Effect of gamma irradiation on the macromolecular integrity of guar gum

The impact of molecular weight on the segregative phase separation-induced molecular fractionation of aqueous gum Arabic/xanthan mixtures

Segregative phase separation of natural polymers has drawn significant research interest because of its diverse applications in the food industry. However, there is limited research on how molecular weight (Mw) influences segregative phase separation. This study aims to investigate the impact of Mw on segregative phase separation-induced molecular fractionation in mixed gum Arabic/Xanthan (GA/XG) solutions. The analysis focused on a single type of gum Arabic (referred to as EM10), with the molecular weights of both solid and liquid xanthan gum (XG) samples being altered through 60Coγ irradiation. These modified samples were evaluated using gel permeation chromatography combined with multi-angle laser light scattering (GPC-MALLS). The results demonstrated that the fractionation process of GA increased the content of the arabinogalactan-protein complex (AGP), increasing from an initial 29 % to a final 40 % within the GA/XG system (fixed with a mixture of 8 % EM10/0.8 % XG). When analyzing phase separation-induced molecular fractionation as a function of Mw, an increase in Mw (3.6 × 105-1.9 × 106) was associated with a corresponding rise in the degree of phase separation-induced fractionation. This was attributed to the irradiation-mediated breakage of XG chains. This study deeply analyzed the effect of Mw on the phase separation behavior and molecular fractionation mechanism of the GA/XG system. The results showed that when the Mw of XG was 3.6 × 105 (XG4) as a minimum, the AGP content was 29 % when mixed with GA, and when the Mw of XG was 1.9 × 106 (Control XG) as a maximum, the AGP content was 40 % when mixed with GA. The increase of Mw optimised the emulsion stabilisation property of GA significantly, which provided great practical value for its industrial applications.

Role of Sterilization on In Situ Gel-Forming Polymer Stability

In recent years, stimulus-sensitive drug delivery systems have been developed for parenteral administration as a depot system. In situ systems incorporate smart polymers that undergo a phase transition at the site of administration. All parenteral and ocular dosage forms must meet sterility requirements. Careful selection of the sterilization method is required for any type of stimuli-sensitive system. Current sterilization methods are capable of altering the conformation of polymers or APIs to a certain extent, ultimately causing the loss of pharmacological and technological properties of the drug. Unfortunately, the issues of risk assessment and resolution regarding the sterilization of stimuli-sensitive systems, along with ways to stabilize such compositions, are insufficiently described in the scientific literature to date. This review provides recommendations and approaches, formulated on the basis of published experimental data, that allow the effective management of risks arising during the development of in situ systems requiring sterility.

Effects of EB irradiation on the properties of xanthan in solid state for utilization as adjuvant to improve foliar applications

In this study, xanthan was irradiated by electron beam accelerator (EB) in solid state and the viscosity and molecular weight of the irradiated xanthan were investigated to provide a better understanding on the EB radiation effect on molecular properties of xanthan. Both viscosity and molecular weight of xanthan were greatly decreased by EB at 25 kGy then slowly decreased with further increase of irradiation dose to 200 kGy. Contact angles and adhesion degrees of the irradiated xanthan solutions were rather smaller than those of commercial xanthan. These results suggested that the xanthan was EB irradiated at 100 kGy can be utilized as a good adjuvant to improve spraying application of foliar fertilizer for promoting the growth and yield of water spinach.

Methylation of guar gum for improving mechanical and barrier properties of biodegradable packaging films

Improving functional properties of biopolymers for use as environment friendly packaging is an area of current interest. Biodegradable films with improved barrier and mechanical properties were prepared from methylated guar gum. Methylation resulted in structural modification of guar gum (GG) promoting greater crystallization thereby enhancing thermal stability towards decomposition. Reduction in radius of gyration (R_g), weight average molecular weight (M_w), and an increase in polydispersity index (PDI) were also observed due to methylation. Methylated guar gum (MGG) films exhibited 40% lower water vapor transmission rate (WVTR) as compared to control purified guar gum (PGG) films. Films prepared by partial replacement of PGG with MGG (10, 25, 50, 75 and 100% w/w) showed gradual improvement in percent elongation. The study gives an insight on the role of methylation in enhancing barrier and mechanical properties of GG based biodegradable films for possible application in food packaging.

