Hydrolysis of β-glucan

Preparation of whey based savory beverage with enhanced bio-accessible zinc

Zinc is an essential micronutrient for numerous catalytic, structural and regulatory functions in human body. However, its direct fortification in the food matrix poses the challenges of decreased bio-accessibility by forming insoluble sediments. Complexing zinc with polysaccharides has been reported as a possible intervention to address this issue by keeping the zinc in soluble form. Present investigation was undertaken to transform paneer whey containing complexed zinc into a sensorially acceptable beverage by varying its pH from 3.5 to 5.5, common salt concentration from 0.5 to 1.5% and spices concentration at 0.2 and 0.4%. Changes in complexed zinc concentration, apparent viscosity, instrumental color parameters and sensory attributes were determined. Complexed zinc concentration increased (p < 0.05) with increasing pH, decreasing salt and increasing spices concentration. Whey beverage having 4.5 pH, 1.0% salt and 0.4% spices concentration was most preferred by the sensory panelists. In-vitro digestion of optimized whey beverage revealed that bio-accessibility of zinc was significantly higher (p < 0.05) in complex form than free from.

Estimation of Iron Availability in Modified Cereal β-Glucan Extracts by an in vitro Digestion Model

For cereal-based foods rich in dietary fibers, iron bioavailability is known to be poor. For native cereal β-glucan extracts, literature has demonstrated that the main factor impacting the bioavailability is phytic acid, which is often found in association with dietary fibers. During food processing, β-glucan can undergo modifications which could potentially affect the equilibrium between phytic acid, fiber, and iron. In this study, an in vitro digestion was used to elucidate the iron dialysability, and hence estimate iron availability, in the presence of native, chelating resin (Chelex)-treated, oxidised, or partially hydrolysed oat and barley β-glucan extracts (at 1% actual β-glucan concentration), with or without phytase treatment. It was confirmed that pure, phytic acid-free β-glucan polysaccharide does not impede iron availability in cereal foods, while phytic acid, and to a smaller extent, also proteins, associated to β-glucan can do so. Neither Chelex-treatment nor partial hydrolysis, 2,2,6,6-tetramethylpiperidine 1-oxyl (TEMPO) or NaIO₄ oxidation significantly influenced the phytic acid content of the β-glucan extracts (ranging 2.0–3.9%; p > 0.05). Consequently, as long as intrinsic phytic acid was still present, the β-glucan extracts blocked the iron availability regardless of source (oat, barley) or Chelex-treatment, partial hydrolysis or NaIO₄-oxidation down to 0–8% (relative to the reference without β-glucan extract). Remarkably, TEMPO-oxidation released around 50% of the sequestered iron despite unchanged phytic acid levels in the modified extract. We propose an iron-mobilising effect of the TEMPO product β-polyglucuronan from insoluble Fe(II)/phytate/protein aggregates to soluble Fe(II)/bile salt units that can cross the dialysis membrane. In addition, Chelex-treatment was identified as prerequisite for phytase to dramatically diminish iron retention of the extract for virtually full availability, with implications for optimal iron bioavailability in cereal foods.

Hulless barley and β-glucanase affect ileal digesta soluble beta-glucan molecular weight and digestive tract characteristics of coccidiosis-vaccinated broilers

