Low Molecular Weight Β-glucan Research Articles

Chemical structure and biological activity of the (1 → 3)-linked β-D-glucan isolated from marine diatom Conticribra weissflogii

Several polysaccharides are considered to be “biological response modifiers” (BRM) — these refer to biomolecules that augment immune responses and can be derived from a variety of sources. Microalgae produce a diverse range of polysaccharides and could be an excellent source of BRM. Here, we describe the chemical structure and biological activity of water-soluble polysaccharide isolated from the marine diatom Conticribra weissflogii. Using chemical and NMR spectroscopic methods, the polysaccharide was identified as a (1 → 3)-linked β-D-glucan with a low proportion of C-6 substitution by single β-glucose units. The biological activity of this low molecular weight β-glucan (11.7 kDa) was investigated with respect to glioblastoma cell lines (U87 MG and U251) and macrophages (RAW 264.7). We observed that this β-D-glucan did not exhibit cytotoxic activity against glioblastoma cells, but did enhance the phagocytic activity of macrophages, suggesting that it possesses immunomodulatory properties.

Production of prebiotic aubasidan-like β-glucan from Aureobasidium thailandense NRRL 58543 and its potential as a functional food additive in gummy jelly

To enhance the yield of Aureobasidium thailandense NRRL 58543 β-glucan, effects of medium ingredients and their optimal concentrations were investigated. The highest yield of β-glucan (37.73 g/L) was obtained in the medium containing sucrose, NaNO3 and sunflower oil at concentrations of 60 g/L, 0.6 g/L, and 81.7 mL/L, respectively. The low molecular weight (LMW) β-glucan (78 kDa) was assessed its prebiotic property in comparison to the native one (>410 kDa). The growth of the probiotics, Lactobacillus casei and L. brevis, was significantly enhanced, although a higher growth was observed in the medium containing the native β-glucan. In addition, the native β-glucan was resistant with simulated salivary and gastrointestinal juice. The addition of β-glucan (2.5 and 5 g/L) in gummy jellies resulted in the increase of the color intensity, hardness, gumminess, and chewiness, while the springiness and cohesiveness decreased compared with the control. The highest score of overall acceptability (7.83 ± 0.75) according to 9-point hedonic scale was obtained from the gummy jellies with 0.5% β-glucan that could be stored at room temperature for seven days without microbial growth. Our findings suggest that A. thailandense β-glucan exhibits an immense potential in the food industry as a functional ingredient and texturing agent.

Synergic degradation of yeast β-glucan with a potential of immunostimulant and growth promotor for tiger shrimp

The synergic effect using γ-irradiation in combination with hydrogen peroxide was applied for preparation of water-soluble and low molecular weight (Mw) β-glucan from yeast water-insoluble β-glucans. The structural characterization by gel permeation chromatography (GPC), Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD) suggested that the γ-irradiation did not cause any change in basic structure of β-glucans, except for the reduction in degree of polymerization. The suitable degradation conditions were determined at 10% β-glucans in pH~9% and 1% hydrogen peroxide. The water-soluble oligoβ-glucan with Mw~15 kDa showed a significantly effect on the increase of body weight and survival rate of Penaeus monodon shrimps challenged with Vibrio parahaemolyticus and White spot syndrome virus (WSSV). The oral administration of 15 kDa-oligoβ-glucan with a daily dose of 1000 ppm strongly stimulated immune factors in tested shrimps such as phagocytosis activity (PA), phenoloxidase (PO) and superoxide dismutase (SOD). Furthermore, dietary of 1000 ppm 15 kDa-oligoβ-glucan also significantly up-regulated the gene expressions of lipopolysaccharide and β-1,3-glucan-binding protein (LGLP) and prophenoloxidase (proPO). The relative percent of survivals (RPS) of shrimps fed with 1000 ppm 15 kDa-oligoβ-glucan were 56.2% and 38.1% post the challenge with V. parahaemolyticus and WSSV, respectively. These results demonstrated that the water-soluble oligoβ-glucan with Mw~15 kDa prepared by synergic degradation method showed a very promising potential for application as a natural growth promotor and immunostimulant in shrimp culture.