Depolymerization using sonochemical reactors: A critical review

Ultrasonic irradiation has been proposed as a novel approach for degradation of polymer compounds, especially considering the fact that the reduction in the molecular weight (also the intrinsic viscosity) is simply by splitting the most susceptible chemical bond without causing any changes in the chemical nature. An overview of the application of ultrasound for the polymer degradation has been presented in this work, discussing the mechanism of degradation, kinetic modeling, effect of operating parameters and the type of reactors generally used for depolymerization. The effect of important operating parameters such as initial polymer concentration, presence of functional groups in the polymer chain, reaction volume, initial molecular weight, temperature, operating frequency, power dissipation and use of process intensifying additives have been discussed also giving guidelines about selection of the optimum parameters. It has been observed that the low concentrations and higher power dissipation (till an optimum) are favorable resulting in higher extents of degradation. Typically low frequency is recommended but for the case of water soluble polymers, higher frequencies would also give similar results due to the dominant action of chemical effects of cavitation. It has been demonstrated that the alkyl group substituent also affects the degradation rate of polymer. An overview of degradation using combined approach based on ultrasound and additives with comparison with individual approach has also been presented. It has been observed that the main contributing factor for the synergy of the combined approach is the selection of optimum loading of additives. Overall, it has been observed that efficient polymer degradation can be achieved using combined process based on the use of ultrasound.

Effect of gamma irradiation on rheological properties of polysaccharides exuded by A. fluccosus and A. gossypinus

In this study, Iranian gum tragacanth (GT) exudates from Astragalus fluccosus (AFG) and Astragalus gossypinus (AGG) were irradiated at 3, 7, 10 and 15 kGy. Fourier transform infrared spectroscopy (FTIR) data showed that irradiation did not induce changes in the chemical structure of either type of gum. Although particle size distribution and both steady shear and dynamic rheological properties were considerably affected by the irradiation process, the magnitude of the effect of irradiation on each of the rheological and size variables was different for the hydrocolloids. For instance, for AGG, increasing the irradiation dose from 3 to 10 kGy, the d(0.5) and D[3,2] values were reduced by one-sixth to one-eighth fold. Colour measurement revealed that the radiation process led to an increase in the yellow index and b* values for both types of GT in powder form, but it was more pronounced for AGG samples. Irradiation led to an approximate 13-fold increase in redness in AFG. Surface and shape changes of the gum crystals were studied by scanning electron microscope (SEM) and a smoother surface for irradiated samples was detected. The notable changes in functional properties of each variety of irradiated gum should be taken into consideration before using the radiation technology as a commercial tool for sterilisation.

Some observations on the effects of bioprocessing on biopolymer stability

A short review is given of some of the effects of the stresses encountered during bioprocessing of protein and carbohydrate-based macromolecular systems. This is of relevance to the effectiveness and safety of protein or peptide drugs themselves (such as insulin and monoclonal antibodies) and for the integrity of delivery systems (such as various carbohydrate-based hydrogel or mucoadhesive polymers). Some carbohydrate polymers are themselves bioactive or immunostimulatory and particular use is being made of polysaccharide and glycoconjugate vaccines whose effectiveness can be severely effected by chain degradation. Stability criteria include molecular weight and conformation and techniques ranging from simple viscomery measurements to sophisticated analytical ultracentrifuge and multi-angle light scattering coupled to size exclusion chromatography and precision viscometry measurements have been useful in this regard. We focus on some recent work on the degradation and aggregation of immunoglobulin G4-based monoclonal antibodies in response to repeated freezing and thawing and long-term storage, looking at the possible connection between conformation change and aggregation, the effects of storage conditions on the stability of chitosan mucoadhesive systems used for nasal and oral delivery. We look at the effects of sterilization conditions (thermal and irradiation) on the stability of a variety of other polysaccharides such as starches, κ-carrageenan, carboxymethylcellulose, alginate, low- and high-methoxy pectins, guar, and xyloglucans and consider the use of a relatively new method for the evaluation of the molecular weight distribution of glycoconjugate vaccines with molecular weights as high as 100 × 10(6) g/mol.

Effect of a viscous fiber bar on postprandial glycemia in subjects with type 2 diabetes

OBJECTIVE

To compare the effect of an experimental viscous fiber (VF) crispy bar on the postprandial glucose, insulin, and C-peptide response in adult subjects with type 2 diabetes to two commercially available control crispy bars.

