAI mice, consistent with amifostine. KGM, as a prebiotic, enhanced gut microbiota abundance, probiotic numbers, and short chain fatty acid production, maintaining gut homeostasis. Moreover, KGM inhibited the apoptosis of irradiated human intestinal epithelial cells. KGM is a promising natural macromolecule against ionizing radiation-induced injury.

A pH-sensitive hydrogel based on carboxymethylated konjac glucomannan crosslinked by sodium trimetaphosphate: Synthesis, characterization, swelling behavior and controlled drug release

The pH-sensitive hydrogel consisting of carboxymethylated konjac glucomannan (CMKGM) and sodium trimetaphosphate (STMP) was prepared for a potential intestinal targeted delivery system. Both the CMKGM and the CMKGM hydrogel were characterized by FT-IR spectra, X-ray diffraction (XRD), and thermogravimetric analysis (TGA). The Congo red and atomic force microscope (AFM) results showed a coil-to-helix transition of CMKGM in alkaline conditions with the degree of substitution (DS) increased from 0.20 to 0.49. Rheological measurements indicated that the DS and the STMP content collectively influence the mechanical stiffness and swelling properties of the obtained hydrogels. In addition, the swelling behavior of the hydrogels revealed that they were sensitive to pH value changes and were following a Korsmeyer-Peppas gastrointestinal release behavior, indicating that the release was controlled by non-Fickian diffusion. Furthermore, all the results suggested that the prepared pH-sensitive hydrogel may serve as a potential biomaterial for the intestine-targeted delivery system.

Porous hydroxyapatite scaffold orchestrated with bioactive coatings for rapid bone repair

Current bioceramic scaffolds for critical-size bone defects are still facing various challenges such as the poor capability of self-resorption, vascularization and osteogenesis. Herein, a composite scaffold (HOD) is fabricated by integrating bioactive coatings of konjac glucomannan (KGM) and deferoxamine (DFO) into porous hydroxyapatite scaffold (HA), where KGM coating induces the self-resorption of HOD after implanting and DFO promoted the vascularization at the defected bone. Porous HA scaffolds with 200-400 μm of pore sizes were prepared and these bioactive coatings were successfully deposited on the scaffold, which was confirmed by SEM. MC3T3-E1 cells could be tightly attached to the pore wall of HOD and the obvious osteogenic differentiation was clearly displayed after 14 days of co-culture. Besides, HOD displayed the potential of promoting the vascularization of HUVECs. Importantly, the accelerated degradation of HOD was observed in a macrophage-associated acidic medium, which led to the self-resorption of HOD in vivo. Micro-CT images showed that HOD was gradually replaced by newly formed bone, achieving a balance between the new bone formation and the scaffold degradation. The rapid bone repairing of the femoral defects in rats was displayed for HOD in comparison to the HA scaffold. Moreover, the therapeutic mechanism of HOD was highly associated with promoted osteogenesis and vascularization. Collectively, the porous ceramic scaffold orchestrated with bioactive coatings may be a promising strategy for repairing of the large bone defect.

Air packaging is obviously beneficial to the heterogeneous hygrothermal degradation of konjac glucomannan

Heterogeneous hygrothermal degradation (HHTD) is a cost-effective and environmentally friendly method for the successful preparation of partially depolymerized konjac glucomannan (DKGM). This study investigated the degradation of konjac glucomannan (KGM) in two packaging methods and detected that compared with natural KGM, the M_w of vacuum-packaged DKGM with 20 % moisture content treated at 130 °C for 40 min was reduced by 23.34 %, while that of air-packaged DKGM was decreased by 63.14 %, the vacuum-packaged DKGM with only 0.5 % H₂O₂ added was dropped by 69.36 %. It was verified that oxygen in air-packaging plays a crucial role in HHTD. Furthermore, the effects of moisture content, treatment temperature and time on the M_w and apparent viscosity of air-packaged DKGM were explored. The properties and structure of DKGM were characterized by rheometer, TGA, XRD, FT-IR and SEM. Results established that treatment temperature had a stronger promoting effect on HHTD. The rheological properties of DKGM samples changed markedly, and the thermal decomposition temperature and crystallinity were increased, with its infrared absorption peaks very close. This research is expected to provide theoretical bases and reference ideas for efficient HHTD method of KGM in actual production.

