Application of wet route extraction and its potential for attaining biologically active compounds from seaweed biomass: The case-study of Gracilaria gracilis
摘要
Seaweeds have been targeted as sustainable feedstock for a biorefinery approach. However, extraction is a challenge and the wet route approach (without drying) may be more sustainable and economically viable. The edible red seaweed Gracilaria gracilis is an excellent case-study, since it is produced for agar preparation. Hence, this study tests different extraction techniques and operational parameters in a wet route approach and compares it with the conventional procedure. The best yield results (> 40% dry matter yield) were registered when wet route was coupled either with overnight agitation (biomass:70% ethanol ratio of 1:10, w:v), pH-shift method (biomass:1 M HCl, 1:10), or ultrasound (biomass:70% ethanol, 1:10), reaching 47.1 ± 0.5%, 46.9 ± 0.1%, and 41.8 ± 0.0%, respectively. Applying overnight agitation to wet instead of dry biomass generally produced higher polyphenol contents: up to an increase from 46.3 ± 6.2 to 287.7 ± 36.9 mg GAE (100 g)−1 dw. Ultrasound-assisted extraction of wet biomass yielded up to 309.1 ± 68.1 mg GAE (100 g)−1 dw. The overnight agitation (wet biomass:70% ethanol, 1:10) and ultrasound-assisted extraction (wet biomass:70% ethanol, 1:10) were chosen for characterization as the best extracts and compared to a conventional dry route extract (biomass:70% ethanol, 1:20). ABTS (2,2'-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid)) identified a benefit of wet route extraction, with 4469.5–5296.3 μmol Trolox Eq. (100 g)−1 dw. Whereas selected ultrasound-assisted extract had a strong anti-inflammatory activity, reaching 38.3 ± 12.5% of COX-2 inhibition, the dry route extract displayed only 6.8 ± 3.0%. Results show the potential of wet route extraction processes, at least to G. gracilis, paving the way for scale-up and industrial development.