DESIGN

The study was a randomized, double-blinded, three period, crossover study.

SETTING

The study was conducted at two sites: Park Nicollet Institute, International Diabetes Center, Minneapolis, MN, and Radiant Research, Inc., Minneapolis, MN.

SUBJECTS

A total of 60 adults with type 2 diabetes taking oral antihyperglycemic medication participated in the study.

INTERVENTION

After an overnight fast, subjects consumed a test meal containing an equicaloric amount (300 kcal) of an experimental VF crispy bar or one of two commercially available crispy bars at each of three test visits, followed by a four hour meal tolerance test. Subjects also completed gastrointestinal (GI) response records for the 24 hours following each test visit.

RESULTS

The VF crispy bars produced significantly lower glucose (p < 0.0001), insulin (p < 0.0001), and C-peptide (p < 0.0001) responses (as measured by positive area under the curve) in subjects with type 2 diabetes, as compared with the two commercially available bars. Intensity (p < 0.05) and frequency (p < 0.05) of flatulence were significantly higher with the VF bar as compared with the 2 commercial bars. While the VF bar produced significant subjective GI tolerance scoring values, the mean value was below 3 on a scale of 0 (no effect) to 10 (most severe effect) for all tested materials.

CONCLUSIONS

The incorporation of VF into a crispy bar provided a means to improve blood glucose levels by reducing postprandial glucose, insulin, and C-peptide responses in subjects with type 2 diabetes. Though associated with some GI symptoms, VF may have application in improving the postprandial glycemic response in people with diabetes attempting intensive glucose control.

Affinity partitioning of a Cellulomonas fimi beta-mannanase with a mannan-binding module in galactomannan/starch aqueous two-phase system

A new approach in affinity separations was studied by partitioning of Cellulomonas fimi beta-mannanase (EC 3.2.1.78) containing a mannan-binding module in galactomannan/hydroxypropyl starch aqueous two-phase system. Comparison was made with a truncated version of C. fimi beta-mannanase which lacked the mannan-binding module. Results showed that affinity partitioning of the beta-mannanase was achieved due to biospecificity of the mannan-binding module towards the top phase containing galactomannan. Experiments were conducted at pH 8 to prevent enzyme degradation of the phase containing galactomannan. Removal of the top phase polymer was accomplished by beta-mannanase degradation allowed by shifting to the optimal pH 6. In the combination with the genetic fusion of any given protein to the mannan-binding module, the results envision a general procedure for primary affinity recovery of such fusion proteins.

Calcium alginate dressings--I. Physico-chemical characterization and effect of sterilization

In order to analyze the alginate components of alginate dressings and the fractions which are released when the dressing is in contact with model biological fluids, the use of various analytical methods was considered. The first step was the conversion of a calcium alginate batch to pure sodium alginate. The recovery of the latter from either insoluble or soluble mixed sodium/calcium alginates was performed by complexation of calcium ions with sodium citrate followed by ultrafiltration. Comparisons were made between sugar analysis, 1H NMR and circular dichroism (CD) data to determinate the contents in guluronic and mannuronic acids of sodium alginate chains. It was shown that CD measurements afford a rapid and nondestructive method for determination of %G when one takes the ratio theta200/theta220 into account. Fractionation of crude alginate (generally ranging from 30 to 70% G) was achieved by the triangle dissolution/precipitation method in order to increase the range of alginate in sugar composition. The various validated procedures were applied to investigate the effects of irradiation sterilization on alginate dressings. It was shown that sugar composition is retained whereas molecular weight decreased dramatically due to chain scission.

The solution molecular weight and shape of the bacterial exopolysaccharides amylovoran and stewartan

Amylovoran, the acidic exopolysaccharide (EPS) of Erwinia amylovora, and stewartan, the capsular EPS of E. stewartii, were characterized by analytical ultracentrifugation and by size exclusion chromatography connected to dual detection of light scattering and mass. The average molecular weights of amylovoran and stewartan were determined as 1.0 x 10(6) and 1.7 x 10(6) Da, with polydispersity values (Mw/M(n)) of 1.5 and 1.4, respectively. Based on the sugar composition and their molecular weight, both exopolysaccharides consist of approximately 1000 repeating units per molecule, this suggests a similar mechanism for chain length determination during biosynthesis of EPS in both organisms.