Phycology, Volume 4, Issue 2 (June 2024) – 7 articles

Brining and dry salting are traditional preservation techniques used to extend the shelf life of foods including seaweeds. In this study, brining (40% NaCl solution weight/volume) and dry salting (30% weight/weight) processes were applied to fresh kelp to achieve a target water activity of less than 0.77, and the effect of salting treatment on consumer acceptance was assessed. The processed samples were stored at 4 °C for 2 weeks until the sensory analysis. Processed kelp samples were used as the primary ingredient in a salad with shredded carrots and sesame dressing. Three salad samples (salad with fresh kelp (control), brined, or dry salted sugar kelp) were presented to the panelists to assess the liking of sensory attributes including salt intensity, color, aroma, flavor, texture, and overall liking. Significant differences in the liking of flavor and texture were observed, with consumers rating both treatments made with salted seaweed higher than a salad made from fresh seaweed. Panelists identified the availability and lack of information regarding nutritional benefits as barriers to their seaweed consumption. These results indicate that in addition to extending shelf life, the preservation of kelp by salting may increase consumer acceptability. Full article

This parametric study aimed to analyze the effects of increased magnetic field exposure (MFE) on the growth and production of the bioactive compounds of Chlorella (C.) vulgaris. With the intent of studying the effect of an increased MFE, the magnetic field typically experienced by life on Earth was amplified by an order of magnitude. In the increased-MFE environment, six treatments of C. vulgaris with two repetitions for each treatment were exposed to a magnetic field of 5 Gauss (500 µT) about each axis, which was generated in a state-of-the-art Helmholtz cage. The treatments and the control were characterized by the duration of exposure, which was varied from 0 min to 120 min with a step increment of 20 min. The treatments were repeated for six days (TR1) and twelve days (TR2) in two separate experiments. From the first day of the treatment, the specimens in both the experiments were propagated for twenty-one days. For parametric analysis, the overall growth, protein, and beta-carotene content were measured every three days for twenty-one days. For TR1 in general, the samples treated with the increased MFE demonstrated a higher growth rate than the control. Specifically, for the specimen treated with 40 min of the increased MFE, the growth on the 21st day was measured to be 38% higher than the control. For the specimen treated with 120 min of the increased MFE, the protein content on the 15th day was measured to be 15.6% higher than the control. For the specimen treated with 40 min of the increased MFE, the beta-carotene content on the 15th day was measured to be 20.4% higher than the control. For TR2 in general, the results were inferior compared to TR1 but showed higher production than the control specimen. Specifically, for the specimen treated with 80 min of the increased MFE, the protein content on the 21st day was measured to be 4.3% higher than the control. For the specimen treated with 100 min of the increased MFE, the beta-carotene content on the 15th day was measured to be 17.1% higher than the control. For the specimen treated with 100 min of the increased MFE, the growth on the 21st day was measured to be 5% higher than the control. Overall, the treated specimens in TR1 exhibited significantly higher production compared to the control specimen. The treated specimen in TR2 demonstrated some adverse impacts, but still exhibited higher production compared to the control specimen. Full article

The term ‘cosmeceutical’ refers to cosmetic products that offer medicinal or drug-like benefits. Marine algae are rich sources of bioactive compounds, particularly carbohydrates and peptides, which have gained attention for their potential in cosmeceuticals. These compounds are abundant, safe, and have minimal cytotoxicity effects. They offer various benefits to the skin, including addressing rashes, pigmentation, aging, and cancer. Additionally, they exhibit properties such as antimicrobial, skin-whitening, anti-aging, antioxidant, and anti-melanogenic effects. This review surveys the literature on the cosmeceutical potentials of algae-derived compounds, focusing on their roles in skin whitening, anti-aging, anticancer, antioxidant, anti-inflammatory, and antimicrobial applications. The discussion also includes current challenges and future opportunities for using algae for cosmeceutical purposes. Full article

