Sargassum fusiforme and Sargassum fulvellum are types of brown algae used for their nutritional value and medicinal properties, including anti-inflammatory, antioxidant, and anticancer effects. Despite their importance in various industries, many seaweed byproducts containing dietary fiber and polysaccharides are discarded in landfills. These byproducts can be recycled and repurposed for different applications. In this study, we investigated the impact of S. fusiforme food processing byproducts (MbP-SFF) and S. fulvellum food processing byproducts (MbP-SFV) on improving intestinal motility and reducing inflammation in mice with constipation induced by loperamide. To evaluate this, mice were orally administered 500 mg/kg/day of the byproducts once daily for 8 days. Constipation was induced by 5 mg/kg/day of loperamide for two days after oral administration for 6 days. Each sample contained approximately 70% carbohydrates. MbP-SFF had 52.0% mannuronic acid and 18.8% guluronic acid, while MbP-SFV had 36.9% mannuronic acid and 32.9% guluronic acid. These byproducts enhanced fecal excretion and intestinal motility by modulating inflammatory responses. Furthermore, they restored the balance of the gut microbiota disrupted by loperamide, increasing beneficial Bifidobacterium and reducing harmful Staphylococcus aureus. Overall, MbP-SFF and MbP-SFV improved intestinal motility and inflammation by influencing the gut microbiota and inflammatory responses in a loperamide-induced mouse model. These byproducts show potential as ingredients in functional foods aimed at enhancing gut health, potentially reducing waste disposal costs and addressing environmental concerns associated with their utilization.

Recently, the extensive spread of some algae along coastlines has surged into unmanageable thick decomposition layers. This study aimed to demonstrate the use of Sargassum horneri as a biomass resource for ethanol production through the continuous hydrolysis, enzymatic saccharification, and fermentation process. Sugars from S. horneri were obtained using a combination of thermal acid hydrolysis and enzymatic saccharification. The optimal conditions for thermal acid hydrolysis involved a 10% (w/v) S. horneri slurry treated with 100 mM H₂SO₄ at 121 °C for 60 min; enzymatic saccharification using 16 U/mL Cellic CTec2 further boosted the monosaccharide concentration to 23.53 g/L. Fermentation experiments were conducted with mannitol-adapted Saccharomyces cerevisiae BY4741 using S. horneri hydrolysate. Enhanced ethanol production was observed in the hydrolysate, particularly with mannitol-adapted S. cerevisiae BY4741, which yielded 10.06 g/L ethanol. Non-adapted S. cerevisiae produced 8.12 g/L ethanol, as it primarily utilized glucose and not mannitol. Regarding ethanol fermentation using 5 L- and 500 L-scale fermenters, the ethanol concentrations reached 10.56 g/L and 7.88 g/L with yields of 0.51 and 0.45, respectively, at 48 h. This study confirmed the economic viability of ethanol production using waste seaweed with optimized pretreatment conditions and the adaptive evolution of S. cerevisiae to mannitol.

This study explores the potential of producing bioethanol from seaweed biomass and reusing the residues as antioxidant compounds. Various types of seaweed, including red (Gelidium amansii, Gloiopeltis furcata, Pyropia tenera), brown (Saccharina japonica, Undaria pinnatifida, Ascophyllum nodosum), and green species (Ulva intestinalis, Ulva prolifera, Codium fragile), were pretreated with dilute acid and enzymes and subsequently processed to produce bioethanol with Saccharomyces cerevisiae BY4741. Ethanol production followed the utilization of sugars, resulting in the highest yields from red algae > brown algae > green algae due to their high carbohydrate content. The residual biomass was extracted with water, ethanol, or methanol to evaluate its antioxidant activity. Among the nine seaweeds, the A. nodosum bioethanol residue extract (BRE) showed the highest antioxidant activity regarding the 2,2-diphenyl-1-picrylhydrazyl (DPPH) activity, ferric reducing antioxidant power (FRAP), and reactive oxygen species (ROS) inhibition of H₂O₂-treated RAW 264.7 cells. These by-products can be valorized, contributing to a more sustainable and economically viable biorefinery process. This dual approach not only enhances the utilization of marine resources but also supports the development of high-value bioproducts.

