Manufacture and Properties of Glucomannans and Glucomannooligosaccharides Derived from Konjac and Other Sources

Konjac glucomannan exerts regulatory effects on macrophages and its applications in biomedical engineering

Konjac glucomannan (KGM) molecular chains contain a small amount of acetyl groups and a large number of hydroxyl groups, thereby exhibiting exceptional water retention and gel-forming properties. To meet diverse requirements, KGM undergoes modification processes such as oxidation, acetylation, grafting, and cationization, which reduce its viscosity, enhance its mechanical strength, and improve its water solubility. Researchers have found that KGM and its derivatives can regulate the polarization of macrophages, inducing their transformation into classically activated M1-type macrophages or alternatively activated M2-type macrophages, and even facilitating the interconversion between M1 and M2 phenotypes. Concurrently, the modulation of macrophage polarization states holds significant importance for chronic wound healing, inflammatory bowel disease (IBD), antitumor therapy, tissue engineering scaffolds, oral vaccines, pulmonary delivery, and probiotics. Therefore, KGM has the advantages of both immunomodulatory effects (biological activity) and gel-forming properties (physicochemical properties), giving it significant advantages in a variety of biomedical engineering applications.

An Isofibrous Diet with Fiber Konjac Glucomannan Ameliorates Salmonella typhimurium-Induced Colonic Injury by Regulating TLR2-NF-κB Signaling and Intestinal Microbiota in Mice

This study aimed to investigate the hypothesis that dietary konjac glucomannan (KGM) could alleviate Salmonella typhimurium-induced colitis by modulating intestinal microbiota. Mice were fed an isocaloric and isofibrous diet supplemented with either 7% KGM or cellulose and were treated with 5 × 108 CFU of S. typhimurium. The results showed that KGM had an average molecular weight of 936 kDa and predominantly consisted of mannose and glucose at a molar ratio of 1:1.22. In vivo studies demonstrated that dietary KGM effectively mitigated colonic lesions, oxidative stress, disruption of tight junction protein 2 and occludin, and the inflammatory response induced by S. typhimurium. Moreover, KGM administration alleviated the dramatic upregulation of toll-like receptor 2 (TLR2) and phosphonuclear factor κB (NF-κB) protein abundance, induced by Salmonella treatment. Notably, dietary KGM restored the reduced Muribaculaceae and Lactobacillus abundance and increased the abundance of Blautia and Salmonella in S. typhimurium-infected mice. Spearman correlation analysis revealed that the gut microbiota improved by KGM contribute to inhibit inflammation and oxidative stress. These results demonstrated the protective effects of dietary KGM against colitis by modulating the gut microbiota and the TLR2-NF-κB signaling pathway in response to Salmonella infection.

Anticancer and anti-angiogenic activities of mannooligosaccharides extracted from coconut meal on colorectal carcinoma cells in vitro

Colorectal carcinoma (CRC) is one of the most common malignancies, though there are no effective therapeutic regimens at present. This study aimed to investigate the inhibitory effects of mannooligosaccharides extracted from coconut meal (CMOSs) on the proliferation and migration of human colorectal cancer HCT116 cells in vitro. The results showed that CMOSs exhibited significant inhibitory activity against HCT116 cell proliferation in a concentration-dependent manner with less cytotoxic effects on the Vero normal cells. CMOSs displayed the ability to increase the activation of caspase-8, -9, and -3/7, as well as the generation of reactive oxygen species (ROS). Moreover, CMOSs suppressed HCT116 cell migration in vitro. Interestingly, treatment of human microvascular endothelial cells (HMVECs) with CMOSs resulted in the inhibition of cell proliferation, cell migration, and capillary-like tube formation, suggesting its anti-vascular angiogenesis. In summary, the results of this study indicate that CMOSs could be a valuable therapeutic candidate for CRC treatment.