Since 2011, massive new strandings of holopelagic Sargassum have been reported on the coasts of the Caribbean, northern Brazil, Guiana, and West Africa, causing severe economic and ecological damage. Three common morphotypes (S. fluitans III, S. natans I, and S. natans VIII) were identified as responsible for these catastrophic events, with dominance shifts between them over time. However, the taxonomic status of these holopelagic Sargassum morphotypes remains unclear. Using an integrative taxonomy framework, combining a morphological study and molecular analyses, this study aimed to clarify their taxonomic status. Morphological analyses of 54 characters revealed no intermediate form between the three morphotypes, with the overall shape, nature of the axis, and size and shape of blades and vesicles being the most discriminating. An analysis of mitochondrial (IGS, cox2, cox3, mt16S rRNA, and nad6) and plastid (rbcL) markers confirmed the genetic divergence among the three morphotypes, with a lower level of divergence between the two S. natans morphotypes. Without additional molecular characterization, these morphotypes cannot be classified as three distinct species. However, due to their distinct morphological characteristics and sympatry within drifting aggregations, a revision of holopelagic species names is proposed, with Sargassum fluitans var. fluitans (for S. fluitans III), Sargassum natans var. natans (for S. natans I), and S. natans var. wingei (for S. natans VIII). This revision provides necessary clarity on the species involved in inundations of the tropical Atlantic. Full article

Pelagic Sargassum landings (hereby referred to as sargasso) increased dramatically in 2011 throughout the equatorial tropical Atlantic due to the formation of the Great Atlantic Sargassum Belt (GASB). Despite increasing reports, understanding of local abundances and vegetative characteristics, especially in South Florida, remains limited. From 2018 to 2021, sargasso was collected at two South Florida beaches, with additional sampling at a third beach to assess nutrient and heavy metal concentrations. Biomass landings varied greatly, with S. fluitans III predominant during the “peak season” (May to July) and S. natans I predominant in the “off season”, while S. natans VIII was consistently least abundant. This suggests that South Florida may receive sargasso from the Sargasso Sea during the low season and from the GASB during the peak sargasso season. Across all three morphotypes, mean nitrogen (N) and phosphorus (P) contents were 0.97% and 0.04% (dry weight), respectively. Out of the 16 heavy metals detected, our values were similar to those reported across the Caribbean. Arsenic was the most prevalent heavy metal, with sargasso containing epibionts having higher arsenic concentrations. These results provide comprehensive information to better understand the characteristics and potential origin of sargasso landings in South Florida. Full article

Core chlorophytes possess glycerol-3-phosphate dehydrogenases (GPDs) with an unusual bidomain structure, consisting of a glycerol-3-phosphate phosphatase (GPP) domain fused to canonical GPD domains. These plastid-localized enzymes have been implicated in stress responses, being required for the synthesis of glycerol under high salinity and triacylglycerols under nutrient deprivation. However, their regulation under varying environmental conditions is poorly understood. C. reinhardtii transgenic strains expressing constitutively bidomain GPD2 did not accumulate glycerol or triacylglycerols in the absence of any environmental stress. Although the glycerol contents of both wild type and transgenic strains increased significantly upon exposure to high salinity, cycloheximide, an inhibitor of cytoplasmic protein synthesis, abolished this response in the wild type. In contrast, GPD2 transgenic strains were still capable of glycerol accumulation when cultured in medium containing cycloheximide and NaCl. Thus, the pre-existing GPD2 protein appears to become activated for glycerol synthesis upon salt stress. Interestingly, staurosporine, a non-specific inhibitor of protein kinases, prevented this post-translational GPD2 protein activation. Structural modeling analyses suggested that substantial conformational rearrangements, possibly triggered by high salinity, may characterize an active GPD2 GPP domain. Understanding this mechanism(s) may provide insights into the rapid acclimation responses of microalgae to osmotic/salinity stress. Full article

Large-scale strandings of Sargassum spp. seaweeds occur annually on the beaches of the Caribbean islands and cause major environmental, health, and economic problems. In order to support an approach of valorisation of algae, an exhaustive characterisation of the composition of these seaweeds has been performed by analysing the contents in alginates, structural carbohydrates (fucans and glucans), minerals, proteins, lipids, mannitol, polyphenols, and heavy metals. Nine batches were collected at different harvesting sites over the years 2021 and 2022, to estimate the spatial and temporal variation in Sargassum composition. A batch of floats was harvested and analysed to estimate the differences in composition between floats and whole algae. Samples collected during the same year (floats or entire plant, freshly collected or stored) showed no significant differences in composition. However, slight differences were observed between batches collected in the two years. Some samples showed significant amounts of heavy metals, especially arsenic. A detailed structural carbohydrates analysis was carried out and discussed with literature data. As the nitrogen content of algae is an interesting parameter for food or agronomic uses, protein analysis enabled us to calculate a new nitrogen–protein conversion factor, specific to these algae species. Full article