Effect of oat β-glucan of different molecular weights on fecal bile acids, urine metabolites and pressure in the digestive tract – A human cross over trial

While the development of oat products often requires altered molecular weight (MW) of β-glucan, the resulting health implications are currently unclear. This 3-leg crossover trial (n = 14) investigated the effects of the consumption of oat bran with High, Medium and Low MW β-glucan (average > 1000, 524 and 82 kDa respectively) with 3 consequent meals on oat-derived phenolic compounds in urine (UHPLC-MS/MS), bile acids in feces (UHPLC-QTOF), gastrointestinal conditions (ingestible capsule), and perceived gut well-being. Urine excretion of ferulic acid was higher (p < 0.001, p < 0.001), and the fecal excretion of deoxycholic (p < 0.03, p < 0.02) and chenodeoxycholic (p < 0.06, p < 0.02) acids lower after consumption of Low MW β-glucan compared with both Medium and High MW β-glucan. Duodenal pressure was higher after consumption of High MW β-glucan compared to Medium (p < 0.041) and Low (p < 0.022) MW β-glucan. The MW of β-glucan did not affect gut well-being, but the perceptions between females and males differed.

Purified β-glucans of Different Molecular Weights Enhance Growth Performance of LPS-challenged Piglets via Improved Gut Barrier Function and Microbiota.

Simple SummaryBeta-glucan is currently under consideration as an alternative to in-feed antibiotics for the sustainable pig production industry in China. Modulating intestinal function by β-glucan treatment in young pigs is one potential way of decreasing disease susceptibility and presumably increasing growth performance. In the present study, as a newly developed commercial product, β-glucans have proved to modulate gut function, and have improved growth performance in lipopolysaccharide (LPS)-challenged piglets. The present study aimed to determine the mechanisms involved inβ-glucan of low and high molecular weight mediated growth alterations in weaned piglets. The results confirmed that β-glucans isolated from Agrobacterium sp. ZX09 could improve growth performance in weaned piglets and they showed intestinal modulatory properties via different mechanisms in regulating the mucosal barrier function and microbial populations between two different molecular weight β-glucans.This study investigated β-glucan derived from Agrobacterium sp. ZX09 with high (2000 kDa) and low (300 kDa) molecular weight (MW) to compare their effects on growth performance and gut function in LPS-induced weaned piglets. Changes in jejunal morphology, mucosal barrier function, microbial populations, and fermentation in the piglets were determined. Data showed that β-glucan prevented body weight loss in LPS challenged piglets. Supplementation with both β-glucan fractions improved jejunal morphology. Compared to low MW, β-glucan of high MW generally up-regulated transcripts of ZO-1, MUC1, and MUC2 in jejunal mucosa to a lesser extent. Mucosal D-lactate, diamine oxidase, and anti-oxidation index were effectively resumed in β-glucan treatment. Both β-glucan diets provoked the emergence of a balanced microbiota and a richer concentration of volatile fatty acids in the colon. The richest community of bifidobacterium and concentration of butyrate emerged after feeding β-glucan with high MW. Results suggested that the effect of Agrobacterium sp. ZX09 β-glucans on the gut-modulatory function is largely linked to their MW. Low MW β-glucan mainly improved the mucosal barrier function in the jejunum, while high MW β-glucan had profound effects on the microbial community and fermentation in the hindgut of piglets.

