Novel biorefinery process for extraction of laminarin, alginate and protein from brown seaweed using hydrodynamic cavitation

This paper investigates a novel biorefinery process designed for the extraction of valuable compounds from brown seaweed Alaria esculenta using hydrodynamic cavitation (HDC). A two-stage process was developed to maximize the value of seaweed biomass by control of the processing time, solvent selection and HDC conditions to extract laminarin, alginate, mannitol and protein in a cascading manner, maximizing the value of seaweed biomass. After the first extraction stage using 0.1 M HCl, membrane ultrafiltration was employed to separate laminarin and mannitol. The purity of the laminarin and mannitol obtained was up to 86.57 ± 3.72 % and 40.49 ± 2.78 % with recovery rates of 55.55 ± 3.10 % and 75.90 ± 4.49 %, respectively. Ethanol precipitation was then carried out to recover sodium alginate after the second extraction stage process using 2 % Na₂CO₃ (w/v). The sodium alginate purity extracted by employing HDC twice (HDC-HDC) was 88.98 ± 4.70 % with a recovery rate of 65.13 ± 5.14 %. The remaining residue after the biorefinery process had an enriched protein content of 17.19 ± 1.33 %. This study demonstrates that an HDC-assisted biorefinery process can significantly (P < 0.05) reduce energy consumption. The laminarin extracts were further characterised by antioxidant activity, anti-inflammation activity, FT-IR, and anti-microbial activity. The laminarin extracted in this study was shown to have identical bioactive activities as the commercially available samples.