Review on Modification of Glucomannan as an Excipient in Solid Dosage Forms

Glucomannan (GM)—a polysaccharide generally extracted from the tuber of Amorphophallus konjac—has great potential as a filler–binder in direct compression, disintegrant in tablets, or gelling agent due to its strong hydrophilicity and extremely high viscosity. However, it has poor water resistance and low mechanical strength when used as an excipient in solid form. Several physical and chemical modifications have been carried out to improve these drawbacks. Chemical modification affects the characteristics of GM based on the DS. Carboxymethylation improves GM functionality by modifying its solubility and viscosity, which in turn allows it to bind water more efficiently and thus improve its elongation and gel homogeneity. Meanwhile, physical modification enhances functionality through combination with other excipients to improve mechanical properties and modify swelling ability and drug release from the matrix. This review discusses extraction of GM and its modification to enhance its applicability as an excipient in solid form. Modified GM is a novel excipient applicable in the pharmaceutical industry for direct compression, as a tablet disintegrant, a film-forming agent, and for encapsulation of macromolecular compounds or drug carriers for controlled release.

Recent Advances of Stimuli-Responsive Polysaccharide Hydrogels in Delivery Systems: A Review

Hydrogels obtained from natural polymers have received widespread attention for their excellent biocompatible property, nontoxicity, easy gelation, and functionalization. Polysaccharides can regulate the gut microbiota and improve the intestinal microenvironment, thus exerting the healthy effect of intestinal immunity. In an active substance delivery system, the extent and speed of the substance reaching its target are highly dependent on the carrier. Thus, the smart active substance delivery systems are gradually increasing. The smart polysaccharide-hydrogels possess the ability in response to external stimuli through changing their volume phase and structure, which are applied in various fields. Natural polysaccharide-based hydrogels possess excellent characteristics of environmental friendliness, good biocompatibility, and abundant sources. According to the response type, natural polysaccharide-based hydrogels are usually divided into stimulus-responsive hydrogels, including internal response (pH, temperature, enzyme, redox) and external response (light, electricity, magnetism) hydrogels. The delivery system based on polysaccharides can exert their effects in the gastrointestinal tract. At the same time, polysaccharides may also take part in regulating the brain signals through the microbiota-gut-brain axis. Therefore, natural polysaccharide-hydrogels are considered as promising biomaterials, which can be designed as delivery systems for regulating the gut-brain axis. This article reviews the research advance of stimulus-responsive hydrogels, which focus on the types, response characteristics, and applications for polysaccharide-based smart hydrogels as delivery systems.

Deacetylation enhances the properties of konjac glucomannan/agar composites

From a microstructural point of view, this work concerns how deacetylation improves the practical characteristics of deacetylated-konjac glucomannan/agar (DK/A) composite films. As disclosed by infrared spectroscopy and X-ray diffraction, the deacetylation of konjac glucomannan (KGM) enhanced the chain interactions in DK/A composites and suppressed the realignment of agar molecules into crystallites. The enhanced associations between acetyl-free regions of KGM and agar reduced the exposure of OH groups and thus increased the hydrophobicity of the composites. Besides, the partial removal of acetyl groups allowed shortened distances between chains; consequently, denser composite matrices emerged with lower water vapor permeability and higher tensile strength. Also, the KGM deacetylation increased the matrix flexibility and elongation at break for DK/A composites, associated with the hindered rearrangement of agar chains. Thus, altering the deacetylation degree of KGM may be an effective way to design KGM-based composites with improved hydrophobicity and mechanical performance.

Effects of konjac glucomannan with different molecular weights on gut microflora with antibiotic perturbance in in vitro fecal fermentation

This study investigated the effect of konjac glucomannan (KGM) of different molecular weight on fecal microflora against antibiotic disturbance. KGM (~1.8 × 10⁷ Da) was partially hydrolysed with trifluoroacetic acid (TFA) for 10 and 60 min to KGM1 (~2.1 × 10⁴ Da) and KGM2 (7413 Da), respectively. The acid treatment caused significant reduction of intrinsic viscosity, average molecular weight (MW) and particle size of KGM, but brought limited change to the molecular structure. Low-MW KGM2 showed the most significant effect on fecal microflora in the presence of two common antibiotics (ampicillin and clindamycin), by increasing the relative abundance of Bifidobacteriaceae while decreasing the proportion of Enterobacteriaceae. Additionally, both the native and acid-treated KGM counteracted the adverse influence of antibiotics on the production of short chain fatty acids. The results have demonstrated the effect of KGM on gut microbiota with antibiotic disturbance.