Exogenous β-glucanase (BGase) in barley-based feed has been shown to reduce digesta viscosity in chickens, and thereby improve performance. Less well studied is the potential for BGase to convert barley β-glucan into low molecular weight carbohydrates, which might influence digestive tract function and enteric disease. Coccidiosis-vaccinated broiler chickens were fed graded levels of hulless barley (HB) and BGase to determine their effects on β-glucan depolymerization and digestive tract characteristics. Broilers were fed high β-glucan HB (0%, 30% and 60% replacing wheat) and BGase (0%, 0.01% and 0.1%) in a 3 × 3 factorial arrangement. A total of 5,346 broilers were raised in litter floor pens and vaccinated for coccidiosis on d 5. Each treatment was assigned to 1 pen in each of 9 rooms. The significance level was set at P ≤ 0.05. At both 11 and 33 d of broiler ages, peak molecular weight of β-glucan in ileal digesta decreased with increasing BGase for 30% and 60% HB. The maximum molecular weight for the smallest 10% β-glucan molecules (MW-10%) decreased with BGase at both ages for 30% and 60% HB; for birds fed 0% HB, only 0.1% BGase decreased MW-10%. The 0.1% BGase increased caecal short chain fatty acids (SCFA) compared to the 0.01% BGase at d 11 only for the 60% HB. Ileal pH increased with increasing HB and BGase at d 11 and 33. Caecal pH was lower for 0.1% BGase than 0% BGase for 60% HB at d 11. Relative mRNA expression of interleukin 6 (IL-6) and IL-8 in the ileum increased with 0.1% BGase at d 11 and 33, respectively, whereas expression of ileal mucin 2 (MUC2) decreased with 0.1% BGase at d 33. In the caeca, interactions between HB and BGase were significant for monocarboxylate transporter 1 (MCT1) and mucin 5AC (MUC5 AC) on d 11, but no treatment effects were found at d 33. In conclusion, BGase depolymerized high molecular weight β-glucan in HB in a dose-dependent manner. Hulless barley and BGase did not increase SCFA concentrations (except for 60% HB with 0.1% BGase at d 11) and caused minor effects on digestive tract histomorphological measurements and relative mRNA gene expression.

Characterization of acid hydrolysates from barley β-glucan concentrate for their physico-chemical and rheological properties

The present study was aimed at assessing the influence of acid hydrolysis on the physicochemical and rheological properties of β-glucan concentrate. Barley β-glucan concentrate was subjected to acid hydrolysis for 30 and 60 min. The molecular weight and viscosity were observed to be a function of hydrolysis time and decreased in a duration-based approach. Significant reduction in water binding capacity and swelling power was observed after acid hydrolysis. Acid hydrolysis dramatically altered the flow properties and a Newtonian behavior was observed for HBG₆₀. The oscillatory measurements revealed enhanced visco-elasticity for HBG₃₀ solutions in comparison to its native counterpart and were greatly reliant on molecular weight and concentration. DSC measurements showed reduced thermal stability of acid hydrolysates in comparison to native β-glucan concentrate. Overall, this study provides useful information on the hydration, thermal and rheological behavior of β-glucan concentrates and could be helpful in optimizing the concentration of β-glucan concentrates in food formulations.

Preparation and characterization of various chitin-glucan complexes derived from white button mushroom using a deep eutectic solvent-based ecofriendly method

Deep eutectic solvents (DESs) have gained great interests as ecofriendly and safe solvents in diverse areas. Herein, various chitin-glucan complexes (CGCs) were prepared from white button mushroom (Agaricus bisporus) using DESs. Ultrasonication of mushroom in five DESs yielded two types of CGCs from each DES, one from the DES-insoluble residue (DES_P) and another from the DES-soluble extract (DES_S). The ten resulting CGCs with varying chitin-to-β-glucan ratios were compared with alkali-insoluble matter (AIM), chemically prepared using NaOH. BU_S and BU_P, prepared using BU comprising betaine and urea, were obtained in the highest yields with reasonably low protein and mineral contents. Despite different acetylation degrees (77.3% and 57.3%, respectively), BU_S and BU_P both degraded at 318 °C and showed remarkably low crystallinity (32.0% and 37.0% for BU_S and BU_P, respectively) compared to AIM, commercial chitin, and the reported CGCs. The surface of BU_S and BU_P was very porous and rough compared with AIM as a result of reduced H-bonds and lowered crystallinity. The DES-based method can potentially enable the preparation of advanced biomaterials from mushrooms under mild and ecofriendly conditions.

In Vitro Infant Faecal Fermentation of Low Viscosity Barley β-Glucan and Its Acid Hydrolyzed Derivatives: Evaluation of Their Potential as Novel Prebiotics

Barley contains high level of β-1,3-1,4-glucans (BBGs) which can be fermented by microbes and are a potential prebiotic. In the present study, native BBG with low viscosity and a MW of 319 kDa was depolymerized by acid hydrolysis to produce a series of four structurally characterized fragments with MWs ranging from 6⁻104 kDa. In vitro fermentation of these BBG samples by infant faecal microbiome was evaluated using a validated deep-well plate protocol as parallel miniature bioreactors. Microbial taxa were identified using 16S amplicon sequencing after 40 h of anaerobic fermentation. Bioinformatics analysis including diversity indexes, predicted metagenomic KEGG functions and predicted phenotypes were performed on the sequenced data. Short chain fatty acids and dissolved ammonia were quantified and the SCFAs/NH₃ ratio was used to evaluate the eubiosis/dysbiosis potential. Correlation analysis showed that most of the parameters investigated showed a parabolic function instead of a monotonous function with the BBG samples having different MWs. Among the five BBGs, it was concluded that BBG with an intermediate MW of 28 kDa is the most promising candidate to be developed as a novel prebiotic.

