Kinetic models and process parameters for ultrasound-assisted extraction of water-soluble components and polysaccharides from a medicinal fungus

This study was on the kinetics and process parameters for ultrasound-assisted extraction (UAE) of water-soluble components and polysaccharides (PS) from the dry mycelium of a medicinal fungus, Cordyceps sinensis Cs-HK1. Four process variables (factors) were evaluated at different levels, ultrasound intensity (2.44-44.1W/cm2), temperature (40-70°C), solid particle size (156.5-750μm), and solid-to-liquid ratio (1/30-1/70g/mL). The experimental data of yields versus time in most cases were fitted closely to two empirical kinetic models for solid-liquid extraction, parabolic diffusion equation (y=yo+y1t1/2) and power law (y=βtn) with high correlation coefficients (R2) of 0.95-0.99 for total extract yield, and 0.90-0.96 for PS yield. The PS yield was increased more significantly than the total extract yield with the ultrasound intensity. Reducing the particle size and increasing the extraction temperature led to a higher yield and extraction rate; increasing the solid-to-liquid ratio (or decreasing the liquid volume) increased the PS yield and extraction rate but had little influence on the total extract. Significant correlations were found between extraction rate (dy/dt) and ultrasound power density (P/V), and between extract yield (y) and energy density (Pt/V). The kinetic and process parameters are useful for rational design and efficient operation of UAE processes.