Kinetic modeling of the ultrasonic-assisted extraction of polysaccharide from Nostoc commune and physicochemical properties analysis.

Based on the theory of extraction and diffusion of Chinese herbal medicine, the dynamic model of ultrasonic-assisted extraction process of polysaccharide from Nostoc commune Vauch. was established according to the second law of Fick, and further verified at different solid-liquid ratio (1/40-1/80 g/mL), temperature (313.15-353.15 K), ultrasonic power (240-600 W) and extraction time (0-25 min), the dynamic parameters including rate constant and relative extraction rate were respectively analyzed. The rate constant (k) gradually increased with the increase of temperature at different solid-liquid ratio. The maximum concentration of polysaccharide (NCVP) from N. commune was obtained with an optimal extraction condition at solid-liquid ratio of 1:50, extraction temperature of 353.15 K, ultrasonic power of 540 W and extraction time of 25 min. NCVP, the non reducing sugar with typical infrared spectrum characteristics of polysaccharide, dissolves in water but not dissolved in ethanol, acetone and petroleum ether and displays a good stability and smooth surface. The results provide the basis for NCVP in depth theoretical study of polysaccharide extraction processing.