Degradation of Tremella fuciformis polysaccharide by a combined ultrasound and hydrogen peroxide treatment: Process parameters, structural characteristics, and antioxidant activities

The degradation effect of ultrasound (US)/hydrogen peroxide (H2O2) on Tremella fuciformis polysaccharide (TFP) were studied. The main process parameters of degradation were evaluated and the structural changes and antioxidant activities of TFP before and after US/H2O2 were analyzed. The results showed that the degradation effect of US/H2O2 was significantly higher than that of US or H2O2 alone, and the degradation of TFP was dependent on the duration of its exposure to US, the ultrasonic amplitude, and the H2O2 and TFP concentrations. US/H2O2 reduced the molecular weight (from 8.14 × 105 Da to 1.27 × 104 Da) and particle size (from 710 nm to 182 nm) of the TFP within 50 min and narrowed its molecular weight and particle size distribution. High performance liquid chromatography, Fourier-transform infrared spectroscopy, Carbon-13 nuclear magnetic resonance, scanning electron microscopy, atomic force microscopy, and Congo red results indicated that the treatment could break down the polysaccharide chains, hinder the aggregation, and improve the conformation flexibility of the TFP molecules without changing the primary structure and monosaccharide composition of TFP. Additionally, the degraded TFPs with low molecular weight exhibited a higher antioxidant activity than the original TFP. These findings suggest that the US/H2O2 treatment is a simple and effective method to prepare a TFP of low molecular weight and high bioactivity.