An investigation of kinetics and mass transfer parameters during ultrasound-assisted extraction of fucoidan from the brown seaweed Ecklonia maxima

Abstract

Fucoidan, a bioactive sulfated polysaccharide from brown seaweed, holds significant industrial potential. This study explores ultrasound-assisted extraction (UAE) using a batch recirculation flow cell for fucoidan extraction. The impacts of ultrasound amplitude (0 – 190 μm), temperature (25 – 85 ℃) and pH (3 – 11) were evaluated on mass transfer parameters – effective diffusivity, mass transfer coefficient, initial extraction rate, and the sulfates equilibrium concentration. These parameters were modelled using Fick’s second law, the mass transfer model and the Peleg model, all of which demonstrated good agreement with experimental data (R² > 0.89). UAE (at 190 μm) significantly enhances extraction kinetics, increasing effective diffusivity from 0.863 to 3.46 × 10⁻¹² m²·s⁻¹ and mass transfer coefficient from 0.451 to 1.84 × 10⁻⁶ m·s⁻¹ compared to no ultrasound. Higher temperatures and higher amplitudes enhance the mass transfer rates, while pH beyond 5 reduces these rates due to alginates co-extraction, but increased sulfates equilibrium concentration, suggesting benefits for maximising final yields. UAE of fucoidan is an internal diffusion-limited process (Biot numbers > 50).