Dylan van Sittert1, Zwonaka Mapholi1 and Neill J. Goosen1
1Department of Process Engineering, Stellenbosch University, Banghoek Road, Stellenbosch 7600
Alginate is an important biomolecule found in brown seaweeds, and is commercially extracted using conventional chemical extraction pathways. Ultrasound-assisted extraction (UAE) and enzyme-assisted extraction (EAE) are two potential alternative extraction methods that can be employed for alginate extraction from brown seaweeds, at operating conditions that are milder than those employed during conventional chemical extraction methods. However, alginate extraction rates that can be achieved using UAE and EAE are poorly described, yet will play an important role in commercialisation of these extraction technologies. The aim of the study was therefore to determine the optimum conditions for extraction of alginate from Ecklonia maxima using enzymatic extraction 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. Optimum 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, despite its less clear impact on the alginate yield. Both the Peleg’s (R2 = 0.893 – 0.997) and Power function (R2 = 0.861 – 0.987) models provided good fit to the experimental data and can suitably be used to describe extraction kinetics of alginate during combined ultrasound-enzymatic assisted extraction.