Effects of dietary supplementation with different levels and molecular weights of fungal β-glucan on performances, health and meat quality in broilers

ObjectiveTo investigate the effects of dietary supplementation with different levels and molecular weights of fungal β-glucan on productive performances, health, carcass traits and meat quality in broilers.MethodsTwo hundred and ten of one-day-old chicks with equal sex were assigned to seven experimental groups in 2×4 factorial arrangement. These groups were supplemented with (0, 10, 30, and 60 ppm) of molecular weight 1–3, 1–6 β-glucan (low or high). High molecular weight β-glucan (H: 943 kDa) was obtained from Ophiocordyceps dipterigena BCC 2073, whereas H with γ-Irradiation treatment was performed to achieve low molecular weight β-glucan (L: 8 kDa).ResultsThere was no statistical significance in productive performances, apparent digestibility and interaction between fixed factors along 42 days of experiment (p>0.05). A higher caecal amylase activity was present in the group that received L, while there was a dramatic decrease in H and the control groups, respectively (p<0.05). The increase of supplemental dose increased caecal amylase activity (p<0.05). Immunomodulatory effects from L was revealed by the marked increase of phagocytic activity, relative weight of thymus and bursa of fabricius (p<0.05). Similarly, the additive dose at 30 ppm provided the same results, whereas the only significant difference with supplementation at 60 ppm was an increase in phagocytic activity (p<0.05). Interestingly, villi height of broilers fed L was higher than other groups (p<0.05). The treatments did not influence haematology, blood chemistry, antibody production level against vaccination, carcass traits and meat quality (p>0.05).ConclusionThe supplementation of L at 30 ppm was suggested to achieve benefits of immune modulation without adverse effects on other parameters.

Radiation Degradation of β-Glucan Extracted from Brewer’s Yeast for Enhancing Growth Promotion and Immunostimulant Activities on Broilers

Water-soluble low molecular weight β-glucan (WSLMG) was successfully prepared via γ-irradiation of insoluble β-glucan extracted from brewer’s yeast cell walls. The WSLMG content in an irradiated sample increased as the irradiation dose increased. The WSLMGs with a molecular weight (Mw) of 49, 25, and 11 kDa, obtained at correlative doses of 100, 200, and 300 kGy, respectively, were tested using growth promotion and immune stimulant effects in broilers. Supplementation with 500 ppm WSLMGs not only increased the survival rate (33.3%) and average body weight (40%) but also reduced the feed conversion rate (35.4%) in tested broilers. In addition, WSLMGs enhanced both nonspecific and specific immune components in the blood of supplemented broilers. The WSLMG with Mw ~25 kDa showed the highest effect on the growth performance and immunomodulatory capability in the immune systems of the tested broilers. In conclusion, this product demonstrates substantial promise as an immunostimulant and growth-promoting additive for poultry.

Aggregation and gelation of oat β-glucan in aqueous solution probed by NMR relaxometry

Nuclear magnetic resonance was used to study water proton transverse relaxation in oat β-glucan aqueous solutions during storage. The molecular weights of the samples ranged from 112 to 494kDa. The polysaccharide structure was identified by IR, GC–MS, NMR spectroscopy, and high performance anion exchange chromatography. In 1% solutions, 494kDa β-glucan formed stable solution phase. Aggregates were generated in the solution of low molecular weight polysaccharide. The transverse relaxation time of water associated with the aggregate microphase was about 15ms. The majority of the solution was bulk water, with a relaxation time of 800–1600ms. The proton exchange rate was about 103s−1, calculated from two-site exchange model. The proportion of β-glucan in the aggregate microphase increased from 0 to over 80% of the total β-glucan during storage of 112kDa samples. In the 4% solutions, the evolution of water proton relaxation associated with the gel network can be explained by the fractal structure theory. The relaxation behavior suggested the growth and syneresis of the gel network during the gelation of the low molecular weight β-glucan solutions.