Determination of Curdlan Oligosaccharides with High-Performance Anion Exchange Chromatography with Pulsed Amperometric Detection

The increasing interest of curdlan oligosaccharides (COS) in medicine and plant protection fields implies a necessity to identify and quantify this product. In the present study, an efficient and sensitive analytical method based on high-performance anion exchange chromatography with pulsed amperometric detection (HPAEC-PAD) was established for the simultaneous separation and determination of D-glucose and ß-1,3-linked COS ranging from (COS)₂ to (COS)₆ within 20 min. Detection limits were 0.01 to 0.03 mg/L. The optimized assay was performed on a CarboPac-PA100 analytical column (4 mm × 250 mm) using isocratic elution with water-0.2 M sodium hydroxide-0.5 M sodium acetate mixture (50 : 30 : 20, v/v/v) as the mobile phase at a flow rate of 0.8 mL/min. Regression equations indicated a good linear relationship (R ² = 0.9992-1.0000, n = 6) within the test ranges. Quality parameters including precision and accuracy were fully validated and found to be satisfactory. More important, the regression of natural logarithm values of retention times (log₁₀ RT) versus the degree polymerization (DP), as well as the slope coefficient of each COS's linear equation versus the corresponding DP, fitted a linear relationship well. These inherent linear relationships could provide valuable information to tentatively identify and quantify the COS even with the DP more than 6 without authentic standard. Furthermore, when the log₁₀ RT was plotted against log₁₀ flow rate for each COS, a perfect linear relationship was also observed.

Oral mucositis caused by Candida glabrata biofilms: failure of the concomitant use of fluconazole and ascorbic acid

OBJECTIVES

Candida glabrata is becoming one of the most prevalent pathogenic yeasts in cases of oral diseases. Mucositis is an recurrent oral infection in immunocompromised patients, and the actual guidelines recommend the use of fluconazole (Flu) for many cases. However, the azole resistance by C. glabrata is renowned, causing a reduced therapeutic response, especially when it occurs in biofilms. In this study, we performed an in vitro evaluation of an alternative pharmacotherapy for C. glabrata biofilm infections, combining ascorbic acid (AA) with Flu. AA is recognized for degrading β-glucans, an important compound of the biofilm matrices, which prevent drug diffusion.

MATERIALS AND METHODS

Routine clinical 30 or 40 mg/l doses of Flu were applied to C. glabrata biofilms simultaneously with 200 or 300 mg/l of AA.

RESULTS

The results showed that this combination effectively promoted the degradation of the biofilm network, but unfortunately, also stimulated the growth of the yeasts population due to release of several glucose monomers during β-glucans hydrolysis.

DISCUSSION

AA lead to the hydrolysis of the β-glucans of the matrix, liberating glucose molecules which are used as carbon souce by the yeasts, thus suppressing the desired antifungal effect of the drug combination with Flu.

CONCLUSIONS

Unlike to what happens in treatment of bacterial infection, AA should not be used together with Flu in the treating oral mucositis caused by Candida.

Physicochemical Properties of β-Glucan from Acid Hydrolyzed Barley

This study was performed to investigate changes in the content and purity, as well as physical characteristics of β-glucan extracted from acid hydrolyzed whole grain barleys. Waxy and non-waxy barleys (Hordeum vulgare) were hydrolyzed with different concentrations of HCl (0.1~0.5 N) for 1 h. As the HCl concentration increased, the contents of total and soluble β-glucan from acid hydrolyzed barley decreased. However the ratio of soluble/total β-glucan content and purities of β-glucan significantly increased. The ratio of β-(1→4)/β-(1→3) linkages, molecular weight, and viscosity of soluble β-glucan of raw barleys were 2.28~2.52, 6.0~7.0×10⁵ g/mol, and 12.8~32.8 centipoise (cP). Those of isolated soluble β-glucan were significantly decreased to 2.05~2.15, 6.6~7.8×10³ g/mol, and 3.6~4.2 cP, respectively, with increasing acid concentration. The re-solubility of raw barley β-glucan was about 50%, but increased to 97% with increasing acid concentration. Acid hydrolysis was shown to be an effective method to produce β-glucan with high ratio of soluble β-glucan content, purity, water solubility, and low viscosity.