The Discovery of a Multidomain Mannanase Containing Dual-Catalytic Domain of the Same Activity: Biochemical Properties and Synergistic Effect

In recent years, the wide application of mannan has driven the demand for the exploration of mannanase. As one of the main components of hemicellulose, mannan is an important polysaccharide that ruminants need to degrade and utilize, making rumen a rich source of mannanases. In this study, gene mining of mannanases was performed using bioinformatics, and potential dual-catalytic domain mannanases were heterologously expressed to analyze their properties. The hydrolysis pattern and enzymatic products were identified by liquid chromatography coupled with high-resolution mass spectrometry (LC-HRMS). A dual-catalytic domain mannanase Man26/5 with the same function as the substrate was successfully mined from the genome of cattle rumen microbiota. Compared to the single-catalytic domain, its higher thermal stability (≤50 °C) and catalytic efficiency confirm the synergistic effect between the two catalytic domains. It exhibited a unique "crab-like" structure where the CBM located in the middle is responsible for binding, and the catalytic domains at both ends are responsible for cutting. The exploration of its multidomain structure and synergistic patterns could provide a reference for the artificial construction and molecular modification of enzymes.

Characteristics of exopolysaccharides from Paecilomyces hepiali and their simulated digestion and fermentation in vitro by human intestinal microbiota

The metabolic process of polysaccharides in gastrointestinal digestions and the effects of the resulting carbohydrates on the composition of gut microbes are important to explore their prebiotic properties. Therefore, the purpose of this study was to investigate the simulated digestion and fecal fermentation in vitro of three fractions (PHEPSs-1, PHEPSs-2 and PHEPSs-3) purified from the crude exopolysaccharides of Paecilomyces hepiali HN1 (PHEPSs) and to explore the potential prebiotic mechanisms. The three purified fractions were characterized by HPLC, UV, FT-IR, SEM and AFM, and they were all of galactoglucomannan family with molecular weight of 178, 232 and 119 kDa, respectively. They could resist the simulated gastrointestinal digestions, but they were metabolized in fecal fermentation in vitro. Furthermore, the mannose in PHEPSs showed a higher utilization rate than that of glucose or galactose. The proliferation effects of PHEPSs on Bifidobacterium and Lactobacillus were weaker significantly than those of fructooligosaccharides before 12 h of fecal fermentation, but stronger after 24 h of fecal fermentation. Meanwhile, higher levels of short-chain fatty acids were found in PHEPSs groups when the fecal fermentation extended to 36 h. Therefore, PHEPSs are expected to have a potent gut healthy activity and can be explored as functional food ingredients.

Effect and characterization of konjac glucomannan on xanthan gum/κ-carrageenan/agar system

A mixed polysaccharide system is an important strategy to improve the performance of a single polysaccharide. Herein, quaternary polysaccharide gels were prepared by konjac glucomannan (KGM), xanthan gum (XG), κ-carrageenan (κ-CA), and agar (AR). The effects of KGM were evaluated by combining water holding capacity (WHC), rheological analysis, scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), and texture profile analysis (TPA). More KGM gradually increased the springiness of the compounded gels. WHC increased and then decreased with the addition of KGM, performing best at KGM4 (KGM: κ-CA:XG:AR = 2:2:1:2). Rheological analysis showed that the compounded gels exhibited a pseudoplastic characteristic of shear thinning, KGM endowed the gel with a stronger shear thinning behavior and improved the solid-like nature of the gels at high temperatures. The thermal stability of the composite gel was improved by the participation of KGM. FTIR analysis showed that the interactions were mainly related to intermolecular hydrogen bonds and acetyl groups. The microscopic morphology of KGM4 was significantly continuous, smooth, and compact, exhibiting the best practical performance and taking the maximum advantage.

Self-healing hydrogels based on biological macromolecules in wound healing: A review

The complete healing of skin wounds has been a challenge in clinical treatment. Self-healing hydrogels are special hydrogels formed by distinctive physicochemically reversible bonds, and they are considered promising biomaterials in the biomedical field owing to their inherently good drug-carrying capacity as well as self-healing and repair abilities. Moreover, natural polymeric materials have received considerable attention in skin tissue engineering owing to their low cytotoxicity, low immunogenicity, and excellent biodegradation rates. In this paper, we review recent advances in the design of self-healing hydrogels based on natural polymers for skin-wound healing applications. First, we outline a variety of natural polymers that can be used to construct self-healing hydrogel systems and highlight the advantages and disadvantages of different natural polymers. We then describe the principle of self-healing hydrogels in terms of two different crosslinking mechanisms-physical and chemical-and dissect their performance characteristics based on the practical needs of skin-trauma applications. Next, we outline the biological mechanisms involved in the healing of skin wounds and describe the current application strategies for self-healing hydrogels based on these mechanisms. Finally, we analyze and summarize the challenges and prospects of natural-material-based self-healing hydrogels for skin applications.