Retardation of oxidation by residual phytate in purified cereal β-glucans

Polysaccharides stabilize emulsions against phase separation and oxidation. This study focused on the role of molecule weight, origin, and residual phytate in the antioxidant activity of β-glucans. The antioxidant activity was investigated by measuring the retardation of lipid oxidation, iron binding capacity and hydroxyl radical scavenging ability of purified oat and barley β-glucans. Low molecular weight β-glucan stabilized the emulsions against phase separation and oxidation better than high molecular weight β-glucan. The oxidative stability of the emulsions, however, correlated to the content of residual phytate in the β-glucan samples. Oat β-glucans which contained higher amount of residual phytate showed higher antioxidant activity than barley β-glucans. When phytate was removed from the β-glucan samples by ion exchange, the antioxidant activity of all β-glucans was reduced to the same level. The study therefore showed that residual phytate played a major role in the antioxidant activity of cereal β-glucans. The study highlights that even at low concentration, phytate content should be considered when evaluating the antioxidant effect of plant polysaccharide extracts.

Hepato- and gastro- protective activity of purified oat 1–3, 1–4-β-d-glucans of different molecular weight

Protective and antioxidant properties of highly purified oat β-glucans of high and low molecular weight in liver and stomach were evaluated. The novelty in approach was to determine whether dietary β-glucans affect the parameters of oxidative stress directly in the stomach and indirectly in the liver, especially in inflammation states. Physicochemical properties e.g. viscoelastic was found as strictly dependent from molecular weight of oat β-glucans hence its metabolic activity could also show dependence. Three groups of rats were fed control diet and diet supplemented with low and high molecular weights oat β-glucans. Animals were divided into controls and individuals with experimentally induced intestinal inflammation. Most active in increasing of total antioxidant status was low molecular weight β-glucan. High molecular weight β-glucan supplementation inhibits lipid oxidation the most in LPS treated animals. The results obtained from experiment encourage for dietary intervention with oat β-glucans for stomach and liver protection during existing enteritis.

High-Molecular-Weight β-Glucan Decreases Serum Cholesterol Differentially Based on the CYP7A1 rs3808607 Polymorphism in Mildly Hypercholesterolemic Adults

Background: β-Glucan, a soluble fiber with viscous property, has a documented cholesterol-lowering effect. The molecular weight (MW) of β-glucan, which contributes to viscosity, and an individual's genotype might influence the cholesterol-lowering efficacy of β-glucan.Objectives: This study was designed to determine whether the cholesterol-lowering efficacy of barley β-glucan varied as a function of MW and the daily dose consumed. Our second aim was to determine whether any gene-diet interactions are associated with the cholesterol-lowering efficacy of β-glucan.Methods: In a randomized controlled crossover trial, 30 mildly hypercholesterolemic adults [12 men and 18 women, aged 27–78 y; body mass index (in kg/m2): 20–40; total cholesterol (TC): 5.0–8.0 mmol/L; LDL cholesterol: 2.7–5.0 mmol/L] were randomly assigned to receive a breakfast that contained either barley β-glucan at 3 g high MW (HMW)/d, 5 g low MW (LMW)/d, or 3 g LMW/d or a control diet, each for 5 wk. The washout period between the phases was 4 wk. Fasting blood samples were collected at the start and end of each phase for blood lipid analysis and genotyping.Results: Consumption of 3 g HMW β-glucan/d lowered TC by −0.12 mmol/L (95% CI: −0.24, −0.006 mmol/L) compared with the control diet (P = 0.0046), but the LMW β-glucan, at either 3 g/d or 5 g/d, did not change serum cholesterol concentrations. This effect of HMW β-glucan was associated with gene-diet interaction, whereby individuals with the single nucleotide polymorphism (SNP) rs3808607-G allele (GG or GT) of the cytochrome P450 family 7 subfamily A member 1 gene (CYP7A1) had greater responses to 3 g HMW β-glucan/d in lowering TC than TT carriers (P = 0.0006).Conclusions: The HMW β-glucan rather than LMW β-glucan reduced circulating TC effectively in mildly hypercholesterolemic adults. The cholesterol-lowering effect of β-glucan may also be determined by the genetic characteristics of an individual. These data show that individuals carrying the CYP7A1 SNP rs3808607-G allele are more responsive to the cholesterol-lowering effect of β-glucan with HMW than TT carriers. This trial was registered at clinicaltrials.gov as NCT01408719.