Synthesis and characterization of fatty acid oat β-glucan ester and its structure-curcumin loading capacity relationship

An amphiphilic fatty acid oat β-glucan ester (FAOGE) was first synthesized, and its structure-curcumin loading capacity (CLC) relationship was investigated. The DS of product increased with the addition of acyl imidazole, decreased with Mw of β-glucan, and did not relate to the acyl chain length. Characterizations by FT-IR and (1)H NMR evidenced the presence of ester groups in FAOGE and confirmed its successful synthesis. The aqueous self-aggregation behavior of FAOGE was revealed by transmission electron microcopy and dynamic light scattering. With the aid of response surface methodology, a quadratic polynomial equation was obtained to quantitatively describe the structure-CLC relationship of FAOGE by using Mw of β-glucan, acyl chain length, and DS as variables. The CLC increased with Mw of β-glucan and acyl chain length but maximized at a medium DS. The maximum CLC value was obtained as 4.05 μg/mg. Hence, FAOGE is a potential candidate in solubilizing and delivering hydrophobic food ingredients.

Synthesis, characterization, and aqueous self-assembly of octenylsuccinate Oat β-glucan

Amphiphilic oat β-glucan derivatives carrying octenylsuccinic groups as hydrophobic moieties have been synthesized. Materials with a different degree of substitution (DS) and weight-average molecular weight (Mw) for oat β-glucan were prepared and characterized using elemental analysis, infrared (IR) spectroscopy, and high performance size exclusion chromatography (HPSEC). Dynamic light scattering (DLS), fluorescence spectroscopy, and transmission electron microscopy (TEM) revealed that octenylsuccinate oat β-glucan (OSG) can self-assemble into spherical micelles in water with an average size ranging from 175 to 600 nm. OSG micelles were negatively charged as indicated by ζ-potential measurement. The critical micelle concentration (CMC) of OSGs varied from 0.206 to 0.039 mg/mL, depending on the DS and Mw of the oat β-glucan. It was found that the presence of OSG micelles in aqueous solution could significantly enhance the solubility of curcumin by 880 fold. Thus, OSG might have great potential in applications as hydrophobic nutrient delivery carriers.

Modulating the structural properties of β-D-glucan degradation products by alternative reaction pathways

The aim of the present study was to compare the degradation of β-D-glucan induced by hydroxyl radical to the degradation induced by heat treatment. β-D-Glucan was quickly and widely degraded by the action of hydroxyl radicals produced by a Fenton system at 85 °C, while thermal hydrolysis at 85 °C induced slow β-D-glucan depolymerization. The hydroxyl radical-induced degradation of β-D-glucan was accompanied by the formation of peroxyl radicals and new oxidized functional groups (i.e. lactones, carboxylic acids, ketones and aldehydes), as detected by ESR and NMR, respectively. In contrast, no changes in the monomer chemical structure of β-D-glucan were observed upon thermal hydrolysis. Therefore, different mechanisms are proposed for the oxidative cleavage of β-D-glucan, which are initiated by the presence of an unpaired electron on the anomeric carbon.

Hydrolysis behavior of bamboo fiber in formic acid reaction system

The process of conversion of bamboo fiber into fermentable glucose in the formic acid reaction system was investigated using cross-polarization/magic angle spinning (13)C-nuclear magnetic resonance (CP/MAS (13)C NMR), X-ray diffraction. The results indicated that formic acid as an active agent was able to effectively penetrate into the interior space of the cellulose molecules, thus collapsing the rigid crystalline structure and allowing hydrolysis to occur easily in the amorphous zone as well as in the crystalline zone. The bamboo fiber was hydrolyzed using formic acid and 4% hydrochloric acid under mild conditions. The effects of temperature (55-75 degrees C), retention time (0-9 h) and catalyst, the concentration of glucose and the degradation pathway of glucose were analyzed. The main degradation pathway of glucose is that the hydroxyl group on the 2-carbon is protonated and cleaved off. Aluminum iso-propoxide prevented the degradation of glucose, and the acetone promoted the degradation of glucose to levulinic acid.