C-Phycocyanin (C-PC) is a photosynthetic pigment found in cyanobacteria, notably in Arthrospira species. The extraction of phycocyanobilin (PCB), the chromophore of C-PC, is a common approach to address the instability of C-PC under light, heat, and acidic conditions. Methanol is typically used for PCB extraction. However, its use poses challenges for industrial applications owing to the need for solvent removal, extensive purification, and safety validation. Therefore, this study proposes ethanol as an alternative to methanol, optimizing the ethanol extraction conditions through response surface methodology (RSM) using a central composite design (CCD) and techno-economic analysis. The parameters evaluated were the extraction temperature, time, and C-PC/solvent ratio. Optimal conditions—68.81 °C, 14.91 h, and a C-PC to solvent ratio of 1:95 (w/v)— yielded a predicted PCB yield of 29.18%, closely aligning with the actual value of 29.67 ± 1.33%. A techno-economic analysis for pilot-scale PCB production showed that optimized ethanol extraction could yield 147.13 kg/year with 506 batches, compared with 84.31 kg/year standard methanol extraction with 317 batches. Furthermore, it was evaluated to have a unit production cost of USD 1,413,588/kg, an internal rate of return (IRR) of 53.36%, and a payback time of 1.6 years with increased yields and reduced toxic solvent disposal costs. This study supports scalable PCB production with a natural blue pigment suitable for the food, beverage, and cosmetics industries.

Microalgae have gained attention as a promising source of chlorophylls and carotenoids in various industries. However, scaling up of conventional bubble columns presents challenges related to cell sedimentation and the presence of non-photosynthetic cells due to non-circulating zones and decreased light accessibility, respectively. Therefore, this study aimed to evaluate the newly developed continuously circulated bioreactor ROSEMAX at both laboratory and pilot scales, compared to a conventional bubble column. There was no significant difference in the biomass production and photosynthetic pigment content of Tetraselmis sp. cultivated at the laboratory scale (p > 0.05). However, at the pilot scale, the biomass cultured in ROSEMAX showed significantly high biomass (1.69 ± 0.11 g/L, dry weight, DW), chlorophyll-a (14.60 ± 0.76 mg/g, DW), and total carotene (5.64 ± 0.81 mg/g, DW) concentrations compared to the conventional bubble column (1.17 ± 0.11 g/L, DW, 10.67 ± 0.72 mg/g, DW, 3.21 ± 0.56 mg/g, DW, respectively) (p ≤ 0.05). Flow cytometric analyses confirmed that the proportion of Tetraselmis sp. live cells in the culture medium of ROSEMAX was 32.90% higher than that in the conventional bubble column, with a photosynthetic efficiency 1.14 times higher. These results support suggestions to use ROSEMAX as a bioreactor for industrial-scale applications.

Massive blooms of Ulva species, commonly known as green tides, pose serious ecological threats by disrupting coastal ecosystems and requiring costly removal efforts. This study presents a nature-based solution by seasonally valorizing Ulva ohnoi, a bloom-forming macroalga dominant in Jeju Island, South Korea. Biomass was collected across all four seasons and subjected to phylogenetic identification, biochemical characterization, and bioresource processing. Despite environmental fluctuations, tufA-based analysis confirmed U. ohnoi as the sole species present year-round. Carbohydrate content peaked in spring (55.35%) and was lowest in summer (45.74%), corresponding to maximum reducing sugar of 36.49 g/L in winter and 36.24 g/L in spring following acid-enzymatic hydrolysis. The maximum ethanol fermentation using Saccharomyces cerevisiae produced up to 17.12 g/L ethanol in spring with a yield of 0.47 g/g. Post-fermentation residues were enzymatically hydrolyzed into Ulva Ethanol Residue Medium (UERM), which supported yeast growth and fermentation comparable to commercial YPD medium, achieving final optical densities of 8.3–8.5 and ethanol production of 16.5–16.8 g/L. Alanine, valine, and proline were the most abundant amino acids in UERM, supporting its suitability as a nitrogen source. These findings highlight the potential of integrating green tide mitigation with renewable energy and nutrient recycling through seasonal, localized biorefineries aligned with circular marine bioeconomy principles.