Recovery of alginate, fucoidan, phenolics, carotenoids, and hydrochar from beach-cast Ascophyllum nodosum using subcritical water extraction
Bibliographic record
Abstract
Beach-cast brown seaweeds are an underutilized biomass with high potential for sustainable valorization within a circular economy framework. This study focuses on subcritical water (SCW) as a green, chemical-free solvent to recover high-value bioactive compounds (crude alginate, crude fucoidan, phenolics, carotenoids) and hydrochar from beach-cast Ascophyllum nodosum . Despite increasing interest in seaweed valorization, limited research has optimized SCW processing for beach-cast seaweeds, and the effects of non-isothermal heating time (critical factor for scale-up) remain largely unexplored. To address this, factor screening followed by a central composite design was used to evaluate the effects of final temperature, heating time, hold time, water-to-biomass ratio, pH, and agitation speed on yields and antioxidant activities. Final temperature and hold time significantly affected all responses. Maximum crude alginate (15.80 dry wt%) and crude fucoidan (38.48 dry wt%) yields were obtained at 120 °C, 20 min and 138 °C, 12 min hold times, respectively. Comparable yields were also achieved under non-isothermal heating conditions (no hold time) at 140 °C (crude alginate) and 160 °C (crude fucoidan). At 160 °C and 20 min hold time (total time of 76 min), the crude extract was richest in phenolics and carotenoids and concomitant antioxidant activities. Hydrochar was also recovered 31.23–61.59 dry wt% over 112–168 °C and 0–24 min hold time (total 38–76 min). This work provides not only a framework to develop SCW processes for other types of seaweeds but also demonstrates the value in beach-cast seaweeds compared to their cultivated counterparts. • SCW was used to extract bioactive compounds and hydrochar from waste seaweed. • Final temperature, heat time, and hold time significantly influenced product yields. • Maximum crude alginate and fucoidan yields were 15.80 % and 38.48 %, respectively. • Crude extract at 160 °C and 20 min had the “best” phenolic and carotenoid contents. • Hydrochar recovered from 31.23 to 61.59 dry wt% among the conditions studied.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.000 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one teacher head, not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".