A pH-sensitive semi-interpenetrating polymer network hydrogels constructed by konjac glucomannan and poly (γ-glutamic acid): Synthesis, characterization and swelling behavior

A novel pH-sensitive semi-interpenetrating polymer network (semi-IPN) hydrogel was prepared by using konjac glucomannan (KGM) and poly (γ-glutamic acid) (γ-PGA) with sodium trimetaphosphate (STMP) as the crosslinking agent. The structure of the semi-IPN hydrogels was characterized by FTIR spectra, thermogravimetric analysis (TGA), X-ray diffraction (XRD), rheological measurements, and scanning electron microscopy (SEM). The pH-sensitive effects were investigated by calculating the equilibrium swelling ratio (ESR) in buffer solutions (pH 2, 4, 6, and 8, respectively) at 37 °C. These results showed that the content of cross-linker and γ-PGA has a significant influence on the hydrogels' structure and swelling behavior. In vitro drug release behavior of semi-IPN hydrogels was investigated under simulated gastric and intestinal fluids using model drug Nicotinamide (NTM), and various models were applied to describe the drug release behaviors. The obtained results indicated that our synthesized semi-IPN hydrogel had the potential to be used as a suitable biomaterial carrier for functional components or drug delivery in the intestine.

Acylation modification of konjac glucomannan and its adsorption of Fe (Ⅲ) ion

A biodegradable adsorbent, modified konjac glucomannan (MKGM), was prepared by konjac glucomannan (KGM) acylated with phthalic anhydride catalyzed using concentrated sulfuric acid. The modified conditions such as reaction temperature, mass ratio of phthalic anhydride to KGM, catalyst dosage and reaction time were investigated, respectively. MKGM exhibited preferable adsorption performance for the removal of Fe (Ⅲ) ion. The adsorption behavior was discussed using the Langmuir and Freundlich isotherm models. The results showed that the Freundlich linear model was suitable for describing the adsorption process of Fe (Ⅲ). The maximum adsorption capacity of MKGM for Fe (Ⅲ) ion was 31.87 mg g^-1 at 298 K. The kinetics studies suggested that adsorption process followed the pseudo-second-order model and the adsorption process was mainly controlled by both surface reactivity and intra-particle diffusion. Together with the evaluation of the thermodynamic parameters such as Gibbs free energy, enthalpy and entropy changes, the results indicated that the adsorption process of Fe (Ⅲ) was endothermic, feasible, and spontaneous in nature. Hence, as a bioadsorbent, the MKGM has a promising potential for the removal of Fe (Ⅲ) ion from aqueous solutions.

Research Article Product Composition Analysis and Process Research of Oligosaccharides Produced from Enzymatic Hydrolysis of High-Concentration Konjac Flour

There is a huge variability in reducing sugars, viscosity, and composition of oligosaccharides in the hydrolyzed products of konjac flour with different concentrations. We analyzed the factors affecting reducing sugars, viscosity, and the average degree of polymerization (DP) during the preparation of oligosaccharides from konjac flour hydrolyzed by β-mannanase under the high-concentration solute hydrolysis model. Hydrolysate of konjac flour, using concentrations ranging from 50 to 200 g/L, was directly added into 20 U/mL of β-mannanase solution. The results showed that when the proportion of the water content in the solution decreased, the viscosity of the solution and the DP of polysaccharides changed significantly. When the viscosity of the hydrolysate was controlled within the range of 30-20 mPa·s, the concentration of the reducing sugars was maintained in the range of 9-13 g/L and the average DP of the polysaccharides was controlled in the range of 2.42-9.78. We also found that a high concentration of hydrolysate was beneficial for decreasing the production of reducing sugars, and the diversification of macromolecular glycan was beneficial to the preparation of functional sugars. Moreover, we observed that the proportion of reducing sugars with free water content was high and that the preparation of oligosaccharides via the high-concentration solid-state method increased product diversity.