High Molecular Weight Barley β-Glucan Alters Gut Microbiota Toward Reduced Cardiovascular Disease Risk.

The physiological cholesterol-lowering benefits of β-glucan have been well documented, however, whether modulation of gut microbiota by β-glucan is associated with these physiological effects remains unknown. The objectives of this study were therefore to determine the impact of β-glucan on the composition of gut microbiota in mildly hypercholesterolemic individuals and to identify if the altered microbiota are associated with bioactivity of β-glucan in improving risk factors of cardiovascular disease (CVD). Using a randomized, controlled crossover study design, individuals received for 5-week either a treatment breakfast containing 3 g high molecular weight (HMW), 3 g low molecular weight (LMW), 5 g LMW barley β-glucan, or wheat and rice. The American Heart Association (AHA) diet served as the background diet for all treatment groups. Phases were separated by 4-week washout periods. Fecal samples were collected at the end of each intervention phase and subjected to Illumina sequencing of 16S rRNA genes. Results revealed that at the phylum level, supplementation of 3 g/d HMW β-glucan increased Bacteroidetes and decreased Firmicutes abundances compared to control (P < 0.001). At the genus level, consumption of 3 g/d HMW β-glucan increased Bacteroides (P < 0.003), tended to increase Prevotella (P < 0.1) but decreased Dorea (P < 0.1), whereas diets containing 5 g LMW β-glucan and 3 g LMW β-glucan failed to alter the gut microbiota composition. Bacteroides, Prevotella, and Dorea composition correlated (P < 0.05) with shifts of CVD risk factors, including body mass index, waist circumference, blood pressure, as well as triglyceride levels. Our data suggest that consumption of HMW β-glucan favorably alters the composition of gut microbiota and this altered microbiota profile associates with a reduction of CVD risk markers. Together, our study suggests that β-glucan induced shifts in gut microbiota in a MW-dependent manner and that might be one of the underlying mechanisms responsible for the physiological benefits of β-glucan.

Effect of γ -irradiation on antioxidant and antiproliferative properties of oat β -glucan

Abstract The present study was undertaken to examine effect of γ-rays on the antioxidant and antiproliferative potential of β-glucan isolated from oats. Irradiation doses of 0, 2, 6 and 10 kGy were given to extracted β-glucan. The samples were characterized by Fourier transform infrared spectroscopy, Gel permeation chromatography and quantitative estimation by (1-3) (1-4) β- d -Glucan assay kit (Megazyme). The average molecular weight of non-irradiated β-glucan was 199 kDa that decreased to 70 kDa at 10 kGy. Both FT-IR spectrum and chemical analysis revealed that the extracted β-glucan was pure having minor impurities. Antioxidant activity was evaluated by DPPH, lipid peroxidation, reducing power, metal chelating ability and oxidative DNA damage assays. Results revealed increased antioxidant activity of β-glucan with the increase in irradiation dose. Irradiated β-glucan also exhibited dose dependent cancer cell growth inhibition with irradiation doses. The study revealed that the low molecular weight β-glucan with increased antioxidant and antiproliferative activities can be produced by irradiation treatment.

Molecular weight of barley β-glucan does not influence satiety or energy intake in healthy male subjects

