Abstract
Scleroglucan, a neutral β(1–3) glucan with β(1–6) glucan branches every third residue, is being considered as an alternative rod-like, shear thinning high molecular weight β-glucan based polysaccharide to xanthan gum for the management of patients with oropharyngeal dysphagia. It is therefore important to understand more fully its hydrodynamic properties in solution, in particular heterogeneity, molecular weight distribution and its behaviour in the presence of mucin glycoproteins. A commercially purified scleroglucan preparation produced by fermentation of the filamentous fungus Sclerotium rolfsii was analysed in deionised distilled water with 0.02% added azide. Sedimentation velocity in the analytical ultracentrifuge showed the scleroglucan preparation to be unimodal at concentrations >0.75 mg/ml which resolved into two components at lower concentration and with partial reversibility between the components. Sedimentation coefficient versus concentration plots showed significant hydrodynamic non-ideality. Self-association behaviour was confirmed by sedimentation equilibrium experiments with molecular weights between ~3 × 106 g/mol to ~5 × 106 g/mol after correcting for thermodynamic non-ideality. SEC-MALS-viscosity experiments showed a transition between a rod-shape at lower molar masses to a more flexible structure at higher masses consistent with previous observations. Sedimentation velocity experiments also showed no evidence for potentially problematic interactions with submaxillary mucin.
Highlights
Oropharyngeal dysphagia is known as swallowing disorder in the upper aero digestive tract (Martino, Pron, & Diamant, 2000)
Sedimentation velocity in the analytical ultracentrifuge showed the scleroglucan preparation was unimodal at concentrations >0.75 mg/ml which resolved into two main components at lower concentration and with partial reversibility between the components (Fig. 2), accounting for ~ 80% of the total distribution
We explored, using analytical ultracentrifugation, the behaviour of mixtures of scleroglucan with submaxillary mucin to assay for the possible presence of deleterious large aggregation effects which might diminish the potential of scleroglucan as a dysphagia agent (Rofes et al, 2014)
Summary
Oropharyngeal dysphagia is known as swallowing disorder in the upper aero digestive tract (Martino, Pron, & Diamant, 2000). The pyruvic acid content of xanthan can vary according to the producing bacterial strain It is a dimeric helical poly saccharide which adopts an extended conformation in solution (Berth et al, 1996) with a large persistence length (a measure of chain rigid ity/flexibility of polysaccharides). The extended rod-like characteristic renders it susceptible to shear thinning in solution, a property which is desirable for managing dysphagia. Scleroglucan is another micro bial/fungal large molecular weight β-glucan based polysaccharide, produced from the filamentous fungus Sclerotium rolfsii. It is being considered as an alternative rod-like, shear thinning high molecular weight β-glucan based polysaccharide. We do this by taking advantage of recent advances in both sedimentation velocity and sedimentation equilibrium in the analytical ultracentrifuge (AUC), together with advances in size-exclusion chro matography coupled to multi-angle light scattering and differential pressure viscometry
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