Ultrasound-assisted extraction of alginate from Ecklonia maxima with and without the addition of alkaline cellulase – factorial and kinetic analysis

Abstract

Ultrasound-assisted extraction and enzyme-assisted extraction are two methods that can be employed to recover valuable compounds from seaweeds at milder operating conditions than conventional chemical extraction methods. The aim of the study was to determine whether pH, enzyme addition and extraction temperature significantly impacted extraction of alginate from Ecklonia maxima in the presence of ultrasonication and to model extraction kinetics. Firstly, a 2³ factorial experimental design was employed at constant sonication rate, with pH (8 and 10), temperature (50 and 60 °C), and enzyme-to-substrate ratio (E:S 0 and 1 %) as the independent variables. Secondly, extraction kinetics of alginate were investigated at different extraction conditions, through fitting of the Peleg and Power models. Highest extraction for alginate was achieved at pH 10, 60 °C, E:S = 0 % within the first 60 min of extraction. The addition of enzyme improved solubilised dry matter content, but it had a less clear impact on the alginate yield. Both the Peleg (R² = 0.893 – 0.997) and Power function (R² = 0.861 – 0.987) models provided good fit to the experimental data and can used to describe extraction kinetics of alginate during combined ultrasound-enzymatic assisted extraction.