1984 Volume 41 Issue 12 Pages 739-744
The ultrasonic degradation of pullulan in solution has been investigated. A few samples of pullulan is irradiated with ultrasonic waves in 0.5% aqueous solution contained 0.9% NaCI at 30°C, and average molecular weights and molecular weight distributions of degraded pullulan samples are evaluated by gel filtration method. <Br>Observed results on the decrease of the average molecular weight and on the changes in the molecular weight distribution indicate the following characteristics in the ultrasonic degradation of pullulan. The degradation proceeds with different behaviors in different regions of the molecular weight (M). Pullulan of high M degrades very rapidly and yields a product having wide molecular weight distribution with a peak around M=3×104, then degrades very slowly and yields a final product of low M with a peak around M=3-5×108. For M below 20×104, the degradation is apparently a first-order reaction and the apparent rate constant decreases with decreasing M. Pullulan with M below 3-5×108 shows no degradation.
The results are compared with those of dextran previously reported.
