MOLECULAR-ORIGIN FOR THE THERMAL-STABILITY OF SCHIZOPHYLLAN

The non-Newtonian behavior, dynamic viscoelasticity and optical rotati on of schizophyllan solutions were measured with a rheogonio-meter and polarimeter. Schizophyllan showed shear-thinning behavior below 0.3%, but plastic behavior above 0.5%. Gelation occurred for native and son ic degraded schizophyllan at concentrations of 0.8 and 2.0% at 0 degre es C, but melted when the temperature reached 5 degrees C, which was e stimated to be a transition temperature. However, the dynamic modulus stayed at a large value during an increase in temperature up to 85 deg rees C. A small decrease in the dynamic modulus of schizophyllan was o bserved upon addition of urea (4.0 M). A transition temperature was ob served when the temperature of schizophyllan reached 60 degrees in 0.1 N NaOH and in 85% dimethyl sulfoxide solution, respectively. Though t he optical rotation remained constant during a decrease in temperature up to 15 degrees 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 bondi ng for schizophyllan was proposed. Copyright (C) 1996 Elsevier Science Ltd