Gluco-oligosaccharides as potential prebiotics: Synthesis, purification, structural characterization, and evaluation of prebiotic effect

Prebiotics have long been used to modulate the gut microbiota and improve host health. Most established prebiotics are nondigestible carbohydrates, especially short-chain oligosaccharides. Recently, gluco-oligosaccharides (GlcOS) with 2-10 glucose residues and one or more O-glycosidic linkage(s) have been found to exert prebiotic potentials (not fully established prebiotics) because of their selective fermentation by beneficial gut bacteria. However, the prebiotic effects (non-digestibility, selective fermentability, and potential health effects) of GlcOS are highly variable due to their complex structure originating from different synthesis processes. The relationship between GlcOS structure and their potential prebiotic effects has not been fully understood. To date, a comprehensive summary of the knowledge of GlcOS is still missing. Therefore, this review provides an overview of GlcOS as potential prebiotics, covering their synthesis, purification, structural characterization, and prebiotic effect evaluation. First, GlcOS with different structures are introduced. Then, the enzymatic and chemical processes for GlcOS synthesis are critically reviewed, including reaction mechanisms, substrates, catalysts, the structures of resultant GlcOS, and the synthetic performance (yield and selectivity). Industrial separation techniques for GlcOS purification and structural characterization methods are discussed in detail. Finally, in vitro and in vivo studies to evaluate the non-digestibility, selective fermentability, and associated health effects of different GlcOS are extensively reviewed with a special focus on the GlcOS structure-function relationship.

Biochemical analyses of a novel acidophilic GH5 β-mannanase from Trichoderma asperellum ND-1 and its application in mannooligosaccharides production from galactomannans

In this study, an acidophilic GH5 β-mannanase (TaMan5) from Trichoderma asperellum ND-1 was efficiently expressed in Pichia pastoris (a 2.0-fold increase, 67.5 ± 1.95 U/mL). TaMan5 displayed the highest specificity toward locust bean gum (K_m = 1.34 mg/mL, V_max = 749.14 μmol/min/mg) at pH 4.0 and 65°C. Furthermore, TaMan5 displayed remarkable tolerance to acidic environments, retaining over 80% of its original activity at pH 3.0-5.0. The activity of TaMan5 was remarkably decreased by Cu²⁺, Mn²⁺, and SDS, while Fe²⁺/Fe³⁺ improved the enzyme activity. A thin-layer chromatography (TLC) analysis of the action model showed that TaMan5 could rapidly degrade mannan/MOS into mannobiose without mannose via hydrolysis action as well as transglycosylation. Site-directed mutagenesis results suggested that Glu²⁰⁵, Glu³¹³, and Asp³⁵⁷ of TaMan5 are crucial catalytic residues, with Asp¹⁵² playing an auxiliary function. Additionally, TaMan5 and commercial α-galactosidase displayed a remarkable synergistic effect on the degradation of galactomannans. This study provided a novel β-mannanase with ideal characteristics and can be considered a potential candidate for the production of bioactive polysaccharide mannobiose.

Dendrobium officinale Polysaccharide Prevents Diabetes via the Regulation of Gut Microbiota in Prediabetic Mice

Dendrobium officinale polysaccharide (DOP), which serves as a prebiotic, exhibits a variety of biological activities, including hypoglycemic activities. However, the effects of DOP on diabetes prevention and its hypoglycemic mechanisms are still unclear. In this study, the effects of DOP treatment on the prediabetic mice model were studied and the mechanism was investigated. The results showed that 200 mg/kg/d of DOP reduced the relative risk of type 2 diabetes mellitus (T2DM) from prediabetes by 63.7%. Meanwhile, DOP decreased the level of LPS and inhibited the expression of TLR4 by regulating the composition of the gut microbiota, consequently relieving the inflammation and alleviating insulin resistance. In addition, DOP increased the abundance of SCFA (short chain fatty acid)-producing bacteria in the intestine, increased the levels of intestinal SCFAs, promoted the expression of short-chain fatty acid receptors FFAR2/FFAR3, and increased the secretion of the intestinal hormones GLP-1 and PYY, which helped to repair islet damage, suppress appetite, and improve insulin resistance. Our results suggested that DOP is a promising functional food supplement for the prevention of T2DM.