Previous studies have shown the ability of high molecular weight barley β-glucan with increased viscosity to attenuate glycemic response, gastric emptying and in vitro starch digestion. The main objective of this study was to investigate the effect of molecular weight of barley β-glucan in a semisolid meal on energy intake and subjective feelings of hunger, fullness, desire to eat and prospective food consumption in healthy male subjects. In a randomised, controlled, crossover trial, 23 healthy male subjects (BMI 24.2 ± 2.5 kg/m2) tested soups equivalent to 25 g available carbohydrate containing high or low molecular weight barley β-glucan (~3 g) as preload after a standard breakfast. The viscosity of soup with high molecular weight β-glucan was 350 Pa·s whereas the soup with low molecular weight β-glucan had a viscosity of 100 Pa·s. Appetite ratings before and for two hours after consumption of β-glucan soups and subsequent ad libitum energy intake at lunch were recorded and compared with a control soup with no β-glucan. There was no significant difference in food intake at the ad libitum meal or for the remainder of the day following consumption of the three test foods (p > 0.05). Similarly, there were no significant differences (p > 0.05) in hunger, fullness, desire to eat or prospective food consumption following β-glucan soups. The current study provides evidence that the molecular weight of barley β-glucan may not impact on perceived feelings of hunger or food intake at the current dose and viscosity.

Physicochemical properties and regulatory effects on db/db diabetic mice of β-glucans extracted from oat, wheat and barley

Physicochemical properties of different β-glucan purified from oat, barley and wheat, were investigated by measuring the composition, molecular weight, intrinsic viscosity ([η]), and rheological properties. The main objective was to investigate the relationship between effects of regulation of cholesterol metabolism and antioxidant property on db/db diabetic mice of β-glucans and their molecular weights and viscosities. Metformin was used as the positive control. The levels of blood glucose, serum lipid, liver lipid, superoxide dismutase (SOD) and malondialdehyde (MDA) in liver were determined. Results showed that average values of molecular weight (MW) of β-glucan from oat, wheat and barley were 172 kDa, 635 kDa and 743 kDa; the viscosities of β-glucans were positively correlated with their corresponded molecular weights, and wheat and barley β-glucan showed significant shear thinning ability compared to oat β-glucan; Barley β-glucans had higher G′ compared to wheat and oat, and the latter had higher G″. Blood glucose differences were not significant due to high variability, however serum TC, TG, liver TC, TG and LDL-C were lower in β-glucan fed groups compared to control. Moreover, the HDL-C was higher in β-glucan fed groups compared to control group. The addition of β-glucan fed to the db/db diabetic mice significantly (P < 0.05) increased their liver SOD activities and reduced their MDA levels (P > 0.05). A correlation between the measured biological parameters and the molecular weight or viscosity of β-glucan was observed. Lack of β-glucanase degeneration was the main cause of the low MW β-glucan and its diminished physiological effect.

Attenuation of glycemic responses by oat β-glucan solutions and viscoelastic gels is dependent on molecular weight distribution

Oat β-glucan attenuates postprandial glycemic responses when solubilized to form viscous solutions. High molecular weight (MW) β-glucan is associated with high solution viscosity, which is in turn associated with lower glycemic responses. However, low MW β-glucan is also able to form viscoelastic gels. The effect of low (145,000 g mol(-1)) and high (580,000 g mol(-1)) MW β-glucan presented as liquid drinks and gels on glycemic responses was determined. Healthy subjects (n = 15) consumed 50 g glucose drinks with no β-glucan; 4 g low MW; or 4 g high MW β-glucan; and gels containing 4 g low MW; 2 g low plus 2 g high MW; or 3 g high plus 1 g low MW β-glucan. Overall, β-glucan solutions elicited lower glycemic responses than gels. For gels, peak blood glucose rise (PBGR) decreased with increasing dose of high MW β-glucan (r(2) = 0.976, P > 0.05), and PBGR for the gel with 3 g high-MW was lower than for the control (P < 0.05). However, β-glucan gels retained glucose better than solutions under in vitro analysis. Observed effects were found to be related to the rheological properties of the foods. β-Glucan solutions and not gels effectively attenuated in vivo glycemic responses.

