Physicochemical characteristics of a high molecular weight bioengineered α-D-glucan from Leuconostoc citreum SK24.002

• Leuconostoc citreum SK24.002 can biosynthesize water-soluble α-D-glucan with high molecular weight.
• Bioengineered α-D-glucan solution (9%, v/w) exhibited a non-Newtonian behaviour.
• Bioengineered α-D-glucan could form a weak gel.
• The glucan solution had good resistance to acidic or thermal hydrolysis.

A high molecular weight bioengineered α-D-glucan was obtained from Leuconostoc citreum SK24.002 and certain physicochemical properties were investigated. Scanning electron microscopy of α-D-glucan demonstrated a cementitious material with agglutinated granules. Atomic force microscopy showed the irregularly dendritic shaped structure, revealing some side chains. The glucan solution (3%, v/w) has opalescent, bluish-white colour and the concentration affected the depth of colour. The degradation process of 265–345 °C and melting point of 133.9 °C were determined from the thermal analysis. The glucan viscosity increased exponentially with concentration in the range of 5%–10% (w/v). The glucan solution (9%, w/v) showed a non-Newtonian pseudoplastic behaviour at shear rates of 0.01–100 1/s. The changes of elastic modulus and viscous modulus indicated the glucan could form a weak gel. The glucan solution also had good resistance to acidic or thermal hydrolysis. Three-dimensional model revealed α-D-glucan molecule has a helical conformation with some inter-molecular hydrogen bonds, suggesting a high viscosity in solution and this could make it suitable for usage as a biothickener or stabilizer agent in food systems.

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