Role of prebiotic dietary fiber in periodontal disease: A systematic review of animal studies

Background

Periodontitis is a chronic inflammatory condition affecting the supporting structures of a tooth in the oral cavity. The relationship between dietary fiber and periodontitis is poorly understood. The objective of this systematic review is to investigate if an intake of dietary fiber modulates periodontal disease in animal models and any concomitant effects on systemic inflammation, microbiota and their metabolites.

Methods

Animal studies using periodontitis models with any form of fiber intervention were included. Studies with comorbidities that were mutually inclusive with periodontitis and animals with physiological conditions were excluded. Search strategy with MeSH and free-text search terms were finalized and performed on the 22nd of September 2021.CINAHL Complete, EMBASE, MEDLINE, SciVerse Scopus® and Web of Science Core Collection databases were used to identify studies. SYRCLE’s risk of bias tool and CAMARADES were used for quality assessment. Results were synthesized utilizing Covidence© web-based platform software to remove duplicates, and the remaining studies were manually filtered.

Results

A total of 7,141 articles were retrieved from all databases. Out of 24 full-text articles assessed for eligibility, four studies (n = 4) were included. Four studies involved the use of β-(1,3/1,6)-glucan (n = 3) and mannan oligosaccharide (n = 1) at differing dosages for different study durations. All studies utilized a ligature-induced model of periodontitis in rats, either Wistar (n = 3) or Sprague–Dawley (n = 1). A dose-dependent relationship between the increased fiber intake and decrease in alveolar bone loss and pro-inflammatory markers was observed.

Conclusion

The number of included studies is limited and narrow in scope. They highlight the importance of pre-clinical trials in this field with broader dietary fiber intervention groups before proceeding to clinical trials. The use of dietary fiber as an intervention shows promise in the reduction of inflammatory conditions like periodontitis. However, further research is required to delineate the relationship between diet and its effects on microbiota and their metabolites such as short chain fatty acids in animal models of periodontitis.

Non-starch polysaccharides in beer and brewing: A review of their occurrence and significance

It has become apparent that beer (both alcoholic and nonalcoholic) contains appreciable amounts of non-starch polysaccharides, a broad subgroup of dietary fiber. It is worth noting that the occurrence of non-starch polysaccharides in alcoholic beer does not imply this should be consumed as a source of nutrition. But the popularity of nonalcoholic beer is growing, and the lessons learnt from non-starch polysaccharides in brewing can be largely translated to nonalcoholic beer. For context, we briefly review the origins of dietary fiber, its importance within the human diet and the significance of water-soluble dietary fiber in beverages. We review the relationship between non-starch polysaccharides and brewing, giving focus to the techniques used to quantify non-starch polysaccharides in beer, how they affect the physicochemical properties of beer and their influence on the brewing process. The content of non-starch polysaccharides in both regular and low/nonalcoholic beer ranges between 0.5 - 4.0 g/L and are predominantly composed of arabinoxylans and β-glucans. The process of malting, wort production and filtration significantly affect the soluble non-starch polysaccharide content in the final beer. Beer viscosity and turbidity are strongly associated with the content of non-starch polysaccharides.

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.

A Purified Glucomannan Oligosaccharide from Amorphophallus konjac Improves Colonic Mucosal Barrier Function via Enhancing Butyrate Production and Histone Protein H3 and H4 Acetylation

A structurally defined konjac glucomannan oligosaccharide (KGMOS) with a relatively high molecular weight and narrow molecular weight distribution (molecular weight ranging from 3000 to 4000 Da, degree of polymerization (dp) 8-11) was prepared from native konjac glucomannan (KGM), and the beneficial effects and molecular mechanisms of KGMOS on colonic functions were investigated in C57BL/6 mice. The results are the first to reveal that KGMOS regulated intestinal microflora composition to facilitate the production of colonic butyrate. Elevated butyrate production further increased the acetylation of histone proteins H3 and H4 and thus enhanced the transcription of the major colonic mucin gene Muc2 and the secretion of mucin elements, which represents a new molecular mechanism of KGM oligosaccharide consumption. The findings indicate that KGM oligosaccharides with specific molecular sizes have highly desirable functional properties and potentially could improve gut health by promoting the barrier function of the colonic mucosa.