Low molecular weight β-glucan stimulates doxorubicin-induced suppression of immune functions in mice

The aim of this study was to evaluate the protective effect of low molecular weight β-glucan (LMG) against doxorubicin (DOX)-induced immune suppression of tumor-bearing mice. The tumor size and spleen cell functions such as spleen cell proliferation, cytokine production (interferon-γ and interleukin-2), and the population of CD4+ and CD8+ T cells were estimated. In the tumorbearing mice, the tumor size was significantly (p<0.05) decreased by DOX treatment. However, there was no significant difference between mice treated with high molecular weight β-glucan (HMG) and mice treated with LMG. Spleen cell proliferation and cytokine production were significantly (p<0.05) decreased in only DOX treated group, but increased in all β-glucan treated groups with DOX. Moreover, the populations of CD4+ and CD8+ T cells were also increased in the LMG-treated group. It appears that LMG effectively reduces the DOX-induced immune toxicity through activation of immune cells such as splenocytes.

Anti-allergic effect of low molecular weight β-glucan prepared by λ-irradiation

This study evaluated the anti-allergic effect of low molecular weight β-glucan (25 kDa) degraded by λ-irradiation. Allergy was induced in mouse models administrated with λ-irradiated low molecular weight and non-irradiated high molecular weight β-glucan, respectively, for 7 days. However, only the mice treated with low molecular weight β-glucan had a significantly decreased the total serum IgE and ovalbumin specific-IgE levels, and significantly increased Th 1 cytokine expression compared to only allergy induced mice. The allergic responses could be reduced by low molecular weight β-glucan treated λ-irradiation through the increased expression of Th 1 response and decreased expression of total IgE and antigen specific IgE.

Interleukin-8 stimulating activity of low molecular weight β-glucan depolymerized by γ-irradiation

Since many studies reveal that the biological properties of various biopolymers depend on their molecular weight. Therefore, it was considered of importance to investigate how molecular weight affected on the interleukin-8 (IL-8) stimulating activity of the β-glucan from Ophiocordyceps dipterigena BCC2073. γ-Irradiation of the glucan with various doses (0–100kGy) was chosen as a clean method to produce different low molecular weight samples. The result showed that average molecular weight (MW) of irradiated samples significantly decreased as the irradiation dose increased whereas the functional groups of before and after irradiated glucans detected by FTIR and 13C-NMR were identical. However, difference in intensity of an absorption peak at 270nm was found in the UV/vis spectra. The biological properties such as cytotoxicity, proliferation and IL-8 secretion of normal human dermal fibroblast contacted with various MW glucans were also tested. It was found that the glucan with MW of approximately 5kDa exhibited the highest ability to induce IL-8 production. Apart from the MW effect, chain conformation seems to be involved. Thus, differences in solution conformation of various MW glucans via Congo red analysis were evaluated.

In Vitro Bile-Acid Binding and Fermentation of High, Medium, and Low Molecular Weight β-Glucan

The impact of beta-glucan molecular weight (MW) on in vitro bile-acid binding and in vitro fermentation with human fecal flora was evaluated. beta-Glucan extracted from oat line 'N979-5-4' was treated with lichenase (1,3-1,4-beta-D-glucanase) to yield high (6.87x10(5) g/mol), medium (3.71x10(5) g/mol), and low (1.56x10(5) g/mol) MW fractions. The low MW beta-glucan bound more bile acid than did the high MW beta-glucan (p<0.05). If the positive control, cholestyramine, was considered to bind bile acid at 100%, the relative bile-acid binding of the original oat flour and the extracted beta-glucan with high, medium, and low MW was 15, 27, 24, and 21%, respectively. Significant effects of high, medium, and low MW beta-glucans on total SCFA were observed compared to the blank without substrate (p<0.05). There were no differences in pH changes and total gas production among high, medium, and low MW beta-glucans, and lactulose. The low MW beta-glucan produced greater amounts of SCFA than the high MW after 24 h of fermentation. Among the major SCFA, more propionate was produced from all MW fractions of extracted beta-glucans than from lactulose. In vitro fermentation of extracted beta-glucan fractions with different MW lowered pH and produced SCFA, providing potential biological function.