Molecular origin for the thermal stability of schizophyllan

Abstract

Abstract The non-Newtonian behavior, dynamic viscoelasticity and optical rotation of schizophyllan solutions were measured with a rheogoniometer and polarimeter. Schizophyllan showed shear-thinning behavior below 0.3%, but plastic behavior above 0.5%. Gelation occurred for native and sonic degraded schizophyllan at concentrations of 0.8 and 2.0% at 0 °C, but melted when the temperature reached 5 °C, which was estimated to be a transition temperature. However, the dynamic modulus stayed at a large value during an increase in temperature up to 85 °C. A small decrease in the dynamic modulus of schizophyllan was observed upon addition of urea (4.0 M). A transition temperature was observed when the temperature of schizophyllan reached 60 ° in 0.1 N NaOH and in 85% dimethyl sulfoxide solution, respectively. Though the optical rotation remained constant during a decrease in temperature up to 15 °C, it increased with further decrease in temperature. The thermostability of the dynamic viscoelasticity of schizophyllan may be essentially attributed to an intramolecular hydrogen bonding in aqueous solution. A possible mode of an intramolecular hydrogen bonding for schizophyllan was proposed.