The TaCslA12 gene expressed in the wheat grain endosperm synthesizes wheat-like mannan when expressed in yeast and Arabidopsis

Mannan is a class of cell wall polysaccharides widespread in the plant kingdom. Mannan structure and properties vary according to species and organ. The cell walls of cereal grains have been extensively studied due to their role in cereal processing and to their beneficial effect on human health as dietary fiber. Recently, we showed that mannan in wheat (Triticum aestivum) grain endosperm has a linear structure of β-1,4-linked mannose residues. The aim of this work was to study the biosynthesis and function of wheat grain mannan. We showed that mannan is deposited in the endosperm early during grain development, and we identified candidate mannan biosynthetic genes expressed in the endosperm. The functional study in wheat was unsuccessful therefore our best candidate genes were expressed in heterologous systems. The endosperm-specificTaCslA12 gene expressed in Pichia pastoris and in an Arabidopsis thaliana mutant depleted in glucomannan led to the production of wheat-like linear mannan lacking glucose residues and with moderate acetylation. Therefore, this gene encodes a mannan synthase and is likely responsible for the synthesis of wheat endosperm mannan.

Prebiotic mannooligosaccharides: Synthesis, characterization and bioactive properties

Functional oligosaccharides are non-digestible food ingredients that confer numerous health benefits. Among these, mannooligosaccharides (MOS) are emerging prebiotics that have characteristic potential bio-active properties. Microbial mannanases can be used to break down mannan rich agro-residues to yield MOS. Various applications of MOS as health promoting functional food ingredient may open up newer opportunities in food and feed industry. Enzymatic hydrolysis is the widely preferred method over chemical hydrolysis for MOS production. Presently, commercial MOS is being derived from yeast cell wall mannan and is widely used as prebiotic in feed supplements for poultry and aquaculture. Apart from stimulating the growth of probiotic microflora, MOS impart anticancer and immunomodulatory effects by inducing different gene markers in colon cells. This review summarizes recent developments and future prospects of enzymatic synthesis of MOS from various mannans, their structural characteristics and their potential health benefits.

Thermostable α-Glucan Phosphorylase-Catalyzed Enzymatic Copolymerization to Produce Partially 2-Deoxygenated Amyloses

α-Glucan phosphorylase catalyzes the enzymatic polymerization of α-d-glucose 1-phosphate (Glc-1-P) monomers from a maltooligosaccharide primer to produce α(1→4)-glucan—i.e., amylose. In this study, by exploiting the weak specificity for the substrate recognition of a thermostable α-glucan phosphorylase (from Aquifex aeolicus VF5), we investigated the enzymatic copolymerization of 2-deoxy-α-d-glucose 1-phosphate (dGlc-1-P), which was produced in situ from d-glucal, with Glc-1-P to obtain non-natural heteropolysaccharides composed of α(1→4)-linked dGlc/Glc units—i.e., partially 2-deoxygenated amylose. The reactions were carried out at different monomer feed ratios using a maltotriose primer at 40 °C for 24 h. The products were precipitated from the reaction medium, isolated by centrifugation, and subjected to 1H NMR spectroscopic and powder X-ray diffraction measurements to evaluate their chemical and crystalline structures, respectively. Owing to its amorphous nature, the partially 2-deoxygenated amylose with adapted unit ratios formed a film when subjected to a casting method.

Modulations of growth performance, gut microbiota, and inflammatory cytokines by trehalose on Salmonella Typhimurium-challenged broilers

Salmonellosis in broilers is not merely a significant disease with high economic costs in the poultry industry but also the foodborne disease with the impact on public health by cross-contamination. This study was to investigate the prebiotic ability of trehalose supplementing in diets (0, 1, 3, and 5%, w/w) against Salmonella by using S. Typhimurium (ST)-inoculated broilers. The improvements (P < 0.05) of feed conversion ratio (FCR) were observed with 5% trehalose supplementation in ST-inoculated broilers' diets. An addition of 3 or 5% trehalose in diets increased (P < 0.05) the abundance of lactobacilli in the duodenum and jejunum but decreased (P < 0.05) the growth of ST in the cecum. The adverse effects on serum levels of aspartate aminotransferase, triglyceride, and albumin and globulin ratio in ST-inoculated broilers were noticed and counteracted by supplementing 3 or 5% trehalose in diets (P < 0.05). Besides, the inclusion of trehalose in diets alleviated the intestinal damages and maintained the integrity of cecal epithelial cells after ST challenge under an haematoxylin and eosin-staining observation. Supplementing trehalose further showed the inhibitions of toll-like receptor 4-mediated nuclear factor-kappa-B pathway, including the downregulation (P < 0.05) of proinflammatory cytokine genes, such as interleukin 1 beta and lipopolysaccharide-induced tumor necrosis factor-alpha factor and the upregulation (P < 0.05) of interleukin 10 and interferon-alpha in ST-inoculated broilers. Overall, supplementing trehalose alleviated the adverse effects from ST challenge on FCR, serum biochemistry, the damage, and inflammation in the liver and cecum. Those improvements on ST challenged broilers also contributed to the overgrowth of lactobacilli, the decrement of ST, and anti-inflammatory effects in affected broilers. Trehalose, therefore, could be a promising prebiotic against salmonellosis to benefit broiler production and promote food safety in the poultry industry.

FTIR-based comparative analysis of glucomannan contents in some tuberous orchids, and effects of pre-processing on glucomannan measurement

BACKGROUND

Glucomannan (GM) is a polysaccharide of the mannan family of compounds found in some plant species. The dried and powdered tubers of some orchid species, collectively known as 'salep powder,' are a commercially important crop for human consumption and are one of the primary sources of GM. GM content is the primary indicator for the yield and quality of salep powder. We hypothesized that it would be more practical and accurate to measure GM content within tuber powder directly, prior to any purification or pre-processing. The GM content of tubers of 14 different orchid species was evaluated and compared using Fourier transform infrared (FTIR) spectroscopy and an enzymatic colorimetric method.

RESULTS

Among the analyzed modes, the sum of the peak areas at 873 and 812 cm^-1 , which represent the CH bending attributed to the β-pyranose form of d-glucose and d-mannose, respectively, gave the only confirmation using colorimetric methods. It was found that the tubers of Himantoglossum caprinum and Serapias vomeracea had the highest GM concentrations among the analyzed species. After conducting different pre-processing steps on Serapias vomeracea tubers, it was found that treating the tubers with milk, or high temperature resulted in an apparent increase in GM concentrations.

CONCLUSION

Himantoglossum caprinum and Serapias vomeracea give the highest yields of GM and should be used for commercial horticulture. GM estimation should be made prior to any pre-processing. FTIR spectroscopy is effective and reliable for directly comparing GM content of different orchid species, without the need for any purification or pre-processing. © 2019 Society of Chemical Industry.

Protective Effects of Konjac and Inulin Extracts on Type 1 and Type 2 Diabetes

OBJECTIVE

The present study was designed to determine whether konjac and inulin extracts or their combination, konjac-inulin (KI) composition, as diet supplementary, can exert beneficial effects against type 1 diabetes and type 2 diabetes using animal models.

METHODS

A total of 60 diabetic (type 1) rats induced by streptozotocin (STZ) were randomly assigned to five groups: vehicle control (STZ group), KI combination at low dose group (KI-L group), KI combination at medium dose group (KI-M group), KI combination at high dose group (KI-H group), konjac extract group (konjac group), and inulin extract group (inulin group). A sham group (without STZ) was also included. Levels of blood glucose were monitored at each week. After continuous treatment of each diet for 24 days, a glucose tolerance test was performed. After 28 days of treatment, plasma biochemical indicators including glycated serum proteins, total cholesterol, and triglycerides were measured and immunohistochemistry staining of the rat pancreas was performed, to study the insulin expressions. Type 2 diabetes was developed in db/db mice. A total of 28 db/db mice were divided into 4 groups: vehicle control (db/db group), KI composition group (KI group), konjac extract group (konjac group), and inulin extract group (inulin group). A wild-type control group (wild-type group) for db/db mice was also included. Levels of blood glucose, body weight, and blood triglycerides were monitored at each week.

RESULTS

Daily use of the KI composition significantly decreased levels of blood glucose and blood triglycerides, as well as improved the insulin production in islets or reduced development of obesity in STZ-induced diabetic rats or in db/db mice. Such effects from KI composition were better than single ingredient of konjac or inulin extract.

CONCLUSION

The results of this study suggest that daily use of KI composition has a protective role on type 1 and 2 diabetes and provided experimental basis for further development of KI composition as a food supplement for diabetic or diabetic high-risk population.

Prebiotic, Immunomodulating, and Antifatigue Effects of Konjac Oligosaccharide

Irregular and long time work schedules not only makes people feel fatigue, but also brings great risks of diseases, due to gastrointestinal disorder and immune dysfunction. Therefore, it has positive significance to help challenged people stay energetic and healthy with food supplement. Konjac oligosaccharide has shown various physiological benefits and been recommended in the fortification of functional foods. However, there have been few reports on its application aimed to simultaneously relieve physical fatigue and keep body healthy. In this paper, the potential prebiotic, immunoregulatory, and antifatigue activities of konjac oligosaccharide were evaluated in vitro and in vivo. The results showed that konjac oligosaccharide could promote probiotics growth and short chain fatty acids production in mice cecum. At the concentration of 50 to 200 μg/mL, konjac oligosaccharide could activate murine macrophage RAW 264.7 to secret NO and cytokines of IL-10 and IL-6. Moreover, this oligosaccharide could alleviate physical fatigue by prolonging exhaustive time, improving the level of superoxide dismutases and glutathione peroxidase, increasing the content of blood glucose, and decreasing the content of blood urea nitrogen. The results suggested that konjac oligosaccharide had prebiotic, immunoregulatory, and antifatigue effects, providing its application potential in functional food aimed at people with irregular and long time work.

Metagenomic Mining and Functional Characterization of a Novel KG51 Bifunctional Cellulase/Hemicellulase from Black Goat Rumen

A novel KG51 gene was isolated from a metagenomic library of Korean black goat rumen and its recombinant protein was characterized as a bifunctional enzyme (cellulase/hemicellulase). In silico sequence and domain analyses revealed that the KG51 gene encodes a novel carbohydrate-active enzyme that possesses a salad-bowl-like shaped glycosyl hydrolase family 5 (GH5) catalytic domain but, at best, 41% sequence identity with other homologous GH5 proteins. Enzymatic profiles (optimum pH values and temperatures, as well as pH and thermal stabilities) of the recombinant KG51 bifunctional enzyme were also determined. On the basis of the substrate specificity data, the KG51 enzyme exhibited relatively strong cellulase (endo-β-1,4-glucanase [EC 3.2.1.4]) and hemicellulase (mannan endo-β-1,4-mannosidase [EC 3.2.1.78] and endo-β-1,4-xylanase [EC 3.2.1.8]) activities, but no exo-β-1,4-glucanase (EC 3.2.1.74), exo-β-1,4-glucan cellobiohydrolase (EC 3.2.1.91), and exo-1,4-β-xylosidase (EC 3.2.1.37) activities. Finally, the potential industrial applicability of the KG51 enzyme was tested in the preparation of prebiotic konjac glucomannan hydrolysates.

Dietary yeast-derived mannan oligosaccharides have immune-modulatory properties but do not improve high fat diet-induced obesity and glucose intolerance

The indigestible mannan oligosaccharides (MOS) derived from the outer cell wall of yeast Saccharomyces cerevisiae have shown potential to reduce inflammation. Since inflammation is one of the underlying mechanisms involved in the development of obesity-associated metabolic dysfunctions, we aimed to determine the effect of dietary supplementation with MOS on inflammation and metabolic homeostasis in lean and diet-induced obese mice. Male C57BL/6 mice were fed either a low fat diet (LFD) or a high fat diet (HFD) with, respectively, 10% or 45% energy derived from lard fat, with or without 1% MOS for 17 weeks. Body weight and composition were measured throughout the study. After 12 weeks of intervention, whole-body glucose tolerance was assessed and in week 17 immune cell composition was determined in mesenteric white adipose tissue (mWAT) and liver by flow cytometry and RT-qPCR. In LFD-fed mice, MOS supplementation induced a significant increase in the abundance of macrophages and eosinophils in mWAT. A similar trend was observed in hepatic macrophages. Although HFD feeding induced a classical shift from the anti-inflammatory M2-like macrophages towards the pro-inflammatory M1-like macrophages in both mWAT and liver from control mice, MOS supplementation had no effect on this obesity-driven immune response. Finally, MOS supplementation did not improve whole-body glucose homeostasis in both lean and obese mice.Altogether, our data showed that MOS had extra-intestinal immune modulatory properties in mWAT and liver. However these effects were not substantial enough to significantly ameliorate HFD-induced glucose